GB2286589A - Sulphonamides for solvent extraction - Google Patents

Abstract

A compound of the general formula (1):- <IMAGE> wherein X is a divalent group which, together with the nitrogen and carbon atoms to which it is attached, forms an optionally 5- or 6-membered heteroaromatic ring; Y is a divalent linking group; m is an integer having a value of 0 or 1; and A is an optionally substituted hydrocarbyl group; wherein A and X taken togerher contain at least sixteen aliphatic carbon atoms in one or more hydrocarbyl group. The heteroaromatic ring is preferably 2-quinolinyl and Y is preferably CO. The compound is useful for the extraction of certain metals from aqueous solutions and has a particular affinity for zinc permitting the selective extraction of zinc from other metals, especially iron.

Description

COMPOUND AND USE The present invention relates to a compound, particularly to a compound which can be used in the solvent extraction of metals, for example zinc.

The solvent extraction of metals is conventionally carried out by contacting an aqueous solution containing the desired metal values with a solution, in a water-immiscible organic solvent, of an extractant compound and thereafter contacting the organic solution, which contains extracted metal values, with an aqueous phase to strip the metal values from the organic solution into the aqueous phase. Zinc may be extracted from oxide ores by treating the crushed ore with sulphuric acid to give an aqueous solution of zinc sulphate. Zinc may be recovered from such aqueous solutions by a solvent extraction process using a suitable extractant. The use of extractants containing the phosphoric acid group, especially di(2-ethylhexyl)-phosphoric acid (D2EPHA), has been proposed, see "Productivity and Technology in the Metallurgical Industries", Edited by M. Koch and J.C. Taylor, in an article by A. Selke and D. de Juan Garcia, pages 695 to 703. However, as is apparent from the Selke et al article, ferric iron is extracted together with the zinc. To prevent build-up of the ferric iron in the organic solution, it is necessary to remove the iron from the organic solution in a stripping stage subsequent to that used to recover the zinc. In this separate stripping stage, the organic solution is contacted with 5 to 6 molar hydrochloric acid to give ferric chloride in hydrochloric acid. Free hydrochloric acid is recovered by a further contacting step in which the ferric chloride in hydrochloric acid is contacted with an organic solution containing tributylphosphate from which the ferric chloride is stripped using water. The additional stages required to remove iron add to the complexity and cost of the procedure and hence are undesirable.

The use of sulphonamido-substituted heterocyclic compounds is disclosed in USP4210759 and USP4100163. The extractants of USP4210759 are sulphonamido compounds containing a group selected from pyridine, pyrimidine, benzothiazole, isoxazole and phenyl benzoxazole, for example 2- (dodecylbenzenesulphonamido) pyridine and similar pyrimidine, benzothiazole, isoxazole and benzoxazole derivatives. The extractants of USP4100163 are 8-sulphonamidoquinoline derivatives, for example 8-(dodecylbenzenesulphonamido)quinoline, B- (dodecylbenzene- sulphonamido)-2-methylquinoline and the like. The sulphonamido derivatives of USP4210759 and USP4100163 are shown to be effective for the extraction of a range of metals from an aqueous sulphate solution.

However, in both of the US Patent disclosures, extraction is effected from an aqueous solution to which ammonia has been added and according to USP4100163 the preferred pH range for the extraction of zinc is about 4.0 to 6.0. Zinc is typically extracted from its ore by acid leaching to form an acidic solution containing a zinc salt and it is desirable to be able to extract zinc from an aqueous solution of iow pH.

Hence, there is a need for a compound which is effective in extracting zinc from an aqueous solution having a pH of less than 4.0 and preferably which has little affinity for ferric iron under the extraction conditions.

According to the present invention there is provided a compound or a mixture of compounds conforming to the general formula (I)

wherein X is a divalent group which, together with the nitrogen and carbon atoms to which it is attached, forms an optionally 5- or 6-membered heteroaranatic ring; Y is a divalent linking group; m is an integer having a value of 0 or 1; and A is an optionally substituted hydrocarbyl group; wherein A and X taken together contain at least sixteen aliphatic carbon atoms in one or more hydrocarbyl group.

Thus, the 16 or more aliphatic carbon atoms may be present in A, or in X, or in both A and X.

Where the groups A and X between them contain at least sixteen aliphatic carbon atoms in one or more hydrocarbyl group, the aliphatic carbon atoms are preferably saturated.

For reasons of economy and availability, the total number of carbon atoms in the groups A and X is preferably not more than sixty, more preferably not more than forty and especially not more than 35.

The substituents which may be present in the group A and/or the group X should be such as to not deleteriously affect the ability of the compound of general formula (1) (hereafter simply "compound (1)") to complex with metals, particularly zinc. Substituents which may be present include halogen, nitro, nitrile, hydrocarbyloxy, hydrocarbyloxycarbonyl, acyl and acyloxy and there may be more than one substituent, in which case substituents may be the same or different. By way of examples of the group A and/or the group X wherein the substituents are the same, there may be mentioned trifluoromethyl. The term halogen includes fluorine, bromine and especially chlorine.

The group A may be an alkyl, alkenyl, cycloalkyl, cycloalkenyl or aryl group or may contain more than one of these groups, for example as in an alkaryl or aralkyl group. A is preferably an aryl group particularly an aryl group having an alkyl group joined thereto either directly or through a divalent linking group such as, for example, -0-, -CO- or especially a -COD-, as in isooctadecyloxycarbonylphenyl. It is generally preferred that the group A is, or contains, at least six and up to 25 saturated carbon atoms in a hydrocarbyl group, preferably at least ten saturated carbon atoms and especially at least thirteen saturated carbon atoms. The saturated carbon atoms are present as one or more alkyl groups and may form a straight chain alkyl group.

Preferably however, especially when containing eight or more carbon atoms, the alkyl group is a branched alkyl group.

Where the invention comprises a mixture of compounds of Formula (I) these may vary in the identity of the group A. In such a mixture the alkyl group forming a part, or the whole, of A may differ from one molecule to another in respect of the number and/or the arrangement of carbon atoms present. Improved solubility in waterimmiscible organic solvents may be achieved by the use of such a mixture especially an isomeric mixture in which the alkyl groups are isomeric.

Examples of the group A are trifluoromethyl, dodecyl, branched dodecyl, 2-hexyldecyl, isooctadecyl, 2 -octyldodecyl and especially alkaryl groups such as 4-dodecylphenyl, 4-decyl-2-methylphenyl, 4- (isodecyloxycarbonyl)phenyl and 4- (isooctadecyloxycarbonyl) phenyl.

