Ethyl mercaptan, decomposition

The molecular mechanisms (3) and (4) are reminiscent of the decomposition of ethyl mercaptan vide infra) and the decomposition of CH3OH from the insertion of 0( D)into CH4. ... 

The photolysis of ethyl mercaptan in an organic matrix at 77 °K was shown to produce CH3CH2S radicals by uv and esr spectrometry . The gas-phase photolysis at 2288 and 2537 A is also initiated by S-H bond rupture, and hot H-atoms are probably produced < (H2) = 1.0. In the Hg( Pi)-sensitized decomposition , C-S cleavage appears to be a major process, although its relative importance could not be determined. The pyrolysis, examined by toluene carrier in the range 512-665 C proceeds by two mechanisms depending on the temperature". At low temperature, H2S and C2H4 are the major products, the former found in quantitative yields a molecular mechanism, similar to the dehydration of alcohol, was proposed, viz. 

Potassium and sodium act with mercaptan as with alcohol, replacing the extra-radical hydrogen. In its behavior tow ard the oxids it more elosely resembles the acids than the alcohols, being capable even of entering into double decomposition to form salts, called sulfethylates or mercaptids. Its action with mercuric oxid is characteristic, forming a white, crystalline sulfid of ethyl, and mereury ... 

For this reason a regulator is added. Regulators are substances with very high transfer constants, and therefore only need to be added in small concentrations. SH compounds in particular (mercaptans, thio-glycolic ethyl ester) are suitable regulators. At 60°C, for example, n-butyl mercaptan possesses a Q of 22 (styrene) or 0.66 (methyl methacrylate). Thus, the value for the n-butyl mercaptan/styrene system is higher than that for the pentaphenylethane/styrene system (Table 20-7). These high transfer constants do not occur with the latter because mercaptans lead to an induced initiator decomposition. 

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