Showing papers on "Benzaldehyde published in 1976"

Isotope effects and structure-reactivity correlations in the yeast alcohol dehydrogenase reaction. A study of the enzyme-catalyzed oxidation of aromatic alcohols.

Abstract: Steady-state kinetic parameters for the yeast alcohol dehydrogenase catalyzed oxidation of a series of parasubstituted benzyl alcohols-1, 1-h2 and -1, 1-d2 by NAD+ are reported. Catalytic constants have been found to be characterized by large deuterium isotope effects: kH/kD=4.8, p-Br; 4.2, p-Cl; 3, 4, p-H; 4, 2, p-CH3; 3, 2, p-CH3O. The observed isotope effects on k(cat)/K(A), K(A), and K(B), where K(A) and K(B) are Michaelis constants for NAD+ and alcohol, indicate a borderline rapid equilibrium-steady-state kinetic mechanism involving the random addition of substrate and coenzyme to enzyme. With the exception of p-CH3 and possible p-CH3O substituted benzyl alcohol, k(cat) is concluded to represent a single, rate-limiting hydrogen transfer step. A multiple linear regression analysis of the combined data for benzaldehyde reduction (Klinman, J.P. (1972), J. Biol. Chem. 247, 7977-7987, expanded to include p-CH(CH3) 2-substituted benzaldehyde) and benzyl alcohol oxidation has been carried out to determine the contribution of electronic, hydrophobic, and steric effects to k(cat) and substrate binding. Benzaldehyde binding is concluded to depend on electronic substituent effects as previously reported [log 1/K(ald)=(-0.92 +/- 0.18)sigma+-(0.80 +/- 0.067)], whereas benzyl alcohol binding correlates with substrate hydrophobicity [(log 1/K(alc)=(0.60 +/- 0.14) log P -(1.2 +/- 0.12)]. In the case of benzyl alcohol oxidation, k(cat) is independent of electronic and steric effects; the best of seven equations indicates a small negative dependence of k(cat) on hydrophobicity, which is within experimental error or zero [log k(o)=(-0.075 +/- 0.25) log P -(0.65 +/- 0.19)]. Data for benzaldehyde reduction are correlated at the 99% significance level by a single variable equation [(log k(R)=(2.1 +/- 0.37) sigma+-(0.093 +/- 0.14)] and a two variable equation [(log k(R)=(1.9 +/- 0.33) sigma+ + (0.46 +/- 0.20) log P-(0.46 +/- 0.20)]; these equations indicate (a) a large dependence on electronic substituent as reported previously and (b) a possible role for hydrophobic factors in facilitating catalysis. As the result of the observed hydrophobic substituent effects, different ground-state interactions are suggested for the binding of benzaldehydes and benzyl alcohols. Electronic substituent effects lead to the conclusion that there is little or no change in charge at C-1 of substrate at the transition state, relative to alcohol in the ground state. The significance of these effects to the detailed properties of the hydrogen transfer step is discussed.

Kinetic transients in the reduction of aldehydes catalysed by liver alcohol dehydrogenase.

Abstract: The transient-state kinetics of enzymic reduction of acetaldehyde and benzaldehyde by NADH, catalyzed by horse liver alcohol dehydrogenase, have been examined under single-turnover conditions, obtained by carrying out reactions either with limiting amounts of enzyme in the presence of 20 mM pyrazole or with limiting amounts of substrate. Analysis of the variation with substrate, coenzyme, and enzyme concentrations of amplitudes and time constants for the exponential transients observed at 328 nm and 300 nm shows that the kinetics of enzymic aldehyde reduction are qualitatively and quantitatively consistent with the relationships derived in the preceding paper for an ordered ternary-complex mechanism involving identical and independent catalytic sites. It is concluded that there is no evidence whatsoever for the kinetic significance of a half-of-the-sites reactivity or any other kind of subunit interaction in the liver alcohol dehydrogenase system. The biphasic transients observed at 328 nm for the reduction of aromatic aldehydes such as benzaldehyde are a normal kinetic characteristic of the ordered ternary-complex mechanism, being attributable to accumulation of the ternary enzyme-NAD-product complex when product dissociation from this complex is slow in comparison to its formation by ternary-complex interconversion.

