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In this article, for the first time, a systematic study of the mechanism of protonation of the following series of styrenes is carried out: styrene - p-methylstyrene - pethylstyrene - p-isopropylstyrene - p-tert-butylstyrene by classical quantum-chemical methods ab initio and DFT on α- and β-carbon atoms of the monomer. It is shown that both directions of proton attack are barrier-free. All reactions are exothermic, and the heat effects of the processes under study do not depend on the nature of the monomers under study when attacking the α-carbon atom, and when attacking Cβ, they decrease in the series of studied styrenes. [ABSTRACT FROM AUTHOR]

For the first time, the mechanism of the reaction of 2,2,3,3-tetrafluoropropanol with thionyl chloride at the electronic level was studied using the classical quantum chemical method ab initio in the 3-21G basis. The reaction was studied in two directions. The first direction is synchronous simultaneous separation of chlorine and the formation of an O-S bond occurs. The second direction goes by the mechanism of the reaction of direct addition at the sulphur atom followed by the elimination of the chloride anion. It was found that the second direction is more energy-efficient than the first, since the reaction is barrier-free and the first direction-synchronous reaction has a barrier of more than 5 kJ/mol. [ABSTRACT FROM AUTHOR]

In this work, we performed a quantum-chemical calculation of a graphene oxide molecule by the MNDO method. An optimised geometric and electronic structure of this compound is obtained. It was found that the studied molecule, graphene oxide, belongs to the class of very weak Brönsted acids (pKa > 14). [ABSTRACT FROM AUTHOR]

For the first time, a quantum-chemical study of the initiation mechanism of the cationic polymerisation monomer p-methylstyrene in the presence of a complex catalyst of aluminum chloride -- hydrochloric acid in toluene with a stoichiometric composition of 1:1:4 by the ab initio method was performed. We showed that the energy barrier is 15 kJ/mol, and the thermal effect of the reaction is 113 kJ/mol. The reaction is of exotermic character and represents the usual acceptance of a proton from the complex catalyst AlCl3-HCl and its attachment to the most hydrogenated carbon atom C(1). [ABSTRACT FROM AUTHOR]

The first quantum-chemical study of the initiation mechanism of propylene in the presence of a complex chloride aluminium catalyst by the ab initio HF/6-311G** method was carried out with optimisation of the geometry in all parameters by a standard gradient method for attacks of the initiating particle on a-carbon monomer atoms. We showed that this reaction is barrier-like and exothermic. The mechanism of initiation is a coordinated process of SN 2-nucleophilic substitution. The energy barrier in the attack of the initiating particle on the a-carbon atom of propylene is 124 kJ/mol, the thermal effect of the reaction equals -49 kJ/mol. [ABSTRACT FROM AUTHOR]

The first quantum-chemical calculation of the molecules 22, 124 and 200 hexagons by the method MNDO was performed with optimisation of the geometry for all parameters by a standard gradient method. The optimised geometric and electronic structures of 22, 124 and 200 hexagons were obtained and their acid strength was theoretically evaluated (pKa = 33). It was found that the molecules belong to the class of very weak CH-acids (pKa > 14). [ABSTRACT FROM AUTHOR]

The first quantum-chemical study of the initiation mechanism of isobutylene in the presence of a complex chloride aluminium catalyst by the ab initio HF/6-311G** method was carried out with optimisation of the geometry in all parameters by a standard gradient method for attacks of the initiating particle on α-carbon monomer atoms. We showed that this reaction is barrier-like and exothermic. The mechanism of initiation is a coordinated process of SN²-nucleophilic substitution. The energy barrier in the attack of the initiating particle on the α-carbon atom of isobutylene is 97 kJ/mol, the thermal effect of the reaction equals 44 kJ/mol. [ABSTRACT FROM AUTHOR]

The first quantum-chemical study of the initiation mechanism of 4-methylpentene-1 in the presence of a complex chloride aluminium catalyst by the ab initio HF/6-311G** method was carried out with optimisation of the geometry in all parameters by a standard gradient method for attacks of the initiating particle on α-carbon monomer atoms. We showed that these reactions are barrier-like and exothermic. The mechanism of initiation is a coordinated process of SN 2-nucleophilic substitution. The energy barrier in the attack of the initiating particle on the α-carbon atom of 4-methylpentene-1 is 94 kJ/mol, the thermal effect of the reaction equals 52 kJ/mol. [ABSTRACT FROM AUTHOR]

The first quantum-chemical study of the initiation mechanism of p-isopropylstyrene in the presence of a complex boron fluoride catalyst by the classical ab initio method in the 6-311G** basis was carried out with optimisation of the geometry in all parameters by a standard gradient method for attacks of the initiating particle on α-carbon monomer atoms. It is shown that these reactions are barrier-like and exothermic. The mechanism of initiation is a coordinated process of SN²-nucleophilic substitution. The energy barrier in the attack of the initiating particle on the α-carbon atom of p-methylstyrene is197 kJ/mol, the thermal effect of the reaction equals 31 kJ/mol. [ABSTRACT FROM AUTHOR]