Alkyl Benzoates Research Articles

Structural models for the cell surface Lipooligosaccharides ofNeisseria gonorrhoeae andHaemophilus influenzae

A structural model is proposed for the surface glycolipids, or lipooligosaccharides (LOS), of gram-negative pathogenic bacteria that colonize human mucosae, e.g. Neisseria gonorrhoeae and Haemophilus influenzae. The development of this model has involved analysis of a series of pyocin-resistant mutants with altered LOS and other recent immunochemical and structural data. A comprehensive approach to determining the necessary structural data has been constructed that utilizes liquid secondary ion mass spectrometry, tandem mass spectrometry, methylation analysis and nuclear magnetic resonance. To prepare purified oligosaccharides for these analyses, chromatographic and chemical techniques have been developed that include high-pH anion-exchange chromatography of underivatized oligosaccharides and reverse-phase chromatography after derivatization with hydrazino alkyl benzoates. The proposed LOS model has several unique features that distinguish it from models developed for the lipopolysaccharides of enteric bacteria. This information should lead to an understanding of the unique structure/function relationship of LOS and to the development of carbohydrate-based vaccines.

Amino and hydrazino alkyl benzoates as derivatizing agents for the separation and mass spectrometric analysis of oligosaccharides from bacterial lipooligosaccharides

In an attempt to develop more sensitive and versatile methods for the structure analysis of oligosaccharides derived from lipooligosaccharides (LOS) of gram-negative bacteria, amino and hydrazino alkyl benzoate derivatives were prepared. These oligosaccharide derivatives were separated by HPLC and then analyzed by liquid secondary ion mass spectrometry (LSIMS). Both the amino and hydrazino alkyl benzoates react with the free reducing termini of acid-treated LOS, increasing the hydrophobicity of the released oligosaccharides and allowing them to be separated by reverse-phase HPLC. In addition, these oligosaccharide derivatives now contain a sensitive uv chromophore for subsequent peak detection and improve the quality of the LSIMS spectra compared to underivatized oligosaccharides. However, the amino alkyl benzoates reacted poorly compared to the analogous hydrazino alkyl benzoates with 3-deoxy-manno-2-keto oetulosonic acid (KDO), and oligosaccharides with KDO at the reducing terminus, especially when the oligosaccharide also contained phosphoethanolamine. Derivatization with the hydrazino compounds can be carried out quickly and under mild conditions using a minimal amount of reagent, and is therefore suitable for microscale analyses. The chromatographic and mass spectrometric characteristics of these derivatives make them excellent alternatives to permethylation and peracetylation techniques for the structural analysis of complex bacterial oligosaccharides derived from glycolipids.

ChemInform Abstract: Radical Anions of Esters of Carboxylic Acids. Effects of Structure and Solvent on Unimolecular Fragmentations.

AbstractPulse radiolysis of alkyl benzoates such as (I) produces the ester radical anions (II) which undergo unimolecular fragmentation to form alkyl radicals (III) and carboxylate anions (IV).

α‐Distonic ions as transient species in the reactions of metastable alkyl benzoate radical cations

AbstractThe key intermediates to the fragmentation of metastable methyl and ethyl benzoate radical cations are α‐ and β‐distonic isomers of the molecular ions. The α‐distocic isomers are also formed by fragmentation of longer chain alkyl benzoates, but may not be long‐lived, stable species. Rearrangement of the α‐distonic ions prior to fragmentation can take place, but (re)formation of the benzoate molecular ions does not occur.

Mechanisms of nucleophilic reactions of 4-benzoyl-4-methylcyclohexa-2,5-dienone and its benzoyl substituted derivatives

Studies have been made of the reactions with nucleophiles of 4-benzoyl-4-methylcyclohexa-2,5-dienone and its 4-chlorobenzoyl- and 4-methoxybenzoyl- analogues. Water effects hydrolysis to 4-methylphenol and the appropriate substituted benzoic acid. Kinetic measurements give a log kobsvs. pH profile with slopes close to –1.0, 0, and 1.0, indicating proton, water, and hydroxide ion catalysis, respectively. The results suggest a mechanistic pattern similar to that found for the cleavage of benzaldehyde hemiacetals. Alcohols and alkoxides effect analogous cleavage to 4-methylphenol and the alkyl benzoates. Reaction of the 4-benzoyl-4-methylcyclohexa-2,5-dienone with dialkyl amines gives varying proportions of 4-methylphenyl benzoate and 4-methylphenol with N,N-dialkylbenzamide. An initial amine-induced rearrangement of the dienone to 4-methylphenyl benzoate is followed by cleavage by the amine to give the phenol and amide.

