Various Reactivity of Cyclocarbonate-Containing Chains of Vegetable Oil Triglycerides as the Cause of the Abnormal Kinet
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Various Reactivity of Cyclocarbonate-Containing Chains of Vegetable Oil Triglycerides as the Cause of the Abnormal Kinetics of Urethane Formation with Their Participation M. V. Zabalova,*, M. A. Levinaa, and R. P. Tigera aSemenov
Institute of Chemical Physics, Russian Academy of Sciences, Moscow, 119991 Russia * e-mail: [email protected] Received March 31, 2020; revised April 13, 2020; accepted May 12, 2020
Abstract—The comparative reactivity of oleic, linoleic, and linolenic fragments of vegetable oil triglyceride chains in the processes of their conversion to the corresponding hydroxyurethanes is studied. According to DFT quantum-chemical calculations, the linolenic fragments of triglyceride chains are the most reactive. The activation barriers of reactions involving the second cyclocarbonate group of the linoleic fragment and the second and third cyclocarbonate groups of the linolenic fragment are lower than the conversion barriers of first cyclocarbonate groups of the corresponding models, which is explained by the catalytic assistance of the OH groups of hydroxyurethanes, which are formed at the first stage of aminolysis, to the proton transfer act. DOI: 10.1134/S1560090420050152
INTRODUCTION The green chemistry of polyurethanes, which is based on the reactions of primary amines with cyclocarbonates, involves not only the exclusion of highly toxic isocyanates from the polymer synthesis process but also the possibility to use renewable plant materials [1–9]. In this respect, certain prospects are demonstrated by cyclocarbonylated derivatives of vegetable oils, which are obtained by oxidizing the latter to epoxy-containing triglycerides, followed by catalytic carbonization under the influence of CO2. This type of oligomers based on soybean and sunflower oil was studied in detail by mass spectrometry in order to establish their molecular composition and distribution of functional groups in chains [10, 11]. These are triglycerides of cyclocarbonylated derivatives of some unsaturated acids (linoleic (L), oleic (O), linolenic (Ln)) and saturated acids (stearic (S), palmitic (P)) of various compositions. For example, in the products obtained from soybean oil, there are about 25 such triglycerides with functionality with respect to cyclocarbonate groups from 0 to 6: PSS (0), SSS (0), PPL (2), POO (2), PLS (2), PLO (3), OOO (3), OLS (3), SLnS (3), PLL (4), PLnO (4), OLO (4), LLS (4), OLnS (4), LLO (5), OLnO (5), PLnL (5), LnLnO (5), LLL (6), LLnL (5), LLnO (6). In sunflower oil products, there are 16 types of triglycerides, and the main difference between oligomers based on soybean and sunflower oil is the absence of Ln fragments in the latter. When studying the kinetics of aminolysis of cyclocarbonate-containing oligomers from vegetable oils in
amine excess in solutions, deviations of the kinetic curves from the first-order law were observed [11–15]. No such deviations was observed in the kinetic study of urethane formation with the participation of simple model compounds, ethylene carbonate and its substit
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