Formation Of Benzaldehyde Research Articles

Small-intestinal transfer mechanism of prunasin, the primary metabolite of the cyanogenic glycoside amygdalin

1. The small-intestinal transfer of prunasin (D-mandelo-nitrile-beta-D-glucoside), the primary metabolite of amygdalin which is not absorbed in the small intestine as such, was studied in rat jejunum and ileum in vitro. 2. As shown by high pressure liquid chromatography, prunasin is transferred essentially intact across the intestinal wall, without cleavage of the glycosidic bond and thus no formation of benzaldehyde or cyanide during the mucosal passage. 3. Only the jejunal transfer of prunasin followed saturation kinetics (vmax = 1.6 mumol cm-1 min-1; KT = 460 mumol l-1) and exhibited a clearsodium-ion dependence. As indicated by the temperature dependence, only the jejunal mucosa-to-serosa transfer and the corresponding tissue uptake of prunasin required apparently high activation energies. Transfer in the terminal ileum showed diffusion characteristics. 4. Jejunal methyl alpha-D-glucoside transfer was inhibited by the presence of prunasin. Furthermore, the tissue uptake of methyl alpha-D-glucoside in rat jejunum was competitively inhibited by prunasin. 5. The results indicate that prunasin is absorbed unmetabolised in the jejunum of the rat via the transport system of glucose.

Neighboring‐Group Participation in the Gas Phase. Loss of benzaldehyde from [(benzyloxy)methyl]dialkylsilyl‐substituted 1,3‐dithianes

Abstract[(Benzyloxy)methyl]dialkylsilyl‐substituted 1,3‐dithianes show in CI‐MS an abundant loss of benzaldehyde from the [M + H]+ quasi‐molecular ion. The fragmentation is explained with an intramolecular redox process, where a hydride is proposed to be transferred from the benzyl position to a neighboring thionium ion. This would form a particle that could readily lose benzaldehyde as a neutral fragment. The CI‐MS results provide an explanation for the unusual instability of (benzyloxy)methyl‐substituted silanes towards acids. In fact, the formation of benzaldehyde was established in the decomposition of a (benzyloxy)methyl‐substituted acylsilane in the presence of Lewis or Brønsted acids and ethanethiol. The CI‐MS study, therefore, represents a useful method to recognize unusual reactions that are – or might be – important in solution.

ChemInform Abstract: Deprotection of Carboxylic Acids from Their Phenacyl Esters by Cu(II)/ O2/DMF‐H2O: Unusual Formation of Benzaldehyde from the Phenacyl Group.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Electrooxidation of benzyl alcohol on Pt-Nafion composite electrode

The electrooxidation of benzyl alcohol was investigated employing a Pt-Nafion composite electrode in both polar and non-polar solvents. The use of hexane as a solvent caused the current efficiency for benzaldehyde formation to increase greatly compared with that in acetonitrile. Furthermore, the stability of the Pt-Nafion composite electrode for the repeated electrolyses was largely improved by the use of hexane.

Deprotection of Carboxylic Acids from their Phenacyl Esters by Cu(II)/O2/DMF-H2O: Unusual Formation of Benzaldehyde from the Phenacyl Group

Phenacyl esters gave the deprotected carboxylic acids, alongwith PhCO2H, PhCHO and CO2 on heating with CuCl2 or CuSO4 in aqueous DMF (50% v/v) at reflux with continuous bubbling of O2.

Deprotection of carboxylic acids from their phenacyl esters by Cu(II)/O2/DMF-H2O: Unusual formation of benzaldehyde from the phenacyl group

Phenacyl esters gave the deprotected carboxylic acids, alongwith PhCO 2 H, PhCHO and CO 2 on heating with CuCl 2 or CuSO 4 in aqueous DMF (50% v/v) at reflux with continuous bubbling of O 2 . Graphic

Mechanistic aspects of benzylic bromide formation and oxidation during the cobalt acetate bromide catalyzed oxidation of alkylbenzenes in carboxylic acids

The formation and fate of benzylic bromides during the cobalt acetate bromide catalyzed oxidation of toluene and 4-chlorotoluene were investigated in carboxylic acid solvents. The rate of formation of benzylic bromides depends on the substrate and catalyst concentrations while the conversion of ionic bromide to benzylic bromides is strongly influenced by the type of solvent and the presence of nucleophilic ligands and metal co-catalysts. The observed effects are best explained in terms of a chain carrier comprising both cobalt acetate and bromide. Oxidation of benzylic bromides under the reaction conditions results in the formation of benzal bromides, benzaldehydes, benzoic acid and molecular bromine. An electron transfer process is proposed to explain the oxidation of benzylic bromides.

