Thioacetone

Compounds with active hydrogen add to the carbonyl group of acetone, often followed by the condensation of another molecule of the addend or loss of water. Hydrogen sulfide forms hexamethyl-l,3,5-trithiane probably through the transitory intermediate thioacetone which readily trimerizes. Hydrogen cyanide forms acetone cyanohydrin [75-86-5] (CH2)2C(OH)CN, which is further processed to methacrylates. Ammonia and hydrogen cyanide give (CH2)2C(NH2)CN [19355-69-2] ix.orn. 6<55i the widely used polymerization initiator, azobisisobutyronitrile [78-67-1] is made (4). 

Treatment of 2-methylthiirane with t-butyl hydroperoxide at 150 °C in a sealed vessel gave very low yields of allyl disulfide, 2-propenethiol and thioacetone. The allyl derivatives may be derived from abstraction of a hydrogen atom from the methyl group followed by ring opening to the allylthio radical. Percarbonate derivatives of 2-hydroxymethylthiirane decompose via a free radical pathway to tar. Acrylate esters of 2-hydroxymethylthiirane undergo free radical polymerization through the double bond. 

Tetramethyl-l,2-oxathietane (138) was prepared by diazotization of 139, which was prepared from the aziridine (140) (86JA3811).Tlie reaction presumably involves the decomposition of the sulfonium ion intermediate (141).Tire dichloromethane solution of 138 at -20°C is sufficiently stable to permit exploration of the chemical reactions. Tire oxathietane 138 undergoes a formal [[Pg.248]

The Ramberg-Backlund reaction has been utilized for the preparation of polyenes. 1,3-Butadienyl allyl sulfones 398 and 399 were transformed into the tri- and tetra-enes 400 and 401 by alkylcuprate addition and the Ramberg-Backlund-type S02 extrusion449. Julia and coworkers450 carried out the Michael addition of various nucleophiles such as ethanol, t-butyl acetoacetate and phenyl thioacetone to allyl dienyl sulfones 402 and then converted them to diallyl sulfones 403. The sulfones were transformed into isoprenoid, 404 by the Ramberg-Backlund reaction. 

C2H4OS 507-09-5) see Acetorphan Captopril Meropenem Omapatrilat Spironolactone Tiomesterone thioacetone... 

Oxidation of tri(thioacetone) by cone, nitric acid is explosively violent. 

A series of heteroatom substituted carbodiphosphoranes C PR2ECH(CF3)2 2 have been prepared in the last 10 years by various groups as shown in Fig. 6. The main synthetic approach consists of the reaction of hexafluoroacetone or thioacetone with the related diphosphines R2P-CH2-PR2 [25, 26]. The bent structure with a P-C-P angle (140°) confirms the double ylidic nature [27] and a related chemistry to C(PPh3)2 is expected however, no reports about coordination activities were reported so far. Theoretically, double alkylation at the heteroatoms of the dianion in Fig. 9 would lead to the substituted carbodiphosphoranes. The amino derivative C(P NMe2 3)2 has a linear structure and was not investigated further [28]. 

Thioacetone polymerizes adventitiously even at very low temperature, in contrast to the inability of acetone to polymerize. 

After thioformaldehyde, the thiocarbonyl compound that has received most attention is thioacetone. Unlike thioformaldehyde, it can be kept in monomeric form, but only if kept below - 50° C (30). It is a red oil that freezes at about — 55° C and boils at about 70° C. If pure it polymerizes to a white solid in a few hours at — 78° C or quite rapidly at room temperature. It also exists as a thioenol tautomer, which is stable at temperatures below — 50° C but which tautomerizes at higher temperatures to give an equilibrium mixture of thioketo and thioenol forms. 

Thioacetone was first made in 1889 by Baumann and Fromm (31). They obtained it by reaction of hydrogen sulfide with acetone in the presence of an acidic catalyst. It was a minor product detected by its very disagreeable odor. The major product was hexamethyl-s-trithiane. In more recent work (32, 33) pyrolysis of this intermediate has been developed into a preferred route to thioacetone. 

Reaction of acetone with hydrogen sulfide in the presence of acidified ZnCl2 at 25° C gives a good yield of a product composed of60-70% hexamethyltrithiane and 30-40% of 2,2-propanedithiol. Thioacetone can be obtained by pyrolysis of either of these compounds. The trithiane is pyrolyzed either on quartz rings heated to 500-650° C at 5-20 mm (30) or by means of a hot wire (32). The dithiol is pyrolyzed on sodium fluoride pellets heated to 150° C at 11 mm (50). In both cases the pyrolysate is immediately collected in a trap cooled to — 78° C. 

Careful examination of the pyrolysis of the trithiane from thioacetone has shown that the product is always a mixture of the thioketone, CH3CSCH3, and the thioenol, CH2=CSHCH3 (50). The amount of thioenol, which is always the lesser component, varies from about 5-15 % depending upon pyrolysis conditions. Below 500° C, the trithiane is completely pyrolyzed. Above 600° C, thioacetone undergoes extensive decomposition. In between 500° C and 600° C, the relative proportion of thioketo tautomer increases with increasing pyrolysis temperature. 

As mentioned earlier, pyrolysis of 2,2-propanedithiol over sodium fluoride at about 200° C also leads to thioacetone. The product obtained at 150° C is more than 90% the thioketo form. At 250° C, the thioenol amounts to over 50% of the product. 

As has been mentioned earlier, thioacetone polymerizes adventitiously even at very low temperatures. The product is a white powder of very high crystallinity. Bailey and Chu (34) state that pure thioacetone gives only polymer, but others always have obtained hexamethyl-s-trithiane in addition to polythioacetone. The... 

The studies described above did not take into account thioenol content. Polymer formed in its presence by either an ionic mechanism or a free-radical mechanism would probably be of lower molecular weight. It was found (30) that thioacetone of greater than 95% thioketo tautomer gives polymer melting at 120-124° C, which is in line with the other products. 

Polymerization of thioacetone is also initiated by visible light. In fact, it has been shown that exposure of frozen crystals of thioacetone monomer to light leads to rapid solid phase polymerization (33). 

Though thioacetone polymerizes spontaneously, by free-radical initiation, and by base initiation, it does not form copolymers in any of these systems. Efforts to obtain copolymers with dienes, vinyl compounds, acrylates, aldehydes, and epoxides have failed. 

Fluorine-substituted thiocarbonyl compounds have been studied even more intensively than thioformaldehyde and thioacetone. These compounds have a very rich chemistry of which polymerization is only a part. The simplest member of this class is fluorothiocarbonyl fluoride, CF2==S, which also forms the most interesting polymers. Other members that have been investigated include a variety of fluorothioacyl halides and a number of fluorothioketones. Because... 

One of the great surprises of fluorothiocarbonyl chemistry is the ease with which these compounds undergo free-radical polymerization. This behavior is unique among thiocarbonyl compounds. Though thioacetone polymerizes in free-radical systems, it does not do so with anything like the avidity of fluorothiocarbonyl compounds. Thioacetone does not copolymerize with compounds containing carbon-carbon unsaturation, which is a most important property of fluorothiocarbonyl compounds. 

The enolate anions of thioacetaldehyde and thioacetone were generated in a flow tube by rapid (presumable) E2 elimination reactions of F with the appropriate sulphide (equations 36 and 37, respectively)181. 

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