Stereochemistry of hexakis (3-methoxyphenyl) benzene and hexakis(3-methylphenyl) benzene. An incremental chemical shift model for meta-substituted hexaphenylbenzenes
✍ Scribed by Henri Pepermans; Rudolph Willem; Marcel Gielen; Cornelis Hoogzand
- Book ID
- 102950109
- Publisher
- John Wiley and Sons
- Year
- 1988
- Tongue
- English
- Weight
- 674 KB
- Volume
- 26
- Category
- Article
- ISSN
- 0749-1581
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✦ Synopsis
The 'H NMR spectrum of hexakis(3-methoxypheny1)benzene exhibits a methoxy absorption which looks exactly like a triplet. The spacing between the signals is, however, proportional to rather than independent of the field strength. The aryl H-5 region of this compound and the methyl region of hexakis(3-methylpheny1)benzene display similar field-proportional, triplet-like splittings. This property of meta-substituted hexaphenylbenzenes cannot be explained by either preferential or residual isomerism, even in the presence of many accidental isochronies. A chemical shift model based on the hypothesis that the metu substitueuts do not disturb the geometry of the hexaphenylbenzene skeleton or the populations of the rotamers explains the spectra in a straightforward manner.