Heterogeneous Oxidation of Toluene in the Bed Region of a Spouted Bed Combustor; Effect of Bed Temperature and Bed Material

Abstract Toluene was used as the fuel in a heterogeneous spouted bed combustor to investigate the effect of bed material on pollutant emissions. Experimental measurements were conducted in the annulus region (preflame) and include Destruction and Removal Efficiency (DRE) of the fuel, and concentrations of three products of Incomplete combustion (PICs) of toluene; CO, benzene and benzaldehyde. Two types of bed material were used: Sand and quartz. Higher conversion of the fuel (higher DRE) and higher concentration of CO, benzene and benzaldehyde (up to one order of magnitude) were observed with sand particles. Predictions of a detailed homogeneous gas phase mechanism for the oxidation of toluene (Emdee et al., 1992), were compared to the experimental data to reveal possible influences of surface reactions on the conversion of toluene and formation of CO, benzene and benzaldehyde.

Requirement of a Second Oxidation Equivalent for Ferryl Oxygen Transfer to Styrene in the Epoxidation Catalyzed by Myoglobin-H 2O 2

Ferric myoglobin (Mb) is oxidized by H 2O 2 to a ferryl (Fe IVO) species and a protein radical, whereas ferrous Mb is similarly oxidized to the ferryl species without the protein radical. The protein radical is unstable and decays within 5 min, but the ferryl species is stable for more than 1 h. Previous studies have shown that styrene is oxidized to styrene oxide and benzaldehyde by ferric Mb and H 2O 2. We demonstrate here that the ferryl species produced from ferrous equine Mb and H 2O 2 does not epoxidize styrene. Furthermore, the EPR signal intensity of the protein radical formed from ferric equine Mb and the ability to oxidize styrene decrease in parallel as a function of the time separating the addition of H 2O 2 and styrene. The ability to oxidize styrene as a function of time after addition of H 2O 2 is lost much more rapidly with the H64V/K102Q/Y103F/Y146F/Y151F mutant of sperm whale Mb than with the native protein or the Y146F/Y151F mutant. The results indicate that styrene epoxidation requires a two-electron oxidized species of Mb in which the ferryl(Fe IVO) complex is coupled to a protein or highly transient (undetectable) porphyrin radical. Benzaldehyde formation appears to be catalyzed by the same oxidizing species. Styrene oxidation thus differs from linoleic acid oxygenation, which is catalyzed by the ferryl species alone.

Indirect anodic oxidation of benzyl alcohol in the presence of phase-transfer catalyst in a CSTER: effect of flow rate and temperature

The current efficiency for producing benzaldehyde, the conversion of benzyl alcohol and the yield and selectivity of benzaldehyde were all indicated by experimental and theoretical results as being significantly affected by the flow rate and the reaction temperature. The dynamic behavior of the indirect oxidation of benzyl alcohol was similar to that of a typical series reaction in a batch reactor, as observed by applying a low flow rate and a large total current towards the two-phase system in a CSTER (continuous stirred tank electrolysis reactor). The rate of formation of benzaldehyde increased and the induction period as well as the power consumption decreased when the flow rate increased. In view of current efficiency, yield and selectivity of benzaldehyde, the optimum temperature being obtained at 20°C was confirmed by the experimental results.

