Kinetics, deuterium isotope effect and mechanism of the reaction of 1,1,1-trifluoro-2,2-bis(4-nitrophenyl)ethane with 1,1,3,3-tetramethylguanidine in aprotic solvents

Abstract

The reaction of 1,1,1-trifluoro-2,2-bis(4-nitrophenyl)ethane with 1,1,3,3-tetramethylguanidine (TMG) in different solvents gives N-[bis(dimethylamino)methylene]-1-fluoro-2,2-bis(4-nitrophenyl)ethenylamine {(O₂NC₆H₄)₂CCF[NC(NMe₂)₂]} as the final product. No intermediates were isolated in the reaction mixture.

The kinetics of this reaction in a series of solvents—acetonitrile (MeCN), benzonitrile (PhCN), tetrahydrofuran (THF) and hexane—are reported. In acetonitrile kinetic curves showed non-exponential behaviour in the first 10–20% of the kinetic run. The rate constants, deuterium isotope effect and activation parameters are discussed in terms of a multistep mechanism. Non-exponential behaviour of kinetic curves in acetonitrile and the lack of intermediate is explained.