Formation Of Benzaldehyde Research Articles

Uranyl-based heterogeneous catalyst for the selective oxidation of benzylic alcohols to form corresponding carbonyl compounds

Uranyl ions (O U O) 2+ immobilized in mesoporous MCM-41 are found to serve as highly active heterogeneous catalyst for the formation of benzaldehyde in liquid–solid-phase oxidation of benzylic alcohols, using tert-butyl hydrogen peroxide ( t-BuOOH) as an oxidant. The benzoic acid was formed on subsequent oxidation of benzaldehyde and therefore its yield increased with the increasing contact time. The solvent employed as a reaction medium influenced the catalyst activity considerably, and the best results were obtained using ethyl acetoacetate as the solvent. In the repeated cycles of activity measurements, fairly reproducible results were achieved after an initial decrease in the activity because of the partial leaching of uranyl ions.

Coupling the deoxygenation of benzoic acid with the oxidation of propylene on a Co molybdate catalyst

An innovating coupling between the deoxygenation of benzoic acid and the oxidation of propylene was set up and gave new information about the mechanism involved in the oxidation of propylene on a Co–Mo based oxide catalyst. The production of CO 2 during the catalytic reaction is bound to the formation of benzene and benzaldehyde. The first case corresponds to the removal of the carboxyl function of the benzoic acid. The second case is the evidence that benzaldehyde and products coming from the oxidation of propylene are formed on the same catalytic sites during the Mars and van Krevelen cycle. In this cycle, the oxygen atoms used for the oxidation come from the benzoic acid by the intermediate of the oxide lattice. In particular, it has been demonstrated that the oxidation of propylene involves lattice oxygen atoms far from each other in such a way that the reaction leaves single oxygen vacancies at the surface of the catalyst. Such coupling between a deoxygenation reaction and an oxidation one is reported for the first time.

A Kinetic Model for Toluene Oxidation Comprising Benzylperoxy Benzoate Ester as Reactive Intermediate in the Formation of Benzaldehyde

During the oxidation of toluene under semibatch conditions, the formation of benzyl alcohol is initially equal to the rate of formation of benzaldehyde. As the overall conversion increases the benzyl alcohol concentration at first decreases much faster than benzaldehyde, but this decrease slows down causing the benzyl alcohol concentration to reduce to zero only very slowly. To account for this phenomenon a new reaction pathway has been proposed where the formation of benzaldehyde out of benzylhydroperoxide is catalysed by benzoic acid. Incorporation of this new reaction in a model improves the description of benzyl alcohol concentration prophiles while maintaining good predictions for benzaldehyde and benzoic acid.

N-Nitrosoamide-Mediated N → O Nitroso Transfer to Alcohols with Subsequent Denitroxylation

Decomposition of certain N-benzyl-N-nitrosoamides is often accompanied by small amounts of benzaldehyde whose formation was postulated to arise from in situ formation and oxidation of benzyl alcohol. Incubation of excess benzyl alcohol with thermostable N-benzyl-N-nitrosoamides at ambient temperatures in inert solvents generates benzyl nitrite, N-benzyl amides, and benzaldehyde as the major products. Benzyl nitrite formation appears to be linked to N --> O nitroso transfer between the N-benzyl-N-nitrosoamides and benzyl alcohol, which is subject to the previously observed electronic and steric features of the acyl substituent although the former appears to play a much larger role than the latter. Benzaldehyde formation evidently arises from dehydronitrosation (denitroxylation) of the nitrite via O-N bond homolysis and H-abstraction from the resultant benzyloxy radical. Although trans-nitrosation occurs with methanol, 1 degree, 2 degree, and 3 degree alcohols, the reaction is evidently subject to steric effects at both the alpha and beta carbons of the alcohol. Additionally, carbonyl formation only occurs with 2 degrees alcohols and those that can derive resonance-stabilized carbonyls.