The divalent group X may be hydrocarbylene which forms an optionally substituted single or a fused ring system, in which the optional substituent (S) is one or more hydrocarbyl groups or substituent groups of the type previously discussed herein, for example hydrocarbyl or hydrocarbyloxy groups, especially alkyl or alkoxyl groups.

Alternatively, X may contain at least one heteroatom, that is an atom other than a carbon or hydrogen atom, which may be a ring atom and/or may be present in a substituent group attached to the ring or fused ring completed by the linking group X.

If X forms a 6-membered ring, it is preferred that any ring heteroatoms contributed by X are nitrogen atoms and especially that X contributes only one further nitrogen atom. Thus, X may be such as to form a pyridine, pyrimidine, pyrazine, quinoline, quinoxaline or quinazoline ring system which may be unsubstituted or which may be substituted with one or more substituent groups which may be hydrocarbyl groups or substituent groups of the type previously discussed herein, for example hydrocarbyl or hydrocarbyloxy, especially alkyl or alkoxy.

If X forms a substituted ring system, the substituents are preferably one or more alkyl, alkoxy, alkoxycarbonyl and/or alkylcarbonyl groups.

If X forms a five-membered ring, X may include a heteroatom which is other than a nitrogen atom and, in particular, a sulphur or oxygen atom. Such a five-membered ring is preferably part of a fused ring system wherein the five-membered ring contains at least two heteroatoms. Examples of separate and fused ring systems are a thiazole, oxazole, imidazole, benzothiazole, benzoxazole and benzimidazole ring system. Such ring systems may be unsubstituted or contain the substituents selected from those present when X forms a sixmembered ring system.

It is preferred that the atom in the group X adjacent to the nitrogen atom in the structure:

is substituted (i.e. carries an atom or group other than hydrogen). The presence of a substituent on this atom has been found to result in the compound having a reduced affinity for iron, while remaining an effective extractant for zinc. Hence, this adjacent atom is preferably common to two rings of a fused ring system or carries a substituent group, preferably an alkyl1 alkoxy, alkoxycarbonyl or alkylcarbonyl group, and especially a group containing at least six carbon atoms.

However, if the atom in X which is adjacent to the nitrogen atom is common to two rings, for example the adjacent carbon atom in a quinolyl group, it is preferred that, in the second ring, the ring atom peri to the nitrogen atom carries a hydrogen atom and is not substituted since we have found that if a substituent group is present in this position, the compound does not complex as strongly with zinc.

Examples of groups represented by X, together with the nitrogen and carbon atoms to which it is attached, are 2-pyridyl, 6 -undecyl-2-pyridyl, 5 -tridecyloxycarbonyl -2-pyridyi, 2 -pyrazinyl, 4,6-dimethyl 2-pyrimidinyl, 2 -quinolyl, 4 -octyloxy-2 -quinolyl, 8-methyl4-octyloxy-2-quinolyl (less preferred), 5, 7-dimethyl-4-octyloxy-2quinolyl, 4-decyloxy-3 -propyl-2 -quinolyl, benzothiazolyl and 1-dodecylbenz-imidazolyl.

The divalent group Y is preferably electronegative as an electronegative group adjacent to the aminosulphonyl group has generally been found to improve the performance of Compound (1). Examples of such groups are oxycarbonyl, sulfonyl, and more especially carbonyl.

It is also preferred that m is 1.

In a preferred Compound (1) both A and X include an alkyl group, for example an alkyl group which contains at least 4 and especially at least 6, and preferably up to 25, carbon atoms. The group X conveniently forms a pyridine or quinoline ring structure, which is preferably substituted, and preferred quinoline ring structures are unsubstituted in the 8-position.

In another preferred Compound (1) the groups A and X between them contain at least twenty saturated carbon atoms in one or more hydrocarbyl groups. There is no upper limit to the number of saturated carbon atoms which may be present in the groups A and X, but no particular advantage is gained when the groups A and X between them contain more than forty saturated carbon atoms. Compound (1) is conveniently one in which the groups A and X between them contain not more than thirty six saturated carbon atoms in one or more hydrocarbyl groups.

Examples of the Compound (1) ( are 2- [4- (isooctadecyloxy carbonyl)phenylsulphonylcarbamoyl]-6-und 2-[4-(isooctadecyloxycarbonyl)phenylsulphonylcarbamoyl]-4-octyloxyquinoline; 2-[4-(isooctadecyloxycarbonyl)phenylsulphonylcarbamoyl]5,7-dimethyl-4-octyloxyquinoline; 2-[4-isooctadecyloxycarbonyl)phenyl sulphonylcarbonyl] -5,7-dimethyl-4-isodecyloxyquinoline; and less preferably, 2-[4-( isooctadecyloxycarbonyl ) phenylsulphonylcarbamoyl - 8-methyl-4-octyloxyquinoline.

Of the foregoing compounds, as discussed hereafter, we have found that the quinoline derivatives which are unsubstituted in the 8-position extract appreciable proportions of zinc even at a pH of less than two.

Compounds in accordance with the present invention can be prepared in any suitable manner, as will be apparent to those skilled in the art. A convenient method of preparation for a compound in which m is 1 and Y is - (CO) - is by the reaction of an acid halide with an amide derivative. More specifically, a sulphonyl or carbonyl halide is reacted with a carbonyl amide or a sulphonamide respectively. For convenience hereinafter, the preparation will be described in respect of the reaction of a carbonylhalide with a sulphonamide but it should be appreciated that similar procedures may be used to effect the reaction of a sulphonylhalide with a carbonamide.

The halide used is conveniently a chloride although the other halides may be used. The reaction of the carbonyl halide with the sulphonamide is conveniently effected in solution in a suitable solvent or mixture of solvents, for example a hydrocarbon solvent such as toluene or a mixture of a hydrocarbon solvent and a halogenated solvent such as dichloromethane. The reaction is effected in the presence of a base, and it is convenient to use an organic base such as a tertiary amine, for example triethylamine. The reaction can be effected at ambient temperature, typically 150C to 25 C, but may be effected at lower or higher temperatures. The reaction time is dependent on the reactants and the reaction temperature and may be in excess of ten hours if the reaction is effected at ambient temperature and at this temperature a satisfactory yield is obtained with a reaction time of not more than 25 hours. The reaction time may be decreased by the use of a higher reaction temperature, if desired.

The reaction product, Compound (1), may be recovered from the solvent or solvent mixture in which it is prepared using any suitable technique, for example washing with water to remove water soluble reaction products, drying and evaporating off the solvent or solvents.

