Organic compounds -- part of the class 532-570 series – Organic compounds – Fatty compounds having an acid moiety which contains the...
Reexamination Certificate
2000-04-06
2001-04-17
Barts, Samuel (Department: 1621)
Organic compounds -- part of the class 532-570 series
Organic compounds
Fatty compounds having an acid moiety which contains the...
C554S090000, C554S177000
Reexamination Certificate
active
06218555
ABSTRACT:
FIELD OF THE INVENTION
This invention pertains to a process for the preparation of alkanoate esters of hydroxybenzenesulfonic acids and salts thereof. More specifically, this invention pertains to a process which comprises the steps of (1) contacting or reacting phenol with an alkanoic acid in the presence of trifluoroacetic acid (TFA) and trifluoroacetic anhydride (TFAA) to produce an aryl alkanoate ester and (2) contacting the reaction mixture of step (1) with a sulfonating agent to convert the aryl alkanoate ester to an alkanoate ester of hydroxybenzenesulfonic acid.
BACKGROUND OF THE INVENTION
Alkanoate esters of hydroxybenzenesulfonic acids and salts thereof are useful as bleach activators in detergent compositions (Allan H. Gilbert,
Detergent Age,
1967, June, pages 18-20 and August, pages 30-33). These ester compounds, also named as alkanoyloxybenzenesulfonic acids and salts thereof, typically are manufactured by contacting a hydroxybenzene-sulfonic acid or salt thereof with a saturated, aliphatic carboxylic (alkanoic) acid, usually an alkanoic acid containing 6 or more carbon atoms, or an ester-forming derivative thereof such as an anhydride or acid halide, under ester forming conditions. Such processes are carried out either in a solvent or the carboxylic acid related to the desired ester product at temperatures of 80 to 200° C. These known methods are well summarized in U.S. Pat. Nos. 4,587,054, 4,588,532, 4,883,612 and 5,069,828. The preferred route for commercial scale synthesis is esterification of sodium 4-phenolsulfonate (SPS) using carboxylic acid anhydrides as the esterification agent. SPS is manufactured by the sulfonation of phenol which initially produces a relatively large (≈40 %) amount of the ortho-hydroxybenzene sulfonic acid. Heating the mixture of ortho- and para-hydroxybenzene sulfonic acids produces a high para (>95%) product, which is neutralized to yield SPS.
An alternative to these methods is the sulfonation of aryl carboxylate esters. An advantage of this alternative is that the sulfonation of a phenyl ester occurs with higher selectivity for the desired para sulfonation product than the sulfonation of phenol described above (see Ansink and Cerfontain
Recl. Trav. Chim. Pays-Bas
1992, 111, 215). U.S. Pat. Nos. 4,695,412 and 5,124,475 disclose the sulfonation of pre-purified aryl esters with sulfonating agents such as sulfur trioxide, oleum or chlorosulfonic acid to produce the desired alkanoate esters of hydroxybenzene sulfonic acids. The methods described in these patents first require the synthesis and purification of an aryl alkanoate ester. U.S. Pat. No. 3,772,389 describes the prior art in the synthesis and manufacture of aryl esters and discloses a process in which a carboxylic acid and a phenol are combined between the temperatures of 75-285° C. using a borate-sulfuric acid catalyst. E. J. Bourne and coworkers in the
Journal of the Chemical Society
1949, 2976-79 disclose the use of trifluoroacetic anhydride (TFAA) as an “impeller” in the synthesis of aryl alkanoate esters using milder conditions. It has been discovered that the effectiveness of the TFAA impeller method is increased when trifluoroacetic acid (TFA) is used as a solvent, in particular for the synthesis of hydroxybenzenesulfonate esters, and that the reactions carried out in this fashion occur in very high yield (>95%). In addition, because these TFAA impeller esterificatons occur at ambient temperatures in minutes rather than hours the common problems of color body or other byproduct formation are minimized.
Sulfonation reactions carried out in TFA are not well known but U.S. Pat. No. 2,628,253 discloses that TFA reacts with SO
3
to yield the mixed anhydride having the structure
Bert H. Bakker and Hans Cerfontain report in the
Eur. J. Org. Chem.,
1999, 1, 91-96 that this mixed anhydride reagent can be used for the sulfonation of alkenes. Tyobeka, et al.,
Tetrahedron,
1988, 44, 1971-78, further discloses that the bis-mixed anhydride of TFA and sulfuric acid:
is produced in equilibria by contacting TFAA with sulfuric acid.
