CONFORMATIONS AND INTERNAL ROTATION BARRIERS IN t- BUTYLACETALDEHYDE AND t-BUTYLACETYL HALIDES
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Date
1979
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Ohio State University
Abstract
Band series from three spectroscopically distinct species are observed in the low resolution microwave (LRMW) Spectra of t-butylacetaldehyde, t-butylacetyl fluoride and t-butylacetyl cyanide. Two of the series from each compound are readily assignable to the syn ($\tau_{OCCC} = 0^{\circ}$) and skew ($\tau_{OCCC} = 120^{\circ}$) conformations. The third band series from each compound is due to a species with average energy about 1.5 Kcal/mol higher than the approximately equally stable syn and skew forms and has a rotational constant B+C value corresponding to $\tau -90^{\circ}$. This species is not a third stable rotamer but is composed of those species freely rotating about $\tau_{OCCC}$ above the internal rotation barrier. The torsional barrier in each compound is essentially 3-fold with a height of 500 (+400, -200) cal/mol. t-Butylactyl chloride only displays bands from a syn rotamer. The skew minimum and low internal rotation barrier appear to be ellminated by the bulky chloride substituent.
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