Vapour Phase Oxidation of Acetophenone to Benzoic Acid Over Binary Oxides of V and Mo

Test data for catalytic oxidation of acetophenone into benzoic acid performed at bench scale with V 2 O 5 –MoO 3 catalyst in a continuous downflow metal reactor are presented. The process parameters such as temperature and flow rate influence the product distribution. The P 2 O 5 , B 2 O 3 and Na 2 O when used as dopant on V 2 O 5 –MoO 3 catalyst showed marked influence on activity and selectivity. An acidic catalyst like V 2 O 5 -MoO 3 –P 2 O 5 favours formation of benzoic acid while a basic catalyst like V 2 O 5 –MoO 3 –Na 2 O favours formation of benzaldehyde. The addition of Na 2 O into V 2 O 5 –MoO 3 binary oxides formed new phases (NaVMoO 6 and Na 2 V 2 Mo 3 O 15 ), which increased Arrhenius activation energy from 18.24 to 31.35 kcal mol −1

Styrene oxidation with H 2O 2 over Ti-containing molecular sieves with MFI, BEA and MCM-41 topologies

A comparative study concerning the use of Ti-containing molecular sieves with MFI (TS-1), BEA (Ti-beta) and MCM-41 (TiMCM-41) topologies for the styrene oxidation in liquid phase by hydrogen peroxide was performed. The major reactions were epoxidation of styrene, the isomerization of styrene oxide into phenylacetaldehyde (PhAA) as well as its oxidative cleavage into benzaldehyde (BzA) and formaldehyde. A high selectivity to PhAA was observed over TS-1, whereas the BzA formation is predominant on Ti-beta and TiMCM-41. Also, the influence of the reaction time and the nature of solvent on the styrene conversion, the selectivity of hydrogen peroxide consumption and on the product distribution were studied.

Steady-State and Laser Flash Photolysis Study of the Carbon−Carbon Bond Fragmentation Reactions of 2-Arylsulfanyl Alcohol Radical Cations

The N-methylquinolinium tetrafluoroborate (NMQ(+))-sensitized photolysis of the erythro-1,2-diphenyl-2-arylsulfanylethanols 1-3 (1, aryl = phenyl; 2, aryl = 4-methylphenyl; 3, aryl = 3-chlorophenyl) has been investigated in MeCN, under laser flash and steady-state photolysis. Under laser irradiation, the formation of sulfide radical cations of 1-3, in the monomeric (lambda(max) = 520-540 nm) and dimeric form (lambda(max) = 720-->800 nm), was observed within the laser pulse. The radical cations decayed by first-order kinetics, and under nitrogen, the formation of ArSCH(*)Ph (lambda(max) = 350-360 nm) was clearly observed. This indicates that the decay of the radical cation is due to a fragmentation process involving the heterolytic C-C bond cleavage, a conclusion fully confirmed by steady-state photolysis experiments (formation of benzaldehyde and the dimer of the alpha-arylsulfanyl carbon radical). Whereas the fragmentation rate decreases as the C-C bond dissociation energy (BDE) increases, no rate change was observed by the replacement of OH by OD in the sulfide radical cation (k(OH)/k(OD) = 1). This suggests a transition state structure with partial C-C bond cleavage where the main effect of the OH group is the stabilization of the transition state by hydrogen bonding with the solvent. The fragmentation rate of 2-hydroxy sulfanyl radical cations turned out to be significantly slower than that of nitrogen analogues of comparable reduction potential, probably due to a more efficient overlap between the SOMO in the heteroatom and the C-C bond sigma-orbital in the second case. The fragmentation rates of 1(+*)-3(+*) were found to increase by addition of a pyridine, and plots of k(base) against base strength were linear, allowing calculation of the beta Bronsted values, which were found to increase as the reduction potential of the radical cation decreases, beta = 0.21 (3(+*)), 0.34 (1(+*)), and 0.48 (2(+*)). The reactions of 1(+*) exhibit a deuterium kinetic isotope effect with values that increase as the base strength increases: k(OH)/k(OD) = 1.3 (pyridine), 1.9 (4-ethylpyridine), and 2.3 (4-methoxypyridine). This finding and the observation that with the above three bases the rate decreases in the order 3(+*) > 1(+*) > 2(+*), i.e., as the C-C BDE increases, suggest that C-C and O-H bond cleavages are concerted but not synchronous, with the role of OH bond breaking increasing as the base becomes stronger (variable transition state). It is probable that, with the much stronger base, 4-(dimethylamino)pyridine, a change to a stepwise mechanism may occur where the slow step is the formation of a radical zwitterion that then rapidly fragmentates to products.

