Ion-Molecular Reactions of Esters of Carbocyclic Alcohols in a Direct Analysis in Real Time (DART) Mass Spectrometer

Journal of Analytical Chemistry - We studied the interaction of acyl derivatives of carbocyclic alcohols of steroid structure with nitrogenous bases in the ion source of a “direct analysis in...     

Forces exerted by a weak shock wave on a wing of complicated shape in plan at supersonic velocities

A method is presented for calculating the supersonic distributed and total aerodynamic characteristics of a wing of complicated shape in plan, including a wing having the shape of an aircraft in plan which encounters a weak shock wave of arbitrary orientation. The problem is solved in the linear formulation.Translated from Izvestiya Akademii Nauk SSSR, Mekhanika Zhidkosti i Gaza, No. 4, pp. 121–127, July–August, 1982.     

Synthesis of new mesogens of the 3-arylisoxazolone and 3-arylpyrazolone series

Acylation of ethyl acetoacetate with mesogenic para-substituted benzoyl chlorides, followed by cleavage of ethyl aroylacetoacetates thus obtained under basic conditions, gave the corresponding ethyl 3-aryl-3-oxopropanoates which were brought into condensations with hydroxylamine and hydrazine to obtain mesogenic 3-arylisoxazolones and 3-arylpyrazolones, respectively.     

Study of synthetic aliphatic copolyamides by time-of-flight matrix assisted laser desorption/ionization mass spectrometry

Synthetic copolyamides based on aliphatic diamines (1,3-propanediamine and 1,4-butanediamine) and dichlorides of aliphatic carboxylic acids (adipic and sebacic acid dichlorides) were investigated using time-of-flight matrix assisted laser desorption/ionization mass spectrometry. Their mass spectra showed peaks for cationized (Na⁺ and K⁺) and protonated (less intense peaks) oligomers with NH₂-NH₂, NH₂-COOH, or COOH-COOH end groups. No cyclic oligomers were detected in the samples. The compositions of oligomers were determined, and the relative reactivities of homologous comonomers in polycondensation were estimated. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 7, pp. 1320–1324, July, 2007.     

Preliminary derivatization during investigation of polymers with labile bonds via matrix-assisted laser desorption/ionization mass spectrometry

The mass spectra of matrix-assisted laser desorption-ionization of poly(?-caprolactone)diols and poly(?-caprolactone)triols and their derivatization (silylation, acetylation, formylation) products, which are used for more reliable structural attributions, are studied. On the basis of the calculation of number-average molecular masses, it is ascertained that acidic agents released during derivatization and severe reaction conditions do not result in the cleavage of ester bonds.     

FTIR study of gamma-irradiated cis-1,4-polyisoprene

The effect of γ-irradiation on the structure and oxidation of cis-1,4-polyisoprene is investigated by ATR-FTIR technique. This method provides the valuable insight into the type of oxidation products produced and the extent and nature of intramolecular cyclization and chain scission reactions. The formation of ketones, alcohols and/or ethers, and hydroperoxides is apparent already at small doses of γ-radiation and it increases with the exposure time significantly. At the highest dose of 309 kGy a decrease in the intensity of C=O stretching mode of ketones (1717 cm⁻¹) was observed while the overall area of the band remained the same as in the case of 188 kGy dose. The shoulders observed at 1740 cm⁻¹ and 1772 cm⁻¹ could be assigned to C=O stretching frequency of esters and five-membered-ring lactones, respectively. Higher doses of γ-radiation also cause the formation of two relatively strong bands in the region of conjugated double bonds. These could origin from the aromatic products or cycloenes with one double bond formed by cyclization and chain scission processes.     

Derivatization by forming Schiff bases in the study of synthetic polymers bearing amino groups by MALDI mass spectrometry

A new approach is proposed to the determination of a number of primary amino groups in polymers. It involves the formation of Schiff bases in reactions with carbonyl compounds followed by MALDI mass spectrometry study. The reaction with 2,3-dihydroxybenzaldehyde appeared to be the most efficient for polyethyleneimine derivatization. This may be due to the better co-crystallization of the matrix (2,5-dihydroxybenzoic acid, DHB) with the polymer by the imine fragment with the structure close to that of the matrix. The proposed method today is the only one for determining the number of NH₂ groups in branched polyethylenimine molecules at the molecular level.     

New Mass Spectra: Electron Ionization Mass Spectra of Triclosan Acyl and Silyl Derivatives

Journal of Analytical Chemistry -