Alkyl Benzoates Research Articles

The ammonolysis of esters in liquid ammonia

The rates of ammonolysis of alkyl benzoate and phenylacetate esters in liquid ammonia increase with the acidity of the leaving group alcohol and show relatively large Brønsted βlg values of −1.18 and −1.34, respectively, when plotted against the aqueous pKa of the alcohol. The Brønsted βlg obtained using the pKa of the leaving group alcohol in liquid ammonia is significantly reduced to ~ −0.7, which indicates that the rate‐limiting step involves a reaction of the tetrahedral intermediate with little C–OR bond fission in the transition state. The solvolysis reaction is subject to significant catalysis by ammonium ion, which, surprisingly, generates a similar Brønsted βlg indicating little interaction between the ammonium ion and the leaving group. It is concluded that the rate‐limiting step for the ammonium‐ion‐catalysed solvolysis of alkyl esters in liquid ammonia is the diffusion‐controlled protonation of the zwitterionic tetrahedral intermediate T+‐ to give T+, which is rapidly deprotonated to give T0 which is compatible with the rate‐limiting step for the uncatalysed reaction being the formation of the neutral T0 by a ‘proton switch’. Copyright © 2013 John Wiley & Sons, Ltd.

Molecular interaction studies in hydrogen bonded polar binary mixtures

The molecular interactions between the polar systems of propan-1-ol (1PN) with alkyl benzoates (methyl benzoate and ethyl benzoate) for various mole fractions at different temperatures are studied by determining the dielectric permittivity in radio, microwave and optic frequency regions, respectively. Dipole moment, excess dipole moment, excess Helmholtz free energy, excess permittivity, relaxation time, excess inverse relaxation time and excess thermodynamical values are calculated using experimental data. Hamiltonian quantum mechanical calculations are performed on both pure and equimolar binary systems of 1PN with alkyl benzoates for the measurement of dipole moment from the ab initio Hartree–Fock and density functional theory (B3LYP) methods with 6-31 + G* and 6-311 + G** basis sets using Spartan 08 modelling software and these theoretical values are in good agreement with the experimental values.

Investigation of the Effects of Different Emollients on the Structure and Skin Moisturizing Potential of the Cosmetic Creams

SUMMARY In this study we investigated the effects of four emollients (cetearyl octanoate, decyl oleate, C12-15 alkyl benzoate and olive oil) incorporated at a concentration of 10% on the structural properties of the cosmetic oil/water (o/w) creams (creams K1-K4, respectively) as well as the in vivo effects of those creams on pH and hydration level of the healthy volunteer’s skin after a single application. Creams’ structure was investigated throughout polarization microscopy. Anisotropic structures were found, i.e. stabilization of creams’ structure was performed by forming lamellar gel-crystalline and liquid-crystalline phase, different for different creams, which was probably caused by the presence of different emollients. The effects of creams (K1-K4) on skin hydration level and pH (30, 90, 150 and 300min after single application) were examined using Multi Probe Adapter (MPA ® 9, Courage& Khazaka Electronic, Germany), with appropriate sonde, Corneometer ® CM 825 for measuring capacitance as a measure of skin moisture level, while the skin pH was measured using Skin-pH-Meter, PH 900 sonde.The results indicate that the presence of the different emollients in o/w creams (10%) led to the creams'different effects on the skin hydration level. Cream with decyl oleate leads to a good initial hydration effect and probably rapid release of large amounts of water from the cream. Creams containing both C12-C15 alkyl benzoate or olive oil had a weaker initial effect on the skin moisture, showing good occlusive properties. A cream containing 10% cetearyl octanoate showed the lowest skin hydration potential.

Safety Assessment of Alkyl Benzoates as Used in Cosmetics

The functions of alkyl benzoates in cosmetics include fragrance ingredients, skin-conditioning agents--emollient, skin-conditioning agents--miscellaneous, preservatives, solvents, and plasticizers. The Cosmetic Ingredient Review Expert Panel reviewed the relevant animal and human data and noted gaps in the available safety data for some of the alkyl benzoates. Similar structure activity relationships, biologic functions, and cosmetic product usage allowed the available data of many of the alkyl benzoates to be extended to the entire group. Carcinogenicity data were not available, but available data indicated that these alkyl benzoate cosmetic ingredients are not genotoxic. Also benzoic acid and tested component alcohols were not reproductive or developmental toxicants, are not genotoxic in almost all assays, and are not carcinogenic. These ingredients were determined to be safe in the present practices of use and concentration.

