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NMR Isotope Shift Evidence for Conformational Structures of Dimethyl-9,10-Dihydroanthracenes and the 1,4,4-Trimethylcyclohexyl Cation

David A. Forsyth ; Department of Chemistry, Northeastern University, Boston, Massachusetts 02115
Adel M. Moussa ; Department of Chemistry, Northeastern University, Boston, Massachusetts 02115
Chitchanun Panyachotipun ; Department of Chemistry, Northeastern University, Boston, Massachusetts 02115

Sažetak

NMR isotope shifts provide evidence of rapidly equilibrating nonplanar conformations in solution for 9,9-dimethyl-9,10-dihydroanthracene and trans-9,10-dimethyl-9,10-dihydroanthracene. In each case, labeling with a single deuterium in the 9- or 10-position results in two different methyl signals in 13C NMR spectra. The separation between methyl signals is temperature dependent and characteristic of isotopically perturbed equilibria. For cis-9,10- dime thvl-9,10-dihydroanthracene-9-c/[, only intrinsic isotope effects on the chemical shifts are present, indicating a single conformation. Similarly, equilibrium isotope shifts are also seen for the C4 methyls in 1,4,4-trìmethyicyclohexyl cation, thereby ruling out the Co twist-boat as a viable conformation.

Ključne riječi

Hrčak ID:

137127

URI

https://hrcak.srce.hr/137127

Datum izdavanja:

15.10.1992.

Posjeta: 654 *