DE1237552B - Process for the preparation of 2, 6-dichlorobenzal chloride and / or 2, 6-dichlorobenzyl chloride-containing reaction mixtures - Google Patents

Description

FEDERAL REPUBLIC OF GERMANY

GERMAN

PATENT OFFICE

EDITORIAL

Int. CL:

C07c

German KL: 12 ο-2/01

Number: 1237 552

File number: S 76925IV b / 12 ο

Filing date: November 30, 1961

Open date: March 30, 1967

It is known that aromatics bearing side chains are halogenated selectively in the core when treated with elemental halogen at low temperatures and in the presence of polarizing catalysts, while at elevated temperatures under irradiation or in the presence of radical-forming catalysts, on the other hand, they are selectively halogenated in the side chain. In the chlorination of 2,6-dichlorotoluene at 180 ^° C. with irradiation, 2,6-dichlorobenzyl chloride was obtained in a yield of 61%. It is also known that in the halogenation of aromatic nitro compounds at elevated temperatures, the nitro group can be replaced by halogen.

The invention relates to a method for producing 2,6-dichlorobenzal chloride and / or 2,6-dichlorobenzyl chloride containing reaction mixtures in high yield and is characterized in that 2-nitro-6-chlorotoluene with chlorine at a temperature of at least 130 ⁰ C. reacted, the reaction being carried out under such conditions that the water formed during the reaction is continuously removed.

This result was surprising. Above all was the continuous drainage according to the invention not obvious, since neither in the side chain chlorination nor in the replacement of the nitro group forms water through chlorine.

It is preferred to operate at temperatures of 160-185 ° C, in particular 175-185 ° C, for example at 180 ⁰ C. The chlorination can optionally be carried out in the presence of a halogenation catalyst, e.g. B. perform sulfur or phosphorus trichloride or under UV irradiation. The reaction time fluctuates within wide limits and depends on the particular reaction conditions, in particular on the temperature and the rate at which the chlorine is fed in and on the contact between the chlorine and the liquid in the reaction vessel.

The process according to the invention is usually carried out at atmospheric pressure; it can however, if necessary, work can also be carried out at overpressure or underpressure.

The water formed during the reaction is continuously removed. This will result in the Reaction less tarry byproducts are formed. It is believed that water formation occurs Side reactions is due, e.g. B. on a reaction between hydrogen chloride and nitrogen oxide.

The mixture obtained by the process according to the invention is used as an intermediate product.

Process for the production of
2,6-dichlorobenzal chloride and / or
Containing 2,6-dichlorobenzyl chloride
Conversion mixtures

Applicant:

"Shell" Research Limited, London

Representative:

Dr.-Ing. F. Wuesthoff, Dipl.-Ing. G. Pulse
and Dr. E. Frhr. v. Pechmann, patent attorneys,
Munich 9, Schweigerstr. 2

Named as inventor:

Johannes Thomas Hackmann, Herne Bay;

John Yates, Whitstable;

Trevor John Willcox, Sittingbourne;

Pieter Ten Haken, Herne Bay;

Derek Alexander Wood,

Sittingbourne, Kent (UK)

Claimed priority:

Great Britain dated December 2, 1960 (41543),
of January 30, 1961 (3434),
dated October 20, 1961

Sometimes it is advantageous to use an inert solvent with an appropriate boiling point as the reaction medium to use, e.g. B. a chlorinated hydrocarbon.

In the process according to the invention, the reactants are preferably brought in countercurrent to one another in touch. Chlorine is introduced in the theoretically required amount or in excess, which is then fed back into the cycle. An inert gas such as nitrogen can also be used as the flushing gas.

The rate at which the chlorine is passed through the reaction zone depends on the reaction temperature, the temperature at which the reactants part were previously heated, the quantitative ratio of the reactants, the presence of

709 547/423

Diluents and the dimensions of the reaction vessel away.

The yield of 2,6-dichlorobenzal chloride is, for. B. 50 to 65 mol percent, based on the 2-nitro-6-chlorotoluene used, if at a temperature between 160 and 185 ⁰ C, preferably 180 ⁰ C, and a reaction time of about 10 to 20 hours chlorine at a rate of about 0 , 6 to 0.7 moles per hour per mole of 2-nitro-6-chlorotoluene is introduced.

