Norman H. Cromwell

Nuclear magnetic resonance spectra of derivatives of various substituted indanones and tetralones

Abstract The proton NMR spectra of a series of 2-benzal-, 2-benzyl-, and 2-benzyl-2-bromo-indanones and a series of substituted 4,4-dimethyltetralones have been determined. The cis and trans isomers of 2-benzalindanones are easily identified through analysis of their PMR spectra. Peculiarities in the complex spectra of 2-benzyl and 2-benzyl-2-bromoindanones and tetralones are partially accounted for on the basis of conformational preference about the carbon-carbon bond attaching the 2-benzyl moiety to the 2-position of the indanone and tetralone rings. An internal complexation between the benzyl phenyl and the carbonyl group may be involved in some of these structures. The 4,4-dimethyltetralones exhibited two methyl resonances as a result of substitution in the 2-position and the stereo-structures are discussed in terms of conformational analysis.

Correlation of molecular mechanics with NMR spectroscopy: molecular geometry of nitrogen heterocycles

In highly mobile molecules, e.g. five-membered rings, the assignment of vicinal coupling constants is difficult due to the similarity of all 3J values. A way of verifying assignments using MM2 calculations is reported. As MM2 calculations deal with the energy and geometry of individual conformations, whereas NMR data are averaged over all conformations, a way of correlating the two methods of study is provided.