Use of organic reagents in inorganic analysis

Summary Eighteen anilic acids have been prepared from maleic anhydride and various aromatic amines and their properties and analytical reactions with various metal ions have been studied. The acid prepared from benzidine was insoluble in all common solvents and, hence, its application could not be studied. Most of these reagents, except those obtained from aniline, o- and p-chloroanilines, nitranilines, p-amino-acetanilide and o-phenylenediamine, produced more or less quantitative precipitations with both thorium and zirconium. Their actions towards thorium and zirconium were very much alike. They also gave precipitations with mercury(I), lead and cerium(IV), but such precipitations were not complete. Ferrous iron showed greyish turbidity with most of the reagents, but ferric iron produced colourations varying from brown to violet, such colours were, however, found to be unstable either on standing for a while or on heating. Gold and platinum underwent reduction in presence of these reagents.Part VIII: See Z. analyt. Chem. 163, 403 (1958).The work has been carried out in the chemical laboratories of Darjeeling Government College, Darjeeling. The author is grateful to the authorities of the College for the laboratory facilities.     

Relative reactivities of glycerophosphates towards permanganate in perchloric acid medium

Summary The reactivities of - and -glycerophosphates towards MnO ₄ ^– in HClO₄ medium have been examined. The reactions between glycerophosphates and MnO ₄ ^– are first order with respect to [glycerophosphate], [MnO ₄ ^– ] and [H⁺]. There is no evidence for cleavage of the C–O–P bond rather than the terminal –CH₂OH group being oxidized to the respective phosphoglyceraldehyde.     

Novel Synthesis of Agaritine,a 4-Hydrazinobenzyl-Alcohol Derivative Occurring in Agaricaceae

The 4-hydrazinobenzyl alcohol ( 3 was prepared (58%)) by diiobutylaluminiumhydride reduction of methyl 4-hydrazinobenzoate ( 4 ), whereas LiA1H₄ or LiBh₄ reduction of 4 proceeded further to yield (via intermediate 3 ) (4-tolyl)hydrazine ( 5 ). The alcohol 3 was stable under O₂-free conditions and exhibited no tendency to eliminate H₂O, neither thermally nor with H⁺ catalysis. Oxidation of 3 with SeO₂ yielded 4-(hydroxymethyl)benzine-diazonium ion ( 8 ), identified by its azo coupling product 9 with 2-naphthol. Condensation of 3 with 1-benzyl 5-Hydrogen N-(benzyloxycarbonyl)-L-glutamate ( 10 ) in presence of dicyclohexylcarbodiimide afforded 81% of N²-(benzyloxycarbonyl)-L- glutamic acid 1-(benzyl-ester) 5-{2-[4-(hydroxymethyl)phenyl]hydrazide} ( 11 ) which upon controlled hydrogenolysis (quinoline-sulfur-poisoned Pd/C catalyst) gave 82% of L-Glutamic acid 5-{2-[4-(hydroxymethyl)phenyl] hydrazide} ( 1 ), i. e. agaritine, a metabolite of Agaricus bisporus. Without poisoning of the catalyst, hydrogenolysis of ( 11 ) yielded L-glutamic acid 5-[2-(4-tolyl)hydrazide] ( 12 ).     

Quadruplex formation by a guanine-rich PNA oligomer

A guanine-rich PNA dodecamer having the sequence H-G4T4G4-Lys-NH2 (G-PNA) hybridizes with a DNA dodecamer of homologous sequence to form a four-stranded quadruplex (Datta, B.; Schmitt, C.; Armitage, B. A. J. Am. Chem. Soc. 2003, 125, 4111-4118). This report describes quadruplex formation by the PNA alone. UV melting curves and fluorescence resonance energy transfer experiments reveal formation of a multistranded structure stabilized by guanine tetrads. The ion dependency of these structures is analogous to that reported for DNA quadruplexes. Electrospray ionization mass spectrometry indicates that both dimeric and tetrameric quadruplexes are formed by G4-PNA, with the dimeric form being preferred. These results have implications for the use of G-rich PNA for homologous hybridization to G-rich targets in chromosomal DNA and suggest additional applications in assembling quadruplex structures within lipid bilayer environments.     

Hybridization of PNA to structured DNA targets: quadruplex invasion and the overhang effect

Peptide nucleic acid (PNA) probes have been synthesized and targeted to quadruplex DNA. UV-vis and CD spectroscopy reveal that the quadruplex structure of the thrombin binding aptamer (TBA) is disrupted at 37 degrees C by a short PNA probe. The corresponding DNA probe fails to bind to the stable secondary structure at this temperature. Thermal denaturation experiments indicate surprisingly high thermal and thermodynamic stabilities for the PNA-TBA hybrid. Our results point to the nonbonded nucleobase overhangs on the DNA as being responsible for this stability. This "overhang effect" is found for two different PNA-DNA sequences and a variety of different overhang lengths and sequences. The stabilization offered by the overhangs assists the PNA in overcoming the stable secondary structure of the DNA target, an effect which may be significant in the targeting of biological nucleic acids, which will always be much longer than the PNA probe. The ability of PNA to invade a structured DNA target expands its potential utility as an antigene agent or hybridization probe.     

Nearly monodispersed ZnS nanospheres: Synthesis and optical properties

ZnS nanoparticles of diameters of 3–4 nm were self-assembled to form dense nanospheres of sizes 100 nm by a colloidal precipitation method using PVP as the stabilizing agent. Studies indicated that the ZnS nanoparticles maintained their individual properties inside the nanospheres. Optical absorption spectra of the samples demonstrated the effect of quantum confinement in the ZnS nanocrystals. Room temperature photoluminescence measurements showed a sharp UV emission at 370 nm, attributed to sulfur vacancies.     

CONDENSING HEAT TRANSFER IN VERTICAL CYCLONE

The heat transfer coefficient for condensation of steam has been determined experimentally for a cyclone surface. Ambient air is used as the coolant and the outer surface is maintained in a free-convection condition. A twofold increase in heat transfer coefficient is observed over a cyclone surface in comparison with a vertical tube.