Electrooxidation of benzyl alcohol at high surface area nickel (NiS x ) electrodes in alkaline solution

The heterogeneous catalytic redox behaviour of NiSx deposited electrodes was investigated with and without benzyl alcohol in KOH solution using cyclic voltammetry and linear sweep voltammetry. The limiting current density for benzyl alcohol oxidation on a NiSx electrode was 22 times larger than that on a polished nickel electrode. The experimental results in galvanostatic electrolysis using fractional factorial design showed that the main and interaction effects of benzyl alcohol concentration, temperature, and OH− concentration are the key variables influencing the selectivity of benzaldehyde formation during electrolysis.

Changes In Composition of Volatile Compounds in High Pressure Treated Peach

The headspace volatile components of high pressure treated (400 MPa, 20 o C, 10 min) white peach (Prunus percica L. cv. Shimizu) were analyzed by capillary gas chromatography-mass spectrometry (GC-MS) and compared with headspace volatiles of ripe intact peach, crushed peach, and heat-treated peach. To examine the flavor quality, the high pressure treated peaches packed in pouches were stored at 25 and 40 o C for various periods and analyzed by GC-MS. The enzymical formation of benzaldehyde, C 6 aldehydes, and alcohols by disruption of the fruit tissues was observed in the high pressure treated fruit and crushed fruit. The influence of high-pressure treatment for β-glucosidase activity related to formation of glycosidically bound volatiles was examined

On the photochemical decomposition of aromatic α-azohydroperoxides

The photochemistry of some α-azohydroperoxides (phenyl(phenylazo)methyl hydroperoxide and its halogenated derivatives) was investigated in various solvents by microsecond and nanosecond flash photolysis methods and steady state product analysis. Photodecomposition of the molecule, demonstrated by the formation of benzaldehyde, is a major, but not the only, photochemical pathway. Investigation of the influence of solvent and substitution on the photoinduced transients provides strong evidence for alternative photoreactions. One of the species produced by flash photolysis was studied in detail and assigned to a transient zwitterion formed from the α-azohydroperoxide by proton transfer via an excited state pathway. Semiempirical calculations add further support to the proposed mechanism.

Photochemical behaviour of poly(organophosphazene)s, 12. Photo‐oxidation of catena‐poly[bis(4‐benzylphenoxy)‐λ5‐phosphazene] at short and long wavelengths under accelerated conditions

AbstractIn this paper the mechanism of the thermo‐and photo‐oxidation of catena‐ poly[bis(4‐benzylphenoxy)‐λ5‐phosphazene] films at short and long wavelengths has been followed under accelerated conditions using FTIR and UV‐visible spectroscopic techniques. The decrease of the band at 1453 cm−1 and the simultaneous appearance of new bands at 3400 and 3481 cm−1, due to free and bonded hydroperoxides, show that the primary hydroperoxidation in this polymer occurs at CH2 groups belonging to benzylic moietics. According to our previous paper, the bands observed in the carbonyl region at 1657, 1704 and 1725 cm−1 during photo‐oxidation have been assigned to the formation of benzophenone, benzaldehyde and benzoic acids (dimmers), respectively. The formation rate of benzophenone groups increases during irradiation at long wavelengths (λ > 400 nm). Under thermo‐oxidative condition (90°C), the benzophenone groups are the main oxidation products derived from hydroperoxide decomposition. In addition, the photooxidation of a film pre‐thermo‐oxidized for 500 h shows clearly that the benzophenone groups can generate aldehydes, benzoic acids and peracids. Crosslinking takes place in high yields by hydrogen abstraction occurring at both benzylic and secondary alcohol units. The regeneration of benzophenone groups has been evidenced during the photo‐oxidation.

Zirconia-supported vanadium oxide catalysts for ammoxidation and oxidation of toluene: A characterization and activity study

