Sensitized reactions

Eye. Adverse effects may be produced by splashes of Hquids or soflds, and by materials dispersed in the atmosphere. The eye is particularly sensitive to peripheral sensory irritants in the atmosphere. Toxic effects that may be induced include transient acute inflammation, persistent damage, and, occasionally, sensitivity reactions. ToxicologicaHy significant amounts of material may be absorbed by the periocular blood vessels in cases of splash contamination of the eye with materials of high acute toxicity (58). 

Characteristic reactions of singlet oxygen lead to 1,2-dioxetane (addition to olefins), hydroperoxides (reaction with aHyhc hydrogen atom), and endoperoxides (Diels-Alder "4 -H 2" cycloaddition). Many specific examples of these spectrally sensitized reactions are found iu reviews (45—48), earlier texts (15), and elsewhere iu the Engchpedia. 

The most suitable method of fast and simple control of the presence of dangerous substances is analytical detection by means of simplified methods - the so-called express-tests which allow quickly and reliably revealing and estimating the content of chemical substances in various objects. Express-tests are based on sensitive reactions which fix analytical effect visually or by means of portable instalments. Among types of indicator reactions were studied reactions of complex formation, oxidation-reduction, diazotization, azocoupling and oxidative condensation of organic substances, which are accompanied with the formation of colored products or with their discoloration. 

The CIO radical in particular is implicated in environmentally sensitive reactions which lead to depletion of ozone and oxygen atoms in the... 

The sensitized reaction on furan led to the formation of a triplet state of 1 then the relaxation of O—Cq, bonds can induce, by crossing onto a energy sheet, the formation of a tt,(j biradical 9 (74JA3486 76T1729 99MI1). 

Semiempirical (PM3) and ab initio (6-3IG basis set) calculations are in agreement with the hypothesis described in Section I (99MI233 OOOJOC2494). In the case of the sensitized reaction, when the excited triplet state is populated, only the formation of the radical intermediate is allowed. This intermediate can evolve to the corresponding cyclopropenyl derivative or to the decomposition products. In a previously reported mechanism the decomposition products resulted from the excited cyclopropenyl derivative. In our hypothesis the formation of both the decomposition products and the cyclopropenyl derivatives can be considered as competitive reactions. 

Dimethylfuran, in a sensitized reaction, gave 1,3-dimethylcyclopropene (the main product), isoprene, cis- and rran.s-l,3-pentadiene, 2-pentyne, and 1-methylcyclopropenyl methyl ketone (Scheme 7) (70JPC574) the ring contraction showed a high selectivity. 

Compound 104 could not be obtained from 103, and a hypothesis about its formation considered the (homolytic or heterolytic) cleavage of the O—N bond (Scheme 43) (68TL2417). The sensitized reaction didnotgive adifferentresult the author supposed that the reaction involved the excited triplet state of the molecule. When the reaction was carried out in methanol, 104 was obtained in 8% yield... 

In reactions in which separated ion pairs are involved, e.g., R4N+, K or Na +, and as a borderline case, Li +, the cation does not contribute to the adjustment of the reaction partners in a dense, well-ordered transition state poor selcctivities arc usually the result of these carbanionic carbonyl additions. Further, the high basicity of such carbanionic species may cause decomposition or racemization of sensitive reactions partners. 

There is a multiplicity of pathways for thermal dediazoniations. An analogous situation is to be expected for photochemical dediazoniations. Based on the general experience that light-sensitive reactions often involve free radical intermediates, it was commonly assumed that all photolytic dediazoniations are free radical reactions. Horner and Stohr s results (1952), mentioned above, could lead to such a conclusion. More sophisticated methods of photochemistry also began to be applied to investigations on arenediazonium salts, e. g., the study of photolyses by irradiation at an absorption maximum of the diazonium ion using broad-band or monochromatic radiation. This technique was advocated by Sukigahara and Kikuchi (1967 a, 1967 b,... 

The thiazide diuretics are contraindicated in patients with known hypersensitivity to the thiazides or related diuretics, electrolyte imbalances, renal decompensation, hepatic coma, or anuria. A cross-sensitivity reaction may occur with the thiazides and sulfonamides. Some of the thiazide diuretics contain tartrazine, which may cause allergic-type reactions or bronchial asthma in individuals sensitive to tartrazine. 

Corticosteroid intrarectal foam, hydrocortisone acetate intrarectal foam Cortifoam Adjunctive therapy in treatment of ulcerative proctitis of the distal portion of the rectum Local pain or burning, rectal bleeding, apparent exacerbations or sensitivity reactions 1 applicatorful once or twice daily for 2 wk and every second day thereafter... 

The mixing in the first five cells is illustrated in Figure 15.16. In the fifth cell, after 50 ms, the reactants are very weU mixed. After the fifth ceU, only the temperature must be controlled to keep the reactants weU mixed [30]. The very good mixing properties were also verified with a mixing-sensitive reaction, that is, the mixing-sensitive diazo coupling between 1-naphthols, 2-Naphthols, and diazotized sulfanilic acid [30]. 

The undoubtedly structure-sensitive reaction NO -r CO has a rate that varies with rhodium surface structure. A temperature-programmed analysis (Fig. 10.8) gives a good impression of the individual reaction steps CO and NO adsorbed in relatively similar amounts on Rh(lll) and Rh(lOO) give rise to the evolution of CO, CO2, and N2, whereas desorption of NO is not observed at these coverages. Hence, the TPRS experiment of Fig. 10.8 suggests the following elementary steps ... 

It has been suggested that in some eases dermal effeets in persons oeeupationally exposed to trichloroethylene may be a sensitivity reaction (Cziijak et al. 1993 Gob and Ng 1988 Phoon et al. 1984). 

F. Feigl, Chemistry of Specific Selective and Sensitive Reactions, Academic Press, New York, 1949, p. 156. 

Kinetics of Structure Sensitive Reactions Over Clean Single Crystal Surfaces... 

Since oxidation of methanol is an electrocatalytic reaction with different adsorption steps, interactions of the adsorbed species with the metallic surface are important. Using platinum single-crystal electrodes, it has been proven that the electrooxidation of methanol is a surface-sensitive reaction. The initial activity of the Pt(llO) plane is much higher than that of the other low-index planes, but the poisoning phenomenon is so rapid that it causes a fast decrease in the current densities. The... 

The Menschutkin reaction was carried out as a test reaction to show the feasibility of such novel micro flow concepts that allow to process fouling-sensitive reactions (see also Section 4.2.6 here another test reaction is decribed for the same purpose) [78]. The reaction of alkyl bromide with ternary bases such as pyridine or triethylamine gives quaternary salts insoluble in most solvents. Often, fairly rapid precipitation of this salt occurs, hence ideally serving as a test reaction for fouling sensitivity of micro-channel devices. The reaction of 4,4 -bipyridyl and ethyl bromoacetate [78] belongs to the category of fast-predpitating Menschutkin reactions, as the halide function is activated by the carbonyl fimction. 

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