Nitrous oxide irradiation

Nitrous Oxide Irradiations. The measured yields of nitrogen and oxygen from one pulse irradiations — 1.6 X 1020 e.v./gram) of nitrous oxide are given in Table II. 

Table II. Yields from Nitrous Oxide Irradiations...

Upon the irradiation the nitrous acid ester 1 decomposes to give nitrous oxide (NO) and an alkoxy radical species 3. The latter further reacts by an intramolecular hydrogen abstraction via a cyclic, six-membered transition state 4 to give an intermediate carbon radical species 5, which then reacts with the nitrous oxide to yield the 3-nitroso alcohol 2 ... 

By pulse radiolysis of nitrous oxide-saturated aqueous solutions of ferricyanide (2 X 10 " M) and various alcohols (0.1 M), Adams and Willson " were able to obtain absolute rate coefficients for the ferricyanide oxidation of the radicals derived from the alcohols by attack of the solvent irradiation product, OH-. 

Irradiation of Hydrocarbon Polymers in Nitrous Oxide Atmosphere... 

Polyisobutylene. The solution viscosity of an irradiated polyisobutylene block was measured in CC14 at 30 °C. to determine the degree of degradation (5). The variation of viscosity-average molecular weight, Mv, with the dose, r, is shown in Figure 3. Nitrous oxide reduced the... 

Polyisobutylene. The viscosity of irradiated polyisobutylene is plotted against N20 pressure in Figure 5. The curve increases monotonically with increasing pressure. If nitrous oxide is effective in reducing the amount of degradation, the behavior of the curve seems to be reasonable since the gas concentration in the polymer solid should increase with the gas pressure. 

Polypropylene. A similar study on polypropylene is interesting because polypropylene has a molecular structure intermediate between polyethylene and polyisobutylene. An atactic polypropylene specimen was prepared by ether extraction and irradiated in a nitrous oxide atmosphere. The changes in gel fraction (insoluble in hot xylene) as a function of N-jO pressure are shown in Figure 6. Gel formation (cross-linking) of polypropylene is also promoted in the presence of nitrous oxide. 

Polyethylene. To determine the role of nitrous oxide during irradiation, the material balance of nitrous oxide was measured (7). A known... 

As shown in Table II, in the presence of polymer, the enclosed nitrous oxide is completely consumed during irradiation. In the place of nitrous oxide, nitrogen and water are formed. The yield of nitrogen or water corresponds stoichiometrically to the loss of nitrous oxide. A large G value, about 2000, is given for the disappearance of nitrous oxide. Estimation of the G value is based on the assumption that the available energy for the consumption is only that absorbed directly by the gas dissolved in the polymer solid. The G values for the formation of water and nitrogen should be equal to 2000. Moreover, the summation of the amount of the excess formation of crosslinks and unsaturation becomes stoichiometrically almost equal to the loss of nitrous oxide, as shown in Table III. The equation of material balance of nitrous oxide, therefore, should be written as follows ... 

Polyisobutylene and Polypropylene. In a similar way, the material balance of nitrous oxide in the case of polyisobutylene was measured as shown in Table IV. In this case, whereas the enclosed nitrous oxide is not completely consumed during irradiation, the consumption proceeds... 

The behavior of nitrous oxide during irradiation seems quite unusual. Whereas, as an irradiation atmosphere, 18 types of well-known inorganic gases and 4 types of saturated hydrocarbon gases were tested previously, the species which evidently showed such a singular effect were limited to nitrous oxide and xenon. In the work reported here, three types of polymers having different types of molecular structure were examined, but examination showed many points of similarity in the behavior of nitrous oxide. 

Nitrous oxide disappears at a high rate in the cases of both polyethylene and polyisobutylene, but no chemical addition to the polymer chain can proceed because the nitrous oxide changes simply to nitrogen and water during irradiation in the polymer solid phase. This behavior of nitrous oxide differs entirely from that of oxygen, chlorine, sulfur dioxide, etc., as an atmosphere during irradiation. In the case of these latter gases, the irradiated polymer should be oxidized, chlorinated, or sulfonated. 

Rearrangement is also observed in the irradiation of Formula 450 which gives the hydroxamic acid (Formula 451) (203). This interesting rearrangement probably involves ring opening in the alkoxy radical (Formula 452) followed by recombination with nitrous oxide and cyclization (203). Oxidative fission of alkoxy radicals produced in nitrite... 