Electrochemical production of OH. radicals and their reaction with toluene

Abstract: The reaction between electrochemically generated Fenton's reagent and toluene was studied. The products arising from this reaction system were consistent with a primary hydrogen atom abstraction from the methyl group of toluene to give benzyl radicals. Benzaldehyde was obtained with a current yield higher than 60%; benzyl alcohol was also produced in smaller quantities in some experiments. The dependence of the yields on reagent concentrations, temperature and coulombs passed was examined. On the basis of the experimental results a mechanism is proposed involving peroxy and alkoxy radicals as intermediates.

The ‘Aldol Condensation’ of Citral and Related Reactions

Abstract: The reaction of citral with anhydrous base leads initially to a cyclohexa-1,3-dienecarbaldehyde. Stronger base and longer reaction times result in deconjugation to a cyclohexa-1,4-diene-carbaldehyde, together with oxidative loss of six carbon atoms to yield 2-methyl-4-(4-methylpent-3-enyl)benzaldehyde. A mixed aldol reaction between citral and 3-methyl-2-butenal (= senecia aldehyde) is described.

Involvement of 4-hydroxymandelic acid in the degradation of mandelic acid by Pseudomonas convexa.

Abstract: A microorganism capable of degrading DL-mandelic acid was isolated from sewage sediment of enrichment culture and was identified as Pseudomonas convexa. It was found to metabolize mandelic acid by a new pathway involving 4-hydroxymandelic acid, 4-hydroxybenzaldehyde, 4-hydroxybenzoic acid, and 3,4-dihydroxybenzoic acid as aromatic intermediates. All the enzymes of the pathway were demonstrated in cell-free extracts. L-Mandelate-4-hydroxylase, a soluble enzyme, requires tetrahydropteridine, nicotinamide adenine dinucleotide phosphate, reduced form, and Fe2+ for its activity. The next enzyme, L-4-hydroxymandelate oxidase (decarboxylating), a particulate enzyme, requires flavine adenine dinucleotide and Mn2+ for its activity. A nicotinamide adenine dinucleotide-dependent, as well as a nicotinamide adenine dinucleotide phosphate-dependent, benzaldehyde dehydrogenase has been resolved and partially purified.

Studies on Leuckart-Wallach Reaction Paths

Abstract: The Leuckart-Wallach reaction paths were investigated by means of catalytic reduction in the Leuckart-Wallach reaction system and on the basis of analogous formic acid reductions. It was determined that, in the early stage of the Leuckart-Wallach reaction, ammonia, amine and also formamide undergo addition reactions to carbonyl compounds. The addition of formamide catalyzed by formic acid plays a significant role only for the more reactive substrates such as benzaldehyde. The behaviors of plausible intermediates for the formic acid reduction are discussed on the basis of the data of similar formic acid reductions.

Kinetics on the Formylation of lodobenzene Catalyzed by Palladium(II) Chloride in a Pyridine Solution

Abstract: Benzaldehyde was obtained in good yields by the formylation of iodobenzene with carbon monoxide and hydrogen catalyzed by palladium(II) chloride in a pyridine solution. The effect of following variables on the rate of producing benzaldehyde was examined kinetically : initial catalyst and iodobenzene concentrations, partial pressure of carbon monoxide and hydrogen, and temperature. A probable reaction mechanism via formyl- and benzoyl-palladium(II) intermediates is discussed on the basis of this kinetic study.

Photochemical formation of amides from t-butylamine and aromatic aldehydes and ketones

Abstract: Irradiation of benzaldehyde, substituted benzaldehydes, benzoin, benzil, and t-butyl phenyl ketone in the presence of t-butylamine leads to N-t-butylarenecarboxamides. In the case of the aldehydes, imine formation also occurs. The imine is reduced by reaction with α-hydroxybenzyl radicals, which are also generated in the photochemical reaction. Benzyl phenyl ketone does not give products via and α-scission reaction, but instead is reduced by the amine. The formation of the amides is rationalised as occurring by attack of benzoyl radicals on the amine.

