Effects of stereochemistry on the rates of hydrogen--deuterium exchange of protons. cap alpha. to the nitrosamino group. [Dibenzazepine]
Measurement of the rates of exchange of four benzylic protons of rigid dibenzazepine were made in tert-butyl alcohol-O-d containing potassium tert-butoxide at several concentrations. Each pseudoaxial proton exchanged 100-fold faster than its geminal partner (pseudoequatorial), likely as a result of a stereoelectronic effect. Each syn proton exchanged 1000-fold faster than the anti proton in the same biaryl environment. The lack of any significant effect of added crown either on the rate of exchange of either a syn or an antiproton indicates lack of involvement of the counterion. A suggested explanation for the unusual preference for syn exchange in this work is based on the symmetry properties of the anionic intermediate. This intermediate, like butadiene dianion, has an attractive interaction between the terminal atoms of the four-atom ..pi.. system in the highest occupied molecular orbital (HOMO). This explanation is similar to that of Epiotis and co-workers, which accounts for the well-established preferential stability of cis over trans dihalo and dialkoxy ethylenes.
- Research Organization:
- Univ. of Ottawa
- OSTI ID:
- 7334366
- Journal Information:
- J. Am. Chem. Soc.; (United States), Journal Name: J. Am. Chem. Soc.; (United States) Vol. 98:19; ISSN JACSA
- Country of Publication:
- United States
- Language:
- English
Similar Records
Dissolving metal reduction of aceanthrylene and NMR analysis of a rigid, boat-shaped 9,10-dihydroanthracene
Related Subjects
400303* -- Organic Chemistry-- Isotope Exchange & Isotope Separation-- (-1987)
ALCOHOLS
AMINES
AROMATICS
BUTANOLS
CHEMICAL REACTION KINETICS
DEUTERIUM
HYDROGEN ISOTOPES
HYDROXY COMPOUNDS
INTERMEDIATE STRUCTURE
ISOTOPES
ISOTOPIC EXCHANGE
KINETICS
LIGHT NUCLEI
NITROSO COMPOUNDS
NUCLEI
ODD-ODD NUCLEI
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
REACTION KINETICS
STABLE ISOTOPES
STEREOCHEMISTRY
SYMMETRY