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Semicontinuum Modeling of Acid-Catalyzed Aqueous Reaction: Ethene Hydration and Mechanochemical Lignin Cleavage.

紀錄類型:	書目-電子資源 : Monograph/item
正題名/作者:	Semicontinuum Modeling of Acid-Catalyzed Aqueous Reaction: Ethene Hydration and Mechanochemical Lignin Cleavage./
作者:	Patel, Darpan Hasmukhbhai.
出版者:	Ann Arbor : ProQuest Dissertations & Theses, : 2020,
面頁冊數:	96 p.
附註:	Source: Masters Abstracts International, Volume: 82-09.
Contained By:	Masters Abstracts International82-09.
標題:	Alcohol. -
電子資源:	http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=28372125
ISBN:	9798597039220

Semicontinuum Modeling of Acid-Catalyzed Aqueous Reaction: Ethene Hydration and Mechanochemical Lignin Cleavage.
Patel, Darpan Hasmukhbhai.

Semicontinuum Modeling of Acid-Catalyzed Aqueous Reaction: Ethene Hydration and Mechanochemical Lignin Cleavage. - Ann Arbor : ProQuest Dissertations & Theses, 2020 - 96 p.

Source: Masters Abstracts International, Volume: 82-09.

Thesis (M.Sc.)--The University of Regina (Canada), 2020.

This item must not be sold to any third party vendors.

Careful studies are still needed to know how to accurately predict energies of reaction and activation in aqueous chemistry. This thesis applies semicontinuum modelling to acid-catalyzed reactions involving consumption or production of water. First, ethene hydration (ethene + H2O + H3O+ → TS+ → ethanol + H3O+) is explored, with 19 different water-placement semicontinuum models for the challenging activation thermodynamics, to learn which are appropriate to reproduce the known Δ‡G, Δ‡H, and Δ‡S values (from temperature-dependent kinetics studies). New tools are developed, particularly (i) a solvent confinement correction (SCC) of 3 kcal mol-1 per confined water and (ii) a Trouton's constant entropy method, which are able to reproduce experimental values to within 2 kcal mol-1. Second, these new tools are applied to explore potential mechanochemicalstretching benefits upon acid-catalyzed cleavage of lignin. Cleavage of several exemplary simple ethers is examined first, and with 1 nN stretching force they all are predicted to cleave substantially faster, allowing for use of milder acids and lower temperatures. For a model lignin fragment (studied experimentally and computationally by Sturgeon et al.), effort was first made to refine the multistep cleavage mechanism (including a side-product channel), and identify the rate-limiting step under zero-force (thermal) conditions. When the effects of mechanochemical stretching were tested, it was found that initially (at low forces) this does not improve the rate of cleavage, but does improve its yield, by shutting off the channel for formation of ring-closed side product. At larger forces, however, a switch in mechanism is predicted to occur, finally improving the cleavage rate.

ISBN: 9798597039220Subjects--Topical Terms:

872287
Alcohol.
Subjects--Index Terms:

Thermochemistry

Semicontinuum Modeling of Acid-Catalyzed Aqueous Reaction: Ethene Hydration and Mechanochemical Lignin Cleavage.
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520 $a Careful studies are still needed to know how to accurately predict energies of reaction and activation in aqueous chemistry. This thesis applies semicontinuum modelling to acid-catalyzed reactions involving consumption or production of water. First, ethene hydration (ethene + H2O + H3O+ → TS+ → ethanol + H3O+) is explored, with 19 different water-placement semicontinuum models for the challenging activation thermodynamics, to learn which are appropriate to reproduce the known Δ‡G, Δ‡H, and Δ‡S values (from temperature-dependent kinetics studies). New tools are developed, particularly (i) a solvent confinement correction (SCC) of 3 kcal mol-1 per confined water and (ii) a Trouton's constant entropy method, which are able to reproduce experimental values to within 2 kcal mol-1. Second, these new tools are applied to explore potential mechanochemicalstretching benefits upon acid-catalyzed cleavage of lignin. Cleavage of several exemplary simple ethers is examined first, and with 1 nN stretching force they all are predicted to cleave substantially faster, allowing for use of milder acids and lower temperatures. For a model lignin fragment (studied experimentally and computationally by Sturgeon et al.), effort was first made to refine the multistep cleavage mechanism (including a side-product channel), and identify the rate-limiting step under zero-force (thermal) conditions. When the effects of mechanochemical stretching were tested, it was found that initially (at low forces) this does not improve the rate of cleavage, but does improve its yield, by shutting off the channel for formation of ring-closed side product. At larger forces, however, a switch in mechanism is predicted to occur, finally improving the cleavage rate.
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