Effect of metal cationization on the tandem mass spectra of glycosyl dithioacetals

The effect of metal cationization on the tandem mass spectra of glycosyl dithioacetals of glucose, mannose, galactose, rhamnose, arabinose and xylose was studied by electrospray ionization mass spectrometry under ammonium and metal (Li, Na, Ag and Cu) ion cationization conditions. The ammonium-cationized glycosyl dithioacetals fragment by loss of ammonia followed by either two molecules of EtSH or one molecule of EtSH and one molecule of H2O. Lithium cationization leads to additional eliminations such as EtSEt and EtSSEt and C-C cleavages. Elimination of EtSH is not observed under sodium cationization. Silver cationization, on the other hand, leads to additional fragmentations involving the elimination of silver as AgOH and AgSEt. Copper cationization results in adducts where copper has undergone a change of oxidation state from II to I. Li+, Ag+ and Cu+ cationization seem to favour cyclization resulting in elimination of EtSH. However, the mechanisms seem to be differently affected by different metal ions. Li+ and Ag+ cationization appear to be non-specific and favour cyclization involving C2-, C4- and C5-hydroxyl hydrogens, whereas Cu+ cationization seems to favour cyclization involving C4-hydroxyl hydrogen.     

Experimental study on novel phase change composites for thermal energy storage

Journal of Thermal Analysis and Calorimetry - In this study, beeswax is studied as a phase change material (PCM) to store heat due to its high latent heat. The disadvantages of using beeswax were...     

A validated liquid chromatographic method for estimation of solasodine in various Solanum species and market formulations

This paper describes an improved liquid chromatographic (LC) method involving a prechromatographic derivatization step for the estimation of solasodine from berries of various Solanum species, market samples of Solanum xanthocarpum herb, extract, and its market formulations. Solasodine has heterocyclic nitrogen but has no conjugated double bonds in its structure. However, in all reported LC methods, detection was made in the ultraviolet range of 200-213 nm. In the present study, a prechromatographic derivatization of solasodine was done by forming an ion-pair complex of the heterocyclic nitrogen using the acidic dye methyl orange and acetate buffer of pH 4.7. Detection could be made in the visible range at 530 nm in this method. The method was validated and successfully applied to determine solasodine content in various plant samples and polyherbal formulations. The relative standard deviation was found to be 0.025% for system precision, and 0.8% for the linearity of the method, and the correlation coefficient was 0.999. Plant samples and market formulations were analyzed and found to contain solasodine in the range of 0.113-0.227% (w/w) on a fresh weight basis in berries; 0.3-1.278% (w/w) and 0.412% (w/w) on a dry weight basis in S. xanthocarpum herb powder and extract, respectively; and 0.245-0.525% (w/w) on dry weight basis in formulations containing S. xanthocarpum herb powder. No matrix interference was encountered. The method was found to be accurate, with a mean recovery of 100.5 +/- 0.83%. The method has good reproducibility and was found to be suitable for estimation of solasodine.     

Synthesis of thiophenes and pyranone fused thiophenes by base induced inter and intramolecular C-S and C-C bond formation: a non-catalytic approach

An efficient and concise one pot synthesis of highly functionalized thiophenes and pyranone fused thiophenes has been delineated through base induced ring transformation of suitably functionalized 2H-pyran-2-ones by ethyl thioglycolate by inter and intramolecular C-S and C-C bond formation.     

Synthesis,structural aspects and nonlinear optical properties of novel phthalimide derivatives: theoretical and experimental approach

Novel phthalimides ( 1 , 2 , 3 ) possessing variability of cyclic amines have been synthesized and characterized by analytical and spectroscopic techniques. Phthalimide 1 and 2 crystallized in a triclinic system with space group Pī; however, an orthorhombic system with a chiral space group of P2₁2₁2₁ was observed for 3 possessing piperidine cyclic amine. The hydrogen atoms attached to the central chiral carbon were oriented anti to each other resulting in minimum steric repulsion. The occurrence of C–H···O hydrogen bonds in 1 , 2 , 3 enabled the building of several supramolecular structures. Hyperpolarizability 197.6096 Debye Ų calculated for 1 was found to be higher than the hyperpolarizabilities, 138.0836 and 165.2521 Debye Ų measured for 2 and 3 , respectively. Subsequently, phthalimides ( 1 , 2 , 3 ) were assessed for second harmonic generation (SHG) response, and a negligible response was recorded for 1 and 2 ; however, 3 showed a significant response of 14.2 mV. In addition to acentric structure, helical structural motifs identified in 3 could be responsible for its enhanced SHG response. Copyright © 2014 John Wiley & Sons, Ltd.     

Quantum chemical investigation of the reaction of O(3 P 2) with certain hydrocarbon radicals

The reaction of ground-state atomic oxygen [O(³ P ₂)] with methyl, ethyl, n-propyl and isopropyl radicals has been studied using the density functional method and the complete basis set model. The energies of the reactants, products, reaction intermediates and various transition states as well as the reaction enthalpies have been computed. The possible product channels and the reaction pathways are identified in each case. In the case of methyl radical the minimum energy reaction pathway leads to the products CO + H₂ + H. In the case of ethyl radical the most facile pathway leads to the products, methanal + CH₃ radical. For propyl radical (n- and iso-), the minimum energy reaction pathways would lead to the channel containing ethanal + methyl radical.     

One-pot regioselective synthesis of dihydronaphthofurans and dibenzofurans

A regioselective approach for the synthesis of substituted naphthofurans and dibenzofurans has been demonstrated through a ring transformation reaction of suitably functionalized 2H-pyran-2-ones by reaction with 6,7-dihydro-5H-benzofuran-4-one and 7-methoxybenzofuran-3-one, respectively, in high yields. The novelty of the procedure lies in the creation of an aromatic ring transformed by 2H-pyran-2-one involving the -COCH₂- moiety of a cyclic ketone.     

Absence of single-particle Bose-Einstein condensation at low densities for bosons with correlated hopping

Motivated by the physics of mobile triplets in frustrated quantum magnets, the properties of a two-dimensional model of bosons with correlated hopping are investigated. A mean-field analysis reveals the presence of a pairing phase without single-particle Bose-Einstein condensation (BEC) at low densities for sufficiently strong correlated hopping, and of an Ising quantum phase transition towards a BEC phase at larger density. The physical arguments supporting the mean-field results and their implications for bosonic and quantum spin systems are discussed.