Department of Chemistry , Indian Institute of Technology Bombay , Powai, Mumbai 400076 India.
Prithwi Chand Vigyan College, Jai Prakash Vishwavidyalaya , Chapra , Saran, Bihar 841301 , India.
J Phys Chem B. 2019 Nov 27;123(47):10083-10088. doi: 10.1021/acs.jpcb.9b08057. Epub 2019 Nov 18.
The potentials of mean force for the dimers of fluorobenzenes sample both π-stacked and T-shaped structures for partially fluorinated benzenes, namely, 1,4-difluorobenzene, 1,3,5-trifluorobenzene, and 1,2,4,5-tetrafluorobenzene, and sample only the T-shaped structures for benzene and hexafluorobenzene. While the free energy for the dimerization in water is very weakly dependent on the number of fluorine atoms, the formation of π-stacked structures is entropy-driven and the T-shaped structures appear due to an enthalpic minimum. Interestingly, the solvation behavior suggests that the accumulation of water around the contact and solvent-separated pairs decreases with the increase in the number of fluorine atoms, which signifies progressive hydrophobicity of fluorobenzenes.
对于部分氟化苯的二聚体，包括π-堆积和 T-型结构的氟苯，如 1,4-二氟苯、1,3,5-三氟苯和 1,2,4,5-四氟苯，我们同时对其进行了研究，而对于苯和六氟苯，我们只研究了 T-型结构。虽然二聚体在水中的自由能与氟原子的数量关系非常弱，但π-堆积结构的形成是熵驱动的，而 T-型结构的出现则是由于焓变的最小值。有趣的是，溶剂化行为表明，随着氟原子数量的增加，在接触对和溶剂分离对周围积累的水分子数量减少，这表明氟苯的疏水性逐渐增强。
