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Title: Effect of Mixed-Solvent Environments on the Selectivity of Acid-Catalyzed Dehydration Reactions

Abstract

The composition of the liquid phase can alter the rates of individual reaction steps and thus alter the selectivity of acid-catalyzed reactions, but these solvent effects are difficult to anticipate for design purposes. Herein, we report the kinetics and selectivity of Brønsted acid-catalyzed 1,2-propanediol dehydration in pure water and in aqueous mixtures of the polar aprotic cosolvents γ-valerolactone, 1,4-dioxane, tetrahydrofuran, N-methyl-2-pyrrolidone, tetramethylene sulfoxide, and dimethyl sulfoxide at 433 K. We find that the major product of 1,2-propanediol dehydration is propanal in most mixed-solvent environments with selectivities between 1 and 68 mol %. In contrast, 1,2-propanediol dehydration in aqueous mixtures of dimethyl sulfoxide affords acetone as the major product with up to 48% selectivity with minimal propanal formation. We use classical molecular dynamics simulations to probe these solvent effects by computing the difference between the solvation free energies of 1,2-propanediol and propanal in aqueous mixtures of polar aprotic cosolvents and in pure water. We find that the difference in the solvation free energies is correlated with the rates of propanal formation in all mixed-solvent environments, indicating that the solvent-mediated stabilization of the product state relative to the reactant state translates to increased selectivity toward the same product. Similar agreement between simulatedmore » solvation free energies and experimental reaction rates/selectivities is established for the acid-catalyzed dehydration of cis- and trans-1,2-cyclohexanediol and 1,3-cyclohexanediol. Finally, analysis of the solvation environment around 1,2-propanediol shows that dimethyl sulfoxide uniquely competes against water to solvate reactive hydroxyl groups, which causes a change in reaction mechanism in this solvent system that leads to the formation of acetone rather than propanal. Here, these results represent a step toward the computationally efficient screening of solvent systems for acid-catalyzed, liquid-phase processes.« less

Authors:
 [1];  [1]; ORCiD logo [1]; ORCiD logo [1];  [1];  [1];  [1]; ORCiD logo [1]; ORCiD logo [1]
  1. Univ. of Wisconsin, Madison, WI (United States)
Publication Date:
Research Org.:
Great Lakes Bioenergy Research Center (GLBRC), Madison, WI (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Biological and Environmental Research (BER); National Science Foundation (NSF)
Contributing Org.:
UW-Madison Center for High Throughput Computing (CHTC); Extreme Science and Engineering Discovery Environment (XSEDE)
OSTI Identifier:
1637444
Grant/Contract Number:  
SC0018409; FC02-07ER64494; ACI-1548562
Resource Type:
Accepted Manuscript
Journal Name:
ACS Catalysis
Additional Journal Information:
Journal Volume: 10; Journal Issue: 3; Journal ID: ISSN 2155-5435
Publisher:
American Chemical Society (ACS)
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY; acid catalysis; biomass conversion; solvent effects; selectivity; classical molecular dynamics

Citation Formats

Chew, Alex K., Walker, Theodore W., Shen, Zhizhang, Demir, Benginur, Witteman, Liam, Euclide, Jack, Huber, George W., Dumesic, James A., and Van Lehn, Reid C.. Effect of Mixed-Solvent Environments on the Selectivity of Acid-Catalyzed Dehydration Reactions. United States: N. p., 2019. Web. https://doi.org/10.1021/acscatal.9b03460.
Chew, Alex K., Walker, Theodore W., Shen, Zhizhang, Demir, Benginur, Witteman, Liam, Euclide, Jack, Huber, George W., Dumesic, James A., & Van Lehn, Reid C.. Effect of Mixed-Solvent Environments on the Selectivity of Acid-Catalyzed Dehydration Reactions. United States. https://doi.org/10.1021/acscatal.9b03460
Chew, Alex K., Walker, Theodore W., Shen, Zhizhang, Demir, Benginur, Witteman, Liam, Euclide, Jack, Huber, George W., Dumesic, James A., and Van Lehn, Reid C.. Fri . "Effect of Mixed-Solvent Environments on the Selectivity of Acid-Catalyzed Dehydration Reactions". United States. https://doi.org/10.1021/acscatal.9b03460. https://www.osti.gov/servlets/purl/1637444.
@article{osti_1637444,
title = {Effect of Mixed-Solvent Environments on the Selectivity of Acid-Catalyzed Dehydration Reactions},
author = {Chew, Alex K. and Walker, Theodore W. and Shen, Zhizhang and Demir, Benginur and Witteman, Liam and Euclide, Jack and Huber, George W. and Dumesic, James A. and Van Lehn, Reid C.},
abstractNote = {The composition of the liquid phase can alter the rates of individual reaction steps and thus alter the selectivity of acid-catalyzed reactions, but these solvent effects are difficult to anticipate for design purposes. Herein, we report the kinetics and selectivity of Brønsted acid-catalyzed 1,2-propanediol dehydration in pure water and in aqueous mixtures of the polar aprotic cosolvents γ-valerolactone, 1,4-dioxane, tetrahydrofuran, N-methyl-2-pyrrolidone, tetramethylene sulfoxide, and dimethyl sulfoxide at 433 K. We find that the major product of 1,2-propanediol dehydration is propanal in most mixed-solvent environments with selectivities between 1 and 68 mol %. In contrast, 1,2-propanediol dehydration in aqueous mixtures of dimethyl sulfoxide affords acetone as the major product with up to 48% selectivity with minimal propanal formation. We use classical molecular dynamics simulations to probe these solvent effects by computing the difference between the solvation free energies of 1,2-propanediol and propanal in aqueous mixtures of polar aprotic cosolvents and in pure water. We find that the difference in the solvation free energies is correlated with the rates of propanal formation in all mixed-solvent environments, indicating that the solvent-mediated stabilization of the product state relative to the reactant state translates to increased selectivity toward the same product. Similar agreement between simulated solvation free energies and experimental reaction rates/selectivities is established for the acid-catalyzed dehydration of cis- and trans-1,2-cyclohexanediol and 1,3-cyclohexanediol. Finally, analysis of the solvation environment around 1,2-propanediol shows that dimethyl sulfoxide uniquely competes against water to solvate reactive hydroxyl groups, which causes a change in reaction mechanism in this solvent system that leads to the formation of acetone rather than propanal. Here, these results represent a step toward the computationally efficient screening of solvent systems for acid-catalyzed, liquid-phase processes.},
doi = {10.1021/acscatal.9b03460},
journal = {ACS Catalysis},
number = 3,
volume = 10,
place = {United States},
year = {2019},
month = {12}
}

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