123150-72-1Relevant articles and documents
A Simple Test for Diffusion-Limited Reactions. Near-Diffusion-Controlled Nitrene Insertion into C-H Bonds
Maslak, Przemyslaw
, p. 8201 - 8207 (2007/10/02)
A test for diffusion-controlled reactions is described.It is based on a simple experiment, wherein a reactive intermediate competes for two reagents containing a different number of reactive sites.This approach allows one to estimate rate constants of rapid reactions (i.e., kr ca. kd without absolute rate measurements.The test is applied to reaction of (diethoxyphosphoryl)nitrene with hydrocarbons in perfluorinated solvents.The photogenerated singlet nitrene undergoes efficient insertion into C-H bonds, and its reactivity is unaffected by the presence of oxygen.The insertion of the nitrene into a tertiary C-H bond is found to be near-diffusion-controlled with kobs ca. 0.3kdif = 3 * 1E9 M-1 s-1.Increased selectivity for insertion into tertiary versus primary C-H bonds is observed in perfluorohexane (9.7) as compared to a hydrocarbon solvent (5.7).This diminished reactivity of the nitrene is considered as evidence for complex formation between the singlet nitrene and a solvent molecule.The rate of the complexed-singlet to triplet intersystem crossing is estimated to be 8 * 1E8 s-1.The triplet nitrene reacts by hydrogen abstraction and is scavenged by oxygen.
