Dynamic control of dichlorocarbene addition to cyclopropene

Abstract

The addition of dichlorocarbene to cyclopropene has been studied with direct dynamics quasiclassical trajectories using B3LYP/6‐31G*. The trajectories yielded 1,1‐dichlorobicyclo[1.1.0]butane and 1,1‐dichloro‐1,3‐butadiene in a ratio of 4.7:1, which is consistent with the experimental ratio of 4:1. The large majority of trajectories formed products within 100 fs of the start of the trajectory and proceeded in a concerted manner to the bicyclobutane or butadiene; no zwitterion or biradical intermediate was observed. Eight trajectories generated bicyclobutane and subsequently dissociated chloride to form an ion pair, which recombined to form 2,3‐dichlorocyclobutene. The lifetime of the ion pair averaged 95 fs, which was too short to be considered an intermediate, consistent with previous calculations that characterized the ion pair as a transition state. This study lends strong support to the previous proposition that the addition of CCl2 to cyclopropene is controlled by dynamic effects. Copyright © 2011 John Wiley & Sons, Ltd.

The Study of Reactive Intermediates in Condensed Phases

“…Even when the branching of reaction paths does occur at a local PES minimum, classical molecular dynamics (MD) simulations have shown that one cannot rely on the validity of the statistical approximation for gas-phase reactions. 15,16,[18][19][20][21][22][23][24][25][26][27][28][29][30][31][32][33][34][35][36] The Figure 1. Schematic depiction of a PES with a bifurcating reaction path.…”

Dichlorocarbene modified butadiene rubber (DCBR): Preparation, kinetic study, and its properties in natural rubber/DCBR blend vulcanizates

“…The effects of the reaction temperature and time, amount of dichlorocarbene precursor, and the type and amount of phase transfer agent on the chlorine content were investigated. The highest chlorine content (30%) in DCBR was obtained using 0.062 mol chloroform and 0.003 mol cetyltrimethylammonium bromide at room temperature for 19 hours although 27.9% was obtained after 12 hours. The kinetics of this dichlorocarbene modification was best described by the pseudo-first order rate law with 2 rate constants.…”

“…Dichlorocarbene modification [16][17][18][19][20][21][22][23][24][25][26][27][28] consists of carbene addition and halogenation and has been used to modify several types of polymer, including styrene butadiene rubber, [17][18][19] natural rubber (NR), [20][21][22][23][24][25] olefin, 16,26,27 and butadiene rubber (BR). [28][29][30][31] Among these rubbers, BR is an important synthetic rubber being the second largest, by volume, synthetic rubber produced in the world after styrene butadiene rubber.…”

Reaction mechanisms: pericyclic reactions

“…Quasiclassical trajectory calculations for the addition of CCl 2 to cyclopropene were also reported and revealed important dynamics effects (Scheme 1). 9 The CCl 2 trajectories for cyclopropene indicated a concerted reaction due the short time required (100 fs). The products from cyclopropene included 1,1-dichlorobicyclo[1.1.0]butane and 1,1-dichloro-1,3-butadiene compounds.…”