Pyramidal Inversion and Configuration at Nitrogen

The best experimental estimate of the inversion barrier in aziridine itself is 19.5 kcal mol-1 after correction for zero-point energy differences and tunneling 75JA6990 . Caution must be used when considering the inversion barrier in A-unsubstituted aziridines, since a net inversion may occur by a protonation-deprotonation mechanism promoted by adventitious water, thus lowering the apparent 

The barrier to pyramidal inversion in 1 A-azirine (3) has been calculated to be 33-46 kcal mol-1, reflecting the unfavorability of the planar transition state, which is proposed to be antiaromatic (Section 1.01.2). 

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