Oxidation of tert-butyl alcohol to isobutylene oxide on a silver(110) surface: the role of unactivated carbon-hydrogen bonds in product selectivity

Brainard, Robert L.; Madix, Robert J.

doi:10.1021/ja00193a012

“…It is also difficult to explain results regarding the stereoselectivity of epoxidation with a mechanism that involves concerted addition of surface oxygen across the ethylene C=C bond. The oxametallacycle intermediate is characterized by an − O − C − C − back-bone bonded to a metal surface via metal-oxygen and metal-carbon bonds [38][39][40][41][42][43][44][45][46]. The results of these experiments are contained in Table 1; these observations argue against the above-postulated concerted addition of oxygen to form C − O bonds.…”

Section: Introductionmentioning

confidence: 95%

Heterogeneous Catalysis of Alkene Epoxidation

Linic

¹

,

Barteau

²

2008

Handbook of Heterogeneous Catalysis

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The sections in this article are Introduction Epoxidation of Ethylene with Silver Catalysts Process Overview Historical Perspectives on the Reaction Network and Mechanism Selectivity Control by a “Common Intermediate” Why Silver is a Unique Catalyst: Activity and Selectivity Improvement of Catalyst Selectivity Extensions of Silver‐Catalyzed Direct Epoxidation to Other Olefins Epoxidation of Larger Alkenes with Titanium‐Based Catalysts Conceptual Differences Compared to Direct Epoxidation Titania–Silica Catalysts and Insights into Mechanism and Active Sites Epoxidation with H 2 O 2 in the Presence of Water: TS ‐1 and Related Materials Strategies for In‐Situ Generation of Peroxides Perspective

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“…In that case, one must solve a set of linear equations for each of the masses (more precisely, mass to charge ratios) observed where the total intensity of each mass is given by the appropriately weighted sum of the contribution of each of the species. 3,4 This is a straightforward procedure if all the products and their corresponding cracking patterns are known. In practice, it is usually possible to identify one of the products based on one unique mass fragment, subtract the contribution of each of its cracking fragments from the other masses observed and proceed to identify all the products.…”

Section: Experimental Techniquesmentioning

confidence: 99%

“…As shown by Brainard and Madix in the oxidation of tert-butyl alcohol on Ag(110), tert-butoxy reacts at significantly higher temperatures (510 K) in the absence of coadsorbed oxygen due to the greater difficulty of activation of the methyl C-H bonds (g-C-H bonds) to yield isobutylene oxide and isobutylene as the major products together with tert-butyl alcohol, water, and CO 2 . 3,38 The reactions of (CH 3 ) 3 COH, (CH 3 ) 3 COD, and (CD 3 ) 3 COH show that the production of isobutylene oxide and isobutylene involves the rate-limiting breaking of the C-H/D bond. This observation is a clear indication of the formation of an oxametallacycle intermediate from tertbutoxy (Scheme 3) that is also involved in the oxidation of tert-butyl alcohol on Cu(110).…”

Section: Oxidation Of Alcohols On Silvermentioning

confidence: 99%

See 1 more Smart Citation

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

Li

¹

,

Madix

²

,

Friend

³

2008

Self Cite

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The coinage metals, copper, silver, and gold, have unique characteristics for selective oxidation catalysis, particularly for partial oxidation of alcohols and olefins. A basic understanding of surface chemistry at the molecular level can help facilitate the improvement of current catalytic processes and the designing of new catalytic systems. In this critical review, the current state of knowledge of these reactions is reviewed. First, both the experimental and theoretical methods necessary for understanding surface reactivity are discussed with a specific set of examples directly related to these reactions. Next the state of understanding of the surface chemistry of the oxidation reactions of alcohols and olefins on these three coinage metals is reviewed and the reaction pathways are compared. Clear relationships between the low pressure surface science studies and more practical catalytic conditions are illustrated. Finally, recent theoretical advances in this area are discussed as well as possible future directions in this field (132 references).

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“…An ion gauge sensitivity of 9.5 was used for CD 3 I using a correlation by S. George as reported by Brainard and Madix[28]. Relative mass spectrometer sensitivity factors of 0.05 for CD 3 I (m/z = 145), 0.23 for CD 2 = CD 2 (m/z = 32), and 0.66 for methane (m/ z = 20 and 19) were determined experimentally.…”

mentioning

confidence: 99%

Reactions of methyl groups on a non-reducible metal oxide: The reaction of iodomethane on stoichiometric α-Cr2O3(0001)

Dong

¹

,

Brooks

²

,

Chen

³

et al. 2015

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The reaction of iodomethane on the nearly stoichiometric α-Cr 2 O 3 (0001) surface produces gas phase ethylene, methane, and surface iodine adatoms. The reaction is initiated by the dissociation of iodomethane into surface methyl fragments, −CH 3 , and iodine adatoms. Methyl fragments bound at surface Cr cation sites undergo a rate-limiting dehydrogenation reaction to methylene, =CH 2 . The methylene intermediates formed from methyl dehydrogenation can undergo coupling reactions to produce ethylene via two principle reaction pathways:(1) direct coupling of methylene and (2) methylene insertion into the methyl surface bond to form surface ethyl groups which undergo β-H elimination to produce ethylene. The liberated hydrogen also combines with methyl groups to form methane. Iodine adatoms from the dissociation of iodomethane deactivate the surface by simple site blocking of the surface Cr 3+ cations.

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Oxidation of tert-butyl alcohol to isobutylene oxide on a silver(110) surface: the role of unactivated carbon-hydrogen bonds in product selectivity

Cited by 60 publications

References 0 publications

Heterogeneous Catalysis of Alkene Epoxidation

Heterogeneous Catalysis of Alkene Epoxidation

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

Reactions of methyl groups on a non-reducible metal oxide: The reaction of iodomethane on stoichiometric α-Cr2O3(0001)

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