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Benzyl Alcohol (benzyl + alcohol)
Selected AbstractsLetter: Benzyl Alcohol Preserved Saline Used to Dilute Injectables Poses a Risk of Contact Dermatitis in Fragrance-Sensitive PatientsDERMATOLOGIC SURGERY, Issue 11 2007ANTOINE AMADO MD No abstract is available for this article. [source] Mechanism of Laccase,TEMPO-Catalyzed Oxidation of Benzyl AlcoholCHEMCATCHEM, Issue 7 2010Sander Abstract The oxidation of benzyl alcohol by air, catalyzed by the organocatalyst TEMPO and the enzyme laccase has been investigated. To establish the kinetically significant pathways and corresponding kinetic parameters, a series of experiments is conducted with synthesized stable oxidized and reduced forms of the organocatalyst, the oxoammonium cation, and hydroxylamine. The time course of TEMPO and its oxidized and reduced derivatives is monitored off line by a combination of GC analysis, UV/Vis spectroscopy, EPR spectroscopy, and FTIR spectroscopy. TEMPO is found to be regenerated through noncatalyzed comproportionation of the oxoammonium cation with hydroxylamine. A kinetic model is presented based on the experimentally determined kinetically significant pathways. The time dependences of the concentrations of the three redox states of TEMPO and benzyl alcohol are adequately described by the model. The results provide new leads for the development of a practical process for a combined laccase,TEMPO-catalyzed selective oxidation of alcohols. [source] Regioselectivity in Lewis Acid Catalyzed X,H (O, S, N) Insertions of Methyl Styryldiazoacetate with Benzyl Alcohol, Benzyl Thiol, and Aniline.CHEMINFORM, Issue 36 2007Yongli Yue Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF. [source] An Alkaloid-Mediated Desymmetrization of meso-Anhydrides via a Nucleophilic Ring Opening with Benzyl Alcohol and Its Application in the Synthesis of Highly Enantiomerically Enriched ,-Amino Acids.CHEMINFORM, Issue 10 2004Carsten Bolm Abstract For Abstract see ChemInform Abstract in Full Text. [source] The Conformation of Alkyl Benzyl Alcohols Studied by ab initio MO Calculations , A Comparison with IR and NMR Spectroscopic DataEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 11 2004Osamu Takahashi Abstract Ab initio MO calculations were carried out for the conformations of a series of alkyl-substituted benzyl alcohols C6H5CH2CHOH,R (R = CH3, C2H5, iPr, tBu) at the MP2/6-311G(d,p)//MP2/6-31G(d) level. It was found that the conformation where the OH group is gauche to the phenyl group is the most stable. The geometry where both the OH and R groups are close to phenyl is the second most stable. This finding has been interpreted on the grounds of the attractive OH/, and CH/, hydrogen bonds and a repulsive van der Waals interaction between vicinal CH groups. NMR nuclear Overhauser effects, spin-coupling data, and IR spectroscopic data are consistent with the conclusion given by the MO calculations. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004) [source] Photooxidation of Benzyl Alcohols with Immobilized FlavinsADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 1-2 2009Harald Schmaderer Abstract Benzyl alcohols are oxidized cleanly and efficiently to the corresponding aldehydes under irradiation using flavin photocatalysts and aerial oxygen as the terminal oxidant in homogeneous aqueous solution. Turnover frequencies (TOF) of more than 800,h,1 and turnover numbers (TON) of up to 68 were obtained. Several flavin photocatalysts with fluorinated or hydrophobic aliphatic chains were immobilized on solid supports like fluorous silica gel, reversed phase silica gel or entrapped in polyethylene pellets. The catalytic efficiency of the heterogeneous photocatalysts was studied for the oxidation of different benzyl alcohols in water and compared to the analogous homogeneous reactions. Removal of the heterogeneous photocatalyst stops the reaction conversion immediately, which shows that the immobilized flavin is the catalytically active species. The immobilized catalysts are stable, retain their reactivity if compared to the corresponding homogeneous systems and are easily removed from the reaction mixture and