A computational study of the steric strain of –N=O groups in saturated nitrosamines

One of the most intensely studied features in the chemistry of nitrosamines is the restricted rotation around the N-N bond and, consequently, the estimation of the energy strain (Estr) determined by the NO group. This is rationalized in terms of the interaction between the electron lone-pairs of the amine nitrogen and the 𝜋 electrons of the –N=O group (nN-πNO* conjugation). Combining the results of DFT calculations on 43 nitrosamines (11 acyclic, 20 mono- and bicyclic and 12 tricyclic) with a multiple linear regression analysis, the paper affords a number of additive increments, which, by appropriate summation, are able to predict with a good accuracy the total energy of the nitroso compound (E) and the energy strain (Estr) values of the –N=O group for any acyclic or cyclic saturated nitrosamines.