Initiating ability of the peroxyacetates of secondary hydroperoxides

The kinetics of ethylbenzene oxidation in the presence of acetic anhydride, the kinetics of acetic anhydride reaction with cyclohexyl hydroperoxide, and the composition of the products of the above reactions were studied in order to evaluate the initiating abilities of 1-phenylethyl and cyclohexyl peroxyacetates generated in situ and to determine the directions of reactions. Anhydride additives significantly accelerated the oxidation of ethylbenzene and the degradation of cyclohexyl hydroperoxide with the predominant formation of corresponding ketones. It was found that the acceleration of ethylbenzene oxidation was due to the homolytic degradation of a peroxy ester, which results in the formation of methyl phenyl carbinol and benzaldehyde (ethylbenzene) or cyclohexanol (cyclohexyl hydroperoxide). The importance of the homolytic degradation of peroxy esters was evaluated using a mixed-initiation method (ethylbenzene) or by measuring the consumption of an inhibitor (cyclohexyl hydroperoxide).

Promotion Effect of Alkali Metal Added to Impregnated Cobalt Catalysts in the Gas-Phase Catalytic Oxidation of Benzyl Alcohol

The effect of the addition of alkali metals on the catalytic activity of cobalt catalysts (Co/NaY, Co/SiO2, etc.) impregnated on inorganic oxides including NaY and SiO2 was studied using the gas-phase catalytic oxidation of benzyl alcohol. The partial oxidation activities, measured by the yield of benzaldehyde, of the supported Co catalysts were selectively promoted by adding alkali metal, with keeping the yield of CO2 low. The amount of added alkali metal under a constant amount of the impregnated cobalt had an optimal value for the catalytic activity of the benzaldehyde formation. The influences of the supporting method of Co, the inorganic oxide support, the amount of supported Co, and the kind of the added alkali metal on the partial oxidation activity were investigated to explore the supported Co catalysts for high catalytic activity. The sorpted oxygen species, rather than gaseous oxygen, were suggested to participate in the formation of benzaldehyde on the basis of a transient response experiment. ...

Activity and stability of bimetallic Co (V, Nb, La)-modified MCM-41 catalysts

A series of bimetallic mesostructured Co (V, Nb, La)-MCM-41 molecular sieves with high surface area and narrow pore-size distribution were obtained by direct hydrothermal synthesis using two different silica sources. Their catalytic activity was tested in the oxidation of styrene and benzene with hydrogen peroxide. Structural and textural properties of the fresh and used catalysts were studied by X-ray powder diffraction, nitrogen adsorption–desorption, TEM and SEM. The influence of the synthesis procedure, composition and metals molar ratio on the structure, catalytic activity and selectivity was discussed. The activity of bimetallic catalysts was compared with that of monometallic Co-, V-, Nb- and La-MCM-41 molecular sieves. It was found that more ordered hexagonal structure favors the selectivity to benzaldehyde and decreases the induction time of reaction. The introduction of V as the second metal ions into Co-MCM-41 decreases or increases sharply the activity in the oxidation of styrene and benzene, respectively. While the introduction of Nb showed an opposite tendency, suggesting that the combination of Co-V favors the oxidation of styrene and Co-Nb the oxidation of benzene and that the catalytic sites for oxidation of styrene and benzene are different. No benefic effect has been observed by incorporation of La into Co-MCM-41 neither in oxidation of styrene nor in oxidation of benzene. It was found that the benzaldehyde formation is structure sensitive.

Autolysis of Lactococcus lactis AM2 stimulates the formation of certain aroma compounds from amino acids in a cheese model

The autolysis of Lactococcus lactis starters accelerates the formation of free amino acids during cheese ripening. The purpose of this study was to evaluate the impact of L. lactis autolysis on the conversion of free amino acids to aroma compounds. The study was conducted with two L. lactis isogenic strains differing by their autolytic behaviour in cheese: the highly autolytic strain AM2 and a non-autolytic derivative. The effect of bacterial lysis on phenylalanine catabolism was first evaluated in buffer solution. L. lactis cells were also included in a cheese paste model with or without α-ketoglutarate, which stimulates the first step of amino acid degradation by lactococci. Amino acid catabolism and volatile aroma compound formation were analysed after 28 days of ripening. When α-ketoglutarate concentration was not limiting, autolysis of L. lactis cells stimulated the catabolism of aromatic amino acids and methionine and enhanced the formation of sulphur aroma compounds and benzaldehyde, which are desirable aroma compounds in cheese.

Synthesis, structure and catalytic activity of low-spin dicyano iron(III) complexes of N, N′-bis(quinolyl)malonamide derivatives

Two low-spin Fe(III) dicyano-dicarboxamido complexes have been prepared from N, N ′-bis(8-quinolyl)malonamide derivatives. Crystal structures show that the four nitrogen donors available to complex the metal are arranged in the equatorial plane with the two cyanides trans to each other in the axial positions when the malonyl moiety is disubstituted. In contrast, the unsubstituted malonyl results in only three nitrogens in the equatorial plane with the fourth in an apical position and the two cyanides occupying cis sites, one equatorial and the other axial. NMR analyses show that the solid state structure of both complexes is retained in solution. Both types of configurational complexes catalyze cyclic olefin oxidations with H 2O 2 but only the cis-dicyano complex catalyzes stilbene oxidation with formation of epoxides, diols and benzaldehyde.

