Reaction with mercaptans

Transfer constants for mercaptans with several monomers are given in Table XV. Results for the two methods described above are in satisfactory agreement. The rate of reaction with mercaptan relative to the rate of monomer addition (i.e., the transfer constant) varies considerably for different chain radicals (see Table XIV). Temperature coefBcients of the transfer constants for mercaptans are very small, which fact indicates that the activation energy for removal of a hydrogen atom from the sulfhydryl group of a mercaptan is nearly equal to that for monomer addition. 

Similarly the chain transfer reactions with mercaptans can be shown as under ... 

The reaction with mercaptans is believed to generate initiating sulfur radicals ... 

Reaction with mercaptans and dimercaptans (12, 16, 21) proceeds normally to produce the 2-hydroxybenzyl thioether compounds XXV and XXVI. 

The addition of amine to the bicyclic salt (96) initially takes place not in position 3, but in position 5, as in the reaction with mercaptans the reaction then proceeds by the same steps to yield the ester of the 1-aminocyclopent-l-ene 2-dithiocarboxylic acid (118). This ester (118) is obtained in yields of 30-65% its structure has been confirmed by independent synthesis from 119. This reaction course is again confined to the special system 118, the homologous tetramethylene-trithionium salts yielding Schiff s bases on reaction with primary amines under the same conditions.50... 

Under the proper mild conditions, chlorine can also be used, but overoxidation and sidereactions often result in some yield loss. Elemental sulfur can be employed, but it must be used in a molar deficiency to prevent the formation of tri- and higher polysulfides as by-products. Conversely, higher-rank polysulfides can be retrograded back to disulfides by reaction with mercaptans. 

The alkoxy group in 2-alkoxy-5,6 dihydro-2H-pyrans (279) can be exchanged for another OR or NR R group when the substrate is heated at 150-200° with suitable alcohols or amines this opens the way to the nucleoside type of compound (e.g. 323). The alkoxy group in 279 can be also be exchanged for a thioalkyl group in a substitution reaction with mercaptans. The reactions are catalyzed by stannic chloride or diluted hydrochloric acid. The 2-alkylthio derivatives (324) are often accompanied by allylic rearrangement products (325). 

Amines react in general more readily than alcohols and aromatic isocyanides are more reactive than ahphatic ones. The ionic diisocyanide complexes react under milder conditions than the neutral monoisocyanide complexes . No reactions with mercaptanes have been reported. Acyclic aminocarbene complexes occur as isomers when R R due to restricted rotation around the C(carbene)—N bond . Dinuclear carbene complexes are formed when the amine complexes [Au(C6F5)NH2(CH2)nNH2] (n = 1 or 2) or the carbene complexes [(C6F5) ,AuC(NHR)NH(CH2)nNH2] (m = 1 or 3) are treated with the isocyanide compound [(C6F5)mAuCNR] (R = Ph or p-tolyl) . ... 

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