Analysis of carboxylic acids by gas chromatography. Derivatisation using chloroacetone

Summary The preparation of the acetonyl esters of nine aliphatic carboxylic acids is described, the general formula of the derivatives being RCOOCH₂COCH₃ where R=alkyl or H. The derivatives show good chromatographic properties on both packed and capillary columns. The electron impact and chemical ionisation mass spectra of the derivatives are discussed.     

Desulphurative approaches to penem antibiotics. VI. From penam methyl esters to penem acetonyl esters: A fully conservative conversion

A straightforward conversion of penam methyl esters into penem acetonyl esters entailing incorporation of all the elements of the former into the latter is described.     

Spectra of 3-benzoxazolonylpropanones

The effect of substituents on the vibrational frequencies of oxazolonyl and acetonyl carbonyl groups was studied by means of the IR and PMR spectra of a series of substituted (in the benzene ring) 3-benzoxazolonylpropanones. The experimental data and the results of correlation analysis show that the carbonyl group of the acetonyl grouping is situated along the axis perpendicular to the plane of the benzene and heterocyclic rings and the substituent. The mechanism of transmission of the effect of substituents on the characteristic frequencies and the chemical shifts of the protons of the acetonyl group in the spectra are discussed.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 2, pp. 191–194, February, 1979     

The heat of formation of the acetonyl radical VLPP studies of acetonyl bromide,isopropenylmethylether, and hexanedione-2,5 in a search for acetonyl stabilization energy

The decomposition of acetonyl bromide, isopropenylmethylether, and hexanedione-2,5 was studied using the very-low-pressure pyrolysis (VLPP) technique. The acetonyl radical is a product of each reaction. Arrhenius parameters determined are or acetonyl bromide ← acetonyl + Br: and for isopropenylmethylether ← acetonyl + CH₃: These lead to values of acetonyl stabilization energy (SE) of 0.8 and ?4.0 kcal/mol, respectively. Comparison of the pyrolyses of hexanedione-2,5 and 2,5-dimethylhexane indicate a value of SE ～ 2 kcal/mol. The total of these results is taken, along with previous work, to indicate that 0 ? SE ? 2 kcal/mol.     

An Ireland-Claisen approach to beta-alkoxy alpha-amino acids

A diastereoselective Ireland-Claisen approach to beta-alkoxy alpha-amino acid esters is reported. Amino acid esters of enol ethereal allylic alcohols undergo facile syn-selective [3,3]-sigmatropic rearrangement via silyl ketene acetals. Substrate synthesis, rearrangement development, stereoselectivity, and product elaboration are discussed.     

Philicity of Acetonyl and Benzoyl Radicals: A Comparative Experimental and Computational Study

In this work, the reactivities of acetonyl and benzoyl radicals in aromatic substitution and addition reactions have been compared in an experimental and computational study. The results show that acetonyl is more electrophilic than benzoyl, which is rather nucleophilic. A Hammett plot analysis of the addition reactions of the two radicals to substituted styrenes clearly support the nucleophilicity of benzoyl, but in the case of acetonyl, no satisfactory linear correlation with a single substituent-related parameter was found. Computational calculations helped to rationalize this effect, and a good linear correlation was found with a combination of polar parameters (σ⁺) and the radical stabilization energies of the formed intermediates. Based on the calculated philicity indices for benzoyl and acetonyl, a quantitative comparison of these two radicals with many other reported radicals is possible, which may help to predict the reactivities of other aromatic radical substitution reactions.     

Photoinitiated copolymerization of acetonyl methacrylate

Synthesis of two methacrylate monomers derivatives of carbonyl compounds: vanillin and acetone are presented. The obtained acetonyl methacrylate was used for copolymerization with methyl methacrylate. Copolymerizations were carried out in the presence of commercially available photoinitiator Irgacure 651. Thermal and mechanical properties of the copolymers with different concentration of acetonyl methacrylate were studied.     

