Kinetic study of the reactions of various types of C-acids with amine bases in acetonitrile. An unusual effect of common BH+ cation on the rate constants

The rates of proton transfer reactions between C-acids of different types s uch as 1-(4-nitrophenyl)-1-nitroalkanes, 4-nitrophenylcyanomethanes, and 2, 4,6-trinitrotoluene, and organic bases such as 1,1,3,3-tetrametylguanidine, 7-methyl-1,5,7-triazabicyclo[4.4.0]dec-5-ene (MTBD), and tri-n-butylamine have been measured in acetonitrile at pseudo-first-order conditions. A gene ral equation for the rates of proton transfer reactions between C-acids and bases with product existing in two forms, ions and ion pairs, has been der ived and its applicability tested. The equation works well except for react ions of 1-(4-nitrophenyl)-1-nitroalkanes with guanidines for which the seco nd-order rate constant is diminished with concentration of guanidinium cati on, while tetrabutylammonium salts accelerate the reactions. Possible reaso ns for this are discussed.