The pressure dependence of the rate of isomerization of cyclopropane at 897 K

1982 ◽  
Vol 60 (7) ◽  
pp. 916-920 ◽  
Author(s):  
Hlroshi Furue ◽  
Philip D. Pacey

The isomerization of cyclopropane has been studied in a flow reactor at 897 K and from 4 to 406 Torr. The pressure dependence of the rate constants from this work and from the literature have been compared with predictions obtained from two models based on the theory of Yau and Pritchard and from three RRKM models. The collisional deactivation efficiency was found to generally decline with increasing temperature. The average energy removed per collision was calculated by the method of Tardy and Rabinovitch and was found to have values from 15 to 23 kJ mol−1 at 897 K. Combining the results of this work with data from the literature from 690 to 1038 K, the limiting high pressure rate constants follow the relation log k∞ = 15.50 ± 0.14 – (276.0 ± 2.1 kJ mol−1)/2.3RT.

2003 ◽  
Vol 81 (1-2) ◽  
pp. 47-53 ◽  
Author(s):  
M B Helgerud ◽  
W F Waite ◽  
S H Kirby ◽  
A Nur

We report on compressional- and shear-wave-speed measurements made on compacted polycrystalline sI methane and sII methane–ethane hydrate. The gas hydrate samples are synthesized directly in the measurement apparatus by warming granulated ice to 17°C in the presence of a clathrate-forming gas at high pressure (methane for sI, 90.2% methane, 9.8% ethane for sII). Porosity is eliminated after hydrate synthesis by compacting the sample in the synthesis pressure vessel between a hydraulic ram and a fixed end-plug, both containing shear-wave transducers. Wave-speed measurements are made between –20 and 15°C and 0 to 105 MPa applied piston pressure. PACS No.: 61.60Lj


2003 ◽  
Vol 58 (12) ◽  
pp. 727-734 ◽  
Author(s):  
Hirokazu Kobayashi ◽  
Takahiro Ueda ◽  
Keisuke Miyakubo ◽  
Taro Eguchi

The pressure dependence of the 129Xe chemical shift tensor confined in the Tris(o-phenylenedioxy) cyclotriphosphazene (TPP) nanochannel was investigated by high-pressure 129Xe NMR spectroscopy. The observed 129Xe spectrum in the one-dimensional TPP nanochannel (0.45 nm in diameter) exhibits a powder pattern broadened by an axially symmetric chemical shift tensor. As the pressure increases from 0.02 to 7.0 MPa, a deshielding of 90 ppm is observed for the perpendicularcomponent of the chemical shift tensor δ⊥, whereas a deshielding of about 30 ppm is observed for the parallel one, δ‖. This suggests that the components of the chemical shift tensor, δ‖ and δ⊥, are mainly dominated by the Xe-wall and Xe-Xe interaction, respectively. Furthermore, the effect of helium, which is present along with xenon gas, on the 129Xe chemical shift is examined in detail. The average distance between the Xe atoms in the nanochannel is estimated to be 0.54 nm. This was found by using δ⊥ at the saturated pressure of xenon, and comparing the increment of the chemicalshift value in δ⊥ to that of a β -phenol/Xe compound.


1960 ◽  
Vol 38 (11) ◽  
pp. 2187-2195 ◽  
Author(s):  
R. J. Cvetanović ◽  
L. C. Doyle

Reaction of oxygen atoms with 1,3-butadiene has been investigated at room temperature. It is found that it conforms to the general mechanism established previously for the analogous reactions of monoolefins. Only 1,2-addition occurs, and the addition products, butadiene monoxide and 3-butenal, possess excess energy when formed as a result of high heats of reaction. The pressure dependence of the formation of the addition products yields the values of the "lifetimes" of the initially produced "hot" molecules. The relative rate constants have been determined at 25 and 127 °C and from these the relative values of the Arrhenius parameters have been calculated.


2017 ◽  
Vol 82 (2) ◽  
pp. 1073-1084 ◽  
Author(s):  
Jennifer Tsoung ◽  
Andrew R. Bogdan ◽  
Stanislaw Kantor ◽  
Ying Wang ◽  
Manwika Charaschanya ◽  
...  

1994 ◽  
Vol 358 ◽  
Author(s):  
Z.P. Wang ◽  
Z.X. Liu ◽  
H.X. Han ◽  
J.Q. Zhang ◽  
G.H. Li ◽  
...  