A Novel Alkaline Esterase fromSporosarcinasp. nov. Strain eSP04 Catalyzing the Hydrolysis of a Wide Variety of Aryl-carboxylic Acid Esters

A novel esterase showing activity specific for esters of aryl-carboxylic acids was discovered in Sporosarcina sp. nov., which was identified by the 16S rDNA sequencing method in addition to morphological and physiological analyses. The aryl-carboxylesterase (named EstAC) was purified 780-fold from crude cell extracts by a 5-step procedure. EstAC was characterized as a monomeric protein with a molecular weight of 43,000, an optimum pH of around 9.0, and an optimum temperature of 40 °C. The pH optimum and the effects of inhibitors together with an internal amino acid sequence suggested that EstAC is a member of family VIII esterases. EstAC was found to be highly active on a wide variety of substrates such as alkyl benzoates, alkyl phenylacetates, ethyl α- or β-substituted phenylpropionates, dialkyl terephthalates, dimethyl isophthalate, and ethylene glycol dibenzoate. However, monomethyl terephthalate was not hydrolyzed. It was suggested that EstAC had 4-hydroxybenzoyl and cinnamoyl esterase activities as well.

Excess Dielectric and Thermodynamical Studies on Hydrogen Bonded Binary Mixtures of Propan-1-ol with Methyl and Ethyl Benzoates

The molecular interactions between the polar systems propan-1-ol with alkyl benzoates (methyl benzoate and ethyl benzoate) for various mole fractions at different temperatures were studied by determining the dielectric permittivity using - LF impedance analyzer, microwave bench and Abbe's refractometer in radio, microwave and optic frequency regions respectively. Dipole moment, excess dipole moment, excess Helmholtz free energy, excess permittivity, relaxation time, excess inverse relaxation time and excess thermodynamical values are calculated using experimental data. Hamiltonian quantum mechanical calculations are performed on both pure and equimolar binary systems of propan-1-ol with alkyl benzoates for the measurement of dipole moment using PC Spartan and Argus lab Modeling softwares and these theoretical values are in good agreement with the experimental values. These studies can give information on its structure and interaction.

UV absorption and scattering properties of inorganic‐based sunscreens

This article first introduces the concepts that underlie the calculations of scattering and absorption of light by small particles. Results of Mie theory calculations of light scattering and light absorption by 20, 50 and 100 nm TiO₂ and ZnO particles are then presented. As the attenuation, or extinction, by these particles is the sum of the scattering and absorption, the attenuation can then be calculated for wavelengths over the UVA and UVB region. These theoretical results are then shown to be in reasonable agreement with experimental results for alkyl benzoate dispersions of three different types of TiO₂ particle whose mean sizes range from 35 to 145 nm. Finally, the link between these measurements and the absorption curves of formulated dispersions of sunscreens are demonstrated and related to in vitro SPF and UVAPF measurements.

Investigations on Binary Mixtures of Propan-2-ol with Methyl Benzoate and Ethyl Benzoate

The molecular interactions between the polar systems propan-2-ol with alkyl benzoates (methyl benzoate and ethyl benzoate), for various mole fractions and different temperatures, were studied by determining the dielectric permittivity using a LF impedance analyzer and Abbe’s refractometer in the static and optical frequency regions, respectively. The effective Kirkwood correlation factor, corrective Kirkwood correlation factor, dipole moment, excess dipole moment, and excess Helmholtz free energy were calculated using the experimental data. Hamiltonian quantum mechanical calculations (ab initio and semiempirical) were performed using PC Spartan and Argus lab Modeling software for both pure and equimolar binary systems of propan-2-ol with alkyl benzoates.

