Formation of a New Benzene鈥揈thane Co-Crystalline Structure Under Cryogenic Conditions

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• 作者：Tuan Hoang Vu ; Morgan L. Cable ; Mathieu Choukroun ; Robert Hodyss ; Patricia Beauchamp
• 刊名：Journal of Physical Chemistry A
• 出版年：2014
• 出版时间：June 12, 2014
• 年：2014
• 卷：118
• 期：23
• 页码：4087-4094
• 全文大小：459K
• 年卷期：v.118,no.23(June 12, 2014)
• ISSN：1520-5215

文摘

We report the first experimental finding of a solid molecular complex between benzene and ethane, two small apolar hydrocarbons, at atmospheric pressure and cryogenic temperatures. Considerable amounts of ethane are found to be incorporated inside the benzene lattice upon the addition of liquid ethane onto solid benzene at 90鈥?50 K, resulting in formation of a distinctive co-crystalline structure that can be detected via micro-Raman spectroscopy. Two new features characteristic of these co-crystals are observed in the Raman spectra at 2873 and 1455 cm^鈥?, which are red-shifted by 12 cm^鈥? from the 蠀₁ (a_1g) and 蠀₁₁ (e_g) stretching modes of liquid ethane, respectively. Analysis of benzene and ethane vibrational bands combined with quantum mechanical modeling of isolated molecular dimers reveal an interaction between the aromatic ring of benzene and the hydrogen atoms of ethane in a C鈥揌路路路蟺 fashion. The most favored configuration for the benzene鈥揺thane dimer is the monodentate-contact structure, with a calculated interaction energy of 9.33 kJ/mol and an equilibrium bonding distance of 2.66 脜. These parameters are comparable to those for a T-shaped co-crystalline complex between benzene and acetylene that has been previously reported in the literature. These results are relevant for understanding the hydrocarbon cycle of Titan, where benzene and similar organics may act as potential hydrocarbon reservoirs due to this incorporation mechanism.