Photoinduced electron-transfer substitution reactions via unusual charge-transfer intermediates.

The photoinduced substitution reactions of halogenated alkanes (1-haloadamantanes, 1-haloronorbornanes, menthyl chloride) with a homologous series of amines or alcohols (methylamine, 2-methyl-2-aminopropane, methanol, or 2-methyl-2-propanol) to form the corresponding alkane-substituted amines or ethers and HCl were investigated. The geometry of the bridgehead carbons made SN2 reactions impossible. Nonpolar reaction conditions were employed which made classical and nonclassical carbocation SN1 reaction pathways unlikely. The reaction rates were measured. Trapping experiments indicated that free radical reactions were uninvolved in the substitution product formation. A novel, photoinduced electron-transfer reaction mechanism involving a charge-transfer intermediate is proposed to explain the observed production of secondary amines and ethers. The excitation wavelength dependence (action spectrum) was measured and found to be comparable to the ultraviolet absorption spectra of the charge-transfer complexes. ...