Preparation of .beta.-haloethylphosphonic acids and half esters thereof

DETAILED DESCRIPTION I claim: 1.
A process for producing .
beta.
-haloethylphosphonic acid which comprises introducing anhydrous HCl or HBr from an outside source into a diester stable at a temperature above 140.
degree.
C.
and having the formula ##STR5## wherein R.
sub.
1 is haloethyl and R.
sub.
2 and R.
sub.
3 represent alkyl or haloalkyl containing no more than 6 carbon atoms, at a temperature of about 140.
degree.
C.
to 165.
degree.
C.
until a product is obtained containing about 3 to 40% of the corresponding monoester of the formula ##STR6## no more than 5% of dehydrohalogenated impurities, no more than about 5% of other impurities, and the balance .
beta.
-haloethylphosphonic acid or anhydride.
2.
A process as defined in claim 1 wherein R.
sub.
1 is chloroethyl.
3.
A process as defined in claim 2 wherein at least one of R.
sub.
2 and R.
sub.
3 is haloalkyl and the anhydrous HCl or HBr is introduced until the product contains about 20 to 40% of the corresponding monoester.
4.
A process as defined in claim 3 wherein R.
sub.
2 and R.
sub.
3 are chloroethyl and anhydrous HCl is introduced into said diester.
5.
A process as defined in claim 1 wherein R.
sub.
1 is chloroethyl and R.
sub.
2 and R.
sub.
3 are alkyl.
6.
A process as defined in claim 5 wherein the anhydrous HCl or HBr is introduced until the product contains about 3 to 20% of the corresponding monoester.
7.
A process as defined in claim 6 wherein anhydrous HCl is introduced into said diester.
8.
A process comprising introducing anhydrous HCl or HBr from an outside source into a diester stable at a temperature above 140.
degree.
C.
and having the formula ##STR7## wherein R.
sub.
1 is .
beta.
-haloethyl and R.
sub.
2 and R.
sub.
3 represent alkyl or haloalkyl containing no more than 6 carbon atoms, at a temperature of about 140.
degree.
C.
to 165.
degree.
C.
until a product is obtained substantially devoid of said diester and containing over 50% of the corresponding monoester of the formula ##STR8## 9.
A process comprising introducing anhydrous HCl or HBr from an outside source into a monoester of the formula ##STR9## wherein R