THE INFLUENCE OF COMMON CATION BH-ACIDS AND STRONG GUANIDINE BASES INACETONITRILE SOLVENT( ON THE PRODUCTS OF REACTIONS BETWEEN C)

The electronic spectra of the pro duc ts of reactions between C-acids (4-nitrophenylcyanoalkanes, 4-nitrophenylnitroalkanes and trinitrotolu ene) and 1,1,3,3-tetramethylguanidine (TMG), pentamethylguanidine (PMG ) and MTBD bases (B) have been recorded in B/BH+ buffers in acetonitri le at 25 degrees C. Large BH+ concentrations had little or no effect o n the spectra of the nitrile or trinitrotoluene anions, while the spec tra of nitroalkane anions were shifted to the blue by some 50-75 nm. T hese shifts were ascribed to the formation of hydrogen-bonded ion pair s. In the case of TMG or PMG reactions two types of ion pairs are form ed due to homoconjugation of BH+ cations, which is why an isosbestic p oint is not observed, while MTBD reactions are free from such complica tions, The spectra of some ion pair products and ion pair dissociation constants were calculated.