reused. TOF of up to 26,h,1, TON of 280 and up to 3 reaction cycles without loss of activity are possible with the heterogeneous flavin photocatalysts. [source] ChemInform Abstract: Chemoselective S-Benzylation of Indoline-2-thiones Using Benzyl Alcohols.CHEMINFORM, Issue 14 2010Mukund Jha Abstract ChemInform 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. [source] ChemInform Abstract: Molecular Iodine Catalyzed C3-Alkylation of 4-Hydroxycoumarins with Secondary Benzyl Alcohols.CHEMINFORM, Issue 9 2010Xufeng Lin Abstract ChemInform 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. [source] ChemInform Abstract: Efficient, Regioselective Palladium-Catalyzed Tandem Heck-Isomerization Reaction of Aryl Bromides and Non-Allylic Benzyl Alcohols.CHEMINFORM, Issue 30 2009Matthew L. Crawley Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 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. [source] ChemInform Abstract: Solid-Supported Acid-Catalyzed C3-Alkylation of 4-Hydroxycoumarins with Secondary Benzyl Alcohols: Access to 3,4-Disubstituted Coumarins via Pd-Coupling.CHEMINFORM, Issue 19 2009Ch. Raji Reddy Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 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. [source] ChemInform Abstract: Chemoselective Etherification of Benzyl Alcohols Using 2,4,6-Trichloro-1,3,5-triazine and Methanol or Ethanol Catalyzed by Dimethyl Sulfoxide.CHEMINFORM, Issue 11 2009Lili Sun Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 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. [source] ChemInform Abstract: AgOTf-Catalyzed Direct Amination of Benzyl Alcohols with Sulfonamides.CHEMINFORM, Issue 9 2008B. Sreedhar Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 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. [source] Solvolysis of Benzyl Alcohols and Ethers in 1,2-Diols and Application to a Deprotection of Benzyl Ether-Type Protecting Groups.CHEMINFORM, Issue 52 2006Hideyoshi Miyake Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF. [source] Facile Oxidation of Benzyl Alcohols with Sodium Nitrate/p-TsOH under Microwave Irradiation.CHEMINFORM, Issue 1 2006Jong Chan Lee Abstract For Abstract see ChemInform Abstract in Full Text. [source] ChemInform Abstract: The Selective Oxidation of Benzyl Alcohols in a Membrane Reactor.CHEMINFORM, Issue 31 2001G. Grigoropoulou Abstract ChemInform 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. [source] Characterization of the aroma-active compounds in five sweet cherry cultivars grown in Yantai (China)FLAVOUR AND FRAGRANCE JOURNAL, Issue 4 2010Shu Yang Sun Abstract This study was conducted to determine the aroma-active compounds of five sweet cherry cultivars grown in Yantai region, China, viz. ,Lapins', ,Rainier', ,Stella', ,Hongdeng' and ,Zhifuhong'. The samples were extracted by headspace solid phase microextraction (HS,SPME) and analysed by gas chromatography,mass spectrometry (GC,MS) on DB-wax and DB-5 columns. A total of 52 volatiles were identified. Among these, hexanal, (E)-2-hexenal, 1-hexanol, (E)-2-hexen-1-ol, benzaldehyde and benzyl alcohol were the main volatile compounds in the five cherries. Furthermore, the aroma compounds of five cherry samples were evaluated using a combination of HS,SPME and GC,olfactometry (GC,O) dilution analysis, and a total of 40 aroma-active compounds were identified. The results suggested that hexanal, (E)-2-hexenal, (Z)-3-hexenal, nonanal, benzaldehyde and geranylacetone (FD , 16), responsible for the green, orange, almond and floral characters of the cherries, were the potentially important common odorants in these cherry cultivars. Benzyl alcohol and linalool were significant aroma compounds in most cherries, with the exception of ,Stella' and ,Rainier'. In addition, (E,Z)-2,6-nonadienal (cucumber-like odour) could be important to ,Hongdeng' and ,Zhifuhong', and (E,E)-2,4-nonadienal (fatty odour) probably made great contributions to the aromas in ,Lapins' and ,Stella'. From the present result, it was concluded that the aroma profiles were similar in the five cherry cultivars, but significant variation was found in the contributions of these compounds to each cherry. Copyright © 2010 