The kinetics of reaction of 4-nitrophenylnitromethane with N′-Propyl-N,N-dipropylbenzimidamide in aprotic solvents. A steric effect on tunneling

Article abstract of DOI:10.1007/BF02767676

Thermodynamic and kinetic parameters have been established for the reaction between the carbon acid, 4-nitrophenylnitromethane, (4-NPNM), and the base N′-n-propyl-N,N-di-n-propylbenzimidamide, (N′PDPBA), in mesitylene and in chlorobenzene. In some cases deuteron transfer from 4-(D₂)NPNM to the base has also been studied. In addition, some results for the proton transfer reaction in tetrahydrofuran have been collected. Spectrophotometric methods have been employed to monitor the on-pair product, which is solvatochromic. In general the solvent dependence of the parameters is as expected, but there is some indication of specific solvation. The kinetic isotope effects of 11 and 8 in mesitylene and chlorobenzene, respectively, are larger than those predicted classically. However, as is discussed the n-propyl group on the secondary nitrogen of the base may serve to reduce the extent of tunneling compared to that in an unsubstituted analogue by a steric effect.