| Full text | |
| Author(s): |
Andrade, Laize A. F.
[1]
;
Silla, Josue M.
[1]
;
Duarte, Claudimar J.
[2]
;
Rittner, Roberto
[2]
;
Freitas, Matheus P.
[1]
Total Authors: 5
|
| Affiliation: | [1] Univ Fed Lavras, Dept Chem, Lavras - Brazil
[2] Univ Estadual Campinas, Inst Chem, BR-13083970 Campinas, SP - Brazil
Total Affiliations: 2
|
| Document type: | Journal article |
| Source: | ORGANIC & BIOMOLECULAR CHEMISTRY; v. 11, n. 39, p. 6766-6771, OCT 21 2013. |
| Web of Science Citations: | 18 |
| Abstract | |
A competition between the terminal fluorine and hydroxyl groups by the central hydroxyl group as hydrogen bond donor in 3-fluoro-1,2-propanediol would be expected to dictate the conformational isomerism of this compound, but also the repulsion between the electronegative and bulky vicinal substituents. Indeed, an intramolecular hydrogen bond has been verified only for a local minimum using QTAIM calculations, while the most stable conformer exhibits an all-gauche conformation with a small stabilizing contribution from the n(F)->sigma(star)(OH) interaction. The preferred orientation of the OH and F substituents was confirmed from the chemical shifts and coupling constants of the diastereotopic hydrogens. This conformational preference, which is calculated to exist both in the gas phase and solution (using implicit CHCl3 and CH3CN solvents), is better described by predominant hyperconjugative interactions over Lewis-type interactions. The strong contribution from antiperiplanar interactions involving sigma(CH) and sigma(CC) as electron donors and sigma(star)(CF) and sigma CO star as electron acceptors dictates the gauche effect in 3-fluoro-1,2-propanediol rather than a hydrogen bond. The absence of J(F,H(O)) and J(H(O)),(H(O)) coupling constants confirms that any influence from a hydrogen bond to the conformational isomerism of 3-fluoro1,2-propanediol is secondary. (AU) | |