John Wiley & Sons, Ltd. [source] Trace Water-Promoted Oxidation of Benzylic Alcohols with Molecular Oxygen Catalyzed by Vanadyl Sulfate and Sodium Nitrite under Mild ConditionsADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 4 2009Zhongtian Du Abstract An inexpensive catalytic system consisting of vanadyl sulfate and sodium nitrite was developed for the oxidation of benzylic alcohols with molecular oxygen under mild conditions. Benzyl alcohols with various substitutions were efficiently converted to their corresponding aldehydes with high conversion and selectivity under 80,°C (e.g., 4-nitrobenzyl alcohol was smoothly oxidized to 4-nitrobenzyl aldehyde with 94% yield under 0.5,MPa of molecular oxygen). Halogen, noble metals, extra base or complicated ligands were avoided. Addition of a trace of water to this system before the reaction was crucial for the high efficiency. [source] Photooxidation of Benzyl Alcohols with Immobilized FlavinsADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 1-2 2009Harald Schmaderer Abstract Benzyl alcohols are oxidized cleanly and efficiently to the corresponding aldehydes under irradiation using flavin photocatalysts and aerial oxygen as the terminal oxidant in homogeneous aqueous solution. Turnover frequencies (TOF) of more than 800,h,1 and turnover numbers (TON) of up to 68 were obtained. Several flavin photocatalysts with fluorinated or hydrophobic aliphatic chains were immobilized on solid supports like fluorous silica gel, reversed phase silica gel or entrapped in polyethylene pellets. The catalytic efficiency of the heterogeneous photocatalysts was studied for the oxidation of different benzyl alcohols in water and compared to the analogous homogeneous reactions. Removal of the heterogeneous photocatalyst stops the reaction conversion immediately, which shows that the immobilized flavin is the catalytically active species. The immobilized catalysts are stable, retain their reactivity if compared to the corresponding homogeneous systems and are easily removed from the reaction mixture and reused. TOF of up to 26,h,1, TON of 280 and up to 3 reaction cycles without loss of activity are possible with the heterogeneous flavin photocatalysts. [source] Sensitization to 26 fragrances to be labelled according to current European regulationCONTACT DERMATITIS, Issue 1 2007Results of the IVDK, review of the literature To study the frequency of sensitization to 26 fragrances to be labelled according to current European regulation. During 4 periods of 6 months, from 1 January 2003 to 31 December 2004, 26 fragrances were patch tested additionally to the standard series in a total of 21 325 patients; the number of patients tested with each of the fragrances ranged from 1658 to 4238. Hydroxymethylpentylcyclohexene carboxaldehyde (HMPCC) was tested throughout all periods. The following frequencies of sensitization (rates in %, standardized for sex and age) were observed: tree moss (2.4%), HMPCC (2.3), oak moss (2.0), hydroxycitronellal (1.3), isoeugenol (1.1), cinnamic aldehyde (1.0), farnesol (0.9), cinnamic alcohol (0.6), citral (0.6), citronellol (0.5), geraniol (0.4), eugenol (0.4), coumarin (0.4), lilial (0.3), amyl-cinnamic alcohol (0.3), benzyl cinnamate (0.3), benzyl alcohol (0.3), linalool (0.2), methylheptin carbonate (0.2), amyl-cinnamic aldehyde (0.1), hexyl-cinnamic aldehyde (0.1), limonene (0.1), benzyl salicylate (0.1), ,-methylionon (0.1), benzyl benzoate (0.0), anisyl alcohol (0.0). 1) Substances with higher sensitization frequencies were characterized by a considerable number of ,++/+++' reactions. 2) Substances with low sensitization frequencies were characterized by a high number of doubtful/irritant and a low number of stronger (++/+++) reactions. 