# US 5,705,670 A · Process for the preparation of alkali metal salts of phosphonic acid monomethyl esters

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- Number: US 5,705,670 A
- Document ID: US5705670A
- Status: Granted
- Kind: A
- Application number: 08/599,485
- Filed: 1996-01-24
- Granted: 1998-01-06
- Earliest claimed: 1995-01-26
- Assignees: Hoechst Aktiengesellschaft
- Inventors: Hans-Jerg Kleiner
- Web page: https://patentgrep.com/patent/US5705670A

## CPC

- C07F 9/4006: {Esters of acyclic acids which can have further substituents on alkyl}
- C07F 9/4075: {Esters with hydroxyalkyl compounds}
- C07F: ACYCLIC, CARBOCYCLIC OR HETEROCYCLIC COMPOUNDS CONTAINING ELEMENTS OTHER THAN CARBON, HYDROGEN, HALOGEN, OXYGEN, NITROGEN, SULFUR, SELENIUM OR TELLURIUM (metal-containing porphyrins C07D487/22)

## Abstract

The invention relates to a process for the preparation of alkali metal salts of phosphonic acid monomethyl esters of the formula (I) ##STR1## in which R is (C.sub.1 -C.sub.14)-alkyl and Me is sodium or potassium, which comprises metering 20 to 50% strength alkali metal hydroxide solution, in a molar ratio of 1:1, into phosphonic acid dimethyl esters of the formula (II) ##STR2## optionally dissolved in water, the total amount of water from the alkali metal hydroxide solution and phosphonic acid dimethyl ester solution being not more than 100% by weight, based on the weight of alkali metal hydroxide and phosphonic acid dimethyl ester, at 90.degree. to 130.degree. C. and distilling off the methanol formed.

## Claims

### Claim 1

A process for the preparation of an alkali metal salt of a phosphonic acid monomethyl ester of the formula I ##STR5## in which R is C.sub.1 -C.sub.14 -alkyl, and
Me is sodium or potassium,
which comprises:
providing an aqueous reaction medium by metering of 20 to 50% strength aqueous alkali metal hydroxide solution, in a molar ratio of 1:1, into a phosphonic acid dimethyl ester starting material of the formula II ##STR6## said metering being regulated such that the pH of the aqueous reaction medium does not exceed 10, said phosphonic acid dimethyl ester starting material being optionally dissolved in water, the total water content of said aqueous reaction medium being not more than 100% by weight, based on the weight of alkali metal hydroxide and phosphonic acid dimethyl ester starting material, said reaction medium being maintained at a temperature in the range of 90.degree. to 130.degree. C.; and
distilling off methanol produced by the resulting reaction between the aqueous alkali metal hydroxide solution and the phosphonic acid dimethyl ester starting material.

### Claim 2 (depends on 1)

The process as claimed in claim 1, wherein R is (C.sub.1 -C.sub.6)-alkyl.

### Claim 3 (depends on 1)

The process as claimed in claim 1, wherein formula (II) is methanephosphonic acid dimethyl ester, propanephosphonic acid dimethyl ester, isopropylphosphonic acid dimethyl ester, octanephosphonic acid dimethyl ester or tetradecanephosphonic acid dimethyl ester.

### Claim 4 (depends on 1)

The process as claimed in claim 1, wherein the total water content from the alkali metal hydroxide solution and any phosphonic acid dimethyl ester solution is between 20 and 80% by weight, based on the weight of alkali metal hydroxide and phosphonic acid dimethyl ester.

### Claim 5 (depends on 1)

The process as claimed in claim 1,
wherein the alkali metal hydroxide solution is metered in at 100.degree. to 115.degree. C.

### Claim 6 (depends on 1)

The process as claimed in claim 1, wherein R is (C.sub.1 -C.sub.3)-alkyl.

### Claim 7 (depends on 1)

The process as claimed in claim 1, wherein the total water content from the alkali metal hydroxide solution and any phosphonic acid dimethyl ester solution is between 30 and 70% by weight, based on the weight of alkali metal hydroxide and phosphonic acid dimethyl ester.

### Claim 8 (depends on 1)

The process as claimed in claim 1, wherein the total water content from the alkali metal hydroxide solution and any phosphonic acid dimethyl ester solution is between 40 and 60% by weight, based on the weight of alkali metal hydroxide and phosphonic acid dimethyl ester.

### Claim 9 (depends on 1)

The process as claimed in claim 1, wherein a phosphonic acid dimethyl ester of said formula II is dissolved in water, and the total water content includes water from the resulting phosphonic acid dimethyl ester solution.