Α-methylbenzyl Alcohol Research Articles

Characterization of the Key Aroma Compounds of Three Kinds of Chinese Representative Black Tea and Elucidation of the Perceptual Interactions of Methyl Salicylate and Floral Odorants.

Jinjunmei (JJM), Keemun (KM), and Dianhong (DH) are the representative black teas in China, and they have always been favored by consumers. In this study, we aim to obtain the aroma characteristic information of volatile components in black tea samples through headspace solid-phase microextraction (HS-SPME), solvent-assisted flavor evaporation (SAFE), and gas chromatography-mass spectrometry combined with gas chromatography-olfactometry technology. The results showed that 70 compounds including α-methylbenzyl alcohol (isomer of β-phenylethanol) were identified as odorants. Among them, 39 compounds such as linalool and geraniol showed a high degree of aroma contribution. Furthermore, the Feller’s additive model was used to explore the perceptual interactions among the methyl salicylate and the floral compounds (10 groups): five groups of binary compounds showed masking effect after mixing, one group showed additive effect, and four groups showed synergistic effect. The ratio (R) was compared with the aroma index (n) of Steven’s law, which found a high-fitness exponential relationship. The results of this study help to provide additional and new theoretical guidance for improving the aroma quality of black tea.

A facile and highly efficient transfer hydrogenation of ketones and aldehydes catalyzed by palladium nanoparticles supported on mesoporous graphitic carbon nitride

A novel transfer hydrogenation methodology for the reduction of ketones (14 examples) and benzaldehyde derivatives (12 examples) to the corresponding alcohols using Pd nanoparticles supported on mesoporous graphitic carbon nitride (mpg-C3N4/Pd) as a reusable catalyst and ammonia borane as a safe hydrogen source in an aqueous solution MeOH/H2O (v/v = 1/1) is described. The catalytic hydrogenation reactions were conducted in a commercially available high-pressure glass tube at room temperature, and the corresponding alcohols were obtained in high yields in 2–5 min. Moreover, the presented transfer hydrogenation protocol shows partial halogen selectivity with bromo-, fluoro-, and chloro-substituted carbonyl analogs. In addition, the present catalyst can be reused up to five times without losing its efficiency, and scaling-up the reaction enables α-methylbenzyl alcohol to be produced in 90% isolated yield.

Hydrogenolysis of α-methylbenzyl alcohol to ethylbenzene over Pd/C catalyst

The hydrogenolysis of α-methylbenzyl alcohol (MBA) to ethylbenzene (EB) over Pd/C catalyst was studied. The XRD and TEM results show that Pd nanoparticles are well dispersed on the carbon support with good crystallinity. There is no 1-cyclohexylethanol or ethylcyclohexane in the products, indicating that Pd/C is excellent for inhibiting the hydrogenation of the aromatic ring. Alcohol solvents are beneficial to increase the catalytic activity because of their strong polarity and good solubility.

RIFM fragrance ingredient safety assessment, α-methylbenzyl alcohol, CAS registry number 98-85-1

RIFM fragrance ingredient safety assessment, α-methylbenzyl alcohol, CAS registry number 98-85-1

Experimental density, viscosity, interfacial tension and water solubility of ethyl benzene-α-methyl benzyl alcohol–water system

Density, viscosity, interfacial tension, and water solubility were measured for the (α-methyl benzyl alcohol (MBA)+Ethyl benzene (EB)) system at different concentrations of MBA in contact with water and sodium hydroxide solution (0.01mol·kg−1) as aqueous phases. The properties were measured to identify the component which plays a governing role in changing the physical properties relevant to mass transfer and phase separation of the ternary system. The concentration of MBA was found to be the major factor influencing all the properties. The water solubility, the density, and the viscosity increased notably at higher concentrations of MBA; while, the interfacial tension decreased strongly. The use of 0.01mol·kg−1 NaOH as an aqueous phase resulted in a decrease of the interfacial tension and a minor decrease in the water solubility. The density data were correlated using a quadratic mixing rule to describe the influence of concentration at any temperature. The viscosity data are correlated using the Nissan and Grunberg and Katti-Chaudhri equations. The Szyzkowski’s equation was used to correlate the interfacial tension data. The water solubility data were described using an exponential relationship. All the correlations described the experimental physical property data adequately.

