Preparation of aliphatic chlorine compounds

Aliphatic chlorine compounds of the formula EQU X--R.sup.1 --Cl I where R.sup.1 is alkylene which may be interrupted by one or more oxygen atoms and which may be substituted by halogen, alkyl or aryl, and X is hydrogen, chlorine or OR.sup.2, where R.sup.2 is alkyl, cycloalkyl, aryl or aralkyl, are prepared by decarboxylating chloroformic acid esters or diesters at elevated temperatures by decarboxylating in the presence of a quaternary ammonium or phosphonium salt as catalyst.

The present invention relates to a process for preparing aliphatic chlorine 
compounds by decarboxylating chloroformic acid esters or diesters at 
elevated temperatures. 
European Pat. No. 25,829 describes the preparation of alkyl chlorides, 
where the alkyl may also be interrupted by oxygen atoms, by 
decarboxylating chloroformic acid esters in the presence of trialkylamine 
hydrochlorides at 90.degree.-170.degree. C. To obtain good conversions, it 
is necessary to use large amounts of the amine hydrochloride. 
Advantageously the decarboxylation is carried out in a melt of 
hydrochloride, and the product isolated from the crude reaction mixture by 
distillation. In the preparation of nonvolatile alkyl chlorides, the 
catalyst concentration should not fall below 3% by weight, based on the 
starting material. If chloroformic acid esters which contain polyether 
groups are used and the amount of catalyst is reduced to 7.5% by weight, 
based on the ester, it is true that decarboxylation takes place in the 
course of a few hours, but the chlorides formed are highly contaminated 
with byproducts, as shown by IR spectra recorded in the course of the 
decomposition reaction. The use of large amounts of ammonium salt has the 
consequence that, in the case of nonvolatile products where direct 
isolation by distillation is not possible, a technically complicated 
aqueous extraction becomes necessary to separate off the salts; in 
addition, there are disposal problems. 
It is an object of the present invention to provide a process for 
decarboxylating aliphatic chloroformic acid esters which requires only 
small amounts of catalyst and gives high conversions in short reaction 
times while substantially suppressing the formation of byproducts. 
We have found that this object is achieved with a process for preparing an 
aliphatic chlorine compound of the formula 
EQU X--R.sup.1 --Cl I 
where R.sup.1 is alkylene which may be interrupted by one or more oxygen 
atoms and which may be substituted by halogen, alkyl or aryl, and X is 
hydrogen, chlorine or OR.sup.2, where R.sup.2 is alkyl, cycloalkyl, aryl 
or aralkyl, by decarboxylating the corresponding chloroformic acid ester 
or diester at elevated temperatures, which comprises decarboxylating in 
the presence of a quaternary ammonium or phosphonium salt as catalyst. 
Preferred starting materials are chloroformic acid esters of the formula 
##STR1## 
where R.sup.4 is alkyl, cycloalkyl, aryl or aralkyl, or is COCl or 
--(CH.sub.2).sub.l OCOCl, R.sup.3 is hydrogen, phenyl or C.sub.1 - to 
C.sub.4 -alkyl which may be substituted by halogen, eg. chlorine or 
bromine, for example methyl, ethyl, propyl, butyl or chloromethyl, k is 0 
to 100, preferably 0 to 50, in particular 0 to 20, and l is 2 to 6. 
Preferably R.sup.4 is alkyl of 1 to 25, in particular 4 to 20 carbon atoms, 
C.sub.5 - or C.sub.6 -cycloalkyl, phenyl, benzyl or alkyl-substituted 
phenyl, for example isopropylphenyl, mono-, di- or tri-butylphenyl, 
amylphenyl, octylphenyl, di-nonylphenyl or dodecylphenyl. 
Starting from diesters where R.sup.4 is --COCl or (CH.sub.2).sub.l --OCOCl, 
the corresponding dichlorides are obtained. 
Advantageously it is also possible to decarboxylate chloroformic acid 
esters of the formula 
EQU H--(CH.sub.2).sub.m --OCOCl III 
where m is for example 1 to 30, in particular 1 to 22, or diesters of the 
formula 
EQU ClOCO--(CH.sub.2).sub.m --OCOCl IV 
to give alkyl chlorides. The alkyl chain can additionally carry inert 
substituents such as halogen atoms, alkyl or aryl, in particular chlorine, 
bromine, C.sub.1 -C.sub.4 -alkyl or phenyl. 
The starting materials are obtainable in a conventional manner, for example 
by reacting the corresponding alcohol with phosgene. They can be 
expediently prepared in situ. 
The decarboxylation is carried out in the presence of a quaternary 
phosphonium or ammonium salt. Ammonium salts are for example those of the 
formula 
##STR2## 
where the radicals R.sup.5 are identical or different hydrocarbon radicals 
of 1 to 20 carbon atoms each, for example C.sub.1 -C.sub.20 -alkyl, 
C.sub.5 - or C.sub.6 -cycloalkyl, aryl, such as phenyl or p-tolyl or 
alkylaryl, such as phenyl-substituted C.sub.1 - to C.sub.4 -alkyl, and 
Y.sup.- is the corresponding base of a mineral acid, for example Cl.sup.-, 
Br.sup.-, I.sup.-, HSO4.sup.-, NO.sub.3.sup.-, HCO.sub.3.sup.- or H.sub.2 
PO.sub.4.sup.-. Furthermore, alkyl radicals R.sup.5 can also be bonded to 
one another, for example to form a piperidine ring. Particular preference 
is given to the quaternary ammonium or phosphonium salts customary for 
phase transfer catalyzed reactions, for example tetraalkylbenzylammonium 
or trialkylbenzylammonium salts such as triethylbenzylammonium or 
tributylbenzylammonium chloride, tetrabutylammonium chloride, bromide or 
hydrogensulfate, dimethyldicetylammonium chloride or 
methyltrioctylammonium chloride. 
The phosphonium salts which can be used as catalysts have basically the 
same structure as V with phosphorus in place of nitrogen as the positive 
center. A specific example is tributylhexadecylphosphonium bromide. 
To decompose the chloroformic acid ester, no more than 0.03 to 10, 
preferably 0.15 to 3, in particular 0.1 to 0.5, percent by weight of 
catalyst is required, based on the chloroformic acid ester, so that it is 
possible to use the end-product for subsequent reactions without further 
working up. 
The decarboxylation can be carried out at from 80.degree. to 170.degree. 
C., preferably from 110.degree. to 140.degree. C., in particular from 
120.degree. to 130.degree. C., without solvent or in the presence of an 
inert aprotic solvent such as, for example, methylene chloride, 
chloroform, polyethers, dioxane or toluene. 
The process is expediently carried out by heating the starting material, 
which, as the case may be, is prepared in situ, to the reaction 
temperature and adding the catalyst. The reaction can be monitored for 
example with the aid of IR spectroscopy. In general, the reaction is 
complete after from 30 to 120 minutes, and the products can be isolated in 
a conventional manner, for example by means of distillation in the case of 
volatile chlorides or in the case of nonvolatile chlorides by extraction 
and distillative purification. On using low levels of catalyst it is 
frequently possible to dispense with working up.

