Nuclear magnetic resonance spectral parameters in bicyclo[3.1.1]heptanes. .alpha.-Pinene, myrtenal, and verbenone

The PMR spcctra of twelve pinene derivatives are reported, analysed and assigned. The proton couplings in the bridged cyclobutane group are compared with those of other strained cyclobutanes, and the relationship between 2 J~f~ and the C.CH,.C angle is shown to be anomalous in these systems, suggesting unusually small H.C.H. angles in cyclobutanes.The very large values of 4 J~~( e q -e q ) in buckled cyclobutanes are interpreted in terms of current M.O. theory and also given a simple geometric rationalisation based on the direct mechanism.The various couplings in the pinene skeleton are discussed in terms of present theories and minor conformational effects in these molecules. Substituent chemical shift (SCS) values for Me and OH groups around the pinene skeleton are obtained, and shown not to agree with calculations based on present theories of chemical shifts.

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“…J45 is also ca. 3.0 Hz in 2 to 4 and 10, and as in the case of JM, does not seem greatly influenced by OH substitution at C,.…”

Section: C1c2c3c4c5 Fragmentmentioning

confidence: 58%

The NMR spectra and conformations of cyclic compoundsV: Proton couplings and chemical shifts in bridged cyclobutanes

et al. 1972

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“…These pinane derivatives may be readily identified by the characteristic chemical shifts of the gem-dimethyl groups in the p.m.r. spectra (14). It is possible that they may be detected in other oils containing smaller amounts of the pinanes by employing g.1.c.…”

Section: Resultsmentioning

confidence: 99%

Gas–liquid chromatography of terpenes. Part XVIII. The volatile oil of the leaves of Juniperus communis L.

Rudloff¹,

Sood²

1969

Can. J. Chem.

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“…This is due to the width of the lines in this spectrum, which are all 0.5 Hz at half height, because of small, unresolved splittings.1° For example, both the 8 and 9 methyl peaks are ca. [1][2][3][4][5] Hz wide at half height. At this phenomenon is a general one in the pinane spectra it should be emphasised that the coupling constants obtained are significant only to this accuracy (f0.3 Hz).…”

Section: R E S U L T S and Discussionmentioning

confidence: 99%

The NMR spectra and conformations of cyclic compounds–III: The conformations of some pinane derivatives

et al. 1969

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The 220 MHz 'H spectra of isoverbanone, nopinone and verbanone are reported. The spectra of the first two are completely assigned but that of verbanone only partially. The coupling constants obtained provide information about the conformation of these molecules. The isoverbanone molecule is almost Y shaped, but that of nopinone is between a Y shape anda half-chair conformation with the six membered ring bent away from the gem dimethyl groups. These conformations are consistent with the known steric interactions in these molecules.

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Nuclear magnetic resonance spectral parameters in bicyclo[3.1.1]heptanes. .alpha.-Pinene, myrtenal, and verbenone

Cited by 30 publications

References 0 publications

The NMR spectra and conformations of cyclic compoundsV: Proton couplings and chemical shifts in bridged cyclobutanes

The NMR spectra and conformations of cyclic compoundsV: Proton couplings and chemical shifts in bridged cyclobutanes

Gas–liquid chromatography of terpenes. Part XVIII. The volatile oil of the leaves of Juniperus communis L.

The NMR spectra and conformations of cyclic compounds–III: The conformations of some pinane derivatives

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