Ring-opening of 2,5-diaryl-3-lithiofurans

Abstract: The 2,5-diaryl-3-bromofurans (1) react with butyl-lithium to give the corresponding 2,5-diarylfurans and the allenes (4) or the acetylenes (6); by carrying out the reaction in hexane at 65–70 °C the allenes and acetylenes can be obtained in good yields. Enolate intermediates (5) are proposed; these can also be intercepted by acetic anhydride, to give the acetylenic enol acetates (7), and by aromatic aldehydes, to give the pentenediones (8). 3-Bromo-1-methyl-2,4,5-triphenylpyrrole (2) does not give products of ring-opening with butyl-lithium, but from 4-bromo-2,5-diphenyloxazole (3) an open-chain intermediate (9) is formed which reacts with benzaldehyde to give the amide (10).

Asymmetric transamination from amino acid (iii) asymmetric synthesis of phenylglycine by chemical transamination from optically active amino acids to benzaldehyde

Abstract: D-Phenylglycine, an important constituent of penicillin and cephalosporin antibiotics, was asymmetrically synthesized by hydrocyanation of the Schiff bases prepared from benzaldehyde and L-amino acid t-butyl esters, followed by oxidative decarboxylation. When L-ψ-leucine t-butyl ester was used as a chiral reagent, the optical yield of D-phenylglycine Increased to 96.5%.

Prins-Reaktionen mit Arylaldehyden, 2. Mitt. Diene

Abstract: By 1,4-addition of arylaldehydes to 2,3-dimethyl-1,3-butadiene in the presence of sulfuric acid 2-aryl-4,5-dimethyl-3,6-dihydro-2H-pyrans are obtained. From 1,3-butadiene and isoprene beside the corresponding 3,6-dihydro-2H-pyrans by reaction with two more molecules aldehydetrans-2,4,7-triphenyl-4a,7,8,8a-tetrahydro-4H,5H-pyrano[4,3-d-1,3-dioxines are formed. With 1,3-cyclohexadiene, however, 1,2-addition of benzaldehyde is observed to givecis-r-2,c-4-diphenyl-4a,5,6,8a-tetrahydro-1,3-benzodioxane.

Prins-reaktionen mit arylaldehyden, 1. Mitt.: Arylolefine

Abstract: Benzaldehyde and substituted benzaldehydes react with styrene (1), α-methylstyrene, (E)-1-propenylbenzene and anethole in presence of sulfuric acid to give 2,4,6-triaryl-1,3-dioxanes. In acetic acid from1 and benzaldehyde (1R,3S)-and (1RS,3RS)-1,3-diacetoxy-1,3-diphenylpropane is formed. The relative configuration of the products is determined by means of1H-NMR spectroscopy.

Process for preparing 3,4-dihydro-2(1H)-quinazolinone derivatives

Abstract: 3,4-Dihydro-2(1H)-quinazolinones and quniazolinethiones such as 1-cyclopropylmethyl-4-phenyl-6-methoxy-3,4-dihydro-2(1H)-quinazolinone and its thione derivative, are prepared in high yield with high purity by heating the corresponding arylurea or thiourea such as N-cyclopropylmethyl-N-(p-methoxyphenyl) urea or its thiourea derivative, with the corresponding aldehyde such as benzaldehyde in the presence of hydrobromic acid in an inert solvent.

Generation of xanthones and benzoxanthones from o-aryloxybenzaldehydes by use of copper(II) halides

Abstract: The reaction of copper(II) halides with o-aryloxybenzaldehydes to give xanthones is shown to be a general one. 2-(6-Methoxy-2-naphthyloxy)benzaldehyde undergoes concomitant nuclear bromination to give 4-bromo-3-methoxybenzo[a]xanthen-12-one.

Kinetics and mechanism of a one-step alternative to the Grignard reaction

Abstract: The kinetics of the ‘one-step alternative to the Grignard reaction’ between bromobenzene, benzaldehyde, and lithium have been studied with tetrahydrofuran as solvent. The rate of formation of the product, diphenylmethanol, is first-order in bromobenzene and in lithium surface area, and zero-order in benzaldehyde. The activation energy is 3.42 ± 0.59 kJ mol–1. These data are consistent with a rate-determining step involving intermediate formation of phenyl-lithium by reaction of bromobenzene with lithium. The one-step process has also been employed with organic bromides to synthesise ketones from nitriles and alkylarylhydroxylamines from 2-methyl-2-nitrosopropane. In the former the yields were poorer than from conventional reactions but in the latter yields compared very favourably with those from the Grignard reaction.

Regulation of growth of Acinetobacter calcoaceticus NCIB8250 on benzyl alcohol in batch culture.