The carbonyl halide and sulphonamide may be readily available materials or may be readily prepared from such materials. Thus, the carbonyl halide may be one derived from 2-pyridinecarboxylic acid or 2-quinolinecarboxylic acid. The sulphonamide may be benzenesulphonamide. Compound (1) contains at least sixteen saturated carbon atoms in one or more hydrocarbyl groups and hence at least one of the reactants is substituted to provide the required number of saturated carbon atoms in the final compound. It is generally preferred that both the carbonyl halide and the sulphonamide contain a group having saturated carbon atoms. Thus, the carbonyl halide is preferably one which contains saturated carbon atoms and similarly the sulphonamide is preferably one which contains saturated carbon atoms.

More specifically, the carbonyl halide is preferably one containing an alkyl group joined directly or indirectly to the ring system. Similarly, the sulphonamide contains an alkyl group and in particularly is a benzenesulphonamide in which an alkyl group is joined directly or indirectly to the benzene ring.

Suitable substituted carbonyl halides and sulphoncmides are not generally available and hence it is preferred to prepare these materials in preliminary steps prior to the reaction of the carbonyl halide with the sulphonamide. It is generally more convenient to prepare a substituted carbonyl halide and a substituted sulphonamide in preliminary steps rather than to react an unsubstituted carbonyl halide with an unsubstituted sulphonamide and thereafter substitute the desired alkyl groups, or alkyl-containing groups, in the sulphonyl carbamoyl product.

The preparation of the substituted carbonyl halide will depend on the particular compound to be obtained and the material from which it is to be obtained. Substituted 2-pyridinecarbonylhalides may be obtained starting from 2-methylpyridine. As an initial step, the 2-methylpyridine can be reacted with an alkyl halide in the presence of a base such as sodamide and the mixture heated to give a longer chain alkyl substituted pyridine, for example the reaction of 2-methylpyridine with isodemyl chloride results in the production of 2-undecylpyridine. The 2-alkylpyridine, which may be 2-methylpyridine, is then oxidised to form the corresponding pyridine-N-oxide.

The pyridine-N-oxide is then reacted with a nitrile compound, for example potassium cyanide, to obtain a 2-alkyl-6-cyanopyridine. This compound may then be hydrolysed to give the corresponding carboxylic acid from which the carbonyl halide may be obtained using known procedures such as by reaction with a halide compound, for example thionyl chloride.

The sulphonamide is preferably a substituted benzenesulphonamide. A convenient material to use for the preparation of a substituted benzenesulphonamide is 4-carboxybenzenesulphonamide from which a 4-alkyloxycarbonylbenzenesulphonamide can be prepared in two stages. Specifically, the 4-carboxybenzenesulphonamide is reacted with a halide compound such as thionyl chloride to give the corresponding carbonyl halide which is then reacted with an alkanol to give a 4-alkoxycarbonyl-benzenesulphonamide.

If the compound (I) is a 2-quinolyl derivative having further substituents in the quinoline ring system, such a product may be obtained using the following reaction sequence:

where R, R1, R2 and R3 are alkyl groups and can be the same or different; and n is zero or an integer from 1 up to 4.

If the value of n is greater than one, the substituents R may be the same or different. Typically the value of n is zero, one or two.

It is preferred to use aminobenzene compounds which are unsubstituted in the positions ortho to the amino-group, that is the 2- and 6-positions.

The groups R, Rl and R2 are preferably lower alkyl groups, that is alkyl groups having not more than four carbon atoms, especially methyl or ethyl groups. The group R3 is preferably a higher alkyl group, that is an alkyl group having more than four carbon atoms, preferably at least six and especially eight or more carbon atoms and preferably up to 25 carbon atoms, such as octyl or isodecyl.

In the first stage of the reaction sequence, an optionally substituted aminobenzene compound is reacted with a diester of oxaloacetic acid at an elevated temperature, for example from 750C up to 1500C, to form a Schiffs Base of formula (A).

In the second stage of the reaction sequence the Schiffs Base is cyclised to form a quinoline derivative (a compound of formula (B)) by heating to an elevated temperature in the presence of a high boiling liquid medium such as diphenyl ether. The temperature of cyclisation is typically at least 1500C and especially at least 2000C, but in general is not more than 2600C.

In the third stage, the quinoline derivative is reacted with an alkyl halide in a basic medium and preferably in the presence of a source of iodide ions to form the alkoxyquinoline derivative of formula (C). The reaction is effected at an elevated temperature which is at least 800C and in general does not exceed 1500C.

In the fourth stage, the compound of formula (C) is reacted with a base to form the corresponding acid which is converted to the corresponding acid chloride by reaction with a molar excess of thionyl chloride to give an acid chloride of formula (D).

The acid chloride is then reacted with a sulphonamide to obtain the Compound (1) using the procedure previously described herein.

Other procedures for preparing suitable substituted carbonyl halide and/or sulphonamide reactants will be apparent to the skilled worker and such procedures may be used to prepare intermediate materials or the final product, Compound (1).

The compounds of the present invention are effective in the selective extraction of certain metal values from aqueous solution.

Thus, according to a further aspect of the present invention there is provided a process for extracting metal values from aqueous solutions of metal salts which comprises contacting the aqueous solution with a solution in a water-immiscible organic solvent of a compound of formula (1):

wherein X, Y, m and A are as previously defined.

The process of the further aspect of the present invention may be applied to the extraction from aqueous solutions containing sulphate ion of any metal capable of forming a stable complex with the Compound (1) in the water-immiscible organic solvent. Examples of such metals include copper, silver, mercury, zinc and cadmium, all of which can form a complex with Compound (1). The process of the present invention is especially suitable for the solvent extraction of zinc from an aqueous solution obtained by the sulphate leaching of zinc oxide containing ores.

It will be appreciated that the process of the present invention may be incorporated into a wide variety of different methods for the overall recovery of metals from their ores or from other metalbearing sources. Details of these methods will vary depending on the metal concerned and the nature and composition of the leach solution.

An integrated process which is especially suitable for sulphate leach solutions can be carried out using procedures known to the skilled worker, for example those described in the documents noted previously herein.

More specifically, the process of the present invention comprises a sequence of stages in which the metal is extracted into an organic solution, stripped into an aqueous phase and recovered from the aqueous phase by any suitable means, for example by electrowinning.

Thus, as a particular aspect of the process of the present invention there is provided a process for extracting metal values from aqueous solution by a sequence of stages comprising: a. contacting an aqueous solution containing metal values with a solution in a water-immiscible solvent of Compound (1); b. separating the aqueous and solvent phases, the latter containing metal complex; c. contacting the solvent phase with an aqueous mineral acid; and d. separating the solvent phase from the aqueous phase containing metal in the form of a salt of the mineral acid.

Preferably the metal is zinc, particularly a solution of zinc sulphate.

