Esters of Sulfonic Acids

Partial esterification of cellulose with p-toluenesulfonyl chloride may be accomplished in the presence of pyridine, or by reaction with alkali cellulose. The tosyl (p-toluenesulfonyl) group has been shown to react quite readily with the primary hydroxyl group of cellulose but much more slowly with the secondary groups. The reaction in the presence of pyridine must be carried out at low temperatures to prevent the introduction of nitrogen and halogen from side reactions.  

Use of the tosyl derivative of cellulose for theoretical study is important. Cramer and Purves have prepared tosyl derivatives of acetone-soluble cellulose acetate. By treatment with sodium iodide, which replaces tosyl groups in the primary position by iodine, they have been able to measure the proportions of primary and secondary hydroxyl groups present in the original product. 

By treatment with aliphatic primary or secondary amines, tosyl groups on cellulose (a low-substituted cellulose, such as methylcellulose, was employed) may be replaced by substituted amino groups. The products obtained are insoluble in water but dissolve readily in dilute acid. 

Organic isocyanates react with cellulose in the presence of dry pyridine to produce the corresponding N-substituted carbamates. Aliphatic isocyanates bring about only partial esterification, while aromatic reagents under proper conditions react readily and completely. Cellulose N-phenylcarbamate is soluble in several organic solvents and is extremely stable toward either acid or alkaline decomposition. Incomplete esteri- 

Sakurada and T. Nakashima, Sci. Papers Inst. Phys. Chem. Research (Tokyo), 6, 214 (1927). 

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Compounds, eg, phenacyl hahdes, ben2yl hahdes, alkyl iodides, or alkyl esters of sulfonic acids, react with DMSO at 100—120°C to give aldehydes (qv) and ketones (qv) in 50—85% yields (eq. 8) (41) ... 

The reactions represented by (191) are all nucleophilic substitutions occurring at a sulfonyl sulfur. Besides cpdisulfones substitutions of this kind are also of frequent occurrence in the chemistry of many other types of sulfonyl derivatives such as sulfonyl halides, aryl esters of sulfonic acids, etc., and many of the general aspects of their behaviour and mechanism have been examined in considerable detail. Most of the remainder of this section will be devoted to consideration of the results of such studies. 

Esters of sulfonic acids can rearrange photochemically to give sulfones in moderate yields [147], Thus, phenyl benzenesulfonate (182) cleaves photochemically producing 15% of ort/to-hydroxyphenyl phenyl sulfone (183) and 31.1% of para-hydroxyphenyl phenyl sulfone (184). Besides, 17.4% of phenol (13) is formed... 

Esters of sulfonic acids give different products depending on the reducing agent, on the structure of the parent sulfonic acid, and especially on the structure of the hydroxy compound, alcohol or phenol. 

Alkyl sulfonates (esters of sulfonic acids), RS02R Ar)... 

Potassium cyanide has been caused to react with salts and esters of sulfonic acids to give nitriles. Thus, an intimate mixture of finely powdered potassium cyanide with the compound may be fused 422 this method was successfully applied428 to tetrahydrofurfuryl p-toluenesul-fonate and methanesulfonate, but failed with l,2 3,4-di-0-isopropylidene-6-O-tosyl-D-galactose. Another method, consisting of treatment of the ester with a stirred, boiling, saturated, aqueous solution of potassium cyanide gave885 a 70 to 83% yield of nitrile with primary p-toluenesul-fonates (ethyl, n-butyl, and n-octyl) and a 43% yield with a secondary p-toluenesulfonate (isopropyl). Similar methods had been applied earlier98 841 to such simple esters, but have not apparently found use with sulfonic esters of carbohydrates. 

This reaction is analogous to similar methods for the preparation of ethers (methods 113 and 116), Both simple and mixed sulfides may be made from aliphatic mercaptans or thiophenols. The sodium mercaptides are formed from the mercaptans and aqueous or alcoholic solutions of sodium hydroxide or alcoholic sodium ethoxide. Alkylation is effected by halides, alkyl sulfates, or esters of sulfonic acids. The over-all yields of sulfides are usually above 70%. r-Butyl mercaptan is alkylated directly by /-butyl alcohol in strong sulfuric acid to give /-butyl sulfide in 87% yield. ... 

Of these other compounds, alkyl esters of sulfonic acids, ArS020R, are most commonly used in place of alkyl halides usually in the study of reaction mechanisms. but also in synthesis. As the anions of strong acids, sulfonate anions are weak bases and hence are good leaving groups in either nucleophilic substitution or. elimination ... 

Let us look at another example of solvolysis. A very commonly studied system is one in which the solvent is acetic acid (HOAc) and the substrates are alkyl esters of sulfonic acids ROTs, alkyl tosylates (alkyl p-toluenesulfonates) ROBs, alkyl... 

Nondrying alkyd resins cross-linked with melamine resins at elevated temperature are used for industrial coatings. Resins containing synthetic fatty acids and resins based on glycidyl esters of Versatic Acid (Cardura E 10, Shell) are used in combination with low-viscosity melamine resins such as hexamethoxymethylmelamine. p-Toluenesulfonic acid and its amine salts are used as catalysts. On account of their high storage life, hydrophobic oxime esters of sulfonic acids are also employed. 

Although nucleophilic attack at the alkyl carbon seldom occurs with esters of carboxylic acids, it is the preferred mode of attack with esters of sulfonic acids (e.g., tosylates, mesylates, and triflates Section 11.10). 

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