Olivato, Paulo R.; Gomes, Roberto da Silva; Rodrigues, Alessandro; Reis, Adriana K. C. A.; Domingues, Nelson L. C.; Rittner, Roberto; Dal Colle, Maurizio published the artcile< Conformational preferences for some 2-substituted N-methoxy-N-methylacetamides through spectroscopic and theoretical studies>, Name: (9Z,12Z)-Methyl octadeca-9,12-dienoate, the main research area is conformer substituted methoxymethylacetamide stabilization IR DFT B3LYP NBO.
The anal. of the IR carbonyl band of the 2-substituted N-methoxy-N-methylacetamides Y-CH2C(O)N(OMe)Me (Y = F for compound 1, OMe for compound 2, OPh for compound 3, Cl for compound 4), supported by B3LYP/6-311++G(3df, 3pd) calculations along with the NBO anal. for compounds 1-4, indicated the existence of cis-gauche conformers i.e. (c) and (g) for 1 and 3, (c1, c2) and (g1, g2) for 2, and (c) and (g1, g2) for 4. In the gas phase, the g conformer population prevails over the c one, for 1 and 3, the (c1 + c2) population prevails over the (g1 + g2) one for 2, and the (g1 + g2) conformer population is more abundant than (c) one for 4. In n-hexane solution, the cis conformer is more abundant for 1-3. The occurrence of Fermi resonance in the ν CO region, in n-hexane, precludes the estimative of relative populations of the (c, g1, g2) conformers for 4. The SCI-PCM calculations agree with the solvent effect on the ν CO band component relative intensities for 1-3. NBO anal. showed that the nN → πCO* orbital interaction is the main factor which stabilizes the gauche (g, g1, g2) conformers for 1-4 into a larger extent relative to the cis (c, c1, c2) ones. The nY → πCO*, σC-Y → πCO*, πCO → σC-Y* and πCO* → σC-Y* orbital interactions still contribute, but into a minor extent for the stabilization of the gauche conformers relative to the cis ones. The existence of some pyramidalization at the nitrogen atom of the Weinreb amides 1-4 is responsible for the occurrence of Yδ-(4)···Oδ-(9) and Yδ-(4)···Nδ-(7) short contacts in the gauche (g, g1, g2) conformers, which originates strong repulsive Coulombic interactions, acting in opposition to the large orbital stabilization of the gauche conformer with respect to the cis one. Therefore, a delicate balance of the Coulombic and orbital interactions seems to be responsible for the observed stabilization of the gauche (g, g1, g2) and cis (c, c1, c2) conformers, both in the gas phase and in the solution for 1-4. However, the cis conformer predominance, in non polar solvents, for the 2-substituted N-methoxy-N-Me acetamides 1-3, bearing in α first raw (fluorine and oxygen) atoms, is in the opposite direction to the gauche conformer preference for the corresponding 2-substituted N,N-dialkyl-acetamides.
Journal of Molecular Structure published new progress about Bond angle, dihedral. 112-63-0 belongs to class esters-buliding-blocks, and the molecular formula is C19H34O2, Name: (9Z,12Z)-Methyl octadeca-9,12-dienoate.
Referemce:
Ester – Wikipedia,
Ester – an overview | ScienceDirect Topics