Dimethyl sulfate is used to make quaternary fatty ammonium compounds used as surfactants and fabric softeners. An example is the quaternary salt in which R is hydrogenated tallow:
The monomethyl sulfate anion of the salt is preferred over other anions, such as chloride, because the sulfate is much less corrosive to laundry and water processing equipment. Dimethyl sulfate is preferred over methyl chloride as a methylating agent, because DMS reacts faster in higher yields and requires less costly processing equipment.
Methylated quaternary salts also serve as flocculants, which are used in water treatment, such as in sewage sludge control. An example is a quarternized Mannich base of low molecular weight polyacrylamides3:
In actual practice, not all of the amide groups of the polyacrylamide are used in the Mannich reaction. The dimethylamine employed in the reaction is also a DuPont product. Information on it can be obtained by calling Product Information, 800-441-7515.
Dimethyl sulfate is used to make ethers, which in turn serve as intermediates to commercial products, such as pesticides, dyes, and fragrances. Examples of useful methyl ethers are anisole and anisole derivatives:
The reaction of DMS with sodium phenolate illustrates ether synthesis.4 Because the phenolate ion is highly reactive in nucleophilic reactions, both methyl groups of DMS can be used:
3 U.S. Pat. 4,137,164 (Jan. 30, 1979), A.T. Coscia and M.N.D. O’Connor (to American Cyanamid Co.).
4 Kirk-Othmer: Encyclopedia of Chemical Technology, Vol. 22, 3rd Edition, page 236, John Wiley & Sons, Inc. (1983).
5 U.S. Pat. 3,925,520 (Dec. 9, 1975), H.G. Franke (to Chevron Research Co.).