The Formation Mechanism and Structure of Organic Liquids in the DFT Challenges

Abstract

In the paper the experimental and theoretical approaches to problem of organic liquids formation mechanism and its structure are reviewed. It was shown that all presented models have the advantages and disadvantages at interpretation of molecular interaction and arrangement in liquid phase. The DFT calculation in different variant of models including paired interaction hydrogen atom transfer, model of transformation and the general conclusion following from this consideration are presented.

Formation of intermediate gas-liquid system in aromatics’ thin layers

“…The conducted DFT calculations with different transformations of the initial molecular geometry predict that the optimal configuration is the stack with a 'chair' shape of the central and two planar rings; the trimers are bonded in a spatial structure by the hydrogen bridges. 17 This concept explained the IR data outside the scope of traditional assignment. In the trimer spectrum, a C-H stretching band assigning to both planar rings should be observed while the C-H central-ring stretching exhibits two bands: the first one assigns to a pair of equivalent (C 1 -H 1 ) and (C 4 -H 4 ) bonds, and the second oneto a quartet: (C i -H i ), i = 2.3, 5.6.…”

“…main manifestations of the thin layer formation could be expected in these ranges, because the first of them is sensitive to the intermolecular "stack" binding and the second one can display the E‧‧‧H (E=C, O, S or N) intermolecular binding in "chains". 17 The most valuable results for benzene were obtained by heating of the sample between optical windows and subsequent evaporation into VTOC (see section "Experimental"). In the experiments with furane and thiophene, the gas-liquid systems were generated in VTOC, while for pyridine, they were obtained by heating between optical windows.…”

“…It is well-known that ab initio quantum chemical calculations simulate the condensed phase for organic molecules as a set of trimers and rarely as polymolecular clusters. 3,17,18 Therefore, our effort to evaluate the intermolecular binding in the gasliquid system of the thin layers is based on the similar conception, including the calculation of the dimer structure parameters for the different molecular shapes. The aromatics' system can exist in spatial arrangements of so called "stack" shape with parallel and perpendicular oriented aromatic rings.…”

“…18 However, the IR data indicate the formation of the C‧‧‧H interstack σ-binding as well. 17,18 The results of DFT study, in terms of the similar concept, are presented in this Section.…”