Chromatographic evaluation of oligomeric C 8 reversed phases for use in high-performance liquid chromatography

Stepwise silanisation of porous silica gel with n-octyldichlorosilane and subsequent hydrolysis of the unreacted chlorine atoms have been shown to produce a dense-layered C 8 chemically bonded stationary phase. Increase in carbon load results in decrease in specific surface area and pore volume of the starting silica material. Chromatographic properties obtained for aromatic hydrocarbons and alkyl benzoates under isocratic conditions were correlated with carbon content of the stationary phases. It was found that at high carbon content (>11%) both capacity factor and separation factor are independent of carbon load.

Excess viscosity .eta.E, excess volume VE, and excess free energy of activation .DELTA.G*E at 283, 293, 303, 313, and 323 K for mixtures acetonitrile and alkyl benzoates

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTExcess viscosity .eta.E, excess volume VE, and excess free energy of activation .DELTA.G*E at 283, 293, 303, 313, and 323 K for mixtures acetonitrile and alkyl benzoatesBegona Garcia and Juan C. OrtegaCite this: J. Chem. Eng. Data 1988, 33, 2, 200–204Publication Date (Print):April 1, 1988Publication History Published online1 May 2002Published inissue 1 April 1988https://doi.org/10.1021/je00052a041RIGHTS & PERMISSIONSArticle Views184Altmetric-Citations51LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (458 KB) Get e-Alerts Get e-Alerts

The reactivity of ruthenium textroxide towards aromatic and etheric functionalities in simple organic compounds

The reactivity of ruthenium tetroxide towards coal-like organic functionalities was investigated by oxidizing model substrates containing aromatic and etheric functionalities with RuO 2.3H 2O in the presence of variable amounts of NaIO 4 as the cooxidant. Molar cooxidant/substrate ratios ( c s ) of between 2 and 8 were employed. Most substrates gave low product yields at low c s ratios, but product distributions obtained at the various c s ratios indicate that most functionalities are initially attacked at more than one site, forming products which can themselves be further oxidized. Phenyl groups are rapidly oxidized to CO 2 when the ring is activated by electron donating substituents, but slowly, or not at all when an electron withdrawing group is present. The alkyl benzyl ether group is oxidized rapidly and exclusively to the alkyl benzoate derivative with two equivalents of cooxidant, and the product ester is inert towards further oxidation at a higher c s ratio. Phenylpentadecane is oxidized at the aromatic ring and at the benzylic methylene, even at low c s ratios, to form hexadecanoic acid, pentadecanophenone, and pentadecanoic acid, Higher c s ratios produce significant amounts of shorter chain acids with no increase in the yield of phenone. Dihydroanthracene is oxidized rapidly to anthracene, but small amounts of anthrone and anthraquinone are also formed. At higher c s ratios anthracene is slowly oxidized to the latter products.

ChemInform Abstract: ANOMALOUS ORIENTATIONAL EFFECTS DURING BENZOYLOXYLATIONS BY SILVER BROMIDE DIBENZOATE

AbstractDie Aromaten (III) lassen sich mit dem aus Silberbenzoat (I) und Brom gebildeten Silberbromidkomplex (II) zu den Arylbenzoaten (IV) oxidativ benzoylieren.

Crystal structure of enol benzoate ( [formula omitted]) obtained from conjugate addition of phenylmagnesium bromide to benzalacetomesitylene ( [formula omitted]); (z)-α-(2,2-diphenylethylidene)-2,4,6-trimethylbenzenemethanol benzoate ( [formula omitted

The title compound ( 1 ) is shown to have a (Z) configuration confirming a previous assignment based on 1H nmr vinyl shielding constants. Bond distances, bond angles, and selected torsion angles are reported. The benzoyl ester grouping is s-trans in accord with the usual conformation for alkyl benzoates in solution. A torsion angle of 6.6° (average) involving the ester grouping for C 8-0 2-C 7-0 1 (or C 8-0 2-C 7-C 1 ) was found. The cyclic mechanism of Lutz and Reveley involving reaction of an s-cis conformation of the α,β-unsaturated ketone with the Grignard reagent explains the (Z)-stereochemlstry observed.