3) There are obviously fragrances among the 26 which are, with regard to contact allergy, of great, others of minor, and some of no importance at all. [source] Protection of lodgepole pines from mass attack by mountain pine beetle, Dendroctonus ponderosae, with nonhost angiosperm volatiles and verbenoneENTOMOLOGIA EXPERIMENTALIS ET APPLICATA, Issue 2 2001D.P.W. Huber Abstract A number of angiosperm nonhost volatiles (NHVs) and green leaf volatiles (GLVs) were tested alone and as supplements to the antiaggregation pheromone, verbenone, for their ability to disrupt attack by the mountain pine beetle (MPB), Dendroctonus ponderosae Hopkins (Coleoptera: Scolytidae), on lodgepole pine, Pinus contorta Dougl. ex Loud. var. latifolia Engel. Preliminary experiments led to a refined NHV blend [benzyl alcohol, guaiacol, benzaldehyde, nonanal, salicylaldehyde, and conophthorin] and a refined GLV blend [(Z)-3-hexen-1-ol and (E)-2-hexen-1-ol]. In a 20-replicate experiment, NHV and GLV groups both singly, and verbenone alone, significantly reduced MPB mass attack on pheromone-baited trees and on trees within 5 m of the pheromone-baited trees. Both blends in combination with verbenone reduced the number of mass attacked, baited trees to three out of 20 compared to 20 out of 20 of the baited controls. Each binary combination was also effective at reducing mass attack. In these experiments, all tested repellents were released from devices stapled to trees at the same point as the pheromone bait, suggesting that the repellency could have been to a point source, rather than to the whole tree. Therefore, in two further experiments bands of release devices were wrapped around the treated trees and the pheromone bait was removed from the treated trees. In one experiment, when the aggregation pheromone bait was suspended between pairs of trees treated with the NHV blend plus GLV blend plus verbenone, only three out of 25 treated pairs had mass attack on at least one member of the pair. In the other 60-replicate experiment, with no pheromone baits present, attack occurred on 13 untreated and 11 banded trees, all in the path of a large advancing infestation. However, the mean attack density on the banded trees was significantly reduced to a level below the 40 attacks m,2 of bark surface required to kill a healthy lodgepole pine. As a result of these experiments, operational trials are recommended. [source] Characterization and uncertainty analysis of VOCs emissions from industrial wastewater treatment plantsENVIRONMENTAL PROGRESS & SUSTAINABLE ENERGY, Issue 3 2010Kaishan Zhang Abstract Air toxics from the industrial wastewater treatment plants (IWTPs) impose serious health concerns on its surrounding residential neighborhoods. To address such health concerns, one of the key challenges is to quantify the air emissions from the IWTPs. The objective here is to characterize the air emissions from the IWTPs and quantify its associated uncertainty. An IWTP receiving the wastewaters from an airplane maintenance facility is used for illustration with focus on the quantification of air emissions for benzyl alcohol, phenol, methylene chloride, 2-butanone, and acetone. Two general fate models, i.e., WATER9 and TOXCHEM+V3.0 were used to model the IWTP and quantify the air emissions. Monte Carlo and Bootstrap simulation were used for uncertainty analysis. On average, air emissions from the IWTP were estimated to range from 0.003 lb/d to approximately 16 lb/d with phenol being the highest and benzyl alcohol being the least. However, emissions are associated with large uncertainty. The ratio of the 97.5th percentile to the 2.5th percentile air emissions ranged from 5 to 50 depending on pollutants. This indicates point estimates of air emissions might fail to capture the worst scenarios, leading to inaccurate conclusion when used for health risk assessment. © 2009 American Institute of Chemical Engineers Environ Prog, 2010 [source] Synthesis and Electrochemical Study of an Original Copper(II)-Capped Salen,Cyclodextrin ComplexEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 29 2010Elise Deunf Abstract A new metallocapped cyclodextrin (CD) was synthesized by the regioselective debenzylation, induced by diisobutylaluminium hydride (DIBAL-H), of perbenzylated cyclodextrins. This reaction allowed for the efficient preparation of an unprecedented CD,salen type copper(II) complex. The electrochemical behavior of both the bound and unbound CD,salen compounds was investigated by cyclic voltammetry. Notably, it was shown that the presence of tert -butyl groups at the ortho - and para -positions of the salen