Mercaptans, alkylating agents

The reduction of sulfonyl chlorides may lead to sulfinates [265-267], thiosulfonates [267], disulfides, and mercaptans depending on the conditions in the presence of alkylating agents [266], sulfones or sulfides are among the products. 

A soln. of p-chlorobenzenediazonium hexafluorophosphate in dimethylform-amide added slowly with stirring at — 5° to a mixture of n-butylamine, powdered Na-carbonate, and dimethylformamide, warmed to 0°, and stirred a few min. until a negative test is obtained with 2-naphthol, ether added, filtered, the filtrate washed and dried, this soln. of the resulting crude l-(n-butyl)-3-(4-chlorophenyl)triazene (Y ca. 100% when isolated) treated with ethereal 3,5-dinitrobenzoic acid, and kept 1-2 hrs. at 25° until Ng-evolution ceases n-butyl 3,5-dinitrobenzoate. Y 63-73%.— Triazenes may be used as alkylating agents for carboxylic acids, phenols, mercaptans, and certain alcohols. F. e. s. E. H. White and H. Scherrer, Tetrah. Let. 1961, 758. 

Nonionic Surface-Active Agents. Approximately 14% of the ethyleae oxide consumed ia the United States is used in the manufacture of nonionic surfactants. These are derived by addition of ethylene oxide to fatty alcohols, alkylphenols (qv), tall oil, alkyl mercaptans, and various polyols such as poly(propylene glycol), sorbitol, mannitol, and cellulose. They are used in household detergent formulations, industrial surfactant appHcations, in emulsion polymeri2ation, textiles, paper manufacturing and recycling, and for many other appHcations (281). 

The ease with which the hydrogen atom is detached from the sulphur is noteworthy (analogy with H2S) even atmospheric oxygen gradually converts the mercaptans into aryl or alkyl disulphides, and mild oxidising agents do so at once ... 

Semitelechelic HPMA polymers were synthesized by free radical polymerization of HPMA using 2,2 -azobis(isobutyronitrile) (AIBN) as the initiator and alkyl mercaptans as chain transfer agents. Alkyl mercaptans with different functional groups, namely, 2-mercaptoethylamine, 3-mercapto-propionic acid, 3-mercaptopropionic hydrazide, and methyl 3-mercapto-propionate, were used as the chain transfer agents ST HPMA polymers... 

The free radical polymerization of HPMA in the presence of mercaptans involves two different initiation mechanisms (Scheme 2) [26]. One is the initiation by RS radicals from chain transfer agent the other appears to be the direct initiation by the primary isobutyronitrile (IBN) radicals formed by the decomposition of AIBN [27]. The RS are formed by either the free radical transfer reaction of alkyl mercaptans with the IBN radicals or the chain transfer reaction of an active polymer chain with the mercaptans. The initiation by the RS radicals produces the ST polymers with a functional group at one end of the polymer chain. The initiation by IBN radicals leads to nonfunctional polymer chains with an IBN end group. The presence of the polymers with IBN end groups effects the purity and the functionality of ST polymers. As expected, the production of nonfunctionalized polymer chains is affected by reaction conditions. The polymerization is mainly terminated by chain transfer reaction with the mercaptans, but other termination mechanisms, such as disproportionation and recombination, take place depending on the reaction conditions [26]. 

Additional uses for higher olefins include the production of epoxides for subsequent conversion into surface-active agents, alkylation of benzene to produce drag-flow reducers, alkylation of phenol to produce antioxidants, oligomerization to produce synthetic waxes (qv), and the production of linear mercaptans for use in agricultural chemicals and polymer stabilizers. Aluminum alkyls can be produced from heavy olefin streams and olefin or paraffin streams have been sulfaled or sulfonated and used in the leather (qv) industry. 

Alkyl Bound to Miscellaneous Elements. Several compounds in which alkyl is bound to a sulfur atom have become quite important in recent years for example, the mercaptans, such as amyl and ethyl mercaptan, are used as warning agents in natural gas because of their intense and disagreeable odor. Mercaptans are also employed in organic syntheses as, for instance, the manufacture of sulfonal by the condensation of ethyl mercaptan (ethanethiol) with acetone, followed by oxidation. In recent years a very considerable amount of mercaptan has been used for controlling the polymerization reaction between butadiene and styrene to form synthetic rubber (GR-S). 

Transfer to modifier. Molar masses can be controlled by addition of a known and efficient chain transfer agent such as an alkyl mercaptan. 

RSH is the alkyl mercaptan chain transfer agent M stands for monomer... 

POly(acryliC acid). Poly(acrylic acid) (PAA) can be prepared by direct tree-radical polymerization of 2 in aqueous solution (6) or by precipitation polymerization in benzene. Alcohols and mercaptans are commonly used chain-transfer agents for regulating polymer molecular weight. Alternatively, PAA can be prepared by hydrolysis of poly(alkyl acrylates) (6) (Fig. 29). 

Fig. 6.1. Reduction and alkylation of interchain disulfide bonds in immunoglobulins. In the absence of dissociating agents (urea, guanidine, etc.) most intrachain bonds remain intact. The reduction with mercaptan is reversible and a large excess of the reagent is therefore employed. The alkylation is essentially irreversible.

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