Organic compounds -- part of the class 532-570 series – Organic compounds – Oxygen containing
Patent
1992-04-20
1993-09-14
Lone, Werren B.
Organic compounds -- part of the class 532-570 series
Organic compounds
Oxygen containing
568715, C07C 3346
Patent
active
052450910
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a process for the preparation of
1,1-bis(chlorophenyl)-2,2,2-trichloroethanol. This product, usually termed "dicofol", is useful as a pesticide. ##STR1##
To date, dicofol has been synthesised from DDT, which is also a pesticide.
Crystalline 1,1-bis(chlorophenyl)-2,2,2-trichloroethane (DDT) is melted and is then converted ##STR2## to 1,1-bis(chlorophenyl)-1,2,2,2-tetrachloroethane (chloro-DDT), either by chlorination or by a dehydrochlorination followed by an addition of chlorine, and the chloro-DDT is then hydrolysed to dicofol in the presence of sulphuric acid and a sulphonic acid. This process is mentioned in the introduction of European Patent EP No. 0,409,689 and U.S. Pat. No. 4,705,902. U.S. Pat. Nos. 2,812,280 and 2,812,362 describe the hydrolysis of chloro-DDT to dicofol. After hydrolysis, a solvent is added and an organic phase containing crude dicofol and an aqueous phase containing sulphuric acid and sulphonic acid are thus obtained. This aqueous phase may be re-used only once for the hydrolysis of chloro-DDT or dicofol. In fact, it has been found that it became loaded with impurities which interfered in the hydrolysis. The sulphonic acid may be benzenesulphonic acid, para-toluenesulphonic acid or butylbenzenesulphonic acid. This acid phase is not usable as such. It is necessary to desulphonate it by means of steam in order to produce residual sulphuric acid and benzene, toluene or butylbenzene. It is thus possible to recover benzene, toluene or butylbenzene of good purity and residual sulphuric acid, which may be used in applications where it is not necessary to have a pure acid. It then suffices to sulphonate the benzene, toluene or butylbenzene in order to reproduce a solution of sulphuric acid and sulphonic acid necessary for the hydrolysis of chloro-DDT.
Moreover, this process requires the handling of DDT in solid form in order to dissolve it in tetrachloroethane or in methanol (examples 2 and 3 of U.S. Pat. No. 2,812,280). In fact, DDT is most often supplied in solid form, as tablets.
A very much simpler process for the preparation of dicofol has now been found which avoids the handling of DDT and the losses of DDT in the for of dust and which avoids the preparation of a solution of sulphuric acid and sulphonic acid and also gives a better yield.
The invention is a process for the synthesis of 1,1-bis(chlorophenyl)-2,2,2-trichloroethanol, in which:
(a) chloral is reacted with an excess of chlorobenzene in the presence of sulphuric acid;
(b) an aqueous phase containing sulphuric acid and para-chlorobenzenesulphonic acid and an organic phase consisting of 1,1-bis(chlorophenyl)-2,2,2-trichloroethane in solution in chlorobenzene are obtained;
(c) the 1,1-bis(chlorophenyl)-2,2,2-trichloroethane is converted to 1,1-bis(chlorophenyl)-1,2,2,2-tetrachloroethane;
(d) the 1,1-bis(chlorophenyl)-1,2,2,2-tetrachloroethane is hydrolysed to 1,1-bis(chlorophenyl)-2,2,2-trichloroethanol in the presence of all or some of the aqueous acid phase of step (b);
(e) at the end of step (d), chlorobenzene is added and an organic phase consisting of 1,1-bis(chlorophenyl)-2,2,2-trichlorethanol in solution in chlorobenzene and an aqueous phase containing sulphuric acid and para-chlorobenzenesulphonic acid are thus obtained; and
(f) the acid aqueous phases originating from steps (b) and (e) are distilled by entrainment in steam to give (i) chlorobenzene, which is recycled, and (ii) residual sulphuric acid.
The principle of the reaction of step (a) is known. It has been described in U.S. Pat. No. 2,932,672. "In the presence of sulphuric acid" implies that it is possible to have any concentration, including the acid in the form of oleum. The condensation reaction of chlorobenzene with chloral is preferably carried out at between -20.degree. and -15.degree. C. The reaction mixture is then heated to about 40.degree. to 75.degree. C. and, if necessary further chlorobenzene is added until two phases are obtained an organic phase consisting of chlorobenzene and containing all of the 1,1-bis(chl
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Castella Sola Jaume
Commandeur Raymond
Gorny Bernard
Palencia Adrubau Jaime
Elf Atochem S.A.
Lone Werren B.
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