The amount of compound (1) used will depend upon the concentration of metal salt in the aqueous solution and the plant design. It is preferred however to use from 5g to 300g of compound (I) per im3 (litre) of organic solution. Higher concentrations afford organic phases of too high viscosity for convenient handling and lower concentrations involve the use of unnecessarily large volumes of solvent.

For use with aqueous solutions containing lg or more per dm3 of a metal such as zinc, it is preferred to use 20 to 200g of compound (I) per dm3 of organic solution. If desired compound (I) can be used together with a compound which modifies the behaviour thereof in the extraction process, for example an alcohol or ester suitably from 10% to 200% of the weight of compound (I), and especially from 20% to 100%.

The first and second steps of the process may conveniently be carried out by bringing together the aqueous solution containing the metal and the solution of compound (I) in the organic solvent at a suitable temperature, usually ambient temperature, although somewhat higher temperatures, for example up to 1000C, but preferably not more than 500C, may be used if operationally convenient. Agitating or otherwise disturbing the mixture of liquids is effected so that the area of the water-solvent interfacial layer is increased in order to promote complex formation and extraction, and then decreasing the agitation or disturbance so that the aqueous and solvent layers settle and can be conveniently separated. The process may be carried out in a batchwise manner but is preferably effected continuously.

The amount of organic solvent to be used may be chosen to suit the volume of aqueous solution to be extracted, the concentration of metals, and the plant available to carry out the process. It is preferred, especially when operating the process continuously, to bring together approximately equal volumes of the organic solution and the aqueous solution. However, the ratio of the organic solution to the aqueous solution can be varied to achieve a desired effect and the ratio may be from 5:1 to 1:5 by volume.

The conditions, particularly pH values, under which first and second steps of the process are carried out are chosen to suit the metal or metals present in the aqueous solution. It is generally desirable that under the chosen conditions any other metals present should not form stable complex compounds with compound (I) in order that substantially only the desired metal is extracted from the aqueous solution. Alternatively, any metals extracted in addition to the desired metal, should be such as to be readily separated from the desired metal, for example by cementation from the acid strip solution using zinc dust. Since formation of the complex compound may involve the liberation of acid, it may be necessary to add, for example, alkali during the process to maintain the pH within the desired range in which a substantial proportion of the metal is present as the metal complex but it is generally preferable to avoid this, especially in a continuously-operated process. The process of the invention is especially suitable for use with zinc since the metal forms a complex with compound (I) whereby a substantial proportion of the zinc is present as a complex at pH values below 3. By increasing the concentration of the extractants of formula I in the organic solvent and using a very non-polar solvent such as kerosene, it is possible to increase the degree of complexation, thus allowing extraction to be effected at pH values of two and below.

As the active extraction centre of Compound (1) is rather polar it is desirable to enhance its solubility by the use of appropriate hydrophobic solubilising groups in and attached to X and A.

However, in so modifying the compound, there is a tendency to increase the molecular size to such an extent that solutions of the compound in the organic solvent become rather viscous. However, it is a matter of simple trial within the knowledge of the person of ordinary skill to select the length, degree of branching, degree of saturation etc of each fatty chain and the number and positioning of such chains to strike a balance between optimum solubility of the compound and optimum viscosity of its solution in the organic solvent.

As organic solvents there may be used any mobile organic solvent, or mixture of solvents, which is immiscible with water and, under the pH conditions used, inert to water, and to Compound (1). The solvents are especially aliphatic, alicyclic and aromatic hydrocarbons and mixtures of any of these. Halogenated, particularly chlorinated, hydrocarbons including, as solvents more dense than water, highly halogenated hydrocarbons such as perchloroethylene, trichloroethane, trichloroethylene and chloroform may also be used but, in view of environmental concerns regarding the use of such halogenated materials, the use of hydrocarbon solvents is very much preferred.

The third and fourth steps of the process may conveniently be carried out by bringing together the metal-bearing solution of compound (I) in the organic solvent, obtained from the second stage of the process, and an aqueous solution of a mineral acid at a suitable temperature, usually ambient temperature, although somewhat higher temperatures may be used if operationally convenient, for example up to 1000C but preferably not more than 500C. Agitating or otherwise disturbing the mixture of liquids is effected so that the area of the aqueous solution - organic solution interfacial layer is increased in order to promote decomposition of the complex and recovery of the metal.

The agitation or disturbance is then decreased so that the aqueous and solvent layers settle and finally the layers are separated.

Suitable relative volumes of organic to aqueous phases are those conventionally used in metal extraction processes and in the stripping stage will be typically not more than 5:1. The process may be carried out in a batchwise manner but is preferably effected continuously. The stripped organic layer, containing regenerated compound (I), the modifier and some residual zinc may be re-used in the first step of the process. The aqueous layer containing metal salt may be treated in any conventional manner, for example by cementation of metal impurities with zinc dust, followed especially by electrolysis to provide the desired metal which is typically zinc.

The stripping acid is preferably sulphuric acid, suitable strengths being from 100 to 250g of acid per dm3 of the solution. After removal of a convenient part of the metal by electrolysis the recovered aqueous acid, containing residual metal salt, may be re-used in the third

C. Preparation of 2-undecyl-6-cyanopyrldlne 2-Undecylpyridine (150 parts), prepared as described in Stage B, was dissolved in glacial acetic acid (450 cm3). Hydrogen peroxide (100 volume strength, 75cm3) was added and the solution was stirred at 70 to 800C for 3 hours. A further addition of hydrogen peroxide (55cm3) was then made and the temperature was maintained at 70 to 800C for a further 9 hours. Most of the acetic acid was then distilled off under a pressure of 20mm of mercury. The residue was extracted with chloroform and the chloroform solution was shaken with excess sodium carbonate solution, then separated and dried over solid sodium carbonate. The chloroform was then distilled leaving 2isodecylpyridine-N-oxide (160 parts) as a colourless oil. To this oil dimethyl sulphate (74cm3) was added dropwise with cooling to maintain a temperature of 20 to 300C. The solution was heated for one hour on a steam bath, cooled to room temperature and diluted with 10cm3 of water.

This mixture was then added dropwise, with cooling to maintain a temperature of 30 to 350C, to a stirred solution of potassium cyanide (70.5 parts) in water (165cm3). The mixture was allowed to cool to 250C and was stirred at this temperature for 16 hours. The mixture was then extracted with chloroform and the chloroform solution was extracted several times with water, separated and distilled to yield 2-undecyl-6cyanopyridine (44 parts) b.p. 116 to 1300C at a pressure of 0.04mum of mercury.

