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One‐Step Paths of the Alkene Hydration Revealed by a DFT Study
Author(s) -
Yamabe Shinichi,
Tsuchida Noriko,
Yamazaki Shoko
Publication year - 2017
Publication title -
chemistryselect
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.437
H-Index - 34
ISSN - 2365-6549
DOI - 10.1002/slct.201701407
Subject(s) - alkene , chemistry , carbocation , ethylene , medicinal chemistry , kinetic isotope effect , styrene , proton , activation energy , solvent , organic chemistry , deuterium , catalysis , physics , polymer , quantum mechanics , copolymer
DFT calculations were carried out for alkene hydration reactions. A model, alkene + H 3 O + (H 2 O) 13 → alcohol + H 3 O + (H 2 O) 12 , was adopted to assure proton transfer routes. The second and larger one, alkene + H 3 O + (H 2 O) 21 → alcohol + H 3 O + (H 2 O) 20 , was also employed for some key reactions. Alkene substrates adopted here are ethylene, propylene, isobutene, styrenes (α‐methyl, para Z‐C 6 H 4 ‐CH=CH 2 , Z=NO 2 , CN, CF 3 , Cl, H, Me, OMe, OH, NH 2 and NMe 2 ). Transition‐state geometries were determined, and the subsequent intrinsic reaction coordinate (IRC) analyses were made. In contrast to the traditional scheme, the stepwise path including the carbocation is quite limited (only for the styrene with Z=OMe, OH, NH 2 and NMe 2 ). Even for the isobutene substrate, the tert ‐Bu + cation intermediate was not found and a one‐step path was obtained. Calculated activation energies, +32.52 kcal/mol (a) for ethylene, +27.10 kcal/mol (b) for propylene, +21.33 kcal/mol (c) for isobutene, +19.79 kcal/mol (d) for styrene and +23.79 kcal/mol (e) for para ‐nitrostyrene, are in good agreement with experimental values, +32.4±1 kcal/mol (a), +26.4±1 kcal/mol (b), +21.1±0.2 kcal/mol (c), +19.2±0.5 kcal/mol (d) and +23.2 kcal/mol (e), respectively. The solvent isotope effect k(H 2 O)/k(D 2 O) was calculated and was compared with the experimental data.