ANOMALOUS ORIENTATIONAL EFFECTS DURING BENZOYLOXYLATIONS BY “SILVER BROMIDE DIBENZOATE”

Abstract The solid complex formed from bromine and silver benzoate reacts with both arenes and alkanes to form aryl and alkyl benzoates, respectively. Highly unusual substituent effects are observed in the benzoyloxylations of arenes. Electron-withdrawing groups (e.g. –NO2, –CN, –CO–) on the aromatic ring facilitate reaction though directing the attacking reagent exclusively to the meta position. In alkanes, tertiary positions are most prone to attack.

On the rearrangement in carbonyl oxide intermediates

Sensitized photooxidation of alkylphenyldiazomethanes under oxygen afforded, in addition to alkyl phenyl ketones, alkyl benzoates, which are probably formed by a rearrangement via dioxirane diradical.

ChemInform Abstract: GENERAL BASE CATALYSES BY α‐CYCLODEXTRIN IN THE HYDROLYSES OF ALKYL BENZOATES

The hydrolyses of seven alkyl benzoates are catalyzed by α-cyclodextrin. These results indicate that the general base catalysis by α-cyclodextrin, previously found for the first time in the hydrolysis of 2,2,2-trifluoroethyl 4-nitrobenzoate, is applicable to other alkyl esters.

GENERAL BASE CATALYSES BY α-CYCLODEXTRIN IN THE HYDROLYSES OF ALKYL BENZOATES

Abstract The hydrolyses of seven alkyl benzoates are catalyzed by α-cyclodextrin. These results indicate that the general base catalysis by α-cyclodextrin, previously found for the first time in the hydrolysis of 2,2,2-trifluoroethyl 4-nitrobenzoate, is applicable to other alkyl esters.

Photo-oxidation of crystalline α-benzoylbenzyl ethers by atmospheric oxygen

Solid α-benzoylbenzyl ethers reacted efficiently with atmospheric oxygen upon irradiation, yielding benzoic acid and alkyl benzoates in high yield, presumably via a benzoyl–benzyl radical pair.

An investigation of the mechanism of single and double hydrogen atom transfer reactions in alkyl benzoates by the ortho effect

AbstractSingle and double hydrogen atom transfers in reactions (1) and (2) in the mass spectra of ethyl benzoate, isopropyl benzoate, and isobutyl benzoate have been investigated with reference to the ortho effect: (1) [C6H5CO2R]+⋅ → [C6H5CO2H]+⋅ (m/z 122) + (R‐H); (2) [C6H5CO2R]+⋅ → [C6H5CO2H2]+ (m/z 123) + · (R‐2H). It is demonstrated that the intermediate ion [C6H5CO2H2]+ has the protonated benzoic acid structure with the hydrogen atom on the carbonyl group.

Substituent effects in infrared spectroscopy. Part 5. Carbonyl stretching frequency in meta- and para-substituted aromatic carbonyl compounds

Substituent effects for carbonyl stretching frequencies of m- and p-substituted acetophenones, benzophenones, benzoic acids, and alkyl benzoates are investigated by means of a correlation analysis. The validity of the Hammett, Hammett–Brown, and Exner equations is checked by means of numerous substituents and several limitations of these equations are shown. Coupling between carbonyl groups in dicarbonyl centrosymmetric molecules, dependence of substituent constants on solvent, and dependence of transmission coefficients of substituent effects along the ArCOY series on the Y group are shown.

An Investigation of Structure of Intermediate Ions from Several Substituted Alkyl Benzoates by the ortho Effect and Kinetic Energy Release

Single and double hydrogen atom transfers in reactions (1) and (2) are found in the mass spectra of n-propyl and n-butyl benzoates, and n-propyl and n-butyl p-hydroxy-benzoates. In contrast, only single hydrogen atom transfer is found in the mass spectra of n-propyl and n-bulyl salicylates and it is concluded that the hydrogen bond prevents the second hydrogen atom transfer. The kinetic energy release for the loss of water from the m/z 138 ion[C7H6O3]+ produced from ethyl and higher alkyl salicylates by a McLafferty rearrangement was nearly equal to that from the molecular ion of salicylic acid (m/z 138). The kinetic energy release for the loss of water from the m/z 137 ion[C7H7NO2]+ from ethyl o-aminobenzoate was also equal to that from the molecular ion of o-amino benzoic acid (m/z 137). However, the corresponding kinetic energy release from the m/z 136 ion[C8H8O2]+ from ethyl o-methylbenzoate was somewhat higher than that from the molecular ion of o-methyl benzoic acid (m/z 136).