aromatic rings stabilized the copper(II) phenoxyl radical species that was generated upon the one-electron oxidation of the starting compound. Importantly, this stabilization remained effective when the salen-type ligand was covalently attached to the CD. This allowed for investigations of the reactivity of the copper(II) phenoxyl radical complex towards a primary alcohol to be performed by cyclic voltammetry. This reaction can be considered as mimicking the behavior of galactose oxidase. However, under these conditions, no reactivity was observed in the presence of benzyl alcohol. This may be due to distortion, either of the initially square planar salen ligand after its grafting to the CD primary face, and/or of the CD itself. On the other hand, the electrochemical reduction of the un-grafted copper(II) salen-type ligand led to a transient anionic species that exhibited significant stability on the time-scale of the slow cyclic voltammetry measurement in the absence of the CD, but was unstable in the presence of the CD. In the latter case, it was demonstrated that the anionic species was protonated by the CD. Importantly, this protonation was not fast enough to prevent catalytic activation of iodomethane by the electro-generated copper(I)-capped salen CD complex. [source] Modulation of P-glycoprotein-mediated multidrug resistance by acceleration of passive drug permeation across the plasma membraneFEBS JOURNAL, Issue 23 2007Ronit Regev The drug concentration inside multidrug-resistant cells is the outcome of competition between the active export of drugs by drug efflux pumps, such as P-glycoprotein (Pgp), and the passive permeation of drugs across the plasma membrane. Thus, reversal of multidrug resistance (MDR) can occur either by inhibition of the efflux pumps or by acceleration of the drug permeation. Among the hundreds of established modulators of Pgp-mediated MDR, there are numerous surface-active agents potentially capable of accelerating drug transbilayer movement. The aim of the present study was to determine whether these agents modulate MDR by interfering with the active efflux of drugs or by allowing for accelerated passive permeation across the plasma membrane. Whereas Pluronic P85, Tween-20, Triton X-100 and Cremophor EL modulated MDR by inhibition of Pgp-mediated efflux, with no appreciable effect on transbilayer movement of drugs, the anesthetics chloroform, benzyl alcohol, diethyl ether and propofol modulated MDR by accelerating transbilayer movement of drugs, with no concomitant inhibition of Pgp-mediated efflux. At higher concentrations than those required for modulation, the anesthetics accelerated the passive permeation to such an extent that it was not possible to estimate Pgp activity. The capacity of the surface-active agents to accelerate passive drug transbilayer movement was not correlated with their fluidizing characteristics, measured as fluorescence anisotropy of 1-(4-trimethylammonium)-6-phenyl-1,3,5-hexatriene. This compound is located among the headgroups of the phospholipids and does not reflect the fluidity in the lipid core of the membranes where the limiting step of drug permeation, namely drug flip-flop, occurs. [source] Characterization of cinnamyl alcohol dehydrogenase of Helicobacter pyloriFEBS JOURNAL, Issue 5 2005An aldehyde dismutating enzyme Cinnamyl alcohol dehydrogenases (CAD; 1.1.1.195) catalyse the reversible conversion of p -hydroxycinnamaldehydes to their corresponding alcohols, leading to the biosynthesis of lignin in plants. Outside of plants their role is less defined. The gene for cinnamyl alcohol dehydrogenase from Helicobacter pylori (HpCAD) was cloned in Escherichia coli and the recombinant enzyme characterized for substrate specificity. The enzyme is a monomer of 42.5 kDa found predominantly in the cytosol of the bacterium. It is specific for NADP(H) as cofactor and has a broad substrate specificity for alcohol and aldehyde substrates. Its substrate specificity is similar to the well-characterized plant enzymes. High substrate inhibition was observed and a mechanism of competitive inhibition proposed. The enzyme was found to be capable of catalysing the dismutation of