A series of samples of vanadia supported on monoclinic zirconia were prepared with nominal loadings from a half up to sixteen theoretical vanadia layers. The samples were characterized with X-ray diffraction, scanning electron microscopy combined with energy dispersive X-ray analysis, high-resolution electron microscopy, Raman and diffuse reflectance infrared spectroscopy, and were used in the oxidation and the ammoxidation of toluene. At loadings in the monolayer range, Raman and infrared bands from decavanadate-like and dehydrated tetrahedral vanadia species were at ca. 990 and ca. 1025 cm−1, respectively. Raman bands at 821 and 880 cm−1 were present only at the lowest loading and are characteristic of orthovanadate and pyrovanadate species, respectively. X-ray diffraction, Raman and infrared spectroscopic results revealed formation of some crystalline V2O5 and ZrV2O7 at loadings exceeding a theoretical monolayer. In this case, consideration of Raman intensity variations allowed the conclusion that additional non-crystalline vanadia must be present. According to high-resolution electron micrographs, this vanadia consists of an amorphous overlayer, 4–8 atomic layers thick. In toluene oxidation zirconia-supported vanadia compared with crystalline V2O5 was found less selective for benzaldehyde formation. In toluene ammoxidation, on the other hand, vanadia on zirconia was found to possess good activity and selectivity for benzonitrile formation. Amorphous vanadia was the most active structure on zirconia, while the selectivities for nitrile and aldehyde formations were almost independent of the loading for one theoretical layer and above.

Slow-Combustion of n-Heptane, iso-Octane and a Toluene/n-Heptane Mixture

Abstract The oxidation of n-heptane, iso-octane and a toluene/n-heptane mixture was studied in a jet-stirred flow reactor operating under pressure at stoichiometric feed ratio in the low-temperature range. In particular, the transition from slow-combustion to a higher reactivity condition was examined by analyzing the composition of the reaction products as the residence time was increased. It was found that high-octane-number fuels, such as iso-octane and toluene, have a high tendency to add O2 keeping intact the original fuel structure forming 2,2,4,4-tetramethyltetrahydrofuran and benzaldehyde, respectively. Conversely, n-heptane has a high tendency to fragment in olefins and light oxygenated species already in slow-combustion. The different tendency to form oxygenated fuel-skeleton retaining species could be responsible for their different reactivity and consequently autoignition tendency. In the oxidation of the toluene/n-heptane mixture the slow-combustion is essentially characterized by benzaldehyde formation indicating that, between the two fuel components, mainly toluene contributes to the fuel reactivity. As the residence time increases n-heptane begins to react forming olefins and light oxygenated compounds causing the passage of the system from slow-combustion to cool flames. In this phase toluene reactivity is reduced as testified by the benzaldehyde disappearance. This is due to the reaction temperature which increasing overcomes the very low ceiling temperature of aromatic radicals and produces, before the backward shift of the heptylperoxy equilibrium, the backward shift of the benzylperoxy equilibrium toward benzyl radicals.

Catalytic and spectroscopic studies of vanadium oxide supported on group IVb and Vb metal oxides for oxidation of toluene

Vanadia was deposited on TiO 2, ZrO 2, HfO 2, Nb 2O 5, and Ta 2O 5 supports using impregnation with either an oxalic acid solution of NH 4VO 3 or a solution of vanadyl acetylacetonate in ethanol. Prepared samples, with a nominal vanadia content in the range 0.5–2 monolayers, were characterized with X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Raman and infrared spectroscopy, and were used in toluene oxidation. XRD did not reveal formation of any vanadia phase. XPS spectra showed deposited vanadium to be present mainly as V 5+ on all the supports. A plot of the V:( support metal) ratio determined by XPS showed agglomeration of vanadia on TiO 2, ZrO 2, HfO 2, and Nb 2O 5 to occur at loadings above 0.5 monolayer, while for Ta 2O 5 the dispersion seemed independent of the loading. Preparations from vanadyl acetylacetonate gave superior dispersion. Raman spectra showed bands from crystalline V 2O 5 on all the supports except Nb 2O 5. Raman and infrared bands from dispersed vanadia were present in the spectra of TiO 2 (three species), ZrO 2 and HfO 2 (both one species) supported catalysts. No bands from vanadium-oxygen vibrational modes were seen in the spectra of Nb 2O 5 supported samples, but a V-OH band was observed, suggesting an amorphous structure. Some evidence was obtained for formation of amorphous VTa 9O 25 on Ta 20 5. The activity for toluene oxidation increased with vanadia loading for each support, and the activity varied with respect to support at all loadings in the order TiO 2 > ZrO 2 > Nb 2O 5 > HfO 2 > Ta 2O 5. The selectivity for formation of benzaldehyde was the highest using TiO 2 and Nb 2O 5 supports, while for benzoic acid TiO 2 was the best support.

