### Abstract

Ab initio Hartree-Fock and Density Functional Theory calculations were used to obtain the geometries and relative energies of the rotamers in the chair conformations of 2-alkyltetrahydro-2H-pyrans and 2- (trimethylsilyl)tetrahydro-2H-pyran. The MP2/6-31G*//6-31G* conformational energies (-ΔG°or A values, kcal/mol) of the 2-alkyltetrahydro-2H-pyrans (Me = 3.18; Et = 3.04; i-Pr = 3.03; t-Bu = 7.56; neo Pent = 2.84) and 2- (trimethylsilyl)tetrahydro-2H-pyran (SiMe_{3} = 4.77) are larger than those calculated for the corresponding alkylcyclohexanes and 2-alkyltetrahydro-2H- thiopyrans (tetrahydrothiopyrans, thiacyclohexanes, thianes). Plots of the calculated conformational energies for the 2-substituted tetrahydro-2H-pyrans versus the calculated -ΔG°values for the corresponding alkylcyclohexanes (slope = 1.34 and r = 0.983) and for the corresponding 2-substituted tetrahydro-2H-thiopyrans (slope = 2.01 and r = 0.986) are linear. (C) 2000 Elsevier Science B.V.

Original language | English |
---|---|

Pages (from-to) | 19-39 |

Number of pages | 21 |

Journal | Journal of Molecular Structure: THEOCHEM |

Volume | 496 |

Issue number | 1-3 |

DOIs | |

State | Published - 7 Jan 2000 |

### Fingerprint

### Keywords

- Conformational energies
- Hyperconjugative orbital interactions
- Oxacyclohexanes
- Rotamers
- Stereoelectronic effects

### Cite this

*Journal of Molecular Structure: THEOCHEM*,

*496*(1-3), 19-39. https://doi.org/10.1016/S0166-1280(98)00517-X

}

*Journal of Molecular Structure: THEOCHEM*, vol. 496, no. 1-3, pp. 19-39. https://doi.org/10.1016/S0166-1280(98)00517-X

**An ab initio molecular orbital study of the conformational energies of 2-alkyltetrahydro-2H-pyrans (tetrahydropyrans, oxacyclohexanes, oxanes).** / Freeman, F.; Kasner, J. A.; Kasner, Marc; Hehre, W. J.

Research output: Contribution to journal › Article › Research › peer-review

TY - JOUR

T1 - An ab initio molecular orbital study of the conformational energies of 2-alkyltetrahydro-2H-pyrans (tetrahydropyrans, oxacyclohexanes, oxanes)

AU - Freeman, F.

AU - Kasner, J. A.

AU - Kasner, Marc

AU - Hehre, W. J.

PY - 2000/1/7

Y1 - 2000/1/7

N2 - Ab initio Hartree-Fock and Density Functional Theory calculations were used to obtain the geometries and relative energies of the rotamers in the chair conformations of 2-alkyltetrahydro-2H-pyrans and 2- (trimethylsilyl)tetrahydro-2H-pyran. The MP2/6-31G*//6-31G* conformational energies (-ΔG°or A values, kcal/mol) of the 2-alkyltetrahydro-2H-pyrans (Me = 3.18; Et = 3.04; i-Pr = 3.03; t-Bu = 7.56; neo Pent = 2.84) and 2- (trimethylsilyl)tetrahydro-2H-pyran (SiMe3 = 4.77) are larger than those calculated for the corresponding alkylcyclohexanes and 2-alkyltetrahydro-2H- thiopyrans (tetrahydrothiopyrans, thiacyclohexanes, thianes). Plots of the calculated conformational energies for the 2-substituted tetrahydro-2H-pyrans versus the calculated -ΔG°values for the corresponding alkylcyclohexanes (slope = 1.34 and r = 0.983) and for the corresponding 2-substituted tetrahydro-2H-thiopyrans (slope = 2.01 and r = 0.986) are linear. (C) 2000 Elsevier Science B.V.

AB - Ab initio Hartree-Fock and Density Functional Theory calculations were used to obtain the geometries and relative energies of the rotamers in the chair conformations of 2-alkyltetrahydro-2H-pyrans and 2- (trimethylsilyl)tetrahydro-2H-pyran. The MP2/6-31G*//6-31G* conformational energies (-ΔG°or A values, kcal/mol) of the 2-alkyltetrahydro-2H-pyrans (Me = 3.18; Et = 3.04; i-Pr = 3.03; t-Bu = 7.56; neo Pent = 2.84) and 2- (trimethylsilyl)tetrahydro-2H-pyran (SiMe3 = 4.77) are larger than those calculated for the corresponding alkylcyclohexanes and 2-alkyltetrahydro-2H- thiopyrans (tetrahydrothiopyrans, thiacyclohexanes, thianes). Plots of the calculated conformational energies for the 2-substituted tetrahydro-2H-pyrans versus the calculated -ΔG°values for the corresponding alkylcyclohexanes (slope = 1.34 and r = 0.983) and for the corresponding 2-substituted tetrahydro-2H-thiopyrans (slope = 2.01 and r = 0.986) are linear. (C) 2000 Elsevier Science B.V.

KW - Conformational energies

KW - Hyperconjugative orbital interactions

KW - Oxacyclohexanes

KW - Rotamers

KW - Stereoelectronic effects

UR - http://www.scopus.com/inward/record.url?scp=0034614323&partnerID=8YFLogxK

U2 - 10.1016/S0166-1280(98)00517-X

DO - 10.1016/S0166-1280(98)00517-X

M3 - Article

VL - 496

SP - 19

EP - 39

JO - Journal of Molecular Structure: THEOCHEM

JF - Journal of Molecular Structure: THEOCHEM

SN - 0166-1280

IS - 1-3

ER -