Influence of Physical Properties and Process Conditions on Entrainment Behavior in a Static-Mixer Settler Setup

This paper examines the role of physical properties (interfacial tension, the viscosity of the dispersed and continuous phase, density difference, and solubility), and process conditions (flow rate, phase ratio, and temperature) on the drop size and entrainment in a static-mixer settler setup. Two extraction systems were investigated, that is, caprolactam–toluene–water and ethylbenzene (EB)−α-methyl benzyl alcohol (MBA)–water/NaOH (pH = 12). Depending on the system, the entrainment increased by a factor of 5–7, because of a change in the physical properties induced by changing the concentration of caprolactam and MBA. Different entrainment trends were observed for the two systems with phase ratio and temperature. The differences are explained by the drop break-up mechanisms reported in literature. The phase ratio effect resulted from on one hand turbulent attenuation and increased coalescence, and on the other hand increased shear and hindered settling at high phase ratios. The temperature influence was determined by its counteracting effects on the interfacial tension and the viscosities of continuous and dispersed phases.

Characterization of Aroma Compounds in Chinese Bayberry (Myrica rubra Sieb. et Zucc.) by Gas Chromatography Mass Spectrometry (GC‐MS) and Olfactometry (GC‐O)

The aroma-active compounds in Chinese bayberry were identified using gas chromatography-olfactometry (GC-O) and GC-mass spectrometry techniques. The volatile compounds were extracted using Liquid-liquid extraction, solvent-assisted flavor evaporation and headspace solid-phase microextraction (HS-SPME), respectively. On the basis of odor intensity, the most important aroma compounds in Chinese bayberry samples were caryophyllene, menthol, 4-terpineol, linalool oxide, linalool, benzyl alcohol, α-methylbenzyl alcohol, β-phenylethanol, 3-methylbutanoic acid and acetic acid, and so on. Moreover, HS-SPME technique was employed to investigate the aroma compounds among immature and mature waxberry fruits. The results showed that terpenes (for example, β-caryophyllene) was predominant and its concentration represented over 89.9% of the overall compounds, and alcohols, aldehydes, ketones, esters, acids, and others were typically present in lesser amounts. Finally, principal component analysis revealed that there was also significant difference between immature and mature waxberry fruits.

Recyclable ionic liquid-bridged chiral dimeric salen Mn(III) complexes for oxidative kinetic resolution of racemic secondary alcohols

Novel chiral dimeric salen Mn(III) complexes bridged with N,N-dialkylimidazolium ionic liquids (ILs) at the C-5 position of the salicylaldehyde moieties were designed and synthesized. The ILs-bridged complexes presented excellent enantioselectivity and catalytic activity in the oxidative kinetic resolution of α-methyl benzyl alcohol, using diacetoxyiodobenzene as oxidant. The complexes combined the high catalytic efficiency of the active centers and the special solubility of the ILs, thus exhibiting notable efficacy of oxidative kinetic resolution and facile recovery from the reaction system by changing the solvent.

Highly active and selective catalytic transfer hydrogenolysis of α-methylbenzyl alcohol catalyzed by supported Pd catalyst

Abstract A novel supported Pd catalyst was synthesized by using plant tannin grafted collagen fiber as the supporting matrix. The as-prepared Pd catalyst was subsequently used for the catalytic transfer hydrogenolysis of α-methylbenzyl alcohol. Due to the fibrous morphology of collagen fiber and the well dispersed Pd nanoparticles anchored by tannins, the as-prepared Pd catalyst showed superior activity for the catalytic transfer hydrogenolysis of α-methylbenzyl alcohol when compared with the Pd catalyst supported on inorganic oxides. Moreover, the as-prepared Pd catalyst can be reused at least 6 times without significant loss of activity and selectivity, suggesting a satisfied reusability.

