Hydrogen sulfide, dehydrogenation

The initial step of the adsorption of cyclic sulfides on a Mo(100) surface is also the formation of adsorbed thiolate groups.395-397 Adsorbed alkyl thiolates decompose to adsorbed sulfur, carbon, and hydrogen on the clean Mo surface, but once the surface is deactivated by adsorbed sulfur, alkanes and alkenes evolve from the surface. Tetrahydrothiophene (34) and trimethylene sulfide decompose on Mo(110) to alkanes and alkenes by way of a common intermediate, which is proposed to be a surface thiolate (33). The thiolate undergoes hydrogenation or dehydrogenation, depending on the surface hydrogen concentration (Scheme 4.115).398 399... 

Hydrogenation and dehydrogenation employ catalysts that form unstable surface hydrides. Transition-group and bordering metals such as Ni, Fe, Co, and Pt are suitable, as well as transition group oxides or sulfides. This class of reactions includes the important examples of ammonia and methanol syntheses, the Fischer-Tropsch and oxo and synthol processes and the production of alcohols, aldehydes, ketones, amines, and edible oils. 

Hydrogen ligands, 689-711 Hydrogen selenide metal complexes, 663 Hydrogen sulfide metal complexes, 516 Hydrogen telluride metal complexes, 670 Hydroporphyrins, 814-856 basicity, 853 dehydrogenation, 853 demetallation, 854 deuteration, 853 mass spectra, 852 metallation, 854 NMR, 852 non-aromatic, 855 photochemistry, 854 redox chemistry, 855 synthesis, 852... 

Hydrogen sulfide generated by dehydrogenation reactions in the fusion process is absorbed by caustic soda solution. The crude melt is ground and dissolved. Insoluble crude melts are digested with caustic soda or sodium sulfide. From the resulting solution, after clarification, the dye is precipitated by air blowing or acidification, then filtered and dried. 

The process is commonly carried out in jacketed stainless steel vessels with stirrer and reflux condenser. As in dry fusion, dehydrogenation reactions give off hydrogen sulfide, which is absorbed in caustic soda solution. 

As is obvious, hydrogen sulfide active under current conditions is one of the reaction products. Its aggressiveness, the ability to interact with S02 even under natural conditions, promotes sulfur accumulation in the system, affects synthesis of condensation products and can alter their catalytic activity. Therefore, despite high effectiveness, oxidative catalytic dehydrogenation of ethylbenzene by sulfur dioxide may be found unacceptable for production management in relation to ecology and protection of the environment. 

Dehydrogenation of 1-methyl-1-azacyclooctane (28) with mercuric acetate, followed by treatment with hydrogen sulfide and hydrochloric acid, gave the hydrochloride of 2,4,6-tris-(6-methylamino-hexyl)trithiane (29) only.48 Analogous compounds have been obtained... 

Diastereomeric 1,3,4-thiadiazolidines may be prepared via a different route. Condensation of the azine derived from pivalaldehyde with an excess of hydrogen sulfide yields diastereomeric thiadiazolidines 12 which on dehydrogenation with diethyl azodicarboxylate gives the 2,5-dihy-dro-l,3,4-thiadiazole 13 as a 1 0.6 mixture of trans- and m-stereomers55. 

Sulfur, Sj, is a dehydrogenating agent that converts compounds containing six-membered rings into their aromatic analogues. In the reaction, sulfur is reduced to hydrogen sulfide [491, 492], Such dehydrogenations occur at lower temperatures compared with those by selenium [493] or noble metals 495, 496, 497]. 

---