Diffusion of Vinyl Bromide through the Crystals of p-Bu(t)-calix[4]arene
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摘要The mechanism for the diffusion of vinyl bromide (VB) through the nonporous van der Waals organic solid of p-tert-butylcalix[4]arene (tBC) is examined by molecular mechanics calculations. In a "squeeze" mechanism, a VB molecule passes through the interstitial space in the rim regions of tBC bowls, after the partial filling of nearby inclusion sites, and couples with the both the rotation of butyl groups and the translational sliding of the bilayers, until it encounters and falls into a empty site. In a "relay" mechanism, translational sliding shifts the skew angle between two tBC bowls and makes it possible to pass a VB from one bowl to another and throughout the solid. The barrier for the "relay" mechanism is 4 kcal/mol lower than the "squeeze" mechanism, although the "squeeze" mechanism is favored by entropy. The "squeeze" mechanism should be more sensitive to the size of the diffusion molecule and should leave residue VB molecules in the interstitial regions. In contrast, the VB molecule hops from one site to another in the "relay" mechanism, and the kinetically limiting step is the translational sliding of the bilayer. Such contrasts should help resolve the relative importance of the two mechanisms in future kinetic studies.
著者Gu X, Zhang L, Gong XA, Lau WM, Liu ZF
期刊名稱Journal of Physical Chemistry B
出版年份2008
月份11
日期27
卷號112
期次47
出版社AMER CHEMICAL SOC
頁次14851 - 14856
國際標準期刊號1520-6106
語言英式英語
Web of Science 學科類別Chemistry; Chemistry, Physical; CHEMISTRY, PHYSICAL

上次更新時間 2021-19-09 於 00:15