Catalytic transfer hydrogenolysis of α-methylbenzyl alcohol using palladium catalysts and formic acid

The catalytic transfer hydrogenolysis (CTH) of α-methylbenzyl alcohol (MBA) was studied using palladium catalysts and formic acid, with the intent of developing a new approach for the production of propylene oxide (PO). The effects of support, hydrogen donor, molar ratio of HCOOH to MBA, water content, reaction temperature and catalyst recycling were evaluated. Using formic acid as hydrogen donor and Pd/C as catalyst, one can convert MBA to ethylbenzene (EB) with very high selectivity (98.8%) and high conversion (98.8%) at 80 °C for 40 min. H+ ion plays an important role, for it promotes the formation of active hydrogen species in the reaction process. A reaction mechanism was proposed to account for the results obtained in the study.

High pressure vapour–liquid equilibria of the binary and some of the ternary and multicomponent mixtures of the carbon dioxide + acetic anhydride + α-methylbenzyl alcohol + acetic acid + α-methylbenzyl acetate system : Experimental and modelling results

Bubble-point pressures of the binary systems CO 2 + acetic anhydride, CO 2 + α-methylbenzyl alcohol, and CO 2 + α-methylbenzyl acetate were measured in the temperature range of 283–363 K up to 15 MPa in a high pressure capillary glass tube apparatus, using the synthetic method. The binary mixture CO 2 + acetic acid was measured for x = 0.4962 and compared with previously published results. For the system CO 2 + α-methylbenzyl alcohol, data of the three-phase line L 2L 1V are given in the temperature range of 283–308 K. UCEP (L 2L 1 = V) was found at P = 7.78 MPa and T = 308.42 K. Bubble-point pressures of the ternary systems CO 2 + acetic anhydride + α-methylbenzyl alcohol, and CO 2 + acetic acid + α-methylbenzyl acetate were also measured at selected compositions. These mixtures corresponded to the reactant and product mixtures in the enzyme-catalyzed esterification of α-methylbenzyl alcohol with acetic anhydride to produce α-methylbenzyl acetate and acetic acid using supercritical carbon dioxide as solvent. The five component mixture occurring at intermediate conversion was measured at x C O 2 = 0.4041 at a fixed equimolar ratio of the organic heavy components. Modelling of the VLE of the binary systems was performed using the Stryjek–Vera modification of the Peng Robinson EOS with the Wong–Sandier mixing rules. The fitted parameters of the binary subsystems were used to predict the phase behaviour of multicomponent mixtures. Validation of the predictions was achieved by comparison with the experimental results.

Highly effective hydration of olefins using a wool-palladium complex as a catalyst

The hydration of styrene, 2-cyclohexen-1-one and 5-hexen-2-one to α-methylbenzyl alcohol, 3-hydroxy-cyclohexanone and 5-hydroxy-2-hexanone was investigated using a wool-supported palladium catalyst under mild conditions of temperature and pressure. The yields amounted to 82.0, 92.0 and 99.3% respectively and were greatly affected by the palladium content in the complex, the ratio of substrate/catalyst, the reaction temperature and the kind of solvent. The catalyst was very stable and could be re-used several times without any remarkable change in the catalytic activity. Copyright © 2006 John Wiley & Sons, Ltd.

Vapor−Liquid Equilibrium for Phenol + α-Methyl Benzyl Alcohol and 2-Ethoxyethanol + n-Butyl Formate

The saturation pressure of α-methyl benzyl alcohol (358 to 398) K and n-butyl formate (313 to 359) K was measured by an ebulliometric method. The vapor−liquid equilibrium (p, T, x, y) at (353.15, 373.15, and 393.15) K was measured by the ebulliometric method for the systems phenol + α-methyl benzyl alcohol and at (333.15, 343.15, and 353.15) K for 2-ethoxyethanol + n-butyl formate. The experimental vapor pressures were correlated with the Antoine and AEOS equations, whereas VLE was correlated with AEOS equation of state.