Preparation of α-Ketophosphonate Derivatives and Their Application in the Synthesis of 1-(N-Alkylcarbamoyl)-1-(diethoxyphosphoryl)alkyl Benzoates via Passerini Reaction

The Passerini reaction of α-ketophosphonates, isocyanides, and benzoic acid derivatives leads to 1-(N-alkylcarbamoyl)-1-(diethoxyphosphoryl)alkyl benzoates in one step at room temperature. The structures of products were assigned on the basis of their 1H NMR, 13C NMR, 31P NMR, and IR spectroscopic data.GRAPHICAL ABSTRACT

Correlations among dielectric and thermodynamic parameters in hydrogen bonded binary mixtures of alcohol and alkyl benzoates

The dielectric and thermodynamic studies on polar binary mixtures of alcohol (propan-2-ol) with, alkyl benzoates (methyl benzoate and ethyl benzoate) have been carried out, at different temperatures and mole fractions, using — LF impedance analyzer, Microwave bench and Abbe's refractometer in radio, microwave (X-Band) and high frequency regions respectively. The experimental data is used to correlate the dielectric and thermodynamic parameters like static permittivity, high frequency permittivity, effective Kirkwood correlation factor, corrective Kirkwood correlation factor, excess Helmholtz free energy, dipole moment, excessive dipole moment, relaxation time and excess thermodynamic parameters . These parameters are used to interpret the molecular interaction between the molecular species of the liquid mixtures.

17O NMR study of ortho and alkyl substituent effects in substituted phenyl and alkyl esters of benzoic acids

17O NMR spectra for 44ortho-,meta- andpara-substituted phenyl and alkyl benzoates (C6H5CO2C6H4-X, C6H5CO2R) at natural abundance in acetonitrile were recorded. Substituent effects on the17O NMR chemical shifts, δ(17O), of the carbonyl oxygen and the single-bonded phenoxy (OPh) and alkoxy (OR) oxygens have been studied. The δ(17O) values of the carbonyl oxygen forparaderivatives showed a good correlation with the σ° constants. The δ(17O) values of carbonyl oxygen fororthoderivatives were found to be described well with the Charton equation containing the inductive, σI, resonance, σ°R, and steric,EsB, substituent constants in case the data treatment was performed separately for electron-donating +Rand electron-attracting –Rsubstituents. The electron-donating +Rorthoandparasubstituents in substituted benzoates caused shielding and the electron-withdrawing –Rsubstituents produced deshielding of the O signal. The steric interaction oforthosubstituents with the ester group decreased the electron density at the carbonyl oxygen. In alkyl benzoates the δ(17O) values were found to be described well with the inductive, σI, and the steric,EsB, substituent constants.

Aromatics from pyrones: para-substituted alkyl benzoates from alkenes, coumalic acid and methyl coumalate

The Diels–Alder reaction of coumalic acid and methyl coumalate with unactivated alkenes provides only para-substituted adducts in good yield.

Thermodynamic, Dielectric and Conformational Studies on Hydrogen Bonded Binary Mixtures of Propan-1-ol with Methyl Benzoate and Ethyl Benzoate

Dielectric relaxation studies of propan-1-ol with alkyl benzoates (methyl benzoate and ethyl benzoate) have been carried out, for various mole fractions, at different temperatures using a LF impedance analyzer, Plunger method, and an Abbe’s refractometer in the radio, microwave and optical frequency regions, respectively. Kirkwood’s effective correlation factor, the corrective Kirkwood correlation factor, Bruggeman parameter, relaxation time, excess inverse relaxation time and thermodynamic parameters were calculated using the experimental data. Conformational analysis of the formation of hydrogen bonds in the equi-molar binary mixtures of propan-1-ol with alkyl benzoates is supported by experimental and theoretical FT-IR values.

Involvement of cyan and ester groups in surface interactions of aerosil–cyanophenyl alkyl benzoate systems with high silica density: Infrared investigations

Composites prepared from aerosil A380 and liquid crystals (LCs) of 4- n-alkyl-4′-cyanophenyl benzoate type, with four to six carbon atoms in the alkyl chain were investigated by infrared spectroscopy. Their high silica content (of 2–7 g aerosil/1 g of LC) was given by thermogravimetric investigations and allows the observation of a rather thin LC layer on the silica particles. Several surface species onto the external surface of the grains were demonstrated. Arguments are given that monomer and dimer species are present in the bulk cyanophenyl benzoate materials while bulk-like species along with hydrogen-bonded ones coexist in the so-called surface layer of the composites. The main interaction of LC molecules with the aerosil surface is by hydrogen bonding taking place with the involvement of the cyan group. There is a contribution of ester carbonyl group to these surface interactions but this cannot be well quantified.

