Conformational analysis by nuclear magnetic resonance—VI

Feltkamp, Herbert; Franklin, Norman C.

doi:10.1016/s0040-4020(01)98318-8

Cited by 33 publications

(4 citation statements)

References 15 publications

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“…A similar chair ratio was determined by Feltkamp and Franklin [52] who investigated the solution conformations of the menthol isomers. Based on NMR coupling constants analysed as sum (bandwidth), they determined a 71:29 (OHax:OHeq) ratio for neoisomenthol.…”

Section: Table 4asupporting

confidence: 70%

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Stereochemical analysis of menthol and menthylamine isomers using calculated and experimental optical rotation data

Reinscheid

2016

Journal of Molecular Structure

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a b s t r a c tThe complete series of menthol isomers and their corresponding amino derivatives (base and protonated/HCl forms), were investigated using experimental and theoretical data. Our study focused on the conformational and configurational analysis, and revealed that experimental data should be used in combination with calculated data. Furthermore, even in the case of the highly studied member, menthol, discrepancies were found among previously published literature values. We show that the correct determination of the population mix is a must for the correct prediction of the absolute configuration (AC) of neoisomenthol. The neoiso forms are of special interest since a number of structural inconsistences can be found in the literature. We present a stringent proof of the AC of neoisomenthol based on literature information. To the best of our knowledge, the AC of neoisomenthylamine is for the first time shown using experimental and calculated optical rotation data. A correction of a series of publications containing an important error in the assignment of (þ)-menthylamine (correct: (þ)-neomenthylamine) is presented. With 26 data pairs (experimental versus calculated) of optical rotation values a regression is performed. The AC of all 12 compounds, even the most difficult neoiso forms, could be predicted correctly using experimental low-temperature NMR data. Furthermore, if only experimental data with an optical rotation outside the range of À10 < [a] > þ10 are used, all 12 compounds would have been correctly assigned without lowtemperature NMR data as restraints.

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Section: Table 4asupporting

confidence: 70%

“…To conclude, the energy calculations of Feltkamp and Franklin [52] and Senda et al [38] erroneously indicated that the equatorial OH chair dominates for neoisomenthol. Based on DFT energies, the axial OH chair dominates (87:13, OHax:OHeq) but this has to be corrected to 67:33 using low-temperature NMR 13 C data [16].…”

Section: Table 4amentioning

confidence: 98%

Stereochemical analysis of menthol and menthylamine isomers using calculated and experimental optical rotation data

Reinscheid

2016

Journal of Molecular Structure

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“…100% and that of 21 ca. 70% population of the conformer with equatorial hydroxyl at 25" (36). Since cyclohexyl nitrate is 73% equatorial (37) and cyclohexanol 65% equatorial (38) For personal use only.…”

Section: Alk~~ibic~cloj221ii7~~~~t~~i Nitrcitc~ (12-18)mentioning

confidence: 99%

Circular Dichroism of Nitrate Esters: A Planar Symmetry Rule for the Nitrato Chromophore

Barton¹,

Hayward²

1972

Can. J. Chem.

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Conformational analysis of nitrate esters based on X-ray and spectroscopic data showed the nitrato group to be coplanar with the a carbon atom and, in the preferred rotamer, the nitro moiety to be antiperiplanar to the /I carbon atom. Three optically active absorption bands not apparent in the isotropicelectronic spectra were resolved in the circular dichroism spectra. Band I (270 nm) reflected nitrato group libration changing sign and magnitude with changes in temperature and solvent polarity. Differences in rotatory strength of band 111 (210 nm) for cis-and trans-dinitrates indicated transition moment coupling. A planar symmetry rule for chromophores in the C, point group correlated the molecular geometry and sign of band I1 for 42 nitrate esters: when the lowest-energy rotamer of the nitrate ester is viewed down the 0-C bond with the nitro group uppermost rotatory contributions to band I1 (230 nm) are positive for perturbing atoms to the right and negative for those to the left of the nitrato symmetry plane.L'analyse conformationnelle des esters nitriques, baste sur les donntes de la spectroscopie et des rayons-)<, montre que le groupe nitrate est coplanaire avec I'atome de carbone en a et que, dans le rotamere priviltgit, le fragment nitro est antiptriplanaire a I'atome de carbone en /I. Trois bandes d'absorption optiquement actives, non apparentes sur le spectre tlectronique isotrope, ont t t t rtsolues dans le spectre de dichroisme circulaire. La bande I (270 nm) reflete la vibration du groupe nitro et change de signe et d'amplitude lorsque la temptrature et la polaritt du solvant changent. Les differences dans le pouvoir rotatoire de la bande I11 (2i0 nm) pour les dinitrates ci.s et trat1.s indiquent un couplage du moment de transition. Une rtgle de symttrie plane pour les chromophores du groupe C, relie la gtomttrie moltculaire au signe de la bande 11 pour 42 esters nitriques: lorsque le rotamtre de plus basse energie de I'ester nitrique est regard6 le long de la liaison 0-C avec le groupe nitro, les contributions rotatoires decisives pour la bande I1 (230 nm) sont positives lorsque les atomes sont situes a droite du plan de symttrie du nitrate et negatives lorsqu'ils sont a gauche.

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“…I1 est voisin de 2 Hz. J,,, l'est donc de 4 Hz, valeur proche du J,, du carqubjanol, ce qui contraste avec les observations rapportCes au sujet de substances analogues [16].…”

Section: Contribution a La Connaissance Des O-menthols Et Des O-menthunclassified

Contribution à la connaissance des o‐menthols et des o‐menthones (carquéjanols et carquéjanones). 3^e communication

Ferretti-Alloise

Jacot‐Guillarmod

Naves

1970

Helvetica Chimica Acta

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Conformational analysis by nuclear magnetic resonance—VI

Cited by 33 publications

References 15 publications

Stereochemical analysis of menthol and menthylamine isomers using calculated and experimental optical rotation data

Stereochemical analysis of menthol and menthylamine isomers using calculated and experimental optical rotation data

Circular Dichroism of Nitrate Esters: A Planar Symmetry Rule for the Nitrato Chromophore

Contribution à la connaissance des o‐menthols et des o‐menthones (carquéjanols et carquéjanones). 3^e communication

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Conformational analysis by nuclear magnetic resonance—VI

Cited by 33 publications

References 15 publications

Stereochemical analysis of menthol and menthylamine isomers using calculated and experimental optical rotation data

Stereochemical analysis of menthol and menthylamine isomers using calculated and experimental optical rotation data

Circular Dichroism of Nitrate Esters: A Planar Symmetry Rule for the Nitrato Chromophore

Contribution à la connaissance des o‐menthols et des o‐menthones (carquéjanols et carquéjanones). 3e communication

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Contribution à la connaissance des o‐menthols et des o‐menthones (carquéjanols et carquéjanones). 3^e communication