THE MICROWAVE SPECTRA OF 2-METHYL-1-BUTEN-3-YNE, trans-AND $cis-1,3$-PENTADIENE
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Date
1969
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Ohio State University
Abstract
The microwave spectra of 2-methyl-1-buten-3-yne, trans-1,3-pentadiene and cis-1,3-pentadiene were all assigned and the methyl group barriers to internal rotation were measured. The results for 2-methyl-1-buten-3-yne are: $A = 9359.58 \pm 0.02 MHz, B \pm 4013.52 \pm 0.01 MHz, C = 2854.80 \pm 0.01 MHz, V_{3} = 2011 \pm 70 cal/mole$. For trans-1,3-pentadiene $A = 28.5 GHz, B = 2161.6 \pm 0.2 MHz, C = 2033.2 \pm 0.2 MHz, V_{3} = 1813 \pm 60$ cal/mole. For cis-1,3-pentadiene: $A = 15.6 GHz, B = 2659.2 \pm 0.1 MHz, C = 2306.1 \pm 0.1 MHz, V_{a} = 750 \pm 50$ cal/mole. The molecular electric dipole moments were also measured in the three molecules. The methyl group barriers to internal rotation will be interpreted in light of present theories.
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Author Institution: Noyes Chemical Laboratory, University of Illinois