benzaldehyde to benzyl alcohol and benzoic acid. This dismutation reaction has not been shown previously for this class of alcohol dehydrogenase and provides the bacterium with a means of reducing aldehyde concentration within the cell. [source] Characterization of the aroma-active compounds in five sweet cherry cultivars grown in Yantai (China)FLAVOUR AND FRAGRANCE JOURNAL, Issue 4 2010Shu Yang Sun Abstract This study was conducted to determine the aroma-active compounds of five sweet cherry cultivars grown in Yantai region, China, viz. ,Lapins', ,Rainier', ,Stella', ,Hongdeng' and ,Zhifuhong'. The samples were extracted by headspace solid phase microextraction (HS,SPME) and analysed by gas chromatography,mass spectrometry (GC,MS) on DB-wax and DB-5 columns. A total of 52 volatiles were identified. Among these, hexanal, (E)-2-hexenal, 1-hexanol, (E)-2-hexen-1-ol, benzaldehyde and benzyl alcohol were the main volatile compounds in the five cherries. Furthermore, the aroma compounds of five cherry samples were evaluated using a combination of HS,SPME and GC,olfactometry (GC,O) dilution analysis, and a total of 40 aroma-active compounds were identified. The results suggested that hexanal, (E)-2-hexenal, (Z)-3-hexenal, nonanal, benzaldehyde and geranylacetone (FD , 16), responsible for the green, orange, almond and floral characters of the cherries, were the potentially important common odorants in these cherry cultivars. Benzyl alcohol and linalool were significant aroma compounds in most cherries, with the exception of ,Stella' and ,Rainier'. In addition, (E,Z)-2,6-nonadienal (cucumber-like odour) could be important to ,Hongdeng' and ,Zhifuhong', and (E,E)-2,4-nonadienal (fatty odour) probably made great contributions to the aromas in ,Lapins' and ,Stella'. From the present result, it was concluded that the aroma profiles were similar in the five cherry cultivars, but significant variation was found in the contributions of these compounds to each cherry. Copyright © 2010 John Wiley & Sons, Ltd. [source] Reductions of Benzene Derivatives Whose Benzylic Positions Bear Oxygen Atoms under Mild ConditionsHELVETICA CHIMICA ACTA, Issue 12 2008Abdullah Menzek Abstract Reductions of compounds whose benzylic positions bear O-atoms, such as benzyl alcohol, dibenzyl ether, styrene oxide, benzaldehyde, acetophenone, and benzophenone, to the corresponding non-conjugated dienes were performed by using t -BuOH, Li, and gaseous NH3 in THF at room temperature. In these reductions, it was observed that the functional groups at benzylic positions were reduced first. [source] Kinetic study of the ruthenium(VI)-catalyzed oxidation of benzyl alcohol by alkaline hexacyanoferrate(III)INTERNATIONAL JOURNAL OF CHEMICAL KINETICS, Issue 7 2002A. E. Mucientes The kinetics of the Ru(VI)-catalyzed oxidation of benzyl alcohol by hexacyanoferrate(III), in an alkaline medium, has been studied using a spectrophotometric technique. The initial rates method was used for the kinetic analysis. The reaction is first order in [Ru(VI)], while the order changes from one to zero for both hexacyanoferrate(III) and benzyl alcohol upon increasing their concentrations. The rate data suggest a reaction mechanism based on a catalytic cycle in which ruthenate oxidizes the substrate through formation of an intermediate complex. This complex decomposes in a reversible step to produce ruthenium(IV), which is reoxidized by hexacyanoferrate(III) in a slow step. The theoretical rate law obtained is in complete agreement with all the experimental observations. © 2002 Wiley Periodicals, Inc. Int J Chem Kinet 34: 421,429, 2002 [source] Copper-Catalyzed N -Alkylation of Sulfonamides with Benzylic Alcohols: Catalysis and Mechanistic StudiesADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 17 2009Xinjiang Cui Abstract The N -alkylation of sulfonamides with alcohols is efficiently performed in the presence of easily available copper catalysts via hydrogen borrowing methodology. Applying a copper acetate/potassium carbonate system the reaction of sulfonamides and alcohols gave the corresponding secondary amines in excellent yield. In situ HR-MS analysis indicated that bissulfonylated amines