The products obtained using the process according to the invention can be 
used for alkylation reactions, for example for sulfite alkylations or 
preparing sulfonates. 
EXAMPLE 1 
Preparation of n-chlorodecane 
71 g of a 30% strength phosgene solution in toluene were added dropwise at 
10.degree. C. to 103 ml of n-decanol and the mixture was subsequently 
stirred at 30.degree. C. for 1 h. 1 g of methyltrioctylammonium chloride 
was then added, and the reaction mixture was slowly heated to 130.degree. 
C. with CO.sub.2 escaping and toluene being distilled off. The residue was 
stirred at 130.degree. C. for 2 h. In the IR spectrum, the carbonyl 
absorption band at 1777 cm.sup.-1 had virtually completely disappeared. 
Analysis: Cl value (found)=19.2% (=96% of theory); Cl value 
(calculated)=20.08%. 
EXAMPLE 2 
Preparation of 
##STR3## 
357 g of a 30% strength phosgene solution in toluene were added dropwise at 
10.degree. C. to 423 g of 
##STR4## 
in 80% strength solution in methylene chloride, and the mixture was 
subsequently stirred at 40.degree. C. for 1 h. After addition of 0.5 g 
(=0.1% based on the ethoxylate) of methyltrioctylammonium chloride, the 
reaction mixture was then treated as described in Example 1. 
Analysis: Chlorine (found)=8.15%; Chlorine (calculated)=8.04%. 
EXAMPLE 3 
Preparation of 
EQU Cl--CH.sub.2 --CH.sub.2 --(O--CH.sub.2 --CH.sub.2).sub.8 --O--CH.sub.2 
--CH.sub.2 --Cl 
55 g of phosgene in 150 ml of toluene were added dropwise at 10.degree. C. 
to 108 g of nonaethylene glycol. The bischloroformic acid ester formed was 
treated with 0.21 g of tributylhexadecylphosphonium bromide, and the 
reaction mixture was treated as described in Example 1. 
Analysis: Cl value (found)=15% (=92% of theory); Cl value 
(calculated)=16.24%.