Differential Reactivity and Structure of Mono- and Dialkoxides:  The Reactions of Ethylene Glycol on Mo(110)

Abstract

The reactions of ethylene glycol on Mo(110) were studied using temperature-programmed reaction, infrared reflection absorption, high-resolution electron energy loss, and X-ray photoelectron spectroscopies. The major reaction pathway is double C−O bond scission to evolve gas-phase ethylene at 350 and 390 K. Both X-ray photoelectron and infrared spectra demonstrate the existence of two surface intermediates, a bidentate (−OCH2CH2O−) and a monodentate (−OCH2CH2OH) species, at saturation coverage of ethylene glycol. We demonstrate that all ethylene glycol in the mixed overlayer of mono- and bidentate species reacts via a bidentate surface intermediate. Furthermore, in contrast to previous studies on other surfaces, the dialkoxide ethylene glycol intermediate is shown to be more reactive than similar monoalkoxides on Mo(110). Finally, analysis of the infrared spectra demonstrates that the bidentate species adsorbs with C 2 (or lower) symmetry at 300 K.

Acetaldehyde reactions over the uranium oxide system

“…Gas [57] Cu(111) [43] ν(CH) powder and UO 2 (111) single crystal [23] and other workers have also observed the same on Mo(110) single crystal [46,47]. This is analogous to obtaining butene from acetaldehyde via a 2,3-butanediolate intermediate as shown in Scheme 1.…”

“…12 and 13 and Refs. [42,46,47] one can conclude the following. The IR band at 1068 cm −1 formed from acetaldehyde at 220 K and disappearing by 380 K is due to ν(O-C) of either ethoxide or pinacolate species.…”

“…In Ref. [47] a band at 1008 cm −1 is observed at low coverage and attributed to ν(O-C) of pinacolates ((a)O-CH 2 -CH 2 -O(a)). When surface saturation was approached, a strong band was observed at a higher frequency (1080 cm −1 ) in addition.…”

“…Several bands are observed (in cm −1 ): 2967 (ν as (CH 3 )), 2927 (ν(CH)), 2866 (ν s (CH 3 )), 1746 (ν(C=O)), 1630 (the gas-phase ν(C=O) of 2,3-butanedione is at ≈ 1750 cm −1 ), 1568 (ν as (COO)), (most likely from a carboxylate formed by further reaction with the surface), 1462 (ν s (COO) of a carboxylate), 1445 (δ as (CH 3 )), 1381 (δ s (CH 3 )), 1349 (δ(CH)) of the diol. The only detailed work of a diolate adsorbed on a surface is that of ethylene glycol (HO-CH 2 CH 2 -OH) on Mo(110) single crystal by HREELS [46,47] and it is with the help of this work and that of ethanol on CeO 2 [37] that the other bands are analyzed. A band at ca.…”

Tracking Site-Specific C–C Coupling of Formaldehyde Molecules on Rutile TiO2(110)

“…5,7 Diolate intermediates formed from other oxygenates (e.g. diols) have been observed on metal catalyst surfaces including NiPt, 15 Ru(111), 16 Mo(110), 17 Ag(110), 18 and oxide surfaces including TiO 2 (110) 19 . The desorption of alkene products from the diolates have been observed on Mo(110) and TiO 2 (110).…”