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NORMAN C. CRAIG, HANNAH A. FUSON AND HENGFENG TIAN, Department of Chemistry and Biochemistry, Oberlin College, Oberlin, OH 44074; THOMAS A. BLAKE, Environmental Molecular Sciences Laboratory, Pacific Northwest National Laboratory, Richland, WA 99352.
Hexatriene-1,1- d 2 with some admixture of the cis -1- d 1 and trans -1- d 1 species was synthesized by reaction of 2,4-pentadienal and (methyl- d 3)-triphenylphosphonium iodide (Wittig reagent). The trans isomer was isolated by preparative gas chromatography, and the high-resolution (0.0015 cm-1) infrared spectrum was recorded on a Bruker IFS 125HR instrument. The rotational structure in two C-type bands for the 1,1- d 2 species was analyzed. For this species the bands at 902.043 and 721.864 cm-1 yielded composite ground state rotational constants of A 0 = 0.801882(1), B 0 = 0.041850(2), and C 0 = 0.039804(1) cm-1. For the cis -1- d 1 species the C-type band at 803.018 cm-1 gave A 0 = 0.809384(2), B 0 = 0.043530(3), and C 0 = 0.041321(2) cm-1. By iodine-catalyzed isomerization, we have obtained some of the much less favored cis isomer and hope to obtain microwave spectra for its three deuterium-substituted species. The rotational constants reported here contribute to data needed for determining a semi-experimental structure for trans -hexatriene, which should show that the structural consequences of pi -electron delocalization increase with the chain length of polyenes.