are formed under air atmosphere, which act as self-stabilizing ligands for the catalytic system. UV-visible measurements suggest the interaction between the copper centre and the bissulfonylated amine. Reactions of benzyl alcohol- d7 with p -toluenesulfonamide, N -benzyl- p -toluenesulfonamide or N -benzylidenetoluenesulfonamide revealed that the reaction proceeds via a transfer hydrogenation mechanism and the whole process is micro-reversible. Competitive reactions of benzyl alcohol and benzyl alcohol- d7 with p -toluenesulfonamide revealed a kinetic isotope effect (kH/kD) of 3.287 (0.192) for the dehydrogenation of benzyl alcohol and 0.611 (0.033) for the hydrogenation of the N -benzylidene- p -toluenesulfonamide intermediate, which suggests that dehydrogenation of the alcohol is the rate-determining step. [source] Aerobic Oxidation of Benzylic Alcohols in Water by 2,2,6,6-Tetramethylpiperidine-1-oxyl (TEMPO)/Copper(II) 2- N -Arylpyrrolecarbaldimino ComplexesADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 16 2009Abstract Novel copper(II) 2- N -arylpyrrolecarbaldimine-based catalysts for the aerobic oxidation of benzylic alcohols mediated by the 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) radical are reported. The catalytic activity for both synthesized and in situ made complexes in alkaline water solutions was studied revealing high efficiency and selectivity (according to GC selectivity always >99%) for both of these catalytic systems. For example, quantitative conversion of benzyl alcohol to benzaldehyde can be achieved with the in situ prepared bis[2- N -(4-fluorophenyl)-pyrrolylcarbaldimide]copper(II) catalysts in 2,h with atmospheric pressure of O2 at 80,°C. Interestingly, these catalysts can utilize dioxygen as well as air or hydrogen peroxide as the end oxidants, producing water as the only by-product. [source] Poly(trimethylene carbonate) from Biometals-Based Initiators/Catalysts: Highly Efficient Immortal Ring-Opening Polymerization ProcessesADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 9 2009Marion Helou Abstract The ring-opening polymerization (ROP) of trimethylene carbonate (TMC) was evaluated in bulk at 60,110,°C using various catalyst systems based on bio-friendly metals, including the metal bis(trimethylsilylamides) Mg[N(SiMe3)2]2, Ca[N(SiMe3)2]2(THF)2, Y[N(SiMe3)2]3, (BDI)Fe[N(SiMe3)2] [BDI=CH(CMeNC6H3 -2,6- i- Pr2)2], Fe[N(SiMe3)2]2, Fe[N(SiMe3)2]3, Zn[N(SiMe3)2]2, (BDI)Zn[N(SiMe3)2] and ZnEt2, associated with an alcohol such as isopropyl or benzyl alcohol. The actual metal alkoxide initiating species has been formed in situ prior to the addition of TMC. Introduction of the alcohol component in excess leads to the "immortal" ring-opening polymerization (ROP) of TMC. According to such an "immortal" ROP process of TMC, whichever the metal species, as many as 200 polycarbonate chains could be successfully grown from a unique metal center in a well controlled ROP process. The best performances were obtained using the discrete (BDI)Zn[N(SiMe3)2] precursor. Under optimized conditions, as many as 50,000 equivalents of TMC could be fully converted from as little as 20,ppm of this metallic precursor, allowing the preparation of a polytrimethylene carbonate (PTMC) with a molar mass as high as 185,200,g,mol,1 with a relatively narrow molar mass distribution (Mw/Mn=1.68). A double monomer feed experiment carried out with the (BDI)Zn[N(SiMe3)2]/BnOH initiating system proved the "living" character of the polymerization. Characterization of the PTMCs by NMR and size exclusion chromatography (SEC) showed well-defined ,-hydroxy-,-alkoxycarbonate telechelic polymers, highlighting the controlled character of this "living and immortal" ROP process. Using the (BDI)Zn[N(SiMe3)2] precursor, varying the alcohol (ROH) to 2-butanol, 3-buten-2-ol or 4-(trifluoromethyl)benzyl alcohol, revealed the versatility of this approach, allowing the preparation of accordingly end-functionalized HO-PTMC-OR polymers. The very low initial loading of metal catalyst considerably limits the potential toxicity and thus allows such polycarbonates to be used in the biomedical field. [source] | |||||||||||||||||||||||||||||||||||||