The 13C-NMR spectra of some bicyclo[3.1.0]hex-3-en-2-ols and of some bicydo[3.1.0]hex-3-en-2-ones are described. The bond parameters of bicydo[3.1.0]hex-3-en-2-one are derived from a structure determination of endo-6-methoxy-1,3,6-tripbenylbicyclo[3.l.O~~ex-3-en-2-one. The electron density is calculated by the EHT method, and correlated with the "C NMR shifts. For comparison the "C NMR spectrum of a bicyclo[4.l.O]hepta-1,5-dione derivative is analysed. The influence of a cyclopropane system attached to a five-membered and to a six-membered ring is elucidated. Whereas the five-membered ring shows conjugation

The substituent parameters of methyl-, halogen-, methoxycarbonyl-and phenyl-substituted cyclopropenes as well as of cyclopropenone and diphenylcyclopropenone are determined from the =C chemical shifts. The Muence of the carbonyl group on the chemical shifts and charge densities is studied in the cyclopropenones. The interaction between the cyclopropene nucleus and the annulated benzene ring in benzocyclopropenes is evaluated with the aid of the "C NMR spectra of di-and tehphenyl-substituted benzocyclopropene derivatives and of dimethyl lH-cycloprope[a]naphthalene-1,l-diauboxylate. The J values are shown to be better indicators of structural changes than the S values. a-Effects of substituents give a good correlation with Hammett ul-values.Fur Methyl-, Halogen-, Ester-und Phenylsubstituierte Cyclopropene und fur Cyclopropenon und Diphenylcyclopropenon werden aus den 13C-chemischen Verschiebungen die Substituentenparameter bestimmt. Bei den Cyclopropenonen interessierte insbesonders der EinfluB der Carbonylgruppe auf die 6-Werte und

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The high-field 'H NMR spectra of 1,3-propanesultams (2), 2,4-butanesultams (3) and 2,4-dimethyl-1,3-butadienesultams (6) are reported. Comparison of 2, 3 and 6 with 1,3-propanesultone (1) and 2,4-dimethyl-1,3-butadienesultone (5) reveals that the paramagnetic shift induced by the NH group is smaller than that induced by oxygen. NMR spectra at lower temperatures show coupling effects with the NH proton. A half-chair conformation was deduced for 2,4-butanesultam from coupling constants and from a conformational analysis based on the R values, but a chair-chair interconversion could not be detected in the temperature range between 210 and 330K. An unambiguous assignment was carried out for the methyl signals in the spectrum of 5 by homodecoupling experiments.

A new approach to the silica gel surface : characterization of different surface regions by 29Si magic angle spinning NMR relaxation parameters and consequences for quantification of silica gels by NMR [Erratum to document cited in CA112(24):223903d].