Stabilities of substituted oxametallzcycle intermediates: Implications for regioselectivity of epoxide ring opening and olefin epoxidation

Journal Article · Thu Dec 16 04:00:00 EST 1999 · Journal of Physical Chemistry B: Materials, Surfaces, Interfaces, amp Biophysical

DOI:https://doi.org/10.1021/jp992812r· OSTI ID:20013663

Medlin, J W; Mavrikakis, M; Barteau, M A

Total energy density functional theory (DFT) calculations were performed to determine the relative stabilities of methyl substituted isomers of oxametallacycle intermediates potentially formed during ring-opening reactions of propylene oxide (PO) and isobutylene oxide (IO) on metal dimers. The relative stabilities of different oxametallacycle isomers may determine the regioselectivity of reactions involving these intermediates. In the ring opening of PO and IO, two oxametallacycle isomers may be formed: one in which the methyl groups are attached to the bridging carbon of the O-C-C backbone and one in which the methyl groups are attached to the surface-bound carbon. DFT calculations consistently indicate that oxametallacycles incorporating methyl groups attached to the bridging C atom are more stable by approximately 2--7 kcal/mol for all 14 metals studied. However, the relatively small thermodynamic stability differences between isomers suggest that kinetic barriers and the manipulation of these by surface modification may control the regioselectivity of reactions involving oxametallacycles in some cases. Computed oxametallacycle stabilities are compared with regioselectivities of epoxide ring opening and olefin oxidation reactions previously reported on metal surfaces and catalysts in order to examine which examples are consistent with the formation of the thermodynamically preferred oxametallacycle intermediate.

• Research Organization: Univ. of Delaware, Newark, DE (US)
• Sponsoring Organization: US Department of Energy
• DOE Contract Number: FG02-84ER13290
• OSTI ID: 20013663
• Journal Information: Journal of Physical Chemistry B: Materials, Surfaces, Interfaces, amp Biophysical, Journal Name: Journal of Physical Chemistry B: Materials, Surfaces, Interfaces, amp Biophysical Journal Issue: 50 Vol. 103; ISSN 1089-5647; ISSN JPCBFK
• Country of Publication: United States
• Language: English

Related Subjects

2-METHYLPROPENE
40 CHEMISTRY
ALKENES
EPOXIDES
OXIDATION
OXIDES
REACTION INTERMEDIATES
STABILITY