Partial oxidation of allylic and primary alcohols with O2 by photoexcited TiO2

Molinari, Alessandra; Montoncello, M.; Rezala, Houria; Maldotti, Andrea

doi:10.1039/b817147e

Cited by 44 publications

(42 citation statements)

References 36 publications

(50 reference statements)

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“…26 As a matter of fact, the two unresolved peaks are suggested to be parts of the quadruple DMPO−OH• adduct 27,28 (α N = α H β = 12.4 G) but overlapped and interfered by the stronger DMPOX signal. As soon as the onset of UVlight, a new six-line EPR signal (with asterisk) characteristic for the DMPO−•CN adduct 29 (α N = 14.5 G, α H β = 22.4 G) was generated; meanwhile, the intensities of DMPOX and OH• radicals were decayed to a certain extent (Figure 3a, blue line).…”

Section: Resultsmentioning

confidence: 95%

Radical-Involved Photosynthesis of AuCN Oligomers from Au Nanoparticles and Acetonitrile

Kobayashi

Tong

et al. 2012

J. Am. Chem. Soc.

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We show here the first radical route for the direct photosynthesis of AuCN oligomers with different sizes and shapes, as evidenced by TEM observations, from an Au nanoparticle/benzaldehyde/CH(3)CN ternary system in air under UV-light irradiation. This photochemical route is green, mild, and universal, which makes itself distinguishable from the common cyanidation process. Several elementary reaction steps, including the strong C-C bond dissociation of CH(3)CN and subsequent •CN radical addition to Au, have been suggested to be critical in the formation of AuCN oligomers based on the identification of •CN radical by in situ EPR and the radical trapping technique, and other reaction products by GC-MS and (1)H NMR, and DFT calculations. The resulting solid-state AuCN oligomers exhibit unique spectroscopic characters that may be a result of the shorter Au-Au distances (namely, aurophilicity) and/or special polymer-like structures as compared with gold cyanide derivatives in the aqueous phase. The nanosized AuCN oligomers supported on mesoporous silica showed relatively good catalytic activity on the homogeneous annulation of salicylaldehyde with phenylacetylene to afford isoflavanones employing PBu(3) as the cocatalyst under moderate conditions, which also serves as evidence for the successful production of AuCN oligomers.

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Section: Resultsmentioning

confidence: 95%

Radical-Involved Photosynthesis of AuCN Oligomers from Au Nanoparticles and Acetonitrile

Kobayashi

Tong

et al. 2012

J. Am. Chem. Soc.

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“…28,37–41,47 Carbon-centred radical adducts afford a larger a H value than the a N value. 28,42 Thus, the type of radical species can be readily distinguished based on the hyperfine splitting pattern of the DMPO spin adducts.…”

Section: Resultsmentioning

confidence: 99%

One-step selective hydroxylation of benzene to phenol with hydrogen peroxide catalysed by copper complexes incorporated into mesoporous silica–alumina

2016

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Benzene was hydroxylated with hydrogen peroxide (H2O2) in the presence of catalytic amounts of copper complexes in acetone to yield phenol at 298 K. At higher temperature, phenol was further hydroxylated with H2O2 by catalysis of copper complexes to yield p-benzoquinone. The kinetic study revealed that the rate was proportional to concentrations of benzene and H2O2, but to the square root of concentration of a copper(II) complex ([Cu(tmpa)]2+: tmpa = tris(2-pyridylmethyl)amine). The addition of a spin trapping reagent resulted in formation of a spin adduct of hydroperoxyl radical (HO2•), as observed by EPR spectroscopy, inhibiting phenol formation. HO2• produced by the reaction of [Cu(tmpa)]2+ with H2O2 acts as a chain carrier for the radical chain reactions for formation of phenol. When [Cu(tmpa)]2+ was incorporated into mesoporous silica-alumina (Al-MCM-41) by a cation exchange reaction, the selectivity to production of phenol was much enhanced by prevention of hydroxylation of phenol, which was not adsorbed to Al-MCM-41. The high durability with turnover number of 4320 for the hydroxylation of benzene to phenol with H2O2 was achieved using [Cu(tmpa)]2+ incorporated into Al-MCM-41 as an efficient and selective catalyst.

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“…Near-UV irradiated suspensions of P25-TiO 2 performed the partial oxidation of different alcohols (geraniol, citronellol, trans-2-penten-1-ol and 1-pentanol, dissolved in CH 3 CN-H 2 O mixture) with good selectivity (>70%) [15]. The selective photocatalytic oxidation of benzyl alcohol to benzaldehyde has been carried out in solvent-free system by using TiO 2 and Ir/TiO 2 photocatalysts [16] or in aqueous solution, under acidic conditions, through the TiO 2 /Cu(II)/solar UV photocatalytic system [17].…”

Section: Introductionmentioning

confidence: 99%

Photoelectrocatalytic selective oxidation of 4-methoxybenzyl alcohol in water by TiO2 supported on titanium anodes

Özcan

Yurdakal

Augugliaro

et al. 2013

Applied Catalysis B: Environmental

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a b s t r a c tThe photoelectrocatalytic partial oxidation of 4-methoxybenzyl alcohol in aqueous solution irradiated by near-UV light was carried out in a three-electrode batch reactor. TiO 2 films were either deposited by dip-coating of a TiO 2 sol onto a Ti foil and subsequent calcination or generated on Ti plates by thermal oxidation in air at 400-700 • C. The effects of the anode preparation method and bias potential values on conversion and selectivity to the corresponding aldehyde were investigated. The photoelectrocatalytic results were compared with the photocatalytic and electrocatalytic ones. The results indicated that no reaction occurred during the electrocatalytic experiments, whereas the photocatalytic reactivity was positively influenced by the application of a small bias (0.75 V vs. saturated calomel electrode). By applying the previous bias the highest initial degradation rates, r 0 , and selectivities to 4-methoxybenzaldehyde, S, were obtained in photoelectrocatalytic experiments by using Ti plate calcined at 500 • C (r 0 = 0.1507 mM h −1 , S = 85%) or TiO 2 film prepared by dip-coating and calcined at 700 • C (r 0 = 0.1339 mM h −1 , S = 90%). In order to investigate the influence of the substituent groups on reactivity and selectivity, photoelectrocatalytic runs with benzyl alcohol, 2-methoxybenzyl alcohol, 3-methoxybenzyl alcohol, 2,4-dimethoxybenzyl alcohol, 2,3,4-trimethoxybenzyl alcohol, 4-nitrobenzyl alcohol and 4-hydroxybenzyl alcohol have been performed. The selectivity and reactivity values increased by increasing the electron-donor properties of the substituent groups. This positive effect, however, was obtained only if the electron-donor group is in para or ortho position with respect to the alcoholic group.

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Partial oxidation of allylic and primary alcohols with O2 by photoexcited TiO2

Cited by 44 publications

References 36 publications

Radical-Involved Photosynthesis of AuCN Oligomers from Au Nanoparticles and Acetonitrile

Radical-Involved Photosynthesis of AuCN Oligomers from Au Nanoparticles and Acetonitrile

One-step selective hydroxylation of benzene to phenol with hydrogen peroxide catalysed by copper complexes incorporated into mesoporous silica–alumina

Photoelectrocatalytic selective oxidation of 4-methoxybenzyl alcohol in water by TiO2 supported on titanium anodes

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