Abstract: SUMMARY: Formation of benzoate and catechol during oxidation of benzyl alcohol by washed suspensions of Acinetobacter calcoaceticus NCIB8250 confirmed earlier results indicating that this organism metabolizes benzyl alcohol via benzaldehyde, benzoate, and the 3-oxoadipate pathway. There was no evidence for feedback inhibition of benzyl alcohol dehydrogenase or benzaldehyde dehydrogenase II. Examination of growth curves and patterns of substrate utilization, as well as measurement of enzyme activities, showed that benzyl alcohol dehydrogenase and benzaldehyde dehydrogenase II are repressed when A. calcoaceticus utilizes L-mandelate or phenylglyoxylate. Growth of bacteria on L-mandelate prior to their inoculation into benzyl alcohol/salts medium leads to an exceptionally long lag period before benzyl alcohol is used at the maximum rate. Benzyl alcohol metabolism is also suppressed during growth on benzoate.

A Novel Synthesis of 2-Trialkylphosphonio-1,3-dithiole-4-carboxylates

Abstract: Acetylene carboxylic acids reacted with trialkylphosphine-carbon disulfide ylides to produce fair to good yields of 2-trialkylphosphonio-1,3-dithiole-4-carboxylates (4) at temperatures as low as −20 to −30 °C. The formation of these zwitterionic products, by a prototropic shift in the ylide 3, differs fron the known reaction of acetylenes, such as ethyl propiolate, with carbon disulfide and tributylphosphine to give tetrathiafuvalene derivatives. The structure of these zwitterionic products was confirmed by alkaline hydrolysis, reaction with benzaldehyde, and their IR and NMR spectra. Alkaline hydrolysis of 4 gave the corresponding carboxyl-substituted 1,3-dithioles 7. Treatment of 2-tributylphosphonio-1,3-dithiole-4-carboxylate (4e) with benzaldehyde in the presence of triethylamine resulted in the formation of 2-benzylidene-1,3-dithiole-4-carboxylic acid 8. The methine proton of the 1,3-dithiole ring of 4 in DMSO-d6, appeared at δ 5.41–6.24 as a singlet peak. These methine protons were readily exchanged...

Syntheses and Reactions of Fluorine-containing Aromatic Ketones

Abstract: Phenyl 1,1,2,3,3,3-hexafluoropropyl ketone(I) and 2,2,3-trifluoro-3-(trifluoromethyl)indanone(II) were synthesized by the radical-addition reaction of benzaldehyde to hexafluoropropene. The reduction with NaBH4 and the Grignard reaction with methylmagnesium iodide of these ketones gave the corresponding secondary and tertiary alcohols respectively. A Clemmensen reduction, alkaline hydrolyses, and reactions with hydroxylamine and with diazomethane were also carried out.

Kinetics and mechanism of the decomposition of α-acetoxy-α-methoxytoluene in aqueous solution

Abstract: The rate-determining step in the hydrolysis of α-acetoxy-α-methoxytoluene in the pH range 3.69–6.27 is the decomposition of the intermediate benzaldehyde methyl hemiacetal which is general-acid and general-base catalysed.

Photochemical Redox Reaction of Aqueous Benzylpentacyanocobaltate(III)

Abstract: Charge transfer excitation of aqueous benzylpentacyanocobaltate(III) led to a redox reaction with formation of Co(CN)₅³⁻ and benzyl radicals in the primary photochemical step. In the absence of oxygen the benzyl radicals dimerized to bibenzyl. At 313 nm irradiating wavelength the quantum yield was 0,13 ± 0,02. In the presence of air oxygen was apparently inserted into the carbon-cobalt bond with the intermediate formation of [Co(CN)₅O₂CH₂C₆H₅]³⁻, which decomposed to give Co(CN)₅H₂O²⁻ and benzaldehyde (ɸ = 0,15 ± 0,02). The significance of these results is discussed with regard to the photochemistry of acidopentacyanocobaltates(III) and organocobalamins.

Nouveaux heterocycles thiopyranniques

Abstract: The thiopyranone-3 has been condensed with arylhydrazines, orthoamino acetophenone and orthoamino benzaldehyde to give some new indoles and quinolines. The Bthoxycarbonyl-2 derivative has given some pyrazolones. RMN and Mass Spectra are examinated.