Theoretical Study on the Mechanism of the Addition Reaction between Cyclopropenylidene and Formaldehyde

Abstract

E-mail: lpsdu@sdu.edu.cnReceived December 22, 2011, Accepted March 14, 2012The reaction mechanism between cyclopropenylidene and formaldehyde has been systematically investigatedemploying the MP2/6-311+G* level of theory to better understand the cyclopropenylidene reactivity withcarbonyl compound. Geometry optimization, vibrational analysis, and energy property for the involvedstationary points on the potential energy surface have been calculated. Energies of all the species are furthercorrected by the CCSD(T)/6-311+G* single-point calculations. It was found that one important reactionintermediate (INTa) has been located firstly via a transition state (TSa). After that, the common intermediate(INTb) for the two pathways (1) and (2) has been formed via TSb. At last, two different products possessingthree- and four-membered ring characters have been obtained through two possible reaction pathways. In thereaction pathway (1), a three-membered ring alkyne compound has been obtained. As for the reaction pathway(2), it is the formation of the four-membered ring conjugated diene compound. The energy barrier of the rate-determining step of pathway (1) is lower than that of the pathway (2), and the ultima product of pathway (2) ismore stable than that of the pathway (1).Key Words : Cyclopropenylidene, Formaldehyde, Addition reaction, Theoretical studyIntroductionCarbene can be defined as divalent carbon intermediates,where the carbene carbon is linked to two adjacent groupsby covalent bonds and possesses two nonbonding electrons.It is well known that carbene plays an important role inorganic chemistry, especially for the addition reaction withC=C and C=O double bond.