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Solvolysis of some vinyl iodonium salts carrying an excellent leaving group is examined, focusing on whether or not a classical primary vinyl cation can be generated. Formation of the primary cation is avoided, when possible, by participation of the beta substituent in the heterolysis to form a vinylenebenzenium ion or a secondary vinyl cation. Definitive evidence against a primary vinyl cation is provided by a chirality probe approach in the solvolysis of 4-methylcyclohexylidenemethyl iodonium salt.

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Crystals of diarylethenes having urethane bonding exhibited photoinduced rapid and explosive fragmentation according to the photochromic reaction. The speed of the photogenerated crystal fragments was as fast as a few meters per second. The kinetic energy was independent of size, thickness, and volume of crystals, and depended on the crystal characters, such as crystal density and strength of intermolecular hydrogen bonding.

The reactions of four (E)-β-alkylvinyl(phenyl)iodonium salts with chloride ion were examined in acetonitrile and in several other solvents at 25 °C. The β-methyl-, β-octyl-, and β-isopropyl-substituted iodonium salts undergo competitive bimolecular nucleophilic substitution to form the corresponding (Z)-1-chloro-1-alkene with inversion of configuration at the vinylic carbon and elimination to form the 1-alkyne. The β-tert-butyl-substituted iodonium salt affords only the products of the elimination reaction. The UV absorption spectra of the reactants show the rapid coversion of chloride and iodonium ions to an equilibrium mixture of the corresponding chloro-λ3-iodane, with an association constant of 5600−7600 mol-1 dm3. A kinetic analysis shows that most of the substitution and elimination products form from reaction of the λ3-iodane. Evidence is presented that the substitution reaction proceeds by a concerted bimolecular SN2 mechanism and that the elimination reaction proceeds by a unimolecular reaction mechanism with intramolecular transfer of the β-proton to the leaving group.

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