Abstract
The gauche conformer in 1-X,2-Y-disubstituted ethanes, that is, the staggered orientation in which X and Y are in closer contact, is only favored for relatively small substituents that do not give rise to large X···Y steric repulsion. For more diffuse substituents, weakly attractive orbital interactions between antiperiplanar bonds (i.e., hyperconjugation) cannot overrule the repulsive forces between X and Y. Our quantum chemical analyses of the rotational isomerism of XCH2CH2Y (X = F, OH; Y = I) at ZORA-BP86-D3(BJ)/QZ4P reveal that indeed the anti conformer is generally favored due to a less destabilizing I···F and I···O-H steric repulsion. The only case when the gauche conformer is preferred is when the hydroxyl hydrogen is oriented toward the iodine atom in the 2-iodoethanol. This is because of the significantly stabilizing covalent component of the I···H-O intramolecular hydrogen bond. Therefore, we show that strong intramolecular interactions can overcome the steric repulsion between bulky substituents in 1,2-disubstituted ethanes and cause the gauche effect. Our quantum chemical computations have guided nuclear magnetic resonance experiments that confirm the increase in the gauche population as X goes from F to OH.
| Original language | English |
|---|---|
| Pages (from-to) | 11625-11633 |
| Number of pages | 9 |
| Journal | Journal of Organic Chemistry |
| Volume | 87 |
| Issue number | 17 |
| Early online date | 19 Aug 2022 |
| DOIs | |
| Publication status | Published - 2 Sept 2022 |
Bibliographical note
Funding Information:The authors are thankful to Coordenação de Aperfeiçoamento de Pessoal de Nível Superior─CAPES (funding code: 001), Conselho Nacional de Desenvolvimento Científico e Tecnológico─CNPq (grant number: 306830/2021-3), Fundação de Amparo à Pesquisa do Estado de Minas Gerais─FAPEMIG (grant number: APQ-00383/15), and the Netherlands Organization for Scientific Research (NWO) for the financial support of this research as well as to the Central de Análise e Prospecção Química─CAPQ and Finep for the technical support and spectroscopic facilities. This work was carried out on the Dutch national e-infrastructure with the support of SURF Cooperative.
Funding Information:
The authors are thankful to Coordenação de Aperfeiçoamento de Pessoal de Nível Superior─CAPES (funding code: 001), Conselho Nacional de Desenvolvimento Científico e Tecnológico─CNPq (grant number: 306830/2021-3), Fundação de Amparo à Pesquisa do Estado de Minas Gerais─FAPEMIG (grant number: APQ-00383/15), and the Netherlands Organization for Scientific Research (NWO) for the financial support of this research, as well as to the Central de Análise e Prospecção Química─CAPQ and Finep for the technical support and spectroscopic facilities. This work was carried out on the Dutch national e-infrastructure with the support of SURF Cooperative.
Publisher Copyright:
© 2022 American Chemical Society.
Funding
The authors are thankful to Coordenação de Aperfeiçoamento de Pessoal de Nível Superior─CAPES (funding code: 001), Conselho Nacional de Desenvolvimento Científico e Tecnológico─CNPq (grant number: 306830/2021-3), Fundação de Amparo à Pesquisa do Estado de Minas Gerais─FAPEMIG (grant number: APQ-00383/15), and the Netherlands Organization for Scientific Research (NWO) for the financial support of this research as well as to the Central de Análise e Prospecção Química─CAPQ and Finep for the technical support and spectroscopic facilities. This work was carried out on the Dutch national e-infrastructure with the support of SURF Cooperative. The authors are thankful to Coordenação de Aperfeiçoamento de Pessoal de Nível Superior─CAPES (funding code: 001), Conselho Nacional de Desenvolvimento Científico e Tecnológico─CNPq (grant number: 306830/2021-3), Fundação de Amparo à Pesquisa do Estado de Minas Gerais─FAPEMIG (grant number: APQ-00383/15), and the Netherlands Organization for Scientific Research (NWO) for the financial support of this research, as well as to the Central de Análise e Prospecção Química─CAPQ and Finep for the technical support and spectroscopic facilities. This work was carried out on the Dutch national e-infrastructure with the support of SURF Cooperative.