First Principle Study of the Anti– and Syn–Conformers of Thiophene–2–Carbonyl Fluoride and Selenophene–2–Carbonyl Fluoride in the Gas and Solution Phases

Abstract

The anti-and syn-conformers of thiophene-2-carbonyl fluoride (A) and selenophene-2-carbonyl fluoride (B) have been studied in the gas phase. The transition states have also been obtained for the interconversion of the antiand syn-conformers. The methods used are MP2 and DFT/B3LYP and the basis sets used for all atoms are 6-311++G(d,p). The optimized geometries, dipole moments, moment of inertia, energies, energy differences and rotational barriers are reported. This study has been extended to include solvent effect. Some of the vibrational frequencies of the conformers are reported with appropriate assignments. The results indicate that in the gas phase the syn conformer is more stable and the CCSD(T)//MP2 energy differences are 2.97 kJ/mol (A) and 3.02 kJ/mol (B) and barriers of rotation are 38.50 kJ/mol (A) and 36.89 kJ/mol (B). The structures and vibrational frequencies of (A) and (B) are not much affected by the solvents but the more polar conformer gets more stabilized. The major effect of the solvents is that energy difference decreases but rotational barrier increases. The peculiar characteristic of fluorine affecting conformational preference is not observed.

Conformers of diheteroaryl ketones and thioketones: a quantum chemical study of their properties and fundamental intramolecular energetic effects

“…The comparison of the difference in relative energy at the highest and lowest energy points on the PESs for 4a with the energy barrier calculated previously for 2-pyrrolyl aldehyde [56,57] shows that the former is approximately twice as large as the latter. Similarly, the energy barrier for 2a demonstrates a higher value when it is collated with the values of energy barriers calculated for 2-thiophenyl aldehyde [58] and thiophene-2-carbonyl fluoride [59]. In principle, the magnitude of maximal relative energies for 2a and 2b is different from that for 4a and 4b.…”

Rotational barrier, energy difference and thermodynamic parameters of 2-furoylfluoride, its sulfur and selenium analogues in the gas and solution phases: A theoretical study

“…In view of the above and in continuation with our work [13,[20][21][22], the present theoretical study targets the syn-OY and anti-OY rotamers of 2-furoylfluoride (Y@O), its sulfur (Y@S) and selenium (Y@Se) analogues (Fig. 1).…”

“…They related the energy difference between the rotamers and internal barrier of rotation with computed Mulliken charges on the different atoms. More recently, we explored the parent molecules of the title compounds namely 2-thiophenecarboaldehyde [20] and 2-selenophenecarboaldehyde [21] and isomeric compounds namely thiophene-2-carbonyl fluoride and selenophene-2-carbonyl fluoride [22].…”