Alkylation Reaction Mechanism Of Binary Phenol And Molecular Dynamics Simulation Of Poly Vinyl Pyrrolidone

Quantum chemistry and molecular dynamics simulation are both of the importantparts of molecular simulation. In the present paper, DFT was used to study alkylationreactions mechanism and molecular dynamics simulation was used to study PolyVinyl Pyrrolidone (PVP) conformations.In our lab we used alkylation reactions of Pyrocatechol andN-methylolacryamide to synthesise capsaicin derivatives applied in antifouling paints,but the products were mostly dialkylation. DFT calculations on the level ofB3LYP/6-311G(d,p) were used to optimize the reactants, the transition state, theintermediats and the products and to analyze frontier molecular orbitals, energies andcharges. The study showed that the alkylation reaction was four steps reaction. Theactivation energies (Ea) of the four steps were61.07kJ/mol,39.69kJ/mol,44.31kJ/mol and31.51kJ/mol. The reaction energy barrier of the dialkylation reaction was44.31kJ/mol, lower than61.07kJ/mol of monoalakylation reaction. In addition, theMulliken charge datas showed that the mulliken charge of the active atom was moreafter the pyrocatechol was substituted, easier to be attacked by the positive ion.At the same time, the water-soluble polymer PVP was investaged. DFTcalculations on the level of B3LYP/6-311G(d,p) were used to optimize the repeat unitN-Vinyl-2-Pyrrolidone (NVP) and to analyze frequency, energies and charges. Thedata showed that NVP had strong chemical polarity. The molecular dynamicssimulation of PVP was studied in COMPASS forcefield. The atomistic simulationshave been adopted to study the conformation state of PVP chains and PVP in watersolution, respectively. The conclusions were as follows:(1) PVP chains were simulated in different length, different temperature. Thechain was longer, the polymer segments were more, and the interaction of segements was stronger. With the density changing, the radius of gyration was up first and thendown. The radius of gyration kept growth with the chain length after PVP90. The PVPchain of50repeat units was simulated in different temperature ranged from323K to373K. The glass transition temperature (Tg) of PVP was359K. As the temperaturewas higher, the polymer segment-segment interactions were enhanced. Then theamorphous cell of a PVP50chain was simulated in353K, but the cell density was notconstrained. When the simulation finished, the density was1.10g/ml. With the densitychanging, the radius of gyration rised first and then droped, and finally it wasbasically constant.(2) More than one PVP50chains in an amorphous cell was simulated in353K.Polymer chains beganto aggregate together, which illuminate that polymersegment-segment interactions were enhanced.(3) For the blend system of1PVP and H2O moleculars, the interactions wasmostly hydrogen-bond interaction between H2O molecular and acyl group of PVP. Forthe blend of more than one PVP and H2O moleculars, a more packed globule wasgenerated with H2O moleculars in gap. For PVP water solution, as water is a goodsolvent, PVP chain was coil conformation.