Colorimetric determination of organic compounds by formation of hydroxamic acids

Carboxylic acids, their chlorides, anhydrides, esters, lactones, amides, lactams and imides react with hydroxylamine to give hydroxamic acids which are then treated with iron(III). Other compounds or groups of compounds can also be determined after a prior conversion into hydroxylamine-reactive derivatives. The calorimetric applications of these reactions are reviewed. The effect of various factors is discussed. A selective procedure for determination of acid chlorides and anhydrides and an improved procedure for determination of carboxylic esters and lactones are presented.     

Preparation and properties of pure lithio esters of some carboxylic acids

Lithio esters of carboxylic acids have been prepared in pure state and their properties are described. Interaction between the lithio esters with alkali metals alkoxides has been demonstrated, and some adducts have been isolated. The IR and UV spectra of these compounds are described, and their structures are discussed.     

Studies on indium-mediated additions to lactones: synthesis of 2-deoxy-2-substituted-3-ulosonic acids

The indium-mediated Reformatsky reaction of a mannose-derived lactone with α,α-disubstituted-α-bromo esters yielded the corresponding ulosonic acid esters as mixtures of anomers. In contrast, the reaction with α-monosubstituted-α-bromo esters is highly stereoselective and afforded a single anomer of the corresponding (2S)-ulosonic acid esters. A mechanistic proposal for the reaction and an explanation of its outcome is discussed. The indium-mediated Reformatsky reaction of the mannose-derived lactone with 2-bromo-lactones was also achieved and the products obtained were consistent with those of our proposed mechanism in all cases. Moreover, indium-mediated allylation of the model sugar lactone was also investigated.     

Action du phényllithium en série pyrazine: Piégeage des intermédiaires réactionnels par le benzoate de méthyle

The action of phenyllithium on pyrazine, 2-methyl pyrazine and acetonyl pyrazine gave mono- or di-addition products with azomethines bonds of pyrazine. The adducts can be condensed with methyl benzoate to give C or N condensed derivatives. No product with initial metalation of methyl or acetonyl groups was observed.     

Synthesis and structure of 5-oxo-1-phenylpyrazoline-3- and 4-alkanoic acids. Antiinflammatory agents

Condensation of appropriate β-keto esters with phenylhydrazine gave 5-oxo-1-phenyl-2-pyrazoline-3-and 4-alkanoic esters 1 and 3 which were saponified to the corresponding alkanoic acids 2 and 4 . Analogous condensation of the same β-keto esters with hydrazobenzene gave 5-oxo-1,2-diphenyl-3-pyrazoline-3-and 4-alkanoic esters 5 and 7 which were similarly converted to acids 6 and 8 . The structures of the oxopyrazolines as revealed by their infrared absorption are discussed, and results of their antiinflammatory screening are reported.     

Boronic esters as ionophores for potentiometric discrimination of the cis-trans isomeric dicarboxylic acids

Boronic esters incorporated into a poly(vinyl chloride) (PVC)-supported liquid membrane electrodes have displayed an anionic ionophore properties enabling their use in the potentiometric high-throughput screening procedures. These compounds belong to the class of ligands in which the anion recognition process can be explained on the concept of Lewis type acid-base interactions. Membranes containing boronic esters showed fairly good sensitivity for maleate (cis-isomer) in comparison to fumarate anions (trans-isomer). The potentiometric selectivity coefficients of proposed electrodes proved that common anions did not interfered with the maleate anion determination. The influence of structure of the three boronic esters ionophores on generation of potentiometric signal by developed liquid membrane electrodes was shortly discussed.     

Morpholinization of aminoacyloxy acids and hydroxyacylamino acids and their esters under mass spectrometry conditions

Summary 1. Free hydroxyacylamino acids and their methyl esters, and also free aminoacyloxy acids, morpholinize under mass spectrometry conditions.2. In the mass spectrometry of methyl esters of aminoacyloxy acids and tert-butyl esters of aminoacyloxy acids and hydroxyacylamino acids no morpholinization takes place. These compounds behave similarly to the esters of acylated peptides and depsipetides.Khimiya Prirodnykh Soedinenii, Vol. 3, No. 5, pp. 325–327, 1967     

Interaction of amino acids, N-acetyl amino acid esters, thymine and adenine with sephadex LH-20 gel.

