A Theoretical and Experimental Study on Esterification of Citric Acid with the Primary Alcohols and the Hydroxyl Groups of Cellulose Chain (n = 1-2) in Parched Condition
| Autor: | Quan T. Pham, Dang T. Nguyen |
|---|---|
| Rok vydání: | 2020 |
| Předmět: |
ONIOM
Article Subject Reaction step Substituent 02 engineering and technology General Chemistry Activation energy Primary alcohol 010402 general chemistry 021001 nanoscience & nanotechnology 01 natural sciences Medicinal chemistry 0104 chemical sciences Chemistry chemistry.chemical_compound chemistry Dehydration reaction Reactivity (chemistry) Cellulose 0210 nano-technology QD1-999 |
| Zdroj: | Journal of Chemistry, Vol 2020 (2020) |
| ISSN: | 2090-9071 2090-9063 |
| DOI: | 10.1155/2020/8825456 |
| Popis: | Esterification of citric acid (CA) with the primary alcohols and the hydroxyl groups of cellulose chain (n = 1-2) in parched condition were investigated by using density functional theory (DFT) method and a two-layer ONIOM approach. Geometry and energy of reactants, products, and transition state (TS) structures were optimized at B3LYP/6-311g (d, p) level and ONIOM (B3LYP/6-311g (d, p):PM3MM) level. The computational results show that the esterification occurs in the two main steps: the first step is the dehydration reaction of CA to form anhydrides of 5-membered ring and 6-membered ring and the second step is the ring opening reaction with the hydroxyl –OH groups to form the ester products. The energy barrier of dehydration reaction step is much higher than that of ring opening reaction step. Effect of substituent R in primary alcohol R-CH2OH (R: CH=CH2, CH2NHCH3, CH2OCH3, CH2Cl) and cellulose chain (1G, 2G) on the reactivity, which has negative inductive effect –I, is significant. The combination of calculation data and experiment data were applied to make findings more rigorous. The activation energy of CA was determined by using differential scanning calorimetry (DSC) and thermal gravimetric (TG) analysis to be E a exp = 47.8 kcal/mol; the experimental data favoured the dehydration reaction step of CA. |
| Databáze: | OpenAIRE |
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