Regeneration Reaction Research Articles

Differential and channel cross sections for the reactions K L0p → K S0p and K L0p → Λ0π+ in the c.m. energy range 1605 to 1910 MeV

The differential and channel cross sections have been measured for the reactions K L 0p → K S 0p and K L 0p → Λ 0 π + in nine energy intervals in the c.m. range 1605 to 1910 MeV. The regeneration reaction is a combination of the KN amplitudes (with I = 0 and 1) and the KN amplitude ( I = 1) and is very sensitive to the various KN phase-shift solutions, some of which show an exotic I = 0, P 1 resonance. Our results have been expressed in terms of frequency distributions and cross sections, normalised by the Λ 0 π + reaction. These results have been compared with the predictions of various partial-wave analyses. Qualitatively we can eliminate the P 1 non-resonant solution, though no solution correctly predicts our results.

A thermobalance for high pressure process studies

A DuPont 950 TG has been modified to permit operation at up to 30 atm, 1100°C, with corrosive atmospheres, and steam partial pressures up to 20 atm. The major areas of instrument development included: weight and temperature measurement at high pressures in a dynamic flow system; modification of a TG to accept corrosive gas atmospheres containing high partial pressures of steam; design of a pressure balanced flow system for safe introduction of corrosive gas atmospheres; design of a working steam generation system for low flows. Process studies illustrating the utility of the high presure thermobalance include the cyclic CO 2-acceptor reaction for half-calcined dolomite ▪ and the cyclic H 2S absorption and regeneration reaction for half-calcined dolomite ▪

Kinetics of heterogeneous oxidation of ammonium sulphite

AbstractThe heterogeneous oxidation of ammonium sulphite was investigated with cobalt sulphate catalyst at 30°C. For a wide range of concentrations the reaction was found to be nearly first order in oxygen and zero order in sulphite. These kinetics contrast with the results of homogeneous experiments which indicate that the reaction is zero order in oxygen and three‐halves order in sulphite. The catalytic effect of cobalt ions was found to be proportional to the square root of the total concentration of cobalt. The apparent activation energy for the overall oxidation was calculated to be 13 kcal/g mol. It is concluded that the kinetics in the heterogeneous system are determined by the catalyst regeneration reaction which is diffusion controlled.

Determination of Conditions for the Suppression of CH3 + Sb(CH3)2→Sb(CH3)3 and Evaluation of D[(CH3)2Sb—CH3

The pyrolysis of trimethylantimony has been studied in a toluene carrier flow system over the temperature range 690–803 °K (total pressures 3.6–173.4 mm, contact times 1.0–13.5 s, decomposition 3.9–89.5%). The progress of the reaction was followed by measuring the amount of methane, ethane, and ethylbenzene formed. In 23 runs the undecomposed alkyl was also determined. The quantity found was in agreement with that expected from the product analysis if three methyl radicals are released for each molecule undergoing reaction. No heterogeneous reaction was detected.Deuterium labeling led to the conclusion that regeneration of the parent alkyl occurred during the course of the decomposition. This regeneration reaction was effectively eliminated by working at toluene pressures above 150 mm. Least squares analysis of the results obtained under conditions where regeneration should not be important givenLog10k/s−1 = 15.33 − (55 900 ± 1 000)/2.3RTThe activation energy should be a good approximation to D[(CH3)2Sb—CH3].Significant decomposition of SbCH3 probably does not occur. It seems most likely that free Sb is formed via 2Sb(CH3) → Sb(CH3)2 + Sb.

Radiation-induced Oxidation of Cytosine and Uracil in Aqueous Solution of Copper (II)

BOTH the hydrated electron, e−aq, and the hydroxyl radical, OH, which are formed as the principal intermediates in water radiolysis, react rapidly with the pyrimidine bases through preferential addition to the 5, 6 double bond to give the hydropyrimidyl radical, BH, and the hydroxypyrimidyl radical, BOH, respectively1–4. The yields for base destruction (molecules/100 eV) in oxygen-free solutions under γ-rays are, however, consistently low, G(−B) ⩽ 1 (refs. 5 and 6), when compared with primary yields of the radical species derived from water, Ge−aq = 2.85, GOH = 2.4 (ref. 7); recent work indicates that secondary reactions of BH and BOH lead to regeneration of the parent compound4. In oxygen-saturated solutions, e−aq, is scavenged by oxygen to form O−2(HO2), the regeneration reaction is quenched, and the yield for base destruction increases to G(−B)∼2 through reactions involving the peroxy radical, B(OH)⨀2. Many organic products are formed, however, from the intermediate, B(OH)⨀2, and the overall product stoichiometries have yet to be fully elucidated8.

Inhibition and acceleration of paraffin decomposition by nitric oxide

Analysis of the products from the thermal decomposition of neopentane and of isopentane in presence of increasing amounts of nitric oxide confirms the validity of pressure change as a measure of extent of reaction over the first 20 % change, provided that certain initial disturbances of a secondary character are corrected for. (These may give initial rates which are apparently too high or too low.) A method of eliminating the disturbance is adopted. For all three pentanes, the rate of decomposition first falls with increase in nitric oxide concentration (‘inhibition curve’) but at high concentrations rises again. This ‘induced reaction’ has now been studied in more detail and shown to be kinetically of the first-order with respect to both nitric oxide and paraffin. A mechanism is proposed for the induced reaction, whereby NO abstracts a hydrogen atom from the parent hydrocarbon, the resulting alkyl radical reacting rapidly with NO. In this reaction the consumption of NO tends to a value of about one molecule for each molecule of paraffin decomposed. Thus regeneration of NO from the products of its reaction with the alkyl radicals seems very unlikely. In the region of the extended flat minimum of the inhibition curve, nitric oxide consumption is small. If that attribu table to the induced reaction is allowed for, then the inhibition of chains involves very little consumption of NO. It is suggested that this small consumption, in the absence of an appropriate regeneration reaction, is unlikely if the NO maintains a steady-state concentration of radicals under the conditions of the minimum rate. Thus a simpler interpretation is that there is in fact a predominantly molecular reaction in these conditions.

Phototropy of New Photosensitive Complexes between a Fluorescent Pigment and SH-Compounds

Abstract The absorption maximum of all pigment-SH compound complexes shifted to a longer wave length range than that of the pigment itself. Although in protein and glutathione the absorption maximum was at 520 mμ from the beginning, in cysteine and thioglycolic acid it was in a shorter wave length range than 520 mμ and shifted to 520 mμ after some photochemical reaction. These complexes with their absorption maxima in a shorter wave length range than 520 mμ fluoresced more weakly than the original pigment, while those at 520 mμ showed the almost complete disappearance of fluorescence. Before these SH-compounds combined with the pigment, its fluorescence was partly instantaneously quenched by them. Both complexes of different spectra showed a phototropy ; i. e., bleaching in light and regeneration in darkness. The regeneration reaction was thermal: its velocity was parallel to the molecular weight of the SH-compound in these SH-compounds used in the present experiment. The degree of regeneration was low in protein but about 100 % in cysteine and thioglycolic acid. The concentration of protein influenced the degree of regeneration but not the velocity of regeneration. This phototropy was discussed from the point of view of an ·S-R free radical and pigment radicals.