The Cyclopropylmethyl−3-Butenyl Rearrangement on Mo(110):  A Radical Clock on a Surface?

Abstract

The mechanism for the transformation of adsorbed cyclopropylmethyloxide into its ring-opened form, 3-butenyloxide, on the Mo(110) surface is explored theoretically. An alternative emerges to the radical clock mechanism that involves the cleavage of the C-O bond in the adsorbate as the critical reaction step. The alternative pathway involves the cleavage of a C-C bond in the three-membered ring leading to a diradical, which could transform via a 1,2-H shift to the same reaction product. Density functional theory (DFT) calculations for relevant reaction intermediates in molecular model systems show an energetic preference for the C-C cleavage in the initial step. The barrier of the subsequent 1,2-H shift of the singlet diradical is slightly lower than the barrier for the radical clock rearrangement, rendering the diradical pathway a possible alternative. Adsorbate structures for the reactant and the product were obtained by DFT slab calculations. We carry out a MO analysis of the bonding in the adsorbate, comparing also C-C and C-O bonding.

Insight into the Preference Mechanism of CHx (x = 1–3) and C–C Chain Formation Involved in C2 Oxygenate Formation from Syngas on the Cu(110) Surface

“…Finally, the three-layer (110) surface model has been widely used in the previous calculations of reactions on the metal surface; for example, Flemmig et al 53 used a three-layer slab Mo(110) surface to investigate the mechanism for the transformation of adsorbed cyclopropylmethyloxide; Classen et al 54 investigated the interaction of trimesic acid with a threelayer slab Cu(110) surface; Wang et al 55 studied the adsorption of CH 3 , CH 3 O, and HCOO on metal Ni using a three-layer slab Ni(110) surface model; Szukiewicz et al 56 employed a three-layer slab Mo(110) surface to investigate the Gd adsorbed layers on the Mo(110) surface; Liao et al 57 used a three-layer slab Rh(110) surface to investigate the adsorption of NO.…”

Unraveling molecular transformations on surfaces: a critical comparison of oxidation reactions on coinage metals

“…119 In addition, the nature of bonding of intermediates to the surface can be analyzed-analogous to a frontier orbital analysis for molecular chemistry-in order to develop predictive frameworks. [120][121][122] Overall, theoretical investigation of the bonding of key surface intermediates, in particular using DFT, is potentially valuable for predicting factors that will change reactions rates and selectivities.…”

11 Reaction mechanisms : Part (i) Radical and radical ion reactions

“…Rather than the radical clock process, these authors suggested a diradical mechanism may be operative involving vicinal C-C bond cleavage, and a 1,2-hydrogen atom shift (Scheme 39). 89 The mechanism of vicarious nucleophilic aromatic substitution of hydrogen (direct nucleophilic addition vs. electron transfer) was probed using a cyclopropyl probe in the anion [eqn (18)]. The failure to detect any ring opened products, arising from the rearrangement depicted in eqn 19 was cited as evidence against the electron transfer pathway.…”