The proton n.m.r. spectrum of this product was obtained using a solution of the compound in deuterochloroform containing tetramethylsilane as an internal standard. The absence of an absorption peak between b= 8.0 and 6= 8.5 ppm indicated the absence of a hydrogen atom on a carbon atom adjacent to the nitrogen in the pyridine ring. Hence, the nitrile group is present in the pyridine ring in the 6-position.

D. Preparation of 2-Undecylpyrldlne-6-Carbonylchlorlde 2-Undecyl-6-cyanopyridine (42.2 parts), prepared as described in Stage C, was hydrolysed to 2-undecyl-6-carboxypyridine by heating at 13500 for 4 hours with a mixture of sulphuric acid (88cm3) and water (88cm3). The mixture was cooled, diluted with water (100rim3) neutralised to pH 4 with sodium hydroxide solution and extracted into chloroform.

The chloroform solution was dried with anhydrous sodium sulphate and the chloroform was distilled yielding the acid (40 parts).

By potentiometric titration with 0.1M aqueous sodium hydroxide solution of a sample of this acid the amount of carboxy group present was found to be 91% of theoretical for molecular weight 277.4.

The acid (2.5 parts) and dimethylformamide (3 drops) were dissolved in toluene (20cm3) and stirred while thionyl chloride (0.70cm3) was added.

The solution was heated at 80 C for two hours during which time a further addition of thionyl chloride (0.30cm3) was made. Excess thionyl chloride and about two thirds of the toluene were removed by distillation and the solution of 2-undecylpyridine-6-carbonylchloride was retained for use in the final stage of the preparation (Stage F).

E. Preparation of 4- (Isooctadecyloxycarbnyl)benzenesulphonamide A mixture of 4-carboxybenzene sulphonamide (100.6 parts), obtainable from Aldrich Chemicals, and thionyl chloride (300cm3) was stirred and boiled under reflux for 16 hours. Toluene (200cm3) was added and the mixture was distilled until the still-head temperature rose to 11000. The solution was cooled and the precipitate of 4- (chlorocarbnyl)benzenesulphonamide was collected (55.0 parts). A mixture of this acid chloride (48.4 parts), dichloromethane (200cm3) a commercial isooctadecyl alcohol (54.2 parts), available from Hoechst, was stirred and boiled under reflux for 18 hours, during which time additions of pyridine (total 16cm3) and further additions of acid chloride (total 5.0 parts) were made, to ensure that, as measured by gas chromatography, all the alcohol had been converted to a higher boiling product. The mixture was cooled and filtered and the methylene chloride was distilled off under a pressure of 20mm of mercury. The residue was dissolved in ethyl acetate, extracted with dilute hydrochloric acid and then with water. The ethyl acetate solution was treated with active carbon and anhydrous magnesium sulphate and filtered and the solvent was distilled yielding 4- (isooctadecyloxycarbonyl)benzenesulphonamide (90.4 parts).

F. Preparation of 2 f4 - (isooctadecyloxycarbonyl phenylsuiphonyl carbamoyll-6-undecylpyridine A portion of the sulphonamide from Stage E (3.7 parts), and dichloromethane (30cm3) were added to the toluene solution of 2-undecylpyridine-6-carbonyl chloride from Stage D. The solution was stirred at 20-250C while triethylamine (4. 0cm3) was added dropwise during 5 minutes. The solution was then left to stand for 18 hours. An equal volume of water was then added and the pH of the stirred mixture was adjusted to pH3 with hydrochloric acid. The methylene chloride solution was separated, extracted three times with an equal volume of water, dried with anhydrous magnesium sulphate and treated with a little active carbon. It was then filtered and the solvent was distilled, the last traces being removed at 70 C under a pressure of 0.5mm of mercury. The residue, a brown oil, consisted essentially of 2-E4-(isooctade- cyloxycarbonyl) phenylsulphonylcarbamoYil ] - 6 -undecylpyridine, wherein the undecyl moiety contains mixed and branched alkyl groups. Its purity was estimated by potentiometric titration of the acidic amino group with O. 1M sodium hydroxide solution as 84% of theoretical for molecular weight 713.

Example2 A. Preparation of 2-ethoxycarbonyl-4-hydroxyqulnollne A mixture of sodium diethyl oxaloacetate (500 parts; obtained from Fluka), toluene (2dm3) and water (1.2dm3) was stirred and maintained at 0-5 C by external cooling whilst a solution of 4 molar aqueous sulphuric acid (440 cm3) was added. The toluene solution was then separated from the aqueous phase, extracted with water until free of mineral acid, dried over anhydrous magnesium sulphate and filtered.

Aniline (240 parts) was added and the solution was stirred and boiled under reflux in an atmosphere of nitrogen below a Dean-Stark trap to collect the water of reaction. After 4 hours the solution was cooled and extracted with portions of 2 molar hydrochloric acid until free of excess aniline, and then with water. The solution was dried over anhydrous magnesium sulphate and concentrated by distillation of toluene under reduced pressure (15-20 mm of mercury) to give an oil (481 parts) which was Schiffs Base of the general formula A wherein R1 and R2 are both ethyl groups and the value of n is zero.

The Schiffs Base was cyclised as follows. The above Schiffs Base (250 parts) were dissolved in diphenyl ether (100cm3) and the solution was added dropwise in nitrogen atmosphere during 0.5hr to diphenyl ether (550cm3) which was being stirred and had been heated to 2200-2400C. The temperature of 2200-2400C was maintained during the addition of the Schiffs Base solution and ethanol produced by the reaction was allowed to distil. Ten minutes after addition was complete, the mixture was allowed to cool to 400C, and diluted with acetone (550cm3). The diluted mixture was then left to cool to 250C and crystallise for 18 hours. The precipitated solid was collected by filtration and well washed with acetone and dried yielding 2ethoxycarbonyl-4-hydroxyquinoline, (109 parts) as pale brown solid.

B. Preparation of 2-ethoxycarbonyl-4-octyloxyWuinoline All of the ester obtained in Stage A and octyl bromide (107 parts) were dissolved in dimethylformamide (750cm3). Potassium carbonate (42.7 parts) and potassium iodide (0.6 parts) were added. The mixture was stirred and heated to 11000 for two hours, allowed to cool and filtered. The filtrate was diluted with water (ldm3) and extracted with a mixture of ethyl acetate (600cm3) and hexane (300cm3). The upper layer was separated and extracted three times with 500cm3 aliquots of water and dried over anhydrous magnesium sulphate. The solvents were distilled under reduced pressure at 15-20 mm of mercury leaving 2-ethoxycarbonyl4-octyloxyquinoline as a white solid (159 parts) from which the last traces of solvent were removed by drying under a pressure of 0.5mm of mercury.