BRIEF SUMMARY OF THE INVENTION
We have developed a process for the preparation of alkanoate esters of hydroxybenzenesulfonic acids and salts thereof by a novel combination of esterification and sulfonation steps. The present invention provides a process for the preparation of an alkanoate esters of hydroxy-benzenesulfonic acids and salts thereof (alkanoyloxybenzenesulfonic acid and salts thereof) by the steps comprising (1) contacting or reacting a phenol reactant with an alkanoic acid in the presence of trifluoroacetic acid (TFA) and trifluoroacetc anhydride (TFAA) to produce an aryl alkanoate ester and (2) contacting the reaction mixture of step (1) with a sulfonating agent to convert the aryl alkanoate ester to an alkanoate ester of hydroxybenzenesulfonic acid, i.e., alkanoyloxybenzenesulfonic acid. The alkanoyloxybenzenesulfonic acid may be treated with a basic compound such as an alkali metal or alkaline earth metal compound to convert the sulfonic acid to an alkali metal or alkaline earth metal salt. Alternatively, the step (2) sulfonation may be carried out in the presence of an alkali metal or alkaline earth metal sulfate to produce an alkali metal or alkaline earth metal sulfonate salt directly from step (2).
DETAILED DESCRIPTION
In the first step of the of the present invention a phenol reactant is contacted or reacted with an alkanoic acid in the presence of TFA and TFAA wherein the mole ratio of TFAA:phenol is about 3:1 to 0.1:1. The phenol reactant may be unsubstituted or substituted with one or more substituents such as unsubstituted or substituted hydrocarbyl, e.g., alkyl containing up to about 12 carbon atoms; hydroxy; alkoxy containing up to about 12 carbon atoms; alkoxycarbonyl containing 2 to about 12 carbon atoms; nitro; cyano; halogen; and the like. The phenol reactant preferably is unsubstituted phenol.
The alkanoic acid reactant may be an unsubstituted or substituted, saturated, aliphatic carboxylic acid containing a total of up to about 20 carbon atoms. The unsubstituted alkanoic acids typically contain 4 to 18, preferably about 6 to 16, carbon atoms. The alkanoic acid may be substituted with one or more, typically not more than one, substituent selected from alkoxy containing up to about 12 carbon atoms, halogen such as chloro and bromo, alkanoylamido containing up to about 12 carbon atoms, alkylsulfonamido containing up to about 12 carbon atoms. The alkanoic acid may be substituted with a second carboxyl group, e.g., adipic acid, azelaic acid and the like, which result in the formation of diphenyl dialkanoate esters. The alkanoic acid reactant preferably is an unsubstituted alkanoic acid containing about 6 to 16 carbon atoms or an alkanoic acid containing about 6 to 16 carbon atoms which is substituted with an alkanoylamido group containing up to about 12 carbon atoms. The preferred alkanoic acid reactant includes mixtures containing two or more alkanoic acids containing about 6 to 16 carbon atoms, e.g. a mixture containing approximately 4% hexanoic, 55% octanoic, 40% decanoic and 1% dodecanoic acids. The carboxylic acid and phenol may be used in carboxylic acid:phenol reactant mole ratios in the range of about 2:1 to 0.5:1, preferably about 1.2:1 to 0.8:1.
TFAA is employed in the first step in an amount which gives a TFAA:phenol reactant ratio of about 3:1 to 0.1:1, preferably about 1.5:1 to 0.75:1. The amount of TFA solvent present initially and during the operation of the first step of the process of the present invention typically gives a TFA:phenol mole ratio of at least 0.1:1 and preferably a TFA:phenol mole ratio in the range of about 0.5:1 to 20:1. Such mole ratios typically provide preferred amounts of TFA greater than 15 weight percent based on the weight of the phenol, carboxylic acid and TFAA present. The amount of TFA present preferably is in the range of about 25 to 75 weight percent based on the weight of the phenol, carboxylic acid and TFAA present. Other inert solvents may be used in conjunction
Hembre Robert Thomas
Holcombe, III Edwin Franklin
Lin Robert
Shelton Mark Robert
Barts Samuel
Blake Michael J.
Eastman Chemical Company
Faulkner Diedra
Gwinnell Harry J.
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