We report a first-principles study on ethyl acetate neutral hydrolysis in which we focus on the activation energy variation resulting from the conformational effect in the transition state. We use the conformers of ethyl formate, ethyl acetate, ethyl fluoroacetate, and ethyl chloroacetate as the ester models and one water molecule with a one-step reaction mechanism. We also consider the long-range interaction and the surrounding water in the form of PCM. Our results show that the various conformers yield a significant range of activation energy. Moreover, the gauche conformer has lower activation energy than the trans conformer. The activation energy in its own right is lowered by the halogen atoms. Finally, we remark that the long-range correction and PCM stabilize the transition state geometry but raise the activation energy.

Acetylcholine, which is associated with Alzheimer’s disease, is widely known to have conformers. The preference of each conformer to undergo neutral hydrolysis is yet to be considered. In this study, we employed density-functional calculations to build the conformers and investigated their preference in one-step neutral hydrolysis. The results showed the preference in ten possible hydrolysis pathways involving seven acetylcholine conformers (reactant), four transition state structures, and two choline conformers (product). Three out of the seven acetylcholine conformers predicted from the results confirmed experimental findings on the conformers stability. We suggested that two out of ten possible pathways were observed in the experimental results based on agreement in reaction energy. Eventually, this study will emphasize the importance of considering acetylcholine conformers in its hydrolysis study.

This study implemented DFT method into the C++ programming language with object-oriented programming rules (expressive software). The use of expressive software results in getting a simple programming structure, which is similar to mathematical formula. This will facilitate the scientific community to develop the software. We validate our software by calculating the energy band structure of Silica, Carbon, and Germanium with FCC structure using the Projector Augmented Wave (PAW) method then compare the results to Quantum Espresso calculation's results. This study shows that the accuracy of the software is 85% compared to Quantum Espresso.

We attempt to study about the solvent effects of the stability of trans-HCOH molecules using the density-functional theory. Experimentally, trans-HCOH rearranges to H₂CO with half-life of two hours [1] which we theoretically proved that it occurs through quantum tunneling. [2] In this work, we calculate the rearrangement rate of the molecules in various solvents. The solvents are selected based on their dielectric constant values, from lower to higher ones; they are benzene, dichloroethane, benzaldehyde, acetone, methanol, ethanediol, dimethylsulfoxide, formic acid, water, and formamide. We use polarizable continuum to model the solvents (PCM). We begin from determining the reaction path from trans-HCOH to H₂CO and its corresponding energy barrier using intrinsic reaction coordinate calculation with PCM. Then, we use Wentzel-Kramers-Brillouin (WKB) approximation to calculate the rearrangement rates. The calculation results showed a general trend in which there were arrangement rate was decreasing inversely proportional to dielectric constant value.