Effect of ortho substituents on carbonyl carbon 13C NMR chemical shifts in substituted phenyl benzoates

Abstract13C NMR spectra of 37 ortho‐, meta‐, and para‐substituted phenyl benzoates, containing substituents in benzoyl and phenyl moiety, 4 ortho‐substituted methyl and 5 ethyl benzoates as well as 9 R‐substituted alkyl benzoates have been recorded. The influence of the ortho substituents on the carbonyl carbon 13C NMR chemical shift, δCO, was found to be described by a linear multiple regression equation containing the inductive, σI, resonance, σ°R, and steric, E, or υ substituent constants. For all the ortho‐substituted esters containing substituents in the acyl part as well as the phenyl part, the substituent‐induced reverse inductive effect (ρI < 0), the normal resonance effect (ρR > 0), and the negative steric effect (δortho < 0) with the E were observed. In the case of ortho substituents in the phenyl part, the resonance effect was negligible. Due to inductive effect, the ortho electron‐withdrawing substituents showed an upfield shift or shielding of the carbonyl carbon, while the electron‐donating substituents had an opposite effect. Because of the sterical consequences, ortho substituents revealed a deshielding effect on the 13C NMR chemical shift of the carbonyl carbon. For all the meta‐ and para‐substituted esters, the reverse substituent‐induced inductive and resonance effects (ρI < 0, ρR < 0) were found to be significant. In alkyl benzoates, the alkyl substituents showed the reverse inductive and steric effects. The log k values for the alkaline hydrolysis in water, aqueous 0.5 M Bu4NBr and 2.25 M Bu4NBr, and the IR frequencies, νCO, for the ortho‐, meta‐, and para‐substituted phenyl benzoates and alkyl benzoates were correlated nicely with the corresponding 13C NMR substituent chemical shifts, ΔδCO. Copyright © 2009 John Wiley & Sons, Ltd.

Chemically and enzymatically catalyzed synthesis of C6–C10 alkyl benzoates

AbstractThe esterification of benzoic acid with n‐hexanol, n‐octanol, 2‐ethyl hexanol and n‐decanol was investigated in detail. An analysis of the reaction kinetics of esterification in the presence of different commercially available chemical catalysts was carried out. The effects of catalyst type and loading on the reaction rate were studied. Although the considered reaction is bimolecular, it showed a first‐order behavior, and a linear dependence with respect to the catalyst concentration was observed. Hence, a new approach is presented to describe the reaction kinetics accurately over a wide range. The application of biotechnological synthesis applying different enzymes as catalysts offers an interesting alternative besides chemical synthesis. Especially an esterase from Bacillus subtilis immobilized on Sepabeads EC‐EP showed high stability and was applied for 2 days in the synthesis of hexyl benzoate. Nevertheless, the chemical reaction route remains superior with respect to the catalyst activities under the applied conditions, which were 25 kU/g for the chemical reaction and 0.7 kU/g for the best enzymatic conversion.

Nitration of Alkyl Benzoates with Mixed Acid

AbstractThe nitration of (substituted) benzoic acid esters is usually performed in fed‐batch operation. The ester is solved in sulfuric acid charged first. The nitric acid dosed keeps the reaction temperature under control. The safety regarding uncontrolled reaction conditions was investigated under variation of the ratio of nitric acid to charged aromatic compound. A significant decrease in thermal stability of the reaction mixture was observed with excess of nitric acid. Safe operation cannot be assumed in general when the acid is close to or exceeds 10 % molar ratio. The investigation was restricted to aromatic carboxylic acid alkyl esters which form homogeneous mixtures with sulfuric acid. The thermal stability was investigated by differential thermal analysis (closed systems), adiabatic storage tests, and dynamic calorimeters. The reaction products were analyzed by means of NMR and mass spectrometry. The experiments showed that the formation of dinitro compounds cannot cause the thermal instability alone. The formation of dinitro compounds starts at temperatures above the reaction conditions. Another component is responsible for the thermal instability which accumulates in the presence of an ester group at excess nitric acid. It could be deduced that the decomposition reaction is primarily caused by the reaction of surplus nitryl cation (NO2+ ion) with the nitrated carboxylic acid ester in the presence of sulfuric acid. The decomposition temperature of the reaction mixture depends on the nature of the ester group and the type and number of further substituents on the aromatic ring.