Hydrogenolysis of α-methylbenzyl alcohol over bifunctional catalysts

Hydrogenolysis of α-methylbenzyl alcohol (MBA), a co-product of propylene oxide (PO) in hydrocarbon peroxide oxidation processes, was studied to develop a by-product-free PO process. The conversion of MBA was mainly affected by the acidity of the support. Among the metals tested, Pd was most active and selective for the formation of ethylbenzene (EB). The hydrogenation of MBA exhibited type II selectivity, meaning that the selectivity to main products is controlled by reaction conditions and metals chosen. On Pd or Ni, the formation of EB is predominant while on Ru or Pt, that of 1-cyclohexylethanol (CHE) prevails. By carefully designing the catalyst and selecting the reaction condition, one could obtain a very high yield of EB with only a small amount of side products. Based on the results, a bifunctional reaction mechanism was proposed.

Stereoselective synthesis of optically active phenyl ethers

Reacting the 1,2-naphthalenedisulfonimide of ( S)-α-methylbenzylamine with phenol gave the corresponding α-methylbenzyl phenyl ether with 46% e.e. Synthesis of the authentic optically active phenyl ethers was accomplished under mild, neutral conditions by generating benzyne in the presence of optically active ( R)-α-methylbenzyl alcohol. Benzyne was generated by reacting anthranilic acid with tert-butyl nitrite in refluxing monoglyme.

Phase Equilibria on Seven Binary Mixtures

Vapor−liquid equilibria are reported for the following five systems: phenol + styrene; ethyl mercaptan + n-butane; tert-butyl mercaptan + propane; dimethyl ether + propane; trifluoroacetic acid + hydrogen chloride. The system pressure and temperature were measured at several charge compositions along two isotherms for each system. Equilibrium vapor- and liquid-phase compositions were derived from the PTx data using the Soave equation of state to represent the vapor phase and the Wilson or NRTL activity coefficient model to represent the liquid phase. Liquid−liquid equilibrium studies were performed on the dimethyl carbonate + water system at two temperatures by analyzing samples taken from each liquid phase. The solubility of hydrogen in α-methyl benzyl alcohol was measured at three pressures at each of three temperatures.

Synthesis of 1-phenyl-1-tolyl ethane by Friedel–Crafts alkylation of toluene with α-methylbenzyl alcohol over acidic zeolites

In the Friedel–Crafts alkylation of toluene to prepare 1-phenyl-1-tolyl ethane (PTE), α-methylbenzyl alcohol was used as an alkylating agent instead of styrene over large- and medium-pore zeolites. The catalysts were characterized by 27Al and 29Si MAS-NMR, NH 3-TPD, SEM, N 2 adsorption/desorption, and other techniques. Among the four zeolites investigated, the acid strength was approximately in the order of HMOR20 > HY5 ≥ HMFI30 > HBEA25 while the initial selectivity to PTE was in the order of HMOR20 > HBEA25 > HMFI30 > HY5. From the reaction and characterization studies, it is concluded that the formation of PTE requires both strong acid sites and suitable pore openings, which prevent heavy oligomers from forming in the channels while facilitating the transport of the reactants and products. HMOR20 showed the best overall performance as it satisfied these requirements.

Preparation and catalytic activity of polymer bound benzotriazole copper complexes

The polymer-bound benzotriazole (P-BTA) was prepared from p-chloromethylated polystyrene resin, benzotriazole and anhydrous K 2CO 3 under phase transfer catalysis. The polymer complex (P-BTA-Cu) was synthesized with P-BTA and metal salts (Cu(OAc) 2·H 2O), and was characterized by IR spectra, XPS, TG-DTA and elemental analysis, which showed that the polymer was stabilized by benzotriazole. The polymer complexes (P-BTA-Cu) have been applied in oxidation of the α-carbon of aromatic hydrocarbon with O 2. The reaction was carried out under 1 atm of O 2, which gives α-methylbenzyl alcohol and acetophenone for ethylbenzene.

