Quantum chemical studies on the potentially important imidates

The conformational space for the imidates 1-5 was explored with the Monte Carlo conformational search varying all the torsional degrees of freedom. Geometry optimization of the most stable conformers of imidates 1-5 were performed at the level B3LYP/6-31+G(d). Computed geometrical parameters were compared with the X-ray reported results. Hydrogen bonding, both intra- and intermolecular with methanol as solvent were computed at different computational levels in gas phase and DMSO. Intramolecular hydrogen bond strength does not exceed the limit of 8.50 kcal/mol due to geometry restrictions while, on the other hand, intermolecular hydrogen bond strength approaches 30.00 kcal/mol. Transition states of the inter-conversion between the most stable conformers (rotamers) were located and activation barrier of the inter-conversion processes was computed at different levels in gas phase and DMSO. Infrared spectra of these compounds were simulated and compared with experimental results. The carbonyl of the ester group shows bond stretching vibrational frequency at 1706-1812 cm−1 which agrees well with the experimentally recorded values at 1708-1740 cm−1.