C. Preparation of 2-carboxy-4-octyloxyqulnollne All of the ester obtained in Stage B was dissolved in ethanol (750cm3) and a solution of sodium hydroxide (29 parts) in water (75cm3) was added with stirring and cooling to keep the reaction temperature below 35 C. Precipitation of the sodium salt of the carboxylic acid produced a thick paste to which sufficient ethanol was added to allow stirring to continue. The precipitate was collected by filtration, washed well with ethanol, again collected and then slurried in ethanol.

The pH of the ethanol slurry was adjusted to between pH 3 and pH 4 by careful addition of concentrated hydrochloric acid (S.G. 1.18). The solvent was distilled under reduced pressure and the residual solid was washed with water and finally slurried in water (ldm3). The suspension was warmed to 50 C in order to extract remaining sodium chloride into the aqueous phase. The solid was then collected and dried under reduced pressure at 15-20 mm of mercury over calcium chloride.

2-carboxy-4-octyloxyquinoline (125 parts), mp 128-130 C was obtained. Titration of the carboxy group with 0.1M sodium hydroxide gave a value of 97.0% of theoretical for molecular weight 301.4.

D. Preparation of 4-octvloxvouinoline-2-carbonvichloride The acid obtained in Stage C was added in portions (total added 120.6 parts) to thionyl chloride (350cm3) at 25 C. The temperature was raised cautiously to reflux temperature (about 800C) and the mixture was boiled at reflux temperature until all of the acid had gone into solution. The solution was allowed to cool and toluene (250cm3) was added. The toluene solution was heated under a pressure of 20mm of mercury to distil excess thionyl chloride and distillation was continued until a small quantity of toluene (about 30cm33 had distilled. A solution of the carbonylchloride in toluene was obtained.

E. Preparation of 2-[4-(isooctadecyloxycarbonyl) phenylsulphonyl carbamoyll-4-octyloxyZuinoline The solution of the carbonylchloride in toluene obtained in Stage D was cooled to 25 C and a solution of 4-(isooctadecyloxycarbonyl) benzenesulphonamide, prepared as described in Stage E of Example 1 (159 parts), in dichloromethane (200cm3) was added.

The combined solution was maintained at 20-25 C by external cooling while triethylamine (100cm3) was added portionwise during 15-20 minutes. The reaction solution was then left to stand, for 18 hours.

The solution was then stirred with water (500cm3) and the pH of the mixture was adjusted to between pH 3 and pH 3.5 by the addition of glacial acetic acid. The organic layer was separated and distilled under reduced pressure at 15-20 mm of mercury until about 200cm3 of solvent (methylene chloride) had been removed. Ethyl acetate was added (200cm3) and the combined organic solution was extracted with 4 portions of water (each 200cm3) containing sufficient sodium chloride to give good phase separation. The solution was then dried over anhydrous magnesium sulphate and the solvents were distilled under reduced pressure at 0.5 mm of mercury yielding an oil (286 parts) which was shown by high pressure liquid chromatography to consist mainly of 2-[(4isooctadecyloxycarbonyl)phenylsulphonylcarbamoyl]-4-octyloxyquinoline but containing as principal impurities 2-carboxy-4-octyloxyquinoline and bis-(4-octyloxyquinol-2-ylcarbonyl)amine. It is believed that the former impurity may deleteriously affect the selectivity of the extractant in certain applications. The oil was therefore purified by column chromatography using silica gel (1300 parts; supplied by Grace Brothers, type 62) and elution with a solvent comprising hexane and ethyl acetate in the volume ratio 80:20, when the former impurity was strongly retained on the column and the latter impurity was eluted, but more slowly than the product. Fractions containing the product were combined, and concentrated by distillation of solvent to a waxy solid (144 parts). The nmr spectrum of the product was fully consistent with the product being 2-[(4-isooctadecyloxycarbonyl) phenylsuiphonyl- carbamoyl]-4-octyloxyquinoline. Potentiometric titration of the acidic (-CONH-SC-) group with O. IM NaOH in a mixture of water and Solvesso 150 gave a value 86% of theoretical for molecular weight 737.06.

Example3 preparation of 2-r4-(isooctadecyloxycarbonyl) phenylsuiphonyl - carbamoyl 1 - 8-methyl-4-octyloxyquinoline Using the procedure of Example 2, p-toluidine was converted into 2-carboxy-8-methyl-4-octyloxyquinoline (mp 78-790) and thereafter into the corresponding acid chloride. Sufficient dichloromethane was added to the toluene solution of the acid chloride to ensure that any acid chloride which precipitated from solution redissolved. The solution of the acid chloride was then reacted with 4-(isooctadecyloxycarbonyl) benzenesulphonamide and the product purified by column chromatography as described in Example 2 to give 2- [4- (isooctadecyloxycarbonyl) phenylsulphonylcarbamoyl -8-methyl-4 -octyloxyquinoline which was estimated by titration (as in Example 2) and found to be 90. 4t of the theoretical strength for molecular weight 751.

Example4 Preparation of 2- f4 - (isooctadecyloxycarbonyl phenylsulphonylcarbamoyll - 5 7-dimethvl-4-octyloxyquinoline Using the procedure of Example 2, 3,5-dimethylaniline was converted into 2-carboxy-5, 7-dimethyl-4-octyloxyquinoline (mp 124-1270C) and thereafter into the corresponding acid chloride. The acid chloride was reacted with 4-(isooctadecyloxycarbonyl)benzene-sulphonamide to give 2-[4-(isooctadecylOxyCarbonyl) phenylsulphonyl-carbamoyl-5, 7-dimethyl4-octyloxyquinoline. By chromatography of the crude material using 14 times its weight of silica gel a very pure sample of the product was obtained (mp 114-1160) but decomposition occurred on the column and the recovery was low. Chromatography using 3.5 times the weight of silica gel gave a product free of carboxy intermediate which was estimated by titration (as in Example 2) to be 52% of the theoretical strength for molecular weight 765. This material was found to be satisfactory when used in metal extraction tests as described in Examples 5 to 14.

Examples 5 to 15 The sulphonylcarbamoyl compounds obtained as the products of Examples 1 to 4 were tested as a solvent extractants for zinc by determining the amounts of zinc extracted from aqueous solution at different equilibrium pH values according to the reversible equilibrium: SnS04 + 2U1 @ ~~~ + H2SO4 (aqueous) (organic) (organic) (aqueous) where LH is the sulphonylcarbamoyl compound.