N-Acetyl aromatic amino acid esters, tryptophan, adenine and thymine show strong retention in Sephadex LH-20 gel in an aqueous phase. The decreased retention in 6 M urea, the absence of retention in absolute methanol and the increased retention at higher temperatures in the aqueous phase indicate that hydrophobic interaction is responsible for the observed retention of the amino acids and their esters in the gel. Adenine was found to be retained by polar interaction in the gel. The increased retention of the solutes in the presence of different electrolytes suggests that the lyotropic effect is more important than the ionic strength effect. The relevance of the results obtained with amino acids and esters to the conformational aspects of proteins in aqueous solution is discussed.     

The [2,3] Sigmatropic Reaction of Acetonyl Allyl Ethers,a new method for preparing certain 2-hydroxyketones

A new [2] [3] sigmatropic rearrangement is described, enabling the conversion of acetonyl allyl ethers to 3-hydroxy-5-en-2-ones.     

Light induced interactions of benzo[a]pyrene with carboxylic acids

Abstract The in vitro photochemical behaviour of benzo[a]pyrene (BP) in presence of short and long chain carboxylic acids is studied. The direct irradiation (295–400 or 320–400 nm) of BP in solution in the presence of saturated carboxylic acids destroys more than 70% of this carcinogen in 72 h with a 150 W Xe arc lamp. Consumption of BP alone under similar conditions is less than 10%. The principal product resulting from direct interaction of BP with carboxylic acids is characterized as 6-acyloxybenzo[a]pyrene by means of UV, IR, NMR and mass spectroscopy. The other pathways of destruction may involve polymerization. Saturated fatty acids are shown to favour photoacyloxyation, while unsaturated fatty acids appear to facilitate polymerization of BP. The effect of different factors, such as the carboxylic acid involved, solvent, and wavelength on photoacyloxylation reaction as well as on the consumption of BP is discussed. Photoinduced interaction of BP with carboxylic acids seems to involve radical cation as well as free radicals of the hydrocarbon. Biological properties of BP esters in terms of primary irritancy and carcinogenic activity have also been tested by mouse skin assay. Both long and short chain esters do not show any carcinogenic activity; conversely, long chain esters are shown to be more severe irritants as compared to short chain esters or BP.     

Optical rotatory dispersion and circular dichroism. LXXV. Circular dichroism of some aryl-amino acids

CD. curves have been recorded for α-aryl-α-amino acids, esters and amides related to α-phenylglycine, α-phenyl-alanine and their N-dimethyl derivatives, and for the corresponding α-cyclohexyl-α-amino acids and esters. Compounds with the (S)-configuration at the single asymmetric carbon atom give strong positive Cotton effects near 220 nm. The conformations of the acids are discussed and compared with those of other α-amino acids.     

Activated esters of substituted pyrazinecarboxylic acids

N-Amidino-3,5-diamino-6-chloropyrazinecarboxamide ( 1 ) has been shown to be an effective potassium sparing diuretic. Various carboxyl activating agents have been employed with 3-amino-pyrazinecarboxylic acids in an effort to synthesize analogs of 1. Stable enol esters were isolated from a number of such acids and N-t-butyl-5-methylisoxazolium perchlorate ( 12 ). Although strong bases in DMF or DMSO catalyze a competing destruction of the enol ester system, these esters are useful acylating agents for a variety of nucleophilic substrates in less polar media. Amides, esters, and thiol esters are produced in good yields under mild conditions from these activated esters.     

The effect of molecular geometry on the fragmentation of methyl esters of cyclobut-3-ene-1,2-dicarboxylic acids

Elimination of CH₃OH from the molecular ions of the methyl esters of cyclobut-3-ene-1, 2-dicarboxylic acids under electron-impact occurs to a much greater extent in stereoisomers having a trans configuration than in the cis analogues. Deuterium labelling shows that this process takes place via different mechanisms in the stereoisomeric esters. The abundance ratio [M ? CH₃OH]^˙+/[M ? CH₃O]+ is suggested as the most sensitive criterion for the deduction of configuration in this system. Determination of the geometry of the cyclobutene esters by n.m.r. spectroscopy as well as by pyrolysis to corresponding isomeric muconates is also discussed.