Oxidative N-Debenzylation of N-Benzyl-N-substituted Benzylamines Catalyzed by Cytochrome P450

Cytochrome P450 (P450)/<TEX>$O_2$</TEX>/NADPH engender electron transfer reaction of N-benzyl-N-substituted benzylamines to yield corresponding radical cation 1 that is simultaneously converted into 2 and 3. Subsequently, expulsion of proton and hydroxylation yielding a-hydroxylamines are followed by formation of benzaldehydes and benzylamines.

On the Mechanism of the Oxidation of Toluenes in Artificial P450 Model Systems: Formation of Benzyl Alcohols, Benzaldehydes, and Phenols

Abstract Systems with pentafluoroiodosylbenzene (PFIB) and hemin (FeTPPCl8Cl) in dichloromethane were adopted to study the activities of the model system using toluenes as substrates for P450 enzymes. The oxidation products were mainly corresponding benzyl alcohols and benzaldehydes. Previously reported suspension systems were extended to homogeneous mixed solution systems of CH2Cl2/CH3OH/H2O to study the oxidation of benzyl alcohols to the corresponding benzaldehydes: the Hammett relation with ρ = −0.86 against σ+. As benzaldehydes were scarcely observed in natural P450 systems, the formation of benzaldehyde seemed characteristic only of the “open” model systems. In suspension systems, the product ratios between corresponding benzaldehydes and benzyl alcohols (ald/alc) were about 0.1–0.4, specific to the substituents and conditions applied. Curiously, the ratios (ald/alc) increased with the electronegativity of the substituents on the phenyl rings of the toluene derivatives. Time course experiments in suspension systems indicated that benzyl alcohols and benzaldehydes were formed not stepwise, but simultaneously from toluene. Separate experiments indicated that the reaction of benzyl alcohol to benzaldehyde was four-fold faster than that of toluene to benzyl alcohol. The rate was not enough to elucidate the amount of benzaldehyde. We suggest that the benzyl radical is formed by hydrogen abstraction and is attacked by the second oxidant, PFIB. Rebounding of the hydroxyl radical and the reaction with the oxidant were competitive depending on the conditions. Additionally, small amounts of phenols were formed from toluenes with electron-donating substituents. This was a minor reaction on which the aromatic hydroxylation occurred via epoxidation under the present conditions.

Studies on the photochemistry of 1,7-diphenyl-1,6-heptadiene-3,5-dione, a non-phenolic curcuminoid model.

The comparative photostability of curcumin 1, and two non-phenolic curcuminoids: 1,7-diphenyl-1,6-heptadiene-3,5-dione 2 (unsubstituted curcumin) and dimethylcurcumin 3 in non-degassed dilute solutions (approximately 3-5 x 10(-5) mol l(-1)) has been established by UV-visible absorption spectroscopy; disappearance quantum yields were measured. The similar behavior of the three studied curcuminoids is indicative of only a moderate role of phenol groups in the photodegradation process. Structural analysis of the photodegradation products of compound 2 in more concentrated solution (approximately 3.6 x 10(-3) mol l(-1)) shows formation of benzaldehyde, cinnamaldehyde, 2'-hydroxy-5',6'-benzochalcone 4, flavanone 5 and some other unidentified photoproducts. Flavanone 5 is formed by irradiation of chalcone 4. It represents a unique example of photochemical conversion of a diarylheptanoid molecule into a flavonoid, another very important class of natural products.

Oxidative N‐debenzylation of N‐benzyl‐N‐substituted benzylamines catalyzed by horseradish peroxidase

AbstractN‐Benzyl‐N‐substituted benzylamines and compound I of horseradish peroxidase engender electron transfer yielding the corresponding nitrogen radical cation 1, which is simultaneously converted into 2 and 3. Subsequently, expulsion of proton and hydroxylation yielding α‐hydroxylamines are followed by the formation of benzaldehydes and benzylamines. Copyright © 2003 John Wiley &amp; Sons, Ltd.

