Thioformaldehyde, polymerization

Not surprisingly, thioformaldehyde polymerizes more avidly than any other carbon-sulfur double bond compound. At first the polymer appeared promising because of its high melting point and highly crystalline character. The promise has not been realized because the polymer undergoes degradation in the molten form. 

Although there are no reported polymerizations of simple cyclic sulfides of ring size 5 and higher, polymerizations of 1,3,5-trithane (the cyclic trimer of thioformaldehyde) (LX), disulfides such as l-oxa-4,5-dithiacycloheptane (LXI), and trisulfides such as norhonene trisulfide (LXII) have heen achieved [Andrzejewski et al., 1988 Baran et al., 1984 Moore et al., 1977 Zuk and Jeczalik, 1979]. 

Photolysis of trans-2-phenyl-3-benzoylthietane yields both cis- and trans-l,3-diphenyl-2-ethenyl ketone and polymeric thioformaldehyde instead of the anticipated thiophene derivative. 

Higher thioaldehydes seem to have been overlooked. Thioketones, however, have received much attention. Work in this area has involved principally thio-acetone. This compound polymerizes spontaneously and rapidly, though it is not as active as thioformaldehyde. Some work has also appeared on higher... 

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. 

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... 

Thiocarbonyl compounds can be generated thermally in the gas-phase from a variety of precursors. Bock et al. [77JCS(CC)287 82CB492] have shown that pyrolysis of 1,2,4-trithiolane derivatives (81) is especially advantageous for this purpose. The fragmentation reactions were monitored by PE spectroscopy. By this method thioaldehydes including thioformaldehyde and thioketones that polymerize readily were obtained. 1,2,4-Trithiolane 4-oxide (82) yields a mixture of thioformaldehyde and thioformaldehyde oxide. 

The simplest chain structure -f-CH2—S- occurs through the polymerization of thioformaldehyde, CH2S, or its cyclic trimer (trithiane). Aliphatic polysulfides with two or more carbon atoms per monomeric unit are available through the polymerization of cyclic sulfides. The start step with organolithium compounds deviates from that of the epoxides in that initially the sulfur atom is attacked and subsequently the carbon atom is attacked. For example, the starting step with propylene sulfide and ethyl lithium initially gives propylene and lithium ethane thiolate ... 

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