Inter- and Intramolecular Mechanisms for Chlorine Rearrangements in Trimethyl-Substituted N-Chlorohydantoins

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• 作者：Billy W. McCann ; Hao Song ; Hasan B. Kocer ; Idris Cerkez ; Orlando Acevedo ; S. D. Worley
• 刊名：The Journal of Physical Chemistry A
• 出版年：2012
• 出版时间：July 5, 2012
• 年：2012
• 卷：116
• 期：26
• 页码：7245-7252
• 全文大小：453K
• 年卷期：v.116,no.26(July 5, 2012)
• ISSN：1520-5215

文摘

The antimicrobial compounds 1-chloro-3,5,5-trimethylhydantoin and 3-chloro-1,5,5-trimethylhydantoin (1 and 2, respectively) have been synthesized and examined via a joint experimental and computational study. The measured rate of loss of oxidative chlorine in the absence and presence of exposure to UVA irradiation determined 2 to be less stable than 1. An interesting migration reaction was observed during UVA irradiation that featured the production of chlorine rearrangement and dechlorinated compounds. Two novel hydrogen atom transfer reaction (HATR) mechanisms have been proposed: (1) an intramolecular process in which a hydrogen atom undergoes a series of sigmatropic shifts, and (2) an intermolecular pathway in which a radical abstracts a hydrogen atom from a neighboring molecule. Density functional theory (DFT) calculations at the UB3LYP/6-311G++(2d,p) theory level have been employed to elucidate the preferred reaction pathway. Both proposed HATR mechanisms predicted 2 to possess a lower free energy of activation, 螖G^{鈥?/sup>, relative to 1 in accordance with the experimental stability measurements. However, the intermolecular route had an overall lower absolute 螖G鈥?/sup> and was more consistent with measured product ratios in solution. The intermolecular reaction pathway, unlike the intramolecular route, also predicted the lack of formation of a migration product featuring a Cl covalently bonded to a methylene group at the 5-position of the hydantoin moiety, which was verified by NMR experiments.}