A 0.2 molar organic solution of the sulphonylcarbamoyl compound was made up by dissolving the compound in a mixture of SOLVESSO 150 and decan-l-ol (9:1 v/v). Aliquots of this solution were then contacted, by stirring at 20 to 250C, with equal volumes of 0.1 molar aqueous zinc sulphate solution containing varying amounts of sodium hydroxide. Stirring was continued until the pH of the aqueous phase became constant. The phases were allowed to separate and both were analysed for zinc. A graph was plotted of the percentage of total zinc present which had passed into the organic solution against pH. For comparative purposes the same procedure was repeated using a 0.2 molar solution of di-2-ethylhexylphosphoric acid (D2EHPA), which is used commercially as a solvent extractant for zinc. Results obtained from the graphs for each extractant are set out in Table One.

TABLE ONE

Ex or Comp Extractant % pH Example (a) Zn (c) (b) 5 1 25 2.6 6 1 50 3.2 7 1 75 4. 0 A D2EHPA 25 2.3 B D2EHPA 50 2.8 C D2EFIPA 75 3.5 8 2 25 2.0 9 2 50 2.4 10 2 75 3.4 11 3 75 6.0 12 4 25 2.2 13 4 50 2.5 14 4 75 3.4 Notes to Table One (a) Numbers represent the product of the numbered Example D2EHPA is di-2-ethylhexylphosphoric acid.

(b) % Zn is the percentage of the total zinc extracted into the organic solution.

(c) pH is the equilibrium pH of the aqueous phase which corresponds to the specified % Zn.

Example 15 A similar procedure to that of Examples 5 to 14 was carried out replacing the zinc sulphate solution by an aqueous solution of iron (III) sulphate which was 0.0667 molar. In this procedure the pH range was restricted to prevent precipitation of ferric hydroxide as a third phase, which occurs at pH values above pH 2. At pH 2.0 it was found that 96% of the iron was extracted by the D2EHPA but that only 1. 5t of the available iron was extracted by the sulphonylcarbamoyl compound of Example 1.

Examples 16 and 17 The selectivity of the extractants of Examples 2 and 4 for zinc over iron in a multi-contact extraction procedure was measured and compared with that shown by D2EHPA. An aqueous feed solution containing 5gdm-3 zinc and 5gdm-3 iron (III) at pH 1.9 was made up by dissolving 21.99g of ZnSO4.7H2O and 35.08g of Fe2 (S04)3 in water and diluting to one dm3. Solutions of the extractants in organic solvents were made up at the concentrations listed in Table Two. For D2EHPA and the product of Example 2, the organic solvent was ESCAID 100. For the product of Example 4, the solvent was SOLVESSO 150 containing 10% by volume of decan-1-ol. Each organic solution was contacted with twice its volume of the aqueous solution by stirring the two together for 30-60 minutes.

The organic solution was then separated and contacted with fresh aliquots of the aqueous feed solution two further times in the same way.

The organic solutions were then analysed by atomic absorption spectroscopy for iron and zinc. The results obtained are set out in Table Two.

TABLE TWO

Ex or Extractant Extractant Concentration Concentration Comp (a) Concentration of zinc of iron Ex (gdm-3) (d) (gdm-3) (e) (gdm-3) (e) D D D2EHPA 161 0.002 15.4 16 2 184 2.5 0.40 17 4 0 164 1.3 0.01 Notes to Table Two (a) is as defined in Notes to Table One.

(d) Extractant Concentration is in the organic phase and is expressed relative to the phenylsulphonylcarbamoyl content of the products of Examples 2 and 4.

(e) The concentration is that of the specified metal in the organic phase after effecting the contacting procedure a total of three times as described.

Example 18 The stripping of zinc from the extractant of Example 2 was demonstrated in the following manner.

A 0.2 molar solution of Extractant 2 was made up in an organic solvent which was SOLVESSO 150 containing 10% by volume of decan-1-ol. This was contacted with an equal volume of 0.1 molar aqueous zinc chloride solution containing sufficient sodium hydroxide to give a pH of 4.8, by stirring at 250C for 40 minutes. The phases were separated and the organic phase analysed by atomic absorption spectroscopy for zinc.

The loaded organic phase from above and an equal volume of dilute sulphuric acid of sufficient strength to give pH 1.0 were contacted by stirring at 250C. After 10 minutes a sample of the organic phase was taken, together with an equal volume of the aqueous phase, and the organic phase analysed by atomic absorption for zinc. Stirring was continued for a total of 50 minutes when the phases were separated and the organic phase was again analysed by atomic absorption spectroscopy for zinc. The results obtained are set out in Table Three.

TABLE THREE

Time Extractant Extractant Concentration of (mins) (a) Concentration zinc (gmd-3) (f) (gmd-3) (d) 0 2 147 5.67 10 2 147 0.655 50 2 147 0.160 Notes to Table Three (a) is as defined in Notes to Table One.

(d) is as defined in Notes to Table Two.

(f) The concentration is that of zinc in the organic phase after the relevant contacting time.

Example 19 Preparation of 2 - [4 - (isoctadecyloxycarbonyl) phenylsulphonyl carbamoyl]-5, 7-dimethyl-4-isodecyloxyquinoline.

Isodecyl bromide was prepared by reacting commercial isodecanol which is a mixture of isomeric branched primary saturated aliphatic alcohols of formula CloH2lOH supplied by ICI plc, with hydrobromic and sulphuric acids and distilled, b.p. 95-980C at 16 trrn of mercury pressure.

2 -Ethoxycarbonyl -4 -hydroxy- 5, 7-dimethylquinoline was prepared from 3,5-dimethylaniline as described in Examples 4 and 2. 50.4 parts of this ester were then stirred and heated with isodecyl bromide (49.8 parts), potassium carbonate (18.9 parts) and potassium iodide (2.6 parts) in dimethylformamide (154 parts by volume) at 1100C for 2.5 hr.

The product was worked up by the procedure of Example 2B and hydrolysed by the procedure of Example 2C to give 2-carboxy-4-isodecyloxy-5, 7- dimethylquinoline (24.8 parts), mp 43.5-470C. This acid was converted to the acid chloride by the procedure of Example 2D and reacted with 4 (isooctadecyloxycarbonyl) benzene sulphonamide by the procedure of Example 2E to give after chromatographic purification with silica gel 2 [4- (isooctadecyloxycarbonyl) phenylsulphonyl-carbamoyl]-5, 7-dimethyl-4- isodecyloxyquinoline of purity 76% theoretical for MW 793 as measured by potentiometric titration with 0.1M NaOH in a mixture of water and Solvesso 150.

