TY - JOUR
T1 - Kinetics and Mechanisms of Hydrothermal Dehydration of Cyclic 1,2- and 1,4-Diols
AU - Bockisch, Christiana
AU - Lorance, Edward D.
AU - Hartnett, Hilairy E.
AU - Shock, Everett L.
AU - Gould, Ian R.
N1 - Funding Information:
This work was supported by NSF Grant OCE-1357243 and NASA grants NNX16AO82G and 80NSSC20K1408. The authors thank all the members of the Hydrothermal Organic Geochemistry (HOG) group at ASU, in particular Kris Fecteau, Kirt Robinson, and Lynda Williams, for many stimulating discussions and helpful suggestions.
Publisher Copyright:
© 2022 American Chemical Society. All rights reserved.
PY - 2022/11/4
Y1 - 2022/11/4
N2 - Hydrothermal dehydration is an attractive method for deoxygenation and upgrading of biofuels because it requires no reagents or catalysts other than superheated water. Although mono-alcohols cleanly deoxygenate via dehydration under many conditions, polyols such as those derived from saccharides and related structures are known to be recalcitrant with respect to dehydration. Here, we describe detailed mechanistic and kinetic studies of hydrothermal dehydration of 1,2- and 1,4-cyclohexanediols as model compounds to investigate how interactions between the hydroxyls can control the reaction. The diols generally dehydrate more slowly and have more complex reaction pathways than simple cyclohexanol. Although hydrogen bonding between hydroxyls is an important feature of the diol reactions, hydrogen bonding on its own does not explain the reduced reactivity. Rather, it is the way that hydrogen bonding influences the balance between the E1 and E2 elimination mechanisms. We also describe the reaction pathways and follow-up secondary reactions for the slower-dehydrating diols.
AB - Hydrothermal dehydration is an attractive method for deoxygenation and upgrading of biofuels because it requires no reagents or catalysts other than superheated water. Although mono-alcohols cleanly deoxygenate via dehydration under many conditions, polyols such as those derived from saccharides and related structures are known to be recalcitrant with respect to dehydration. Here, we describe detailed mechanistic and kinetic studies of hydrothermal dehydration of 1,2- and 1,4-cyclohexanediols as model compounds to investigate how interactions between the hydroxyls can control the reaction. The diols generally dehydrate more slowly and have more complex reaction pathways than simple cyclohexanol. Although hydrogen bonding between hydroxyls is an important feature of the diol reactions, hydrogen bonding on its own does not explain the reduced reactivity. Rather, it is the way that hydrogen bonding influences the balance between the E1 and E2 elimination mechanisms. We also describe the reaction pathways and follow-up secondary reactions for the slower-dehydrating diols.
UR - http://www.scopus.com/inward/record.url?scp=85140324965&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=85140324965&partnerID=8YFLogxK
U2 - 10.1021/acs.joc.2c01769
DO - 10.1021/acs.joc.2c01769
M3 - Article
AN - SCOPUS:85140324965
SN - 0022-3263
VL - 87
SP - 14299
EP - 14307
JO - Journal of Organic Chemistry
JF - Journal of Organic Chemistry
IS - 21
ER -