Hydrogen bonds between acetylene and formic acid: An ab initio study

Abstract

Theoretical calculations using both the second‐order Møller–Plesset and B3LYP levels of calculation with the 6‐31++G(d,p) and 6‐311++G(3df,3pd) basis sets were performed to determine stable structures, binding energies, and molecular properties for the H‐bonded complexes involving acetylene and formic acid. Three complexes were characterized as minima because no imaginary frequency was found. The calculations indicate that the most stable complex presents two H‐bonds forming a quasi‐cyclic structure. As expected, the HO stretching frequency of the formic acid is shifted downward after complexation, whereas its IR intensity is enormously increased. Finally, we have also studied the R1C2HHOOCR2 H‐bonded complexes with R1 and R2CH3 and C6H5 to compare their binding energies with that obtained to the HCOOHC2H2 complex. In this procedure, we have considered the most stable structure obtained to this latter using the B3LYP theoretical calculations with the 6‐31++G(d,p) basis set. © 2012 Wiley Periodicals, Inc.