122540-70-9Relevant academic research and scientific papers
Laser flash photolysis study of alkylhalocarbenes generated from non-nitrogenous precursors
Robert, Marc,Likhotvorik, Igor,Platz, Matthew S.,Abbot, Sarah C.,Kirchhoff, Mary M.,Johnson, Richard
, p. 1507 - 1513 (1998)
Previously we have studied the photochemistry of alkylchlorodiazirines using laser flash photolysis methods and the pyridine ylide technique (White et al. J. Org. Chem. 1992, 17, 2841). The yield of trappable carbene was found to be a sensitive function of the alkylcarbene structure. This was attributed to ring opening of the diazirine to form a biradical which could suffer rearrangement, in addition to fragmentation to a carbene. It was also possible to explain the data in terms of a carbene-pyridine complex which can either rearrange or collapse to an ylide. In this work, alkylchlorocarbenes are generated from phenanthridenes. The results do not rule out the intermediacy of a carbene-pyridine complex; however, if this species is formed, it does not rearrange to chloroalkene in competition with collapse to form an ylide. This study reduces the urgency with which to postulate carbene-olefin complexes (Tomioka et al. J. Am. Chem. Soc. 1984, 106, 454).
Benzylchlorocarbene: Kinetics parameters for 1,2-H migration, UV absorption spectrum, and mechanism for addition to alkenes
Liu, Michael T. H.,Bonneau, Roland
, p. 3915 - 3919 (2007/10/02)
Laser flash photolysis (LFP) of 3-benzyl-3-chlorodiazirine, 1, in isooctane, produces benzylchlorocarbene which reacts with pyridine to form an ylide or undergoes 1,2-H migration to form the (Z)- and (E)-β-chlorostyrenes. The rate for the 1,2-H migration is determined by plotting the pseudo-first-order rate constants for the growth of the ylide vs [pyridine] and extrapolating to [pyridine] = 0. From such measurements, performed at various temperatures, the kinetic parameters Ei = 4.5 kcal/mol and Ai = 1011.1 s-1 are obtained, LFP of 1 in the absence of pyridine produces a transient absorption (280-330 nm) assigned to benzylchlorocarbene. Monitoring the carbene decay directly at 310 nm over the same temperature range gives similar values: Ei = 4.8 kcal/mol and Ai = 1011.3 s-1. Three independent methods-LFP, products ratios (Z/E and cyclopropane/chlorostyrenes) - yield a single value, (6.2 ±0.2) 108 M-1 s-1 for kt, the rate constant for the addition of benzylchlorocarbene to tetramethylethylene. These results are consistent with a mechanism involving the formation of a complex between benzylchlorocarbene and tetramethylethylene.