The effect of zirconium in metal/bromide catalysts on the autoxidation of p-xylene

Abstract Metals, such as Fe, V, Ti, Hf, have the same properties as Zr(IV), i.e. the ability to activate a Co/Mn/Br catalyst and to enhance the rate of benzaldehyde formation. There is a perfect correlation with the pK of hydrolysis, a measure of Lewis acidity, and the degree of activation of the metals. The data is consistent with the activation mechanism being a Lewis acid catalyzed dehydration of the benzyl peroxides. Certain metals, including zirconium, inhibit the formation of the undesirable black, insoluble MnO2, during Co/Mn/Br catalyzed autoxidations. In general, the increasing ability of a metal to avoid MnO2 formation is correlated to increasing Z2/r values (Z is the formal valence state and r the ionic radius). It is proposed that the metal can avoid MnO2 formation by decreasing the precursor concentration of Mn–OH2. The solid MnO2 produced during an autoxidation can produce radicals derived from p-xylene which further react to form undesirable dimeric by-products. The presence of Zr(IV) or Hf(IV) kinetically and thermodynamically inhibit the precipitation of the Co(II) and Mn(II) pyromellitic acid (PMA) complexes. The phenomena of activation, prevention of Mn(IV) formation, and solubilization in the presence of select carboxylic acids all occur when the metal has high Lewis acidity. This is consistent with the ability of Zr and Hf to preferentially complex with the acid. Mechanisms are suggested for the above phenomena which illustrates the intimate role that the solvent, acetic acid, performs in these autoxidations.

Co-oxidation of styrene and iso-butyraldehyde in the presence of polyaniline-supported metalloporphyrins

Abstract Co-oxidation of styrene and iso- butyraldehyde with gas phase oxygen in the temperature range 20–35 °C has been studied in the presence of Co-, Fe- and Mn-T( p -SO 3 H)PP porphyrins in the liquid phase and supported on polyaniline (PANI) as catalysts. The reaction is proceeding along two parallel pathways: formation of benzaldehyde and epoxystyrene with products of its tautomeric isomerization, mainly phenylacetaldehyde. Iso- butyraldehyde is mediating the transfer of oxygen from the gas phase to styrene through generation of radicals by interaction with the porphyrin molecules and formation, by reaction with oxygen molecules, iso- butyracylperoxy radicals. Supporting the porphyrin molecules on polyaniline modifies their catalytic properties. The mechanisms of the two parallel reaction pathways to benzaldehyde and epoxystyrene+phenylacetaldehyde are discussed.

Oxidative deamination of benzylamine by glycoxidation

In the present study, model reactions for the oxidative deamination by glycoxidation using benzylamine were undertaken to elucidate the detail of the reaction. Glucose, 3-deoxyglucosone (3-DG), and methylglyoxal (MG) oxidatively deaminated benzylamine to benzaldehyde in the presence of Cu2+ at a physiological pH and temperature but not glyoxal. 3-DG and MG were more effective oxidants than glucose. We have determined the effects of metal ions, pH, oxygen, and radical scavengers on the oxidative deamination. The formation of benzaldehyde was greatest with Cu2+, and was accelerated at a higher pH and in the presence of oxygen. EDTA, catalase, and dimethyl sulfoxide significantly inhibited the oxidation, suggesting the participation of reactive oxygen species. From these results, we propose a mechanism for the oxidative deamination by the Strecker-type reaction and the reactive oxygen species-mediated oxidation during glycoxidation.

Degradation of benzyldimethylalkylammonium chloride by Aeromonas hydrophila sp. K.

The aim of this work was to study the biodegradation of benzyldimethylalkylammonium chloride (BAC) by Aeromonas hydrophila sp. K, an organism isolated from polluted soil and capable of utilizing BAC as sole source of carbon and energy. High performance liquid chromatography and gas chromatography-mass spectrometry (GC-MS) analysis was used to study BAC degradation pathway. It was shown that during BAC biodegradation, formation of benzyldimethylamine, benzylmethylamine, benzylamine, benzaldehyde and benzoic acid occurred. Formation of benzyldimethylamine as the initial metabolite suggested that the cleavage of Calkyl-N bond occurred as the first step of BAC catabolism. Liberation of benzylmethylamine and benzylamine likely resulted from subsequent demethylation reactions, followed by deamination with formation of benzaldehyde. Benzaldehyde was rapidly converted into benzoic acid, which was further degraded. Aer. hydrophila sp. K is able to degrade BAC. A degradation pathway for BAC and related compounds is proposed. These findings are significant for understanding biodegradation pathways of benzyl-containing quaternary ammonium compounds.