The thermodynamic properties of alkylated γ-lactones

The enthalpies of formation of γ-pentanolactone (I), γ-hexanolactone (II), and γ-nonanolactone (III) were determined by combustion calorimetry. The enthalpies of vaporization of these lactones were measured by the transfer method. Conformational analysis was performed and equilibrium structures, sets of fundamental vibrations, moments of inertia, and total energies of the stablest conformers of I, II, and III were calculated by the B3LYP/6-311G(d,p), G3MP2, and CBS-QB3 methods. The experimental IR spectra and calculated vibrational frequencies were used to obtain sets of fundamental vibrations of the stablest conformations. The thermodynamic properties of I–III in the ideal gas state were determined over the temperature range 0–1500 K. Additive and quantum-chemical methods were applied to estimate the Δ_f H ^o(g) values of a number of γ-lactones. Composite quantum-chemical methods were used to obtain the energies of monomethyl γ-butyrolactones and estimate their relative stability depending on the position of the methyl substituent in the ring.     

The effect of γ-irradiation on laser ablation of polyketone

Results of a pioneering study of the effect of laser radiation in vacuum on the surface of a polyketone (alternating terpolymer of ethylene, propylene, and carbon monoxide, POK) plate are presented. It has been found that laser beam irradiation leads to the surface heating of the plate, its melting, and the formation of a characteristic surface microrelief, an ablation crater, from which the gas flow of the ablation plume carries away products that are deposited on surfaces outside the laser beam area to form a coating with a chemical composition close to that of the substrate POK. A rim grows from molten POK around the crater. The melting point of the crystalline modification (377 K), the molecular flow temperature (427 K), and the molecular weight of the coating (25560) are much lower than those of the initial POK (464 K, 477 K, and 159200, respectively), thereby indicating laser-induced chain degradation of POK. The preliminary γ-irradiation of POK to a dose of 100 kGy enhances its laser ablation rate.     

The Crystallinity of γ-Irradiated Poly(tetrafluoroethylene)

The influence of absorbed -radiation dose over the range 0–220 kGy on the heat of fusion and the crystallinity of industrial specimens of bulk PTFE and PTFE films were studied using the techniques of adiabatic and differential scanning calorimetry. The thermodynamic characteristics of transitions in the interval 287–310 K in the original and the irradiated polymer were determined. Based on the results obtained, a new crystal modification other than the one present in the unirradiated material was assumed to be formed during -irradiation.     

On cardioactive steroids: The synthesis of γ-isobufalin1

γ-Isobufalin¹ l was synthesized from testosterone. A novel use of α-furans as masking groups of a carboxylic acid is also reported.     

The Kinetics of Crystallization of Poly(tetrafluoroethylene) by the Action of γ-Radiation

The kinetics of crystallization of PTFE over the temperature range 287–310 K upon its -irradiation to a dose of 220 kGy was studied using calorimetric procedures. Parameters for the models of radiation-induced growth in the degree of crystallinity (expressed as the mass fraction) of bulk and film polymer specimens were calculated. It was shown that the degree of perfection of crystals produced upon irradiation can be determined from the heat of transition at T 293 K characteristic of PTFE.     

The dispersity of γ-alumina supported rhenium from hydrogen pulse chemisorption

The applicability of hydrogen chemisorption in a pulse chromatographic system for determining the dispersity of -alumina supported rhenium catalysts (10.4 wt.% and 1.04 wt.%) preheated in hydrogen at 550–800 °C is shown.

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, - (10,4 .% 1,04 .%), 550–800°C.

     

The natural radioactivity of aluminium as determined by γ-ray spectroscopy

The intrinsic radioactivity of aluminium has been investigated by a shielded Ge(Li) -spectrometer. Strong disequilibrium was found in the natural decay chains of U and Th caused by the elimination of Ra during aluminium production.     

