Dipole Moments of Tropolone and Related Compounds

概要

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The dipole moments of tropolone (cycloheptatriene-2,4,6-ol-2-one-1) and related compounds were measured in benzene solution. The values obtained are:— tropolone, 3.71 D (25°) and 3.64 D (35°) ; tribromotropolone (3,5,7-tribromo-), 1.84D(25°); hinokitiol(4-isopropylcycloheptatriene-2,4,6-ol-2-one-1), 4.04 D (33°); α-monobromohinokitiol (7-bromo-), 4.32 D (33°); α-dibromohinokitiol (3,7-dibromo-), 4.27 D (33°); β-dibromohinokitiol (5,7-dibromo-), 3.14 D (20°); α-mononitrohinokitiol (3- or 7-nitro-), 6.19 D (25°); dinitrohinokitiol (3,5- or 3,7-dinitro-), 4.63 D (20°). The high dipole moments of tropolone and hinokitiol were explained adequately by taking into consideration the contribution of various resonance structures with a formal positive charge at the ring C-atoms. The resonance was supposed to give a certain amount of double bond character to each bond in the ring, causing plane cycloheptatrienolone ring. The position of substituents in the substituted tropolone and hinokitiols were determined and are given immediately after each name of these compounds in parentheses.
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