Steric Effects Vs. Electron Delocalization
RSC Advances PAPER View Article Online View Journal | View Issue Steric effects vs. electron delocalization: a new look into the stability of diastereomers, conformers Cite this: RSC Adv.,2021,11, 20691 and constitutional isomers† Sopanant Datta and Taweetham Limpanuparb * A quantum chemical investigation of the stability of compounds with identical formulas was carried out on 23 classes of compounds made of C, N, P, O and S atoms as core structures and halogens H, F, Cl, Br and I as Received 13th April 2021 substituents. All possible structures were generated and investigated by quantum mechanical methods. The Accepted 24th May 2021 prevalence of a formula in which its Z configuration, gauche conformation or meta isomer is the most stable DOI: 10.1039/d1ra02877d form is calculated and discussed. Quantitative and qualitative models to explain the stability of the 23 classes rsc.li/rsc-advances of halogenated compounds were also proposed. hyperconjugation in a similar vein to the ethane case,17,18 but Creative Commons Attribution-NonCommercial 3.0 Unported Licence. 1. Introduction the reasoning underlying the preference for meta isomer is still Steric effects, non-bonded interactions leading to avoidance of lacking. spatial congestion of atoms or groups, are oen the central In addition to carbon-backbone compounds in Table 1, there theme in the discussion of stability of diastereomers, are many experimental and theoretical studies for other back- 21 ] 22,23 ] 24 conformers and constitutional isomers. Reasoning based on bones discussed in this paper, namely, C3, C N, C P, 25–31 32 33,34 35 36,37 38–40 41 steric effects is relatively intuitive and gives rise to a generally N]N, N]P, P]P, C–N, C–P, C–O, C–S, N– 38,42–44 38,43 38,43,45,46 38,42,47 47 48,49 50 accepted rule of thumb that an E conguration, anti conformer N, N–P, P–P, N–O, N–S, P–O, P–S, O– 38,42,51,52 53,54 38,55 and para isomer in diastereomers, conformational and consti- O, O–S, and S–S.
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