DE2260314A1 - pH-indicator 2-carboxy-4'-morpholino-azobenzene - which changes from red to yellow at value 5.0 - Google Patents

Abstract

Title cpd of formula (I): is prepd by diazotising o-aminobenzoic acid and either (a) coupling with N-phenyl-morpholine in acidic soln, or (b) coupling with aniline and subjecting the resulting 2-carboxy-4'-amino-azobenzene to (i) condensation with a cpd of the formula XCH2CH2OCH2CH2X (where X is a reactive acid residue) or (ii) condensation with 2 mol of a cpd of the formula XCH2CH2OH followed by dehydration, or (c) coupling with N,N-bis(2-hydroxyethyl)-aniline and subsequently dehydrating. The chief advantages of (I) is advantageously used in indicator mixts. esp. those contg. indicators which change from yellow, yellow-green or colourless to blue or violet in the range from pH 6 to pH9. Test papers impregnated with such mixts are esp. useful as diagnostic aids for determining urinary pH.

Description

2-Carboxy-4'-morpholino-azobenzene and its use as an agent for pH determination The present invention relates to 2-carbo; y-41-morpholino-azobenzene and its use as an improved diagnostic agent for determining pH in Liquids, especially urine, in a pH range between 4 and 9.

The pH determination with color indicators, which depend on the pH value of the solution, protons attach or split off and change their color in the process, has been known for a long time. In addition to their use to control chemical reactions it was used in medical diagnostics at an early stage, since the The pH of various body fluids, especially urine, is an indication of can cause pathological changes in the patient.

These tests were included at an early stage for easier handling Test papers impregnated with appropriate indicators carried out a A well-known example of this is litmus paper. This, as well as other test papers, which are impregnated with only one indicator allow a quantitative statement only in an area approximately equal to pH above and below the transition point of the relevant indicator. In order to cover a wider pH range, were therefore indicator mixtures are also used relatively early on, with the individual indicators change at different pH values. Mixed indicators from 3 and more components, the one statement in the entire, technically interesting range from 1 to 12 pH incorporation allow are very good because of the relatively weak differentiation of the parbulean strokes inaccurate and have an error of 1 to 2 pH units. Mixed indicators No In contrast, only 2 components allow an accuracy of approx. 0.5 pH units, but usually only cover a pii range of 2 - 4 units.

For medical diagnostics, especially for examinations of urine, it is necessary to determine a pH range from Wr t - pH 9. The former occurs in certain somatous conditions, the latter in certain kidney diseases before. Most of the test papers known for this purpose allow either a determination in the pH range of 4-8 or in the pH range of 5-9. One of the notifying parties in the Commercial indicator paper made with a mixture of methyl red and bromothymol blue and special additives is impregnated, allows a relatively precise determination of the entire pH range of 4 - 9, but has the disadvantage that the for the The necessary additives can be easily washed out of the paper, which with combined test strips an additional disturbance of the neighboring test can cause.

Whereby occurring in the urine in changing concentrations, colorless fabrics have a certain falsification of the color.

The object of the present invention was therefore to provide a new indicator to find a simple and accurate determination of the whole physiologically important pH range of 4 - 9 permitted, the color of which depends on the nature of the test medium is independent and does not require bleeding supplements.

It has surprisingly been found that the new compound of the following formula, which is relatively similar to methyl red (2-carboxy-4-dimethylamino-azobenzene) which bears the chemical name 2-carboxy-4'-morpholino-azobenzene, which has many advantages.

The new compound can be carried out in analogy to known azo dyes Coupling of diazotized o-aminobenzoic acid with N-phenylmorpholine in neutral or acidic solution (Organic Syntheses, Volume 1, p. 374). You get the dye in the same way if you put a solution of the amino component in a solution of the diazonium salt enters or vice versa a solution or a stable, solid Introduces diazonium salt (e.g. a tetrafluoborate) into a solution of the amino component. The reaction is preferably carried out at room temperature or with additional cooling carried out to prevent decomposition of the diazonium component.

Since N-Pllenylmorpholine as a coupling component only slowly and with reacts in moderate yield, the compound according to the invention can also be obtained by coupling diazotized o-aminobenzoic acid with aniline and the 2-carboxy-4 -amine-azobenzene with a) a compound of the following formula 1 X-CH2-CH2-O-CH2-CH2-X I, in which X is a reactive acid radical, reacts, or with b) '2 moles of one Compound of the formula II X-CH2-CH2-OH II, in which X has the above meaning, converts, then the 2-carboxy-4 '- [diß-hydroxyethyl-amino] azobenzene obtained cyclized with dehydrating agents to give 2-carboxy-4'-morpholino-azobenzene will.

