<p>Several
allylic azides with different double bond substitution were studied to
understand the factors governing their equilibrium using density functional
theory along with quantum theory of atoms in molecules, Non-covalent Interactions
and Natural Bond Orbitals approaches. The results showed the hydroxyl group or
heteroatoms in allylic azides interact with the molecule through an
electrostatic weak interaction in each pair of regioisomers. The equilibrium
shifts of substituted allylic azides, compared to non-substituted allylic
azides, are not attributed to the presence of specific interactions, such as
hydrogen bond. The observed equilibrium shifts stem mainly from the strengthening
and weakening of negative
hyperconjugative interactions, which is affected by the weak interaction
involving the proximal substituent in each regioisomer. A good linear correlation
was obtained between the hyperconjugative energies of pC=C→s*<i>Z</i><sub>b</sub> interactions and the calculated percentages of
secondary azide and tertiary azides in the equilibrium mixture. Also, the
effect of aromatic ring substituent was analysed using such approaches. This
study not only provides insight into the factor controlling the stabilities of
the substituted allylic azides, but also settle the basis to predict the regioisomer predominance in
the equilibrium mixture.</p>