Protonation of γ-Butyrolactone and γ-Butyrolactam

Abstract : γ-Butyrolactone and γ-butyrolactam were reacted in the superacidic systems XF/MF₅ (X=H, D; M=As, Sb). Salts of the monoprotonated species of γ-butyrolactone were obtained in terms of [(CH₂)₃OCOH]⁺[AsF₆]⁻, [(CH₂)₃OCOH]⁺[SbF₆]⁻ and [(CH₂)₃OCOD]⁺[AsF₆]⁻ and the analogous lactam salts in terms of [(CH₂)₃NHCOH]⁺[AsF₆]⁻, [(CH₂)₃NHCOH]⁺[SbF₆]⁻ and [(CH₂)₃NDCOD]⁺[AsF₆]⁻. The salts were characterized by low temperature Raman and infrared spectroscopy and for both protonated hexafluoridoarsenates, [(CH₂)₃OCOH]⁺[AsF₆]⁻ and [(CH₂)₃NHCOH]⁺[AsF₆]⁻, single-crystal X-ray structure analyses were conducted. In addition to the experimental results, quantum chemical calculations were performed on the B3LYP/aug-cc-pVTZ level of theory. As in both crystal structures C⋅⋅⋅F contacts were observed, the nature of these contacts is discussed with Mapped Electrostatic Potential as a rate of strength.     

The stable planar conformation of the γ-butyrolactone ring in solution

<正>The conformations ofγ-butyrolactone ring in solution were deduced on the basis of ~1H NMR spectra of geminal protons of the butyrolactone ring.A series of optically pure(Z)-(-)-4-(1'-alkoxyl-1'-carbalkoxy-methylene)-5(R)[(1R)-menthyloxy]-γ-butyr-olactones with a stable planar conformation of γ-butyrolactone ring were found.     

The Effects of γ-Irradiation on the Electrokinetic and Thermal Behaviour of Zirconium Hydroxide

Zirconium hydroxide particles produced by rapid precipitation at pH 10.4, 7 or 2 were subjected toγ-irradiation up to a final dose of 20 MGy. The effects of the γ-irradiation were examined by X-ray powder diffraction, laser Raman spectroscopy, differential scanning calorimetry and microelectrophoretic measurements. It was found that γ-irradiation had no influence on the behaviour of zirconium hydroxide during calcination and subsequent cooling. The results of microelectrophoretic measurements showed that γ-irradiation influences the surface properties of zirconium hydroxide as a function of the precipitation pH. Zirconium hydroxide precipitated at pH 2 proved to be the most susceptible to γ-irradiation, while the sameγ-irradiation had very little (if any) effect on the surface properties of zirconium hydroxide precipitated at pH 10.5. After γ-irradiation, the electrophoretic mobility of zirconium hydroxide precipitated at pH 2 was increased at both low and high pH, thereby indicating an increase in its adsorption capacity. The analogy observed between the pH-dependence of the effects of γ-irradiation on the electrokinetic behaviour of zirconium hydroxide and the influence of ball-milling on the thermal behaviour of zirconium hydroxide [8] suggested that the susceptibility of amorphous zirconium hydroxide increases with decrease of the precipitation pH. This revised version was published online in July 2006 with corrections to the Cover Date.     

The in vitro Pulmonary Deposition of a Budesonide γ-Cyclodextrin Inclusion Complex

The interest in dry powder inhalers (DPIs) has recently increasedbecause the problems associated with the propellants used in pressurized metered-dose inhalers (PMDIs) will be avoided. Cyclodextrins (CDs) may be used as excipients in inhalation powders;e.g., in order to increase the solubility, stability and absorption of an inhaled drug. In thepresent study, the effect of complexation of budesonide with -CD on its pulmonary deposition wasstudied in vitro. In the presence of -CD, the aqueous solubility of budesonidefollowed B_S-type phase-solubility behaviour. A precipitationcomplexation method was used to prepare the solid budenoside/-CD complexes. The pulmonary in vitrodeposition of budenoside was evaluated after inhalation of plain budesonide and budenoside/-CDcomplexes (lactose carrier used in both formulations) by using the ``Andersen' cascadeimpactor. The novel Taifun® was used as the DPI. The respirable fractionsof the emitted budesonide dose (initially and after the storage in 40 °C, RH 75%) werecomparable for both plain budesonide and budesonide/-CD complexes. The present studyindicates that a drug/CD-complex can be used in inhalation powderswithout lowering the pulmonary deposition of the drug.     