As reacti @@@ Säurerest @mmen preferably the @alogenides, especially <. Chlorides a. bromide, as well as sulfone. acidic residues such as Tolylsul @ onyl- or @ thylsulfonyl residue in question The @ re released during the implementation can by adding a base, e.g.

of a tertiary amine, or of an alkali metal carbonate, bound wc; -uen.

Dehydration can be achieved by cooking with concentrated mineral acids or by reaction with a water-binding Lewis acid, e.g. with phosphorus pentoxide, Aluminum trichloride, zinc chloride etc. in a suitable solvent, e.g.

Ether, benzene, etc., can be carried out.

The 2-carboxy-4 '- (diß-hydroxyethyl-aminol -azobenzene can also be obtained by direct coupling of diazotized o-amino-benzoic acid can be obtained with N, N-di-hydroxyethyl aniline.

The 2-carboxy-4'-morpholino-azobenzene, which in the following in analogy to be referred to as morpholine red for methyl red, is a wine-red solid, which is in acidic solution with red color and in neutral to alkaline solution with yellow paint dissolves. The transition point is at a pii value of approx.

5.0.

Since the change in the pH range from 4 - 6 due to the strong color contrast from red The yellow can be read relatively easily, morpholine red is an indicator for this pH range usable.

Other color indicators in this area, such as methyl orange and its isomers, as well as methyl red and its isomers, are jec: also usable out. The remarkable advantage of morpholine red over the other well-known indicators for the same area lies in its significantly improved usability in indicator mixtures. In particular, dye indicators that are in the range of pH 6 to pH 9 change their color @on, yellow-green or colorless to blue or purple, @@@ en @n Mixture with morpholine red should be used advantageously.

@@@@@ ele @@ r such @ indicators are preferably the known @u @@@ phthaleine, Bromxylanol blue and bromothymol blue.

Test papers made with a mixture of morpholine red and the above indicators mentioned are impregnated, allow a good pH determination in the range from 4 - 9 pH units, with those obtained in water and urine at the same pH value There is practically no difference in colors.

The indicator according to the invention is used in amounts of 0.05-0.1%, preferably 0.015 - 0.030%, added to the impregnation solution.

This amount will depend on the desired shade of color. The formulation can also contain customary additives such as thickeners and color stabilizers and in particular wetting agents can be added. As wetting agents, apart from the non-ionic, in particular the anionic wetting agents in question. Dioctyl sodium sulfosuccinate has proven particularly useful, which, in addition to its net effect, also has the property of being the envelope area of the sulfophthaleins shift slightly into the alkaline, which is the reading in the range from pH 8 to 9 further improved.

As usual, the substances to be impregnated are highly volatile Solvents dissolved and impregnated on the absorbent carrier. Has proven itself an addition of strongly polar solvents such as dimethyl sulfoxide or dimethylformamide, a more even distribution, especially in the presence of wetting agents effect of the indicators on the absorbent carrier.

Filter paper, asbestos, or plastic can be used as absorbent carriers Fiberglass tile etc. in question, with filter paper being the preferred carrier.

According to the invention, prefabricated test strips or sticks can be used Soak directly with the impregnation solution, dry and as such use. Preferably, however, a larger sheet is made from the absorbent carrier soaked with the impregnation reading, dried and then cut into manageable pieces cut up. It is of course possible to have the impregnated pieces on one Glue or seal on the handle or between two plastic films or one Sealing plastic film and a fine mesh network, in the last two In some cases, test agents that are largely secured against contact and contamination are obtained.

Although the test papers described are preferably used as a diagnostic aid They can of course be used to determine the pH value in urine can also be used to determine the pH value in other liquids.

The invention is to be explained in more detail in the following examples.

Example 1 2-Carboxy-4'-morpholino-azobenzene Variant A: In a Solution of 32.6 g (0.2 mol) of phenylmorpholine in 250 ml of 20% acetic acid with 16.7 ml concentrated hydrochloric acid, 47 g (0.2 Mol) o-carboxyphenyldiazonium tetrafluoborate. Then it is stirred for one hour at 20 ° C, adjusted to pH 4 by the dropwise addition of saturated sodium acetate and another two Stirred at 200 hours. After cooling with ice, the formed wine-red color Sucked off crystals, washed with 2N acetic acid and crystallized from glacial acetic acid. 10.21 g = 16.4% dark red, chromatographically obtained.

uniform 2-carboxy-4'-morpholino-azobenzene (morpholine red), m.p. 196-198 ° C.

Variant B: In a 1 liter three-necked flask with stirrer, dropping funnel, Thermometer and dry ice bath are 20 g of o-aminobenzoic acid in 600 ml of water and 60 ml conc., Dissolved hydrochloric acid and add 10 g sodium nitrite at 0 ° -50 ° C. while stirring diazotized in about 30 minutes. The diazonium salt solution is stirred for a further 30 minutes.

