No abstract

Absolute rate constants for the ylide-forming reactions of 16 carbenes with pyridine range from 1.4 x 1010 to 1.2 x lo5 dm3 mol-1 s-1, and can be rationalized by frontier molecular orbital theory.

No abstract

Cyclopropylmethoxycarbene undergoes ambiphilic‐nucleophilic intermolecular reaction with alkenes and methanol, but its intramolecular chemistry (1,2‐carbon migration) is suppressed (k < 3 × 103 s−1) by the α‐methoxy substituent.

A Additions of phenylchlorocarbene and phenylfluorocarbene to representative alkynes are rapid (106-107 I mol -' s ~ I).The variation of the rate constants with alkyne structure parallels that observed with analogous alkene substrates. The addition of phenylchlorocarbene to 3-hexyne is characterized by a very low activation energy ( -2 kcal m o l~ ') and a large, negative entropy of activation ( --20 e.u.).