| Abstract
| - The 13C chemical shifts of six tertiary amines of unambiguous conformational structure are comparedto predicted 13C NMR chemical shifts obtained via empirically scaled GIAO shieldings for geometriesfrom MM3 molecular mechanics calculations. An average deviation, |Δδ|av, of 0.8 ppm and amaximum deviation, |Δδ|max, of 2.8 ppm between predicted and experimental 13C shifts of the sixtertiary amines of unambiguous structure are found. In several cases of tertiary amines subject torapid exchange, where experimental 13C shifts at room temperature are weighted averages ofmultiple conformers, a comparison of calculated 13C shifts of all reasonable MM3 predictedconformers with experimental 13C shifts via a multiple independent variable regression analysisprovides an efficient method of determining the major and minor conformers. The examplespresented are 2-methyl-2-azabicyclo[2.2.1]heptane and 1,6-diazabicyclo[4.3.1]decane, which eachhave two expected contributing structures, and 2-(diethylamino)propane and 1,8-diazabicyclo[6.3.1]dodecane, where ten and seven low-energy conformers, respectively, are predicted by MM3calculations.
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