Recent abvances in chemistry of acylaminyl radicals (RCON-R' or RCONCOR') are reviewed. The article covers the generation, electronic structure, and reactions including some mechanistic considerations and synthetic apllications.
The preparations and structures of nitroxides are briefly surveyed. The major portions are concerned with their applications of the spin labelings and spin trappings, which are written with the intention of arousing interests in the fields.
Chemistry of iminoxyl radicals is reviewed concerning their generation, structure, and reactions. The iminoxyl radical is a σ-radical and some unique features of its ESR spectra are mentioned. The properties of di-t-butylimjnoxyi, a stable iminoxyl radical, are described in some details.
Alkyl- and aryldiazenyl radicals proposed in the investigation of azoalkanes and arylazoalkanes were reviewed with respect to the products derived from them, to the contributions to the decomposition in solution and under pressure, to the life time, and to the possibility of their out-of-cage reaction. Based on the findings from the product and CIDNP studies, the life time of phenyldiazenyl radical was estimated to be 10-5 and 10-8-10-10sec, respectively.
Since Oenslager discovered aniline as vulcanization accelerator at 1906, many compounds have been investigated, but, development of vulcanization accelerators was complicated. I think so that, a process of development was very important fact, especially, discovered aniline and introduced thiocarbanilide (by reaction of aniline with carbon disulfide). Namely, (1) effect of aniline as aromatic amine was enlarged to aliphatic, alicyclic and heterocyclic amines. (2) To improve these toxity and volatility, for exmple, the above amines were treated with aldehydes or carbon disulfide to give the thiourea derivatives or amine salt of dithiocarbamic acids. (3) Since the amine salt of dithiocarbamic acids having a “scorching”, thiuram disulfide (or mono sulfide) have become to be applied instead of these amine salts. (4) Guanidine derivatives and mercapto benzothiazole have become to be used instead of aromatic thiourea derivatives since their “scorching” property, especially inrnercapto benzothiazole derivatives, dibenzothiazyl disulfide and benzothiazole sulfenamides through have become to be prefered to 2-mercapto benzothiazole. These vulcanization accelerators have been advanced in opposite site, progressing of “cure efficiency” and improvement of “scorching”. These development of vulcanization accelerators was arranged to the diagram.
Phthalic acid yielded N-methylphtalimide (1) and N-methylthiophthalimide (2) when heated at 190220°C with hexamethylpho sphoric triamide (HMPA) in the presence of sulfur. Phthalic anhydride gave N, N, N'N'-tetramethylthiophthalamide (4) and N, N, N, N', N'-tetramethyldithiophthalamide (5) under the same conditions. Phthalic thioanhydride also yielded (4) and (5) when heated at 200220°C with HMPA without sulfur, and at 150°C only dimers of phthalic thioanhydride were formed.
The reaction of tetraphenyldiphosphine with s -alkyl iodides or isopropyl p-toluenesulfonate gave a mixture of s-alkyldiphenylphosphines and di-s-alkyldiphenylphosphonium salts in good yields. The reaction of methyl diphenylphosphinite with isopropyl iodide gave only 4% yield of isopropyldiphenylphosphine oxide.