Synthesis of 1-phenyl-1-xylyl ethane by Friedel–Crafts alkylation of xylene with α-methylbenzyl alcohol over mordenite

In the Friedel–Crafts alkylation of xylene to prepare 1-phenyl-1-xylyl ethane (PXE), α-methylbenzyl alcohol was used as an alkylating agent over a mordenite catalyst. The catalyst was characterized by MAS-NMR, N2 adsorption/desorption, NH3-TPD, and various other techniques and was found to possess strong Bronsted acid sites. When temperature was low, the main product was bis-(α-methylbenzyl) ether. However, as the temperature went up, PXE and heavies, styrene trimers and heavier oligomers, became main products. The formation of PXE, occurring on strong acid sites, is favored by raising temperature, space velocity, pressure, and xylene/MBA ratio within the experimental ranges. As the catalyst deactivates, the selectivities to PXE and heavies decrease and those to linear dimer and styrene increase. A reaction mechanism is proposed.

Biphasic Synthesis of 2-Phenylpropionic Acid and Ester by Interfacial Carbonylation of α-Methylbenzyl Bromide

An interfacial synthesis technique has been successfully extended to the carbonylation of α-methylbenzyl bromide in an organic−aqueous sodium hydroxide mixture at 35−60 °C and 1 atm using surface-active palladium−(4-dimethylaminophenyl)diphenylphosphine complex as the catalyst and dodecyl sodium sulfate as the emulsifier. Depending on the reaction conditions, 2-phenylpropionate in the form of sodium salt and an ester was obtained in 0−83% yield, along with varying amounts of side products that included α-methylbenzyl alcohol, 2,3-diphenylbutane, di(α-methylbenzyl)ether, and an asymmetric ether derived from the substrate and an alcoholic medium. When 2-methyl-1-butanol or 2-ethyl-1-hexanol was used as the organic phase, 2-phenylpropionate ester and sodium salt were obtained in 40−83% yield, with a maximum yield obtained at an optimal aqueous base concentration of about 5 M. At a lower aqueous base concentration, more of α-methylbenzyl alcohol was formed, whereas at a higher aqueous base concentration, more of 2,3-diphenylbutane and asymmetric ether were formed. When toluene was used as the organic phase, 2-phenylpropionate salt was obtained in less than 13% yield, and the major side product was α-methylbenzyl alcohol at a low aqueous base concentration and 2,3-diphenylbutane at a high aqueous base concentration. In all cases, the formation of 2,3-diphenylbutane was accompanied by a stoichiometric formation of carbonate. The latter implicates the involvement of an oxidative intermediatetentatively identified as hypobromous acidthat could deactivate the catalyst complex through ligand degradation. Along with the carbonylation reaction, carbon monoxide also underwent a slow, base-induced hydrolysis reaction to form formic acid. With 2-ethyl-1-hexanol as the organic phase, the carbonylation of α-methylbenzyl bromide showed an apparent temperature-dependent activation energy, a first-order dependence each on the substrate, catalyst, and ligand concentrations up to the catalyst concentration of 0.0020 M and a ligand:catalyst ratio of 3:1, and a variable-order dependence on the carbon monoxide pressure that switched from first to zeroth order as the carbon monoxide pressure was increased above 450 mmHg. A reaction mechanism is proposed which yields model rate and yield expressions in accord with the experimental findings. Results of control experiments with α,α-dibromotoluene in a toluene−aqueous sodium hydroxide mixture indicate that replacement of the α-methyl group in α-methylbenzyl bromide by a second bromo group suppressed the formation of substituted benzyl alcohol and coupled product. They suggest that the broad product distribution in the carbonylation of α-methylbenzyl bromide relative to the carbonylation of benzyl chloride and α,α-dibromotoluene is attributable to the electron-releasing α-methyl group making the substrate susceptible to hydrolysis and coupling reactions.