In a 2 liter three-necked flask with stirrer, condenser and dropping funnel 24.8 g of phenylmorpholine in 200 ml of water and 20 ml of conc. Dissolved hydrochloric acid and the diazonium salt solution was added dropwise in about 10 minutes. The dark red solution is with 200 g of krist. Sodium acetate added, a yellow precipitate @@@ about 30 ° C occurs again with a red coloration @@ @@ ch., Nuch four-time stirring 40 ° C is abqeküblt and shaken out with chloroform. The chloroform solution will Shaken several times with Zn sodium hydroxide solution, the dye being used as the sodium salt removed from the chloroform solution approx.

The aqueous solution is adjusted to pH 4 by adding acetic acid and then extracted again with chloroform. After concentrating the dried Chloroform solution, the residue is recrystallized from glacial acetic acid, 4.63 is obtained g of morpholine red (10.2% of theory), melting point 196-197 ° C.

Variant C: 10.0 g of 2-carboxy-4 '- [di-ß-hydroxyethyl-amino] -azobenzene are concentrated in 100 ml. Sulfuric acid dissolved in the cold and five hours to 10,000 warmed up. It is then poured onto one liter of ice and adjusted to pH 4 with sodium hydroxide solution and extracted three times with 100 ml of chloroform each time. After evaporation of the solvent the residue is recrystallized from glacial acetic acid. 6.3 g of morpholine red are obtained (56% of theory), m.p.

194-197 ° C.

The 2-carboxy-4 '- [di-ß-hydroxyethyl-amino] azobenzene used as the starting product is obtained as follows: In a 1 liter three-necked flask equipped with a stirrer, thermometer and dropping funnel is added to a mixture of 250 ml of 20% acetic acid while cooling with ice and 16.7 ml conc. Hydrochloric acid 36 Q N, N-di- (2-hydroxyethyl) aniline and contributes under Stir in 46 g of o-carboxyphenyldiazonium tetrafluoborate. After that it will be two hours stirred at room temperature and the acidic solution (pH 2) by adding 99 ml adjusted to pH Z with saturated sodium acetate solution. Titan stirs after two hours after and leaves stand in the refrigerator overnight. After suction, Washing with dilute acetic acid and drying over diphosphorus pentoxide are 55.61 g of 84.4% red-violet colored crystals of 2-carboxy-4 '- [di-ß-hydroxyethyl-amino] -azobenzene from Schmp.

154-1570C obtained.

Example 2 Filter paper becomes red with a solution of 20 mg of morpholine and 80 mg of bromoxylenol blue impregnated in 100 ml of methanol @ and dried at 40.degree. The colors with urine or water of different pH values are summarized in Table 1.

Table 1 pH value F @ 4 orange: 5 orange 6 @@ 7th 8 g @ 9 blah Example 3 Filter paper is impregnated with a solution of 30 mg of morpholine red, 100 mg of bromothymol blue and 2.0 g of hydroxypropyl cellulose in 100 ml of methanol and dried at 40.degree. The colors with urine or wax at different pH values are shown in Table 2.

Table 2 pH color 4 orange red 5 orange yellow 6 yellow 7 light green 8 green 9 blue Example 4 Filter paper is impregnated with a solution of the following composition and dried at 80.degree.

Morpholine red 0.025 g bromoxylenol blue 0.075 g dioctyl sodium sulfosuccinate 0.5 g dimethyl sulfoxide 30.0 ml methanol ad 100.0 ml The reaction colors with urine or water at different pH values are listed in Table 3.

Table 3 pH color 4 orange red 5 orange yellow 6 light olive 7 green 8 8 blue-green blue

Claims (6)

P a t e n t a n s p r ü c h e 1. 2-Carboxy-4'-morpholino-azobenzene. 2. Process for the preparation of 2-carboxy-4'-morpholino-az benzene, characterized in that o-aminobenzoesäu is diazotized and either a) with N-phenylmorpholine couples in acidic solution, or b) couples with aniline and the formed 2-curbboxy-4'-amino-azobenzene a) with a compound of the formula I X-CH2-CH2-O-CH2-CH2-X (I), in which X represents a reactive acid residue, condensed or ß) with 2 mol a compound of the formula II - - (T in which X represents a reactive acid residue, condensed and then debydra @ c) with N, N-Di-ß-hydroxyethyl-aniline kupp @@@ dehydrated. 3. Use of 2-carboxy-4'-morpholino-azobenzene as a pH indicator. 4. Use of 2-carboxy-4'-morpholino-azobenzene in a mixture with a pE range of 6 - 9 changing from yellow or colorless to blue or violet Indicator for testing a pH range of 4 - 9. 5. Use according to claim 4, characterized in that the second Indicator bromoxylenol blue or bromothymol blue is used. 6. PE indicator papers, characterized by a content of 2-carboxy-4'-morpholino-azobenzene.