ABSTRACTWe have performed photoluminescence (PL) measurements at liquid nitrogen temperature under high pressure up to 5.5 GPa and in the temperature range 10-300 K at atmospheric pressure on {(ZnSe)30(ZnSe0.92Te0.08)30(ZnSe)30[(CdSe)1(ZnSe)2]9}x5 multiple quantum wells. The PL peaks, EB, E1 and Ew corresponding to the band edge luminescence in ZnSe barrier layer, the transitions from the first conduction subband to the heavy-hole subband in ZnSe0.92Te0.08 layers and [(CdSe)1(ZnSe)2]9 ultra short period superlattice quantum well (SPSLQW) layers have been observed. Experimental results show that ZnSe0.92Te0.08/ZnSe forms a type-I superlattice (SL) in contrast to the type-II ZnSe/ZnTe SL. The pressure coefficients of the EB, E1 and Ew exciton peaks have been determined as 67, 63 and 56 meV/GPa, respectively. With increasing temperature (or pressure), the E1 peak-intensity drastically decreases which is attributed to the thermal effect (or the appearance of many defects in ZnSe0.92Te0.08 under higher pressure).


2020 ◽  
Vol 10 ◽  
pp. 34-47
Author(s):  
V. A. Gribkov ◽  
◽  
S. V. Latyshev ◽  
V. N. Pimenov ◽  
S. A. Maslayev ◽  
...  

The features of the destructive effect of high-pressure generated under comparable conditions, namely, upon irradiation of target samples with pulsed laser radiation and beam-plasma flows created in Plasma Focus (PF) devices, on metal materials were studied. In both cases, close parameters of radiation-heat treatment were provided: power density q ~ 1010–1011 W/cm2 and pulse duration τ ~ 10 –100 ns. It have been shown that the double exposure of laser radiation to thin samples of vanadium and molybdenum with a thickness of 0.3 mm and 0.1 mm, respectively, leads to the formation of molten zones in the materials, inside which there were deep craters. The craters extended over the entire thickness of the samples, on the reverse side of which the recesses end with holes of ~ 0.1 mm for V and 0.2 mm for Mo. In a tungsten sample 0.2 mm thick, the depth of the craters in the molten zone was less than its thickness and there were microcracks on the back of the sample. Based on numerical estimates of the process under study, it was suggested that the observed effects are associated with the creation of high pressure zones of ~ 1 – 10 GPa in the irradiated targets, localized in microregions of radius r ~ 0.1 mm. In these zones, the behavior of the solid phase of the target materials, for which the tensile strength σB ≤ 1 GPa (V, Mo, W), under high pressure became close to the behavior of the liquid. The pseudo-liquid phase of the material was displaced from the center of the crater, where the pressure was maximum, to its periphery to the region of low pressure with the subsequent release of matter from the target through the irradiated surface at a speed of ~ 103 m/s. In experiments using the PF, the mechanism responsible for the formation of craters when a powerful pulsed laser radiation is applied to the target is not realized due to the different nature of the distribution of the absorbed energy density in the surface layer of the irradiated sample. The region in which the energy absorbed during the of particles implantation into the material was determined mainly by the average energy and the diameter of the ion beam (Еi ≈ 100  keV, d ~ 2 – 10 mm) and exceeds by one or two orders of magnitude the corresponding volume under laser irradiation.


1982 ◽  
Vol 37 (1-2) ◽  
pp. 51-56 ◽  
Author(s):  
H. Hauer ◽  
H.-D. Lüdemann ◽  
R. Jaenicke

From the pressure dependence of 1H high resolution NMR spectra of two dipeptides (glycylsarcosine and N-acetyl-ʟ-proline-NH-methylamide in the range 0.1 MPa ≤p ≤ 150 MPa the activation volumes ⊿V≠ for the amide rotation are derived. This conformational transition is characterized for glycylsarcosine by ⊿V≠ = 4 ± 1 cm3 · mol-1 and for. the proline derivative by ⊿V≠ = 7.5±1 cm3 · mol-1. From the given results the maximum contribution of proline cis ⇌ trans isomerisation to the pressure dependence of the rate of reactivation of proteins can be estimated to ~ - 30% per MPa and proline present.


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