Kinetic study of hydrolysis of benzoates. part xxvii. ortho substituent effect in alkaline hydrolysis of phenyl esters of substituted benzoic acids in aqueous Bu4NBr

The second-order rate constants k (in dm3 mol–1 s–1) for alkaline hydrolysis of phenyl esters of meta-, para- and ortho-substituted benzoic acids, X-C6H4CO2C6H5, have been measured spectrophotometrically in aqueous 0.5 and 2.25 M Bu4NBr at 25 °C. The substituent effects for para and meta derivatives were described using the Hammett relationship. For the ortho derivatives the Charton equation was used. For ortho-substituted esters two steric scales were involved: the EsB and the Charton steric (υ) constants. When going from pure water to aqueous 0.5 and 2.25 M Bu4NBr, the meta and para polar effects, the ortho inductive and resonance effects in alkaline hydrolysis of phenyl esters of substituted benzoic acids, became stronger nearly to the same extent as found for alkaline hydrolysis of C6H5CO2C6H4-X. The steric term of ortho-substituted esters was almost independent of the media considered. The rate constants of alkaline hydrolysis of ortho-, meta- and para-substituted phenyl benzoates (X-C6H4CO2C6H5, C6H5CO2C6H4-X) and alkyl benzoates, C6H5CO2R, in water, 0.5 and 2.25 M Bu4NBr were correlated with the corresponding IR stretching frequencies of carbonyl group, (ΔνCO)X.

Preparation of lipophilic alkyl (hydroxy)benzoates by solvent-free lipase-catalyzed esterification and transesterification

Long-chain alkyl benzoates, e.g., lauryl 4-hydroxybenzoate, palmityl 4-hydroxybenzoate, and oleyl 4-hydroxy-3-methoxybenzoate, are formed in high to moderate conversion by lipase-catalyzed transesterification of the corresponding short-chain alkyl benzoates (0.3 to 1 mmol) with fatty alcohols in an equimolar ratio. The substrates are reacted in vacuo in the absence of solvents and drying agents in the reaction mixture. Immobilized lipase B from Candida antarctica (Novozym 435) demonstrates higher activity for the transesterification of various methyl (hydroxy)benzoates with long-chain alcohols than for the corresponding esterification reactions. For example, transesterification activity is around 25-fold higher than esterification activity for the preparation of oleyl 4-hydroxybenzoate. The relative transesterification activities of methoxy- and hydroxy-substituted methyl benzoates found for Novozym 435 are as follows: 2-methoxybenzoate approximately 3-methoxybenzoate > 4-methoxybenzoate > 3-hydroxybenzoate approximately 2-hydroxybenzoate > 4-hydroxybenzoate approximately 4-hydroxy-3-methoxybenzoate approximately 3-hydroxy-4-methoxybenzoate > > 3,4-dihydroxybenzoate. With respect to the position of the substituents at the phenyl moiety of methyl benzoates, transesterification activity of Novozym 435 increases in the order ortho approximately meta > para. Compounds with inverse chemical structure, e.g., (methoxy)benzyl alkanoates, are formed in much higher rates both by esterification and transesterification than the analogous alkyl benzoates. Purification by deacidification, crystallization, or vacuum distillation yielded 74% to 89% of the reaction products.

Reactions of Chlorine Gas on Benzaldehyde‐di‐n‐alkyl Acetals

Reactions of chlorine gas on six aromatic acetals, the benzaldehyde di‐n‐alkyl acetals, C6H4‐CH(OR)2 where R=ethyl (1a), n‐propyl (2a), n‐butyl (3a), isobutyl (4a), n‐amyl (5a) and isoamyl (6a) were studied. The products were analyzed by IR and 1H NMR spectroscopic techniques and were found to be ring chlorinated alkyl benzoates. A plausible mechanism has been proposed based on the experimental observations and the effect of the alkyl groups on the product yield.