Alkaline hydrolyses of alkyl nitrites and related carboxylic esters

Alkaline hydrolysis of alkyl nitrites and related carboxylic esters was investigated. Marked differences between alkyl nitrites and the corresponding esters in hydrolysis are as follows. (1) Alkaline hydrolysis of alkyl nitrite is much slower than that of the corresponding ester. (2) However, acid hydrolysis of alkyl nitrite is markedly faster than that of the corresponding ester. (3) There is no concurrent oxygen exchange between the nitroso-oxygen of n-hexyl nitrite and hydroxide in alkaline hydrolysis at 45.0 and 55.1°C. (4) The polar effect of substituents on the leaving alkoxide group in alkaline hydrolysis of alkyl nitrites is roughly two-fold larger than that for the esters, i.e.ρ° 1.46 for substituted benzyl nitrites, 0.994 for substituted benzyl benzoates, 0.764 for substituted benzyl acetates ρ* 2.54 for alkyl nitrites, 1.26 for alkyl benzoates, 1.28 for alkyl acetates. (5) The steric requirements for alkaline hydrolysis of alkyl nitrites are less than those for the esters, i.e. Taft δ-values 1.03 for alkyl nitrites, 1.52 for alkyl benzoates, 1.50 for alkyl acetates. These differences are rationalized in terms of the two main differences of the electrophilic centres, (1) the greater electronegativity of nitrogen than of carbon, and (2) the presence of a lone pair on nitrogen but not on carbon.

3233. Genetic damage from p-aminobenzoic acid? : Hodges, N.D.M., Moss, S.H. & Davies, D.J.G. (1976). Evidence for increased genetic damage due to the presence of a sunscreen agent, para-aminobenzoic acid, during irradiation with near ultraviolet light. J. Pharm. Pharmac.28, 53P

The idea of increasing the performance of sunscreens without adding more UV-filters is very attractive. Early studies reported an influence of solvents on the absorbing properties of UV-absorbers which was shown to be connected to the solvent polarity. However, the polarity differed a lot between tested solvents and most were unsuitable UV-filter solubilizers. The aim of the present study was to focus exclusively on emollients pertinent for sunscreens and investigate their impact on the performance of UV-filter combinations. The UV absorbance of Bis-ethylhexyloxyphenol Methoxyphenyl Triazine, Ethylhexyl Triazone, Diethylamino Hydroxybenzoyl Hexyl Benzoate, and Ethylhexyl Methoxycinnamate was measured in suncare relevant emollients comprising C12–15 Alkyl Benzoate, Dibutyl Adipate, Caprylic/Capric Triglyceride, Coco-caprylate, Isopropyl Myristate, Dicaprylyl Carbonate. The wavelength of maximum absorbance (λmax) and specific extinction at λmax (E1,1 (λmax)) were assessed for each UV-filter – emollient system. The performance of market relevant UV-filter combinations based on the studied UV-filters was simulated for each emollient with a computational method using the absorbance values measured for each UV-filter - emollient system. The difference in polarity of emollients led to a 2-3 nm bathochromic shift and a variation of the E1,1 (λmax) ranging from 4 to 20% for tested UV-filters. The emollient type showed nearly no influence on the sun protection factor (SPF) of market relevant UV-filter combinations probably due to a different influence an emollient shows on the UVB filters resulting in cancelling of the corresponding effect. Conversely, for all UV-filter combinations the UVA protection decreased with a decrease in the emollient polarity. Whilst the SPF was not impacted by standardly used cosmetic oils, the results advocate to use polar emollients to optimize the UVA protection. This is of advantage since polar emollients better dissolve crystalline UV-filters. From tested emollients, Dibutyl Adipate performed the best for both SPF and PPD factors.