Self‐Reaction of Benzylperoxy Radicals in the Oxidation of Toluene. A Chemiluminescence and Product Study

AbstractThe CL study of the oxidation of toluene initiated by AIBN has shown that both triplet and singlet benzaldehyde is formed (T/S ≈︁ 10.5). The lifetimes in toluene are: τ5 ≈︁ 4 · 10−9 s and τT ≈︁ 1.9 · 10−7 s. – In the presence of DPA the kinetic curve of the CL light shows a maximum at [DPA] > 10−4 M. The CL spectrum of the oxidation of toluene lacks both the fluorescence and phosphorescence peaks of the excited benzaldehyde (due to the very low efficiency of photon emission and very strong quenching by O2 and toluene). – Analysis of product distribution by HPLC revealed the formation of benzaldehyde, benzylalcohol, benzylhydroperoxide and benzoic acid. A small amount of H2O2 was also detected by spectrophotometry. Since the ratio of aldehyde/alcohol is always higher than unity detailed study of all circumstances led us to the conclusion that benzylperoxy radicals terminate both by the Russell‐mechanism and by the transition state containing two five‐membered rings suggested by Bennett and Summers. – The activation energy of hydrogen abstraction from toluene by benzylperoxy radicals is 53 kJ/mol and the rate constant of this reaction does not differ essentially from the same reaction of ethylbenzene. The kinetic chain length of oxidation calculated from the analytical data is equal to 2±0.2 (75–90°C).

Catalytic epoxidation of alkenes with molecular dioxygen activated by CuXn–ascorbic acid systems (X = F, Cl, Br or I; n= 1 or 2)

Copper-(I) or -(II) salt–ascorbic acid systems have been found to catalyse facile epoxidation of trans-stilbene without concomitant formation of benzaldehyde, by utilizing molecular dioxygen under mild conditions.

Synthesis, photopolymerization and photochemistry of novel polysiloxane photoinitiators

Three novel polysiloxane photoinitiators have been synthesized and their photochemistry and photopolymerization activities related to their structure using absorption and luminescence spectroscopy and conventional microsecond and nanosecond laser flash photolysis techniques. A comparison with the properties of a model photoinitiator 2,2-diethoxyacetophenone (DEAP) has also been made. Extinction coefficients for the polysiloxanes at the absorption maxima are generally higher than those of the model initiator while the phosphorescence spectra exhibit typical nπ* carbonyl symmetry similar to that of the model but with longer phosphorescence lifetimes in the millisecond region. Photopolymerization rates for methyl methacrylate in ethyl acetate using the polysiloxanes as initiators are higher than those of the model and dependent on structure and molecular weight. Photopolymerization rates for both the model and the polysiloxanes correlate with their absorption maxima and phosphorescence quantum yields while the presence of a tertiary amine ( N-methyldiethanolamine) had a variable effect. End-of-pulse transient absorption spectra of the polysiloxanes on the microsecond time scale using conventional flash photolysis are assigned to the benzoyl radical produced on direct photolysis of the acetophenone chromophores and closely match those of the model. The transient absorption spectra also correlate with the photopolymerization rates of methyl methacrylate, indicating that the benzoyl radical is the key initiating species. This is confirmed by the formation of benzaldehyde in the photolysis products of repetitive flash photolysis in tetrahydrofuran produced by the benzoyl radical abstracting a hydrogen atom from the solvent system. Second-order derivative absorption spectroscopy confirms the presence of acetophenone end groups in the poly(methyl methacrylate) samples. On the nanosecond time scale laser flash photolysis revealed the formation of long-lived transient spectra which are also assigned to the benzoyl radical for both the polysiloxanes and the model. No triplet precursor is observed since in the presence of oxygen no quenching occurs. In fact, the transient absorption is enhanced followed by its decay to the same spectrum as that observed under nitrogen. Possible complexation between the initiator and oxygen is considered to be responsible for this observation. The significance of these results in terms of the structure and activity relationship of these novel polysiloxanes is discussed.