ASM 2019

Poster (P7)


Metal-free Nitrene insertion into C-H bond: A DFT calculation

Shougaijam Premila Devi and Rita Kakkar*

Computational Chemistry Group, Department of Chemistry, University of Delhi-110007

 

Nitrene insertion to C-H bonds forming amines, amides and related products is one of the important nitrene reactions. This C-H bond functionalization may proceed without or with a metal catalyst. The DFT method B3LYP/6-31G(d, p) and B3LYP/6-311G(d, p) were used to calculate the singlet and triplet nitrene addition reaction to different types of C-H bonds. Three nitrenes RN (R = H, Me, Ac) are reacted with alkane substrates forming amine products. The B3LYP/6-311G(d,p) method of calculation gives lower energy than the B3LYP/6-31G(d, p) method and MeN does not exist in B3LYP/6-311G(d, p) method. The concerted addition of singlet nitrene to C-H bond is exothermic with an appreciable barrier, where the facility order H > Ac > Me points to electrophilicity of the nitrene reactant. In the case of triplet nitrene, abstracts a proton from the alkane and followed by rapid coupling of anilio radical with alkyl radical forming N-alkylaniline. The initial step of triplet nitrene addition to C-H bond involves smaller barriers with endothermic due to the formation of radicals as intermediate product and the final step is coupling of radicals so it is exothermic. Geometries of the transition states for various reaction steps studied here are described as early or late in good accordance with the Hammond postulate.

 

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