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The insertion of singlet 1CH2 , 1CHF , and 1CF2 into polar N–H bonds of RNH2 ( R = –CH3, –C2H5, –C3H7 or –CH(CH3)2 ) has been investigated at HF, MP2, and DFT levels using 6-31g (d, p) basis set. The insertions proceed via a two-step mechanism. The potential energy surface exploration identifies an ylide formation followed by the 1,2-proton shift concertedly giving the secondary amine. The barrier height varies with the type of carbene and amine. HOMO of amines and LUMO of carbenes control the initial interactions and it is confirmed by NBO charge analysis.

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Abstract. The insertion reactions of singlet mono and dichlorocarbenes ( 1 CHCl and 1 CCl 2 ) into primary, secondary and tertiary C-H bonds of methane, ethane, propane, n-butane and iso-butane have been investigated at ab initio (MP2) and DFT levels invoking 6-31g(d, p) basis set. Among the σ and π insertions into the said alkane C-H, both MP2 and DFT predict that the σ approach is slightly favoured over the π approach. For inverted σ approach the barrier heights have been found to be ca. 2 to 5 times that of the normal σ approach.

Transition states for the insertion reactions of singlet mono and dichlorocarbenes ( 1 CHCl and 1 CCl 2 ) into C-H bonds of alkanes (methane, ethane, propane and n-butane) have been investigated at MP2 and DFT levels with 6-31g (d, p) basis set. The p π of 1 CHCl and 1 CCl 2 may interact with alkane's filled fragment orbital of either σ or π symmetry. So chlorocarbenes insertion reactions have been investigated for both (σ/π) approaches. The σ approach has been adjudicated to be the minimum energy path over the π approach both at the MP2 and DFT levels. Mulliken, NPA and ESP derived charge analyses have been carried out along the minimal energy reaction path using the IRC method for 1 CHCl and 1 CCl 2 insertions into the primary and secondary C-H bonds of propane. The occurrence of TSs either in the electrophilic or nucleophilic phase has been identified through NBO charge analyses in addition to the net charge flow from alkane to the carbene moiety.