Synthesis of γ-mercuridinitrohydrocarbons

Summary The denitration of -mercurinitro compounds has been studied and the corresponding organomercury dinitro derivatives have been obtained.     

The 3-amino-derivative of γ-cyclodextrin as chiral selector of Dns-amino acids in electrokinetic chromatography

The enantioseparation of the enantiomeric pairs of 10 Dns derivatives of α-amino acids was successfully carried out by using for the first time the 3-amino derivative of the γ-cyclodextrin. The effects of pH and selector concentration on the migration times and the resolutions of analytes were studied in detail. 3-Deoxy-3-amino-2(S),3(R)-γ-cyclodextrin (GCD3AM) shows very good chiral recognition ability even at very low concentrations at all the three investigated values of pH, as shown by the very large values of selectivity and resolution towards several pairs of amino acids. The role played by the cavity, the substitution site and the protonation equilibria on the observed properties of chiral selectivity, on varying the specific amino acid involved, is discussed.     

Syntheses and structures of tetraphenylantimony γ-phenyl-and γ-thiobutylacetylacetonates

Tetraphenylantimony γ-phenylacetylacetonate (I) and tetraphenylstibium γ-thiobutylacetylacetonate (II) are synthesized by the reaction of pentaphenylantimony with γ-phenylacetylacetone or γ-thiobutylacetylacetone in toluene. According to the X-ray diffraction data, the antimony atoms in complexes I and II have a distorted octahedral coordination. In complex I, the Sb-C bond lengths are 2.155(2)–2.170(1) Å, and the Sb-O(1), Sb-O(2) and O(1)-C(2), O(2)-C(4) in the heterocycle are 2.215(1), 2.227(1) and 1.282(2), 1.277(2) Å, respectively. In complex II, the bond lengths are the following: Sb-C 2.147(3)–2.161(3), Sb-O(1, 2) 2.281(2), 2.215(2), and O-C 1.267(3)–1.278(3) Å.     

The role of oxidizing radicals in neptunium speciation in γ-irradiated nitric acid

The irradiation of aqueous nitric acid solutions generates transient, reactive species that are known to oxidize neptunium. However, nitrous acid is also a long-lived product of nitric acid irradiation, which reduces neptunium. When we irradiated nitric acid solutions of neptunium and measured its speciation by UV/Vis spectroscopy, we found that at short irradiation times, oxidation of Np(V) to Np(VI) occurred due to reactions with radicals such as ^?OH, ^?NO₃ and ^?NO₂. However, at higher absorbed doses and after a sufficient amount of nitrous acid was produced, reduction of Np(VI) to Np(V) began to occur, eventually reaching an equilibrium distribution of these species depending on nitric acid concentration. Neptunium(IV) was not produced.     

When theory and experiment hold hands: The thermochemistry of γ-pyrone derivatives

In this work, we have determined the experimental standard $(p^{°}=0.1\text{MPa})$ molar enthalpies of formation, in the gas phase, of 2,6-dimethyl-4-pyrone ?(261.5 ± 2.6) kJ · mol^?1 and 2-ethyl-3-hydroxy-4-pyrone ?(420.9 ± 2.8) kJ · mol^?1. These values were obtained by combining the standard molar enthalpy of formation in the condensed phase, derived from combustion experiments in oxygen, at T = 298.15 K, in a static bomb calorimeter, with the standard molar enthalpy of sublimation, at T = 298.15 K, obtained by Calvet microcalorimetry. Additionally, high-level density functional theory calculations using the B3LYP hybrid exchange-correlation energy functional with extended basis sets have been performed for these two compounds. Good agreement was obtained between the experimental and computational results. Using the same methodology, we calculated the standard molar enthalpy of formation of gaseous 2-methyl-3-hydroxy-4-pyrone.