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Catalytic Application of Atomically Precise Metal Nanoclusters as Heterogeneous Catalysts in Industrially Important Chemical Reactions
Published in Yan Zhu, Rongchao Jin, Atomically Precise Nanoclusters, 2021
Another important oxidation reaction is the alcohol oxidation to produce aldehydes or acids. Tsukuda and co-workers found that more amounts of residual thiolates on Au25 gave rise to higher selectivity for benzaldehyde from selective oxidation of benzyl alcohol, but lower activity [5]. The thiolate ligands not only reduced the oxidation ability of Au25, but also inhibited the esterification reaction on the surface of the Au25 nanocluster by site isolation (Fig. 9.3). They also found that single Pd atom doping into Au33 and Au43 formed PdAu33 and PdAu43 that improved the catalytic activity for selective oxidation of benzyl alcohol [6]. Especially, Pd1Au24 supported on carbon nanotubes showed distinct catalytic activity for the oxidation of benzyl alcohol, mainly because the electron transfer from Pd to Au led to more negative Au sites [7].
Innovative industrial technology starts with iodine
Published in Tatsuo Kaiho, Iodine Made Simple, 2017
Many studies up to now have reported on the various reactivities of trivalent hypervalent iodine compounds, as represented by phenyliodine diacetate (PIDA) and phenyliodine bistrifluoroacetate (PIFA). However, trivalent hypervalent iodine compounds are stoichiometric oxidants, producing a monovalent iodobenzene as a byproduct. Recently, as demand for high quality and high purity in the chemical synthesis of drugs, agrochemicals, electronic materials, etc., has grown, removal of the byproduct iodobenzene, which is produced in large quantities, must be addressed in order to achieve commercial application. In response, development of a recyclable hypervalent iodine oxidant is underway. First, a new recyclable hypervalent iodine (III) reagent which introduces four PIDA or PIFA into one molecule with adamantane or methane as the nucleus has been developed. When used in an alcohol oxidation reaction, ketone or aldehyde is produced at high yield. Furthermore, after this reaction is completed, the byproduct iodobenzene may be collected simply by filtering the reaction solution. In addition, by reoxidizing iodobenzene with meta-chloroperoxybenzoic acid, iodobenzene can once again be an active species and be reused in oxidation reactions [41a].
A carboxylate-bridged Mn(II) compound with 6-methylanthranilate/bipy: oxidation of alcohols/alkenes and catalase-like activity
Published in Journal of Coordination Chemistry, 2018
Yalcin Kilic, Serkan Bolat, Ibrahim Kani
The Mn(II)/TBHP/alcohol/CH3CN catalytic system exhibits very high activity for the oxidation of cinnamyl alcohol, moderate activity for benzyl alcohol and cyclohexanol, and very low activity for 1-octanol and 1-heptanol. The time-dependent catalytic activity results are shown in Figure 3 and Table 4. Among the studied alcohols, the catalytic oxidation of cinnamyl alcohol resulted in ~100% conversion in 90 min (TON ~ 266 h−1). The catalytic rate of cinnamyl alcohol oxidation is extremely high: TOF = 11,057 h−1 in the first minute of the reaction. Other reaction products of cinnamyl alcohol are benzaldehyde (46.3%), cinnamyl aldehyde (15.9%), styrene (14.2%), benzoic acid (14.0%), and 3-phenylglycidol (5.9%). Primary aliphatic alcohols (1-heptanol and 1-octanol) were oxidized to carboxylic acids as their secondary oxidation products, whereas secondary alcohol (cyclohexanol) was oxidized to cyclohexanone (43.6% in 6 h) without a carbon-carbon chain cleavage (Table 4). These results support the reports that the compound is more reactive in the oxidation of benzylic alcohols than that of aliphatic alcohols [45]. Benzaldehyde and benzoic acid were detected during the catalytic oxidation of benzyl alcohol. After a 24-h reaction, the total conversion was recorded at 80.2% for benzyl alcohol oxidation with an aldehyde selectivity of 46.6% (Table 4).
Experimentally formulated and theoretically rationalized alumina immobilized copper catalyst for alcohol oxidation
Published in Journal of Coordination Chemistry, 2020
Tania Chowdhury, Sourav Chatterjee, Priyabrata Banerjee, Dipankar Sukul, Madhulata Shukla, Tanmay Chattopadhyay
Initially benzyl alcohol was chosen as the model substrate to optimize the reaction conditions for alcohol oxidation to aldehyde. Both the catalyst [CuL] and oxidizing agent H2O2 concentration varied between 1-2 mmole for 1 mmole of benzyl alcohol. The reaction time was extended from 2 h to 7 h. Product yield was found to be maximized with 1 mmole of [CuL] and 1.25 mmole of H2O2 on performing the reaction for 3 h. No increment of yield was obtained on increasing catalyst concentration or on increase of reaction time. The oxidation mechanism is believed to proceed via the formation of copper-hydroperoxo species as we got evidence from ESI-MS and UV-vis spectral studies. In order to investigate the intermediate species in the alcohol oxidation reaction by the assistance of [CuL] we added H2O2 to our homogeneous catalyst [CuL] and monitored the reaction through ESI-MS where we found a peak at m/z = 410.2720 amu and 388.2227 amu along with the main peak of complex at m/z = 356.9445 amu (reported earlier in Figure S3, supplementary material). These two peaks may be attributed to the formation of copper(II)-hydroperoxo species [CuL(OOH)Na]+ and [CuL(H2O2)]+ having the exact molecular formula C11H13Cl2CuNO6Na+ and C11H12Cl2CuNO6+, respectively, demonstrated pictorially in Figure 10. A change in UV-vis spectral pattern also occurred during the reaction between [CuL] and H2O2. The newly generated band at 375 nm may be assigned to the ligand to metal charge transfer band of the Cu-OOH species. Complex [CuL] showed 4 lines in X-band EPR spectra due to having one unpaired electron and nuclear spin of copper being +3/2. On adding H2O2, the bands became a little bit blunt and slightly shifted with respect to complex [CuL] (Figure S5, supplementary material). This was also in accordance with the formation of Cu-OOH. By this experiment it can be inferred that copper-hydroperoxo species is the intermediate of [CuL] catalyzed alcohol oxidation reaction (Schemes 1 and 2). On getting an evidence of formation of this intermediate species in the ESI-MS spectra, we have proposed a plausible mechanism showing how our homogeneous [CuL] help catalyzing oxidation of alcohol to aldehyde (given in Scheme 3).