FR2537574A1 - PROCESS FOR CHLORINATING AROMATIC COMPOUNDS - Google Patents

Abstract

PROCESS FOR THE MANUFACTURING OF PARACHLOROARYL BY, IN A FIRST STEP, CHLORINATION IN THE LIQUID PHASE BY FERRIC CHLORIDE OF AROMATIC COMPOUND HAVING AN ORTHO AND PARA ORIENTER SUBSTITUTE WITH, IN A SECOND STEP, REGENERATION BY CHLORINATION OF THIS CHLORIDE CHLORIDE IN A SECOND STEP. STEPS ARE CARRIED OUT IN THE PRESENCE OF THE SAME SOLVENT WHOSE MELTING POINT IS LESS THAN 50 AND THE BOILING POINT HIGHER THAN 200C.

Description

1 - The invention relates to a process 6 for the chlorination of compounds

  aromatics having an ortho and para orienting substituent for the manufacture of parachloroaryls Parachloroaryls are known as chemical intermediates such as, for example, parachlorotolune in the manufacture of

  pesticides, dyes or pharmaceuticals.

  They can also be used as such, for example

  example paradichlorobenzene as a deodorant.

  The chlorination of aromatic compounds having

  an ortho or para orienting substituent is usually carried out-

  liquid phase in the presence of ferric chloride

  as a chlorinating agent This technique, described for chloro-

  ration of toluene or monochlorobenzene in J Gen Chem. USRR 8, 1780, 1938 C A 33 4037, 1939 or also in J A C S 1954, 5, 5491-94, has the disadvantage of leading to reaction products whose isomeric ratios

para / ortho are relatively low.

  To allow the para / ortho ratio to be increased, it has been proposed (J Org Chem 1961, 26, 214-17) to combine ferric chloride with another metallic chloride such as

Ti C 14 or Al C 13.

  Finally according to DE-OS 2 230 369 we prepare the

  parachloroaryls and more particularly parachloro-

  toluene by chlorination of toluene by Fe C 13 catalyzed by Al C 13 using trichlorobenzene as solvent for the reaction The ferrous chloride must then be separated by filtration, washed thoroughly with carbon tetrachloride to avoid any presence of trichlorobenzene which

  is significant in the subsequent regeneration step, because

  dragging the formation of heavy products The regeneration of ferrous chloride is effected by suspension in carbon tetrachloride and chlorination It is necessary to

  filter the ferric chloride formed again, wash it

  made with trichlorobenzane to remove carbon tetrachloride capable of reacting with toluene in a Friedel and Crafts reaction catalyzed by Fe C 13 This process has the drawback of having a complex cycle due to the need to use two solvents which it must be eliminated and recovered at

each manipulation.

  According to the invention, this drawback is remedied by

  carrying out the chlorination in liquid phase of the aromatic compounds

  materials having an ortho and para-orienting substituent with ferric chloride in the presence of a single solvent in the chlorination stage of the aromatic compound and that of regeneration of the ferrous chloride formed by chlorination A

  such a process is particularly interesting for chlora-

  toluene and monochlorobenzene for the manufacture of

  cation of parachlorotoluene and paradichlorobenzene.

  The solvent retained, of course inert as part of the whole reaction, is preferably a halogenated, chlorinated or fluorinated solvent, the melting point of which

  is less than 50 C and the boiling point is higher than

  less than 2000 CA indicative, mention may be made, as solvent, of fluorinated oils meeting the above characteristics, hexachlorobutadiene, hexachlorocyclopentadieneo. Such a solvent is particularly advantageous in the chlorination of toluene and of monochlorobenzene because, in addition to the simplification of the two stages due to its higher boiling point than monochlorotoluenes and dichlorobenzenes,

  separation of the reaction products without having to distill

  remove the solvent beforehand In this case, the synthetic products are recovered first by distillation, the remaining solvent being able to be recycled directly numerous times without purification after in situ regeneration of the ferric chloride. Illustratively, this type of synthesis being known in itself and described in numerous publications and patents such as French patent 2,144,709,

  react, in a first step, the aromatic compound possessed

  dant an ortho and para orienting substituent, in the presence of the solvent according to the invention, with ferric chloride By fractional distillation the chloroaryl forms are recovered, the aromatic compound which has not reacted being recycled into

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  -3- a second step, the ferrous chloride formed, dispersed in the residual distillation solvent, is regenerated in situ by chlorination in ferric chloride, the final solvent-ferric chloride assembly being recycled The table in the appendix shows the complete cycle of the reaction in the case of chlorination

  toluene and monochlorobenzane.

  It is possible to combine with ferric chloride, without disadvantage and without changing the reaction cycle, a known catalyst chosen from metal chlorides

  like: Al C 13, Ta C 15, Ti C 14, Mo C 14, Hf C 14, W C 16, Ga Cl 3.

