Strengthening of the intramolecular hydrogen bond in 7-ethylsalicylidene aniline due to steric repulsion

摘要

In a newly synthesized orthohydroxy Schiff base, 7-ethylsalicylidene aniline (ESA), the hydrogen atom in C-C(H)=N group is replaced by an ethyl group. The crystal structures of ESA determined by X-ray crystallography and ab initio calculations at the level of B3L YP/6-31G~* are performed. The results obtained indicate that the steric effects lead to the strengthening of intramolecular hydrogen bond (O-H…N) of ESA. We have compared the results of ESA with the results of another two previously studied Schiff bases, 2-(N-methyl-α-iminoethyl)-phenol (II). We have also constructed the potential energy surfaces on which the proton is supposed to move and analyzed the reaction path.