Example 20 The extractant of Example 19 was tested for its ability to extract zinc in the presence of iron by the following method. A 0.2 molar solution of the extractant in kerosene (ESCAID 100) was stirred with twice its volume of an aqueous solution containing zinc (5.0 parts per litre) and iron (III) (5.0 parts per litre) in the form of their sulphates. The pH of the mixture was adjusted to 2.3 by addition of 1 molar NaOH solution and stirring was continued for 0.25 hour without further pH change. The organic layer was allowed to separate and found to contain zinc (2.13 parts per litre) and iron (0.010 parts per litre) by atomic absorption spectroscopy.

Claims (30)

1. CLAIMS 1. A compound of the general formula (I) :

   wherein X is a divalent group which, together with the nitrogen and carbon atoms to which it is attached, forms an optionally

   5- or 6-membered heteroaromatic ring; Y is a divalent linking group; m is an integer having a value of O or 1; and A is an optionally substituted hydrocarbyl group; wherein A and X taken together contain at least sixteen aliphatic carbon atoms in one or more hydrocarbyl group.
2. 2. A compound as claimed in claim 1 wherein the groups A and X between them contain at least sixteen saturated carbon atoms in one or more of the hydrocarbyl groups.
3. 3. A compound as claimed in either claim 1 or claim 2 wherein the groups A and X do not contain more than sixty carbon atoms.
4. 4. A compound as claimed in any one of claims 1 to 3 wherein any substituent present in the group A and/or the group X is such as not to deleteriously affect the ability of the compound to complex with metals.
5. 5. A compound as claimed in any one of claims 1 to 4 wherein the substituents present in the group A are halogen, nitro, nitrile, hydrocarbonoxy, hydrocarbonoxycarbonyl, acyl or acyloxy.
6. 6. A compound as claimed in claim 5 wherein the group A contains more than one substituent.
7. 7. A compound as claimed in any one of claims 1 to 6 wherein the group A is an aryl group having an alkyl group joined thereto either directly or through a divalent linking group.
8. 8. A compound as claimed in claim 7 wherein the divalent linking group is -O-, -CO- or -COO-.
9. 9. A compound as claimed in claim 8 wherein the group A is an aryl group having an alkoxycarbonyl group joined thereto.
10. 10. A compound as claimed in any one of claims 1 to 9 wherein the group A is, or contains, at least thirteen saturated carbon atoms.
11. 11. A compound as claimed in any one of claims 1 to 10 wherein the group A is, or contains, a mixture of alkyl groups.
12. 12. A compound as claimed in any one of claims 1 to 11 wherein the group X is a divalent hydrocarbon group which forms a single or a fused ring system which may be substituted with at least one hydrocarbyl group or substituent group which is halogen or a nitro, nitrile, hydrocarbyloxy, hydrocarbyloxycarbonyl, acyl or acyloxy or is a divalent group which contains at least one heteroatom which is a ring atom and/or is present in a substituent group attached to the ring or fused ring completed by the divalent group X.
13. 13. A compound as claimed in claim 12 wherein the group X forms a six-membered ring in which any ring heteroatoms contributed by the group X are nitrogen atoms.
14. 14. A compound as claimed in claim 13 wherein the group X is such as to form an unsubstituted or substituted pyridine, pyrimidine, pyrazine, quinoline, quinoxaline or quinazoline ring system.
15. 15. A compound as claimed in claim 12 wherein the group X forms a five-membered ring in which any ring heteroatoms contributed by the group X are nitrogen, sulphur or oxygen atoms.
16. 16. A compound as claimed in claim 15 wherein the group X is such as to form an unsubstituted or substituted thiazole, oxazole, imidazole, benzothiazole, benzoxazole or benzimidazole ring system.
17. 17. A compound as claimed in any one of claims 12 to 16 wherein the group X forms a substituted ring system in which the substituents are one or more alkyl, alkoxy, alkoxycarbonyl, or alkylcarbonyl groups.
18. 18. A compound as claimed in any one of claims 1 to 17 wherein the group X is one in which the atom which is part of the group X and which is adjacent to the nitrogen atom of the structure:

    is substituted with an atom or group other than a hydrogen atom.
19. 19. A compound as claimed in any one of claims 1 to 18 wherein m is 1 and Y is carbonyl.
20. 20. 2-[4-(IsooctadecyloxycarbonylVphenylsulphonylcarbamoyl]-6- undecylpyridine; 2 - [4- (isooctadecyloxycarbonyl) phenyl - sulphonyl - carbamoyl] -4-octylquinoline; 2 - [4- (isooctadecyloxy-carbonyl) phenyl- sulphonylcarbamoyl] -5 ,7-dimethyl-4 -octyloxyquinoline; 2- [4- (isooctadecyloxycarbonyl) -phenylsulphonylcarbamoyl] -B-methyl- 4 -octyloxylquinoline; or 2 - [4- (isoctadecyloxycarbonyl) phenylsulphonyl carbamoyl] -5, 7-dimethyl-4 -isodecyloxyquinoline.
21. 21. A process for the production of a compound as claimed in claim 19 which comprises reacting a sulphonyl or carbonyl halide with a carbonylamide or a sulphonamide respectively wherein the carbonyl group is joined to the structure and the sulphonyl group is joined to the group A and A and X are as defined.
22. 22. A process as claimed in claim 21 which is effected in the presence of an organic base.
23. 23. A process as claimed in either claim 21 or claim 22 which comprises reacting a 2-alkylpyridine-6-carbonyl halide or an optionally substituted quinoline-2-carbonyl halide with an alkoxycarbonylsubstituted benzenesulphonamide.
24. 24. A process for extracting metal values from aqueous solutions of metal salts which comprises contacting the aqueous solution with a solution in a water-immiscible organic solvent of a compound of formula (1) as defined in any one of Claims 1 to 20.
25. 25. A process as claimed in claim 24 wherein the aqueous solution is obtained by the sulphate leaching of zinc oxide-containing ores.
26. 26. A process as claimed in either claim 24 or claim 25 which comprises a. contacting an aqueous solution containing metal values with a solution in a water-immiscible solvent of the compound of formula (1); b. separating the aqueous and solvent phases, the latter containing metal complex; c. contacting the solvent phase with an aqueous mineral acid; and d. separating the solvent phase from the aqueous phase containing metal in the form of a salt of the mineral acid.
27. 27. A process as claimed in any one of claims 24 to 26 wherein the solution of the compound of formula (1) in the water-imniscible solvent also contains an alcohol or ester.
28. 28. A compound substantially as hereinbefore described with particular reference to any one of Examples 1 to 6.
29. 29. A process for the production of a compound substantially as hereinbefore described with particular reference to any one of Examples 1 to 6.
30. 30. A process for extracting metal values from aqueous solutions of metal salts substantially as hereinbefore described with particular reference to any one of Examples 7 to 19.