Molecular Orbital Study of Torsional Potentials, Physicochemical Properties and Electronic Spectra of Methyl Acrylate in Different Electronic States
Year: 2001
Type: article
Abstract: A systematic study of the possible conformations of methyl acrylate and their stabilities in the ground (So) and first excited (S 1 ) electronic states has been undertaken using ab initio and MNDO(AM1) molecular orbital techniques by plotting potential energy curves. Methyl acrylate was considered as a three rotor system having internal rotation about C-C and C-O single bonds with the possibility of hindered rotation of the methyl group. Four stable conformers Cc, Tc, Ct and Tt have been identified in the So state in increasing order of energy with methyl group having staggered conformation with respect to carbonyl group in each case. The enthalpy difference between the two most stable conformers Cc and Tc in the S 0 state is 0.425 kcal/mol, well within the experimental range 0.43 ′ 0.20 kcal/mol, and reduces to 0.325 kcal/mol in the S 1 state. Unlike acrolein and other conjugated compounds, the conformations remain unchanged on nπ * excitation. Geometries of the stable conformers in the two states have been optimized using 4-31 G extended basis set. The barrier to internal rotation about the C-O bond in So state is larger than that about the C-C bond and further increases in the S 1 state. Complete Mulliken population analysis has been carried out in the two electronic states to identify the possible resonance structures in the S 1 state. A theoretical assignment has been provided in CNDO/2 approximation to the electronic transitions in Cc and Tc conformers and compared with experimental results.
Authors: Virdi, Ajit, Sharma, Archna, Gupta, V P
Language: English
Subfield: Atomic and Molecular Physics, and Optics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: green
OpenAlex ID: W2513372002