Roots R, Chatterjee A, Blakely E, Chang P, Smith K, Tobias C (1982) Radiation responses in air-, nitrous oxide-, and nitrogen-saturated mammalian cells. Radiat Res 92 245-254 Roots R, Chatterjee A, Chang P, Lommel L, Blakely EA (1985) Characterization on hydroxyl radical-induced damage after sparsely and densely ionizing irradiation. Int J Radiat Biol 47 157-166 Roti Roti JL, Cerutti PA (1974) Gamma-ray induced thymine damage in mammalian cells. Int J Radiat Biol 25 413-417... 

The next experiments consisted of irradiating the unbleached TMP pulp suspension in the presence of 1% hydrogen peroxide or 0,3% sodium borohydride. This was done to measure the influence of an oxidizing and a reducing chemical co-irradiated with the pulp suspension. Also, H202 is known to react with e solv to produce OH (equation 8). The effect of saturated nitrous oxide in pulp suspension was also studied. In presence of yrays, N20 is known to react with e-solv to generate OH. The experimental results are shown in Figure 5. 

Figure 17. Variation of laser-excited CN fluorescence intensity with laser spectral irradiance in a nitrous oxide-acetylene slot torch...

Irradiation Procedure. 30% w/w solutions of poloxamer were prepared in distilled water by the cold process and saturated with nitrous oxide. This agent is a known scavenger of hydrated electrons and is known to enhance crosslinking of poly(oxyethylene) chains (9). Vials containing these solutions were irradiated at ambient temperature in a 2000 Ci ° Co source at a dose rate of 0.5 Mrad h- Physicochemical measurements were performed on solutions prepared by dilution of these irradiated samples. 

Following the realisation that the reactions of the hydrated electron played an important role in the radiation chemistry of liquid water it was not long before evidence was sought, and found, that the electron and the counter cation could be involved in chemical reactions in non-polar liquids before they underwent neutralisation. Scholes and Simic (1964(49)) showed that on irradiation of solutions of nitrous oxide in hydrocarbons nitrogen was formed in the dissociative attachment reaction analogous to reaction (6). Similarly, Buchanan and Williams (1966(50)) attributed the formation of HD in Y lrradiated solutions of C2H3OD in cyclohexane to the transfer of a... 

MisceUaneous Reactions.—Details of the formation of nitrous oxide by photofragmentation of methyl nitrite have been reported.Photorearrangement is observed, however, on irradiation of the nitrites (183) derived from 6-methyl- and 4,4,6-trimethyl-cholest-5-en-3-ol to give the cyclic hydroxamic acids (184). There is ample precedent for these transformations, the likely pathway for which is outlined in Scheme 12. An alkoxyl radical (185) is also thought to be involved in the photochemicaUy induced conversion of O-nitrobenzoin (186) into benzaldehyde (187) and 2-phenylbenzo[b]furan (188). Reductive photoelimination of vicinal dinitro-groups takes place by... 

Gzapki and Jortner studied the effects of nitrous oxide on the y-ray irradiation of ferrous ion solution and estimated... 

Knight and Sutton (see section 5.12) in their study of y-ray irradiation of saturated solutions of nitric oxide examined the effect of adding nitrous oxide to the solution. From the results obtained in these experiments they were able to estimate the ratio 152/ 154 = 2.5+0.2, where ki64 refers to... 

The main-chain scission yield was recently compared at room and liquid nitrogen temperatures [415] in the presence of a large number of additives known as radical, cation or electron scavengers. The results are given in Table 31. The protection index, in this case defined as 100(7V0 — N)/N where N0 and N are the number of scissions per chain in the absence and in the presence of additive, respectively, is nearly independent of the irradiation temperature marked protection is observed for all the additives studied with the exception of nitrous oxide. It must therefore be concluded that the mechanism of main-chain scission is identical at room and liquid nitrogen temperatures and that ions and radicals are involved in the radiolysis. A detailed study of the effect of ethyl mercaptan on main-chain scission and volatile formation was then undertaken [395]. About 75% protection of main-chain scission was obtained at 313 and at 77°K when the polymer contained 1.49 wt. % of ethyl mercaptan the protection index increases to 90% for concentrations of the order of 10 wt. %. The yield of volatile products was, however, unaltered by the presence of 1.5 wt. % ethyl mercaptan. 

Dosimetry. The intensity of the flux at the sample site was measured periodically with a ferrous sulfate dosimeter, using GFe(iii) = 15.5. Energy absorbed in liquid samples was based on this dosimetry and was corrected for the electron density of the samples. To determine energy absorbed in the vapor samples, nitrous oxide was irradiated, at comparable electron densities, in the vessel used for the hydrocarbons the G value for nitrogen production was taken to be 11.0 (7). 

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