In various cases, however, it is not necessary to obtain a maximum yield of 2,6-dichlorobenzyl chloride or to achieve 2,6-dichlorobanzal chloride, but a maximum yield of both compounds, regardless of the ratio the two ingredients are present in the final reaction mixture.

The method according to the invention is explained using the following examples:

B is ρ ie 1 1 _ao

500 g of 2-chloro-6-nitrotoluene were heated in a 1-1 flask equipped with a stirrer, reflux condenser, gas inlet tube and phase separator and, as soon as the 2-chloro-6-nitrotoluene had melted, chlorine was passed in with vigorous stirring . The reaction conditions are summarized in Table 1. An organic phase also containing 2-chloro-6-nitrotoluene and 2,6-dichlorotoluene and an aqueous phase containing _{HCl and HNO 3 separated in the separating device.} The organic phase was returned to the reaction vessel and the aqueous phase was discarded. The water formed was thus continuously removed from the reaction mixture.

In the columns of the table marked with χ, the reaction mixture was after the end of the Chlorination fractionated and each fraction analyzed using gas-liquid chromatography. In the columns marked xx the reaction mixture was distilled and using gas-liquid partition chromatography analyzed. Most of the residues from the distillation and fractional distillation consisted of trichlorobenzaldehyde, 1,2,3-trichlorobenzene and tetrachlorobenzene.

Tabel

Temperature, ° C

Time, hours

Chlorine supply moles per hour per mole of chloronitrotoluene

Weight of the reaction mixture, g ..

Yield a) g; b) Mol percent based on chloronitrotoluene

2,6-dichlorobenzal chloride

!, o-dichlorobenzyl chloride

2-chloro-6-nitrobenzyl chloride

unknown

1,2,3-trichlorobenzene

2,6-dichlorobenzonitrile

Loss of distillation

Residue

140 63

0.17 557

a)

124.8

211.1

123.7

41.2

1.7 17.8 36.8

b)

19th

37

160

35

0.17
545

xx

a) b)

417 84.5

43.6 62

15th

180
9

0.68
606

a)

b)

363

115
35
33

61

54
20th

180
15th

0.68
616

a)

b)

432.4

55.4

23.4

34.5

8.6

61.6

65
10

180
15.9

0.17
605

294.0
177.9

31.5

26.0
75.6

Example 2

The following experiments were carried out in order to investigate the influence of the drainage of water during the chlorination carried out.

500 g of 2-chloro-6-nitrotoluene were chlorinated at 180 ⁰ C in the above manner. The rate of chlorine feed was 0.17 moles per hour per mole of 2-chloro-6-nitrotoluene.

In experiment A, according to Example 1, the water was continuously removed. In experiment B, the water formed was returned to the reaction vessel via a reflux condenser. Both experiments were terminated after 4 hours, since in experiment B a temperature of 180 ^° C. could not be maintained. After the end of the chlorination, distillation was carried out and the distillate was analyzed by gas-liquid partition chromatography.

The results of these tests are shown in Table 2. The favorable influence of drainage the conversion of the chloroitrotoluene can be clearly seen.

Table 2

A. b) B. a) b) Reaction mixture, g
yield
a) g;
b) mole percent on vice
set chloronitrotoluene 535 30th 518 24
88
41
325
40 12th 2,6-dichlorobenzyl chloride ..
o-chloro ^ -nitrobenzyl chloride
2,6 dichlorotoluene a) - 2-chloro-6-nitrotoluene
Residue 85
150
30th
250
20th

Claims (2)

Claims: ^ 1 "01 *}? Chlorine converts at a temperature of at least 130 C and during the reaction 1. Process for the production of 2,6-DichIor- the water formed is continuously removed, benzal chloride and / or 2,6-dichlorobenzyl chloride 2. The method according to claim 1, characterized containing reaction mixtures, characterized in that the reaction is characterized at a temperature that 2-nitro-6-chlorine temperature between 175 and 185 ⁰ C is carried out. 709 547/423 3. 67 © Bundesdruckerei Berlin