  The following examples illustrate the

  vention Yields are given in weight percent.

EXAMPLE 1

  In a reactor, 700 g of hexa-

  chlorobutadiene, 2 moles of anhydrous ferric chloride, 30 g

  of Ti Cl 4 which is brought to 80 C. It is introduced at this temperature

  rature 1.3 moles of toluene in 30 minutes The mixture is then maintained at 90 1100 C for approximately 2 h, ie until the end of the release of hydrochloric acid The medium is degassed for 30 minutes by a stream of nitrogen with a flow rate of 30 1 / hour The apparatus is then put under

  vacuum of 30 mm of mercury so as to separate by distillation

  tion unreacted toluene and the monochlorotoluenes formed.

  Ti Cl 4 is collected with the toluene fraction and is recycled.

key to the next reaction.

  At the end of the distillation, the vacuum is cut on the apparatus and 1.25 mole of chlorine is introduced in 1 h 15

  at a temperature of 110 1250 C A second cycle is started

  by introducing recycling toluene and completing

  at 1.3 mole with fresh toluene After 7 cycles, the results

states obtained are as follows: 4-

Monochlorine yield

  toluenes with respect to total iron Yield in monochlo para + meta rotoluenes with respect to + mt with toluene consumed ortho, 7 1 1 14.7 14, 85 The precise balance of operations is carried out by weighing the fractions and chromatographic analysis in the vapor phase.

  The average meta content in monochloroto-

luenes is 2%.

EXAMPLE 2

  The conditions of Example 1 are repeated, but replacing the Ti C 14 with 5 g of aluminum chloride. The results after three cycles are as follows:

Monochlorine yield

  toluenes compared to the total iron present 68.6 52.8 Yield in monochlo rotoluenes compared to para + meta to toluene consumed ortho 6.45 11.7

EXAMPLE 3

  The conditions of Example 1 are repeated, but using 5 g of tantalum chloride (Ta C 15) in place of Ti C 14 The results after four cycles are as follows:

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Monochlorine yield

  toluenes relative to the total iron present 84,4,6

Yield in monochlo-

  rotoluenes compared to toluene consumed, 8 76.4 para + meta ortho 7.3 13.1 14.6 17.6

EXAMPLE 4

  We take again the conditions of example 1 but in

  replacing toluene with monochlorobenzene and in effect

  killing the reaction at 100 125 C The results obtained after six cycles are as follows:

Dichloro- yield

  benzenes compared to the total iron present

94

Dichloro- yield

benzenes compared to

monochlorobenzene con-

  summed 93.5 98.5 96.5 para / ortho 27.7 22.2 31.2 22.2 24.5, 7 The composition of the dichlorobenzenes formed is

  in all cases close to o / m / p = 3.65 / 0.15 / 96.2.

EXAMPLE 5

  In a reactor, 50 g of hexachlo-

  rocyclopentadiene, 0.2 mole of anhydrous ferric chloride,

  g of Ti Cl which is brought to 1200 ° C. for 3 hours before

0.2 mol of toluene.

  At the end of the reaction, the monochlorotoluenes are collected by distillation with a yield of 75 relative to the

  Fe C 13 engaged and a para ratio of 7.

  ortho After regeneration of Fe C 13 we start a new one

reaction cycle.

6 -

EXAMPLE 6

  Example 5 is repeated, replacing the hexachloro-

  cyclopentadiene with a fluorinated oil of boiling point

  of 256 C and freezing point of -45 C (Voltalef 3 S).

  At the end of the reaction, the monochloro-moons are collected with a yield of 95 relative to the Fe C 13 used.

and a para ratio of 8.5.

  ortho After regeneration of Fe C 13 we start a new one

reaction cycle.

-7.

Claims (1)

CLAIMS 1 Process for the manufacture of parachloroaryl by, in a first step, chlorination in the liquid phase with ferric chloride of aromatic compound having an ortho and para-orienting substituent with, in a second step, regeneration by chlorination of the ferrous chloride formed characterized in that the two stages are carried out in the presence of a mema solvent whose melting point is less than 50 and the boiling point greater than 200 C. 2 A method according to claim 1 characterized in that the solvent is a halogenated compound. 3 Method according to claim 2 characterized in that the solvent is a fluorinated or chlorinated compound. 4 Method according to claim 3 characterized in that the solvent is hexachlorobutadiane. Method according to one of claims 1 to 4 characterized in that in the second step, the ferric chloride is regenerated in situ in the solvent of the first step. 6 Application of the method according to one of claims   1 to 6 in the manufacture of parachlorotoluene and paradichlo-   robenzene from toluene and monochlorobenzene.