Gleeson, Duangkamol

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Gleeson, Duangkamol
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duangkamol.gl@kmitl.ac.th

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    Theoretical studies to estimate the skin sensitization potential of chemicals of the Schiff base domain
    (2020-06-15)
    Gleeson, Duangkamol
    ;
    Gleeson, Matthew Paul
    Skin sensitization occurs when an exogenous chemical substance forms a covalent adduct with a dermal protein electrophile or nucleophile. This instigates an immune response which leads to inflammation. The local lymph node assay is an in vivo model used in the assessment of relative skin sensitizing potency of chemicals. The method is time consuming and expensive, as well as poses ethical questions given that a number of mice must be sacrificed for each compound assessed. In this work, we investigate the use of an inexpensive, rapid, and ethical method to predict the skin sensitization potential of Schiff base chemicals. We employ quantum chemical methods to rationalize the sensitization potential of 22 compounds with a diverse range of activities. To this end, we have evaluated the mechanistic profile associated with this type of reaction using gas-phase models. We subsequently use the predicted rate determining barriers and key physico-chemical parameters (such as logP) to establish stucture activity relationship (SAR) guidelines to predict the skin sensitization potential for new chemicals. We find that the predicted rate determining barriers for aldehydes, ketone, and 1,2 and 1,3 diones generally decrease in the given order, which concurs with the overall trends in sensitization. We find that lipophilicity also plays a role, with those chemicals displaying both low barriers to reaction, and lower lipophilicity (ie, diones), being more likely to display undesirable skin sensitization effects. These findings are in line with experiment-based observations in the literature and point to the value 3D quantum chemical calculations could have if combined with other orthogonal approaches to estimate skin sensitization potential of chemicals.
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    DFT Investigation of the catalytic conversion of acetic acid to acetone on the zeolite H-ZSM5
    (2022-12-01)
    Konsue, Adchatawut
    ;
    Gleeson, M. Paul
    ;
    Gleeson, Duangkamol
    Biomaterials processing has become increasingly important in the chemical industry. Identification and optimization of processes to facilitate biomass conversion is therefore recognized as being of great importance. Carboxylic acids derived from biomaterials are important building blocks that can be used in a wide variety of industrial applications. As such, methods to process them in an efficient and cost-effective manner are highly desirable. In this study we report the use of theoretical methods to explore the catalytic conversion of acetic acid to acetone on the zeolite H-ZSM5. We have employed a 46T DFT cluster model to explore mechanistic proposals reported in the literature. We investigate the relative energetics associated with the formation of the proposed intermediates, including acyl-zeolite complexes, enols, acylium cations, ketenes, anhydrides, and beta-keto acids, that could potentially connect acetic acid to the desired product, acetone. This assessment would allow us to identify the most probable mechanism connecting the reactant to products. We predict a low energy pathway starting with the generation of a surface acyl, followed by an anhydride, with the rate determining step involving methyl group migration. The reaction is predicted to be bi-molecular and involves C-C bond formation, in line with proposals based on isotopic labelling experiments.