Abnormal reactions

Industrial hygiene/toxicology people need to develop acute and chronic toxicology information on all the materials used and produced in the process. This information should also include the potential products of abnormal reactions. The industrial hygiene member of the team should be prepared to explain the toxicology information on the material safety data sheet (MSDS) to the review team. 

Sensitivity The ability of a chemical analysis to detect low levels of the analyte. Also, any abnormal reaction of the human body to chemical substances. 

The mechanism proposed for this abnormal reaction is illustrated by reference to the conversion of qumoxalin 3-one-2-carboxyanilide (48)... 

Attainment of abnormal reaction conditions, e.g. overpressure, over-temperature, segregation of reactants, excessive reaction rate, initiation of side reactions. 

As compared to the carbamate synthesis above, an abnormal reaction course was observed in the reaction of m-tolyloxythiocarbonylimidazole with benzylmethylamine here the phenolate is exchanged instead of the imidazole, obviously because the substituent with the lower pK is eliminated 2163... 

Toxicity, corrosivity or flammability of raw materials and normal/ abnormal reaction products... 

Abnormal reactions with other, incompatible materials that may also serve to initiate self-reactions that are more energetic are also possible. These can be addressed by the scenario approach that goes with Question 12.)... 

How had they arrived at such a conclusion In the mid-1920s, Kirrmann and Prevost both began working on problems posed by Lespieau on reactions of unsaturated hydrocarbons, in particular allylic and conjugated systems. Kirrmann s research topic became focused on bromated aldehydes and the "abnormal" reactions in which, for example, these aldehydes behave as if they were acid bromides, that is,... 

Persistent photosensitivity developed in eight men after occupational exposure to hot epoxy resin fiimes. The condition was limited to sites contacted by the resin. Small doses of ultraviolet-A light evoked abnormal reactions consisting of erythema, edema, and papules in the clinically involved skin. Positive photopatch tests were observed to epoxy resin in four subjects and to bisphenol A in all subjects. Another study showed that bisphenol A can be released during the thermal decomposition of epoxy resin in the temperature range of 250-350°C. Photosensitizing activity was explained by the formation of ftee radicals during exposure to ultraviolet-B radiation of bisphenol A vapor, to form a semiquinone derivative of bisphenol A ... 

The products from the reaction of PTAD with substituted triazoles may arise from a 1,3-dipolar addition <92BCJ3315>. Abnormal reaction products also occur from the reaction with oxazoles <92BCJ2998>. 

In this and the following Sections, the reactions of the various classes of aldose oxirane are summarized in a series of Charts. Unless otherwise indicated, reactions classified as normal give the diaxial product indicated as the preponderant or the only product (or as the only product isolated, although, in some studies, the yield of product isolated was <50%). Conversely, abnormal reactions give the diequa-... 

The vicinal methylbenzyl alcohols have been prepared in general by the abnormal reaction of the appropriately substituted Grignard reagent with formaldehyde. The present method is preferred because it yields purer products than the Grignard approach. 

An extreme case of the Cope rearrangement proceeds via dissociation to an ion-pair. [228], Complementary donor and acceptor stabilization of the ionic species is the cause for this abnormal reaction. 

List known reaction rate data on the normal and possible abnormal reactions... 

A few significant illustrations have been selected to call attention to (1) the directive influence of substituents (2) the Btereonpocifiv mode of addition and (3) the existence of an abnormal reaction. 

Rearrangement of several substituted chlorohydrins of fixed conformation has recently been reported by Curtin and Harder,3M and attention is directed to this interesting paper, since it is related to the abnormal reaction of a-haloketonos with Grignard reagents and hence pertinent to epoxide chemistry,... 

To what extent the putative epoxide in such an abnormal reaction in a long-lived species cannot be inferred from this example, since Foumeau and Tiffeneau578 observed that 1,2-epoxy-2-methylbutane yields the same product on treatment -with ethylmagneeium bromide. 

Moat reoently Addy and co-workers1 17 made the notable discovery that the normal reaction ( .e. terminal attack) of benzyl mine with p-sub tituted styrene oxides exhibits a positive p-value in the Hammett plot, while the abnormal reaction (, , bonxylio attack) exhibits a negative p -value. These facts are consistent with a transition state of appreciable carbonium ion character for the latter reaction. 

When the catalytic reaction of 6-hydroxymellein synthase is carried out in the absence of NADPH or with monomeric enzyme, keto-reduction of the carbonyl group of the triketomethylene chain does not take place, and the synthase liberates triacetic acid lactone instead of 6-hydroxymellein [64, 71]. However, the efficiencies of product formation are markedly lower than for the normal reaction. Two mechanisms could account for the low efficiency of triacetic acid lactone formation observed in the monomeric and the NADPH-depleted dimeric forms of 6-hydroxymellein synthase. These are 1) Reduced affinity of the cosubstrates acetyl-CoA and/or malonyl-CoA for the enzyme protein with the incomplete reaction centers 2) Reduced rate of reaction of acyl-CoA condensation and/or product liberation. To examine these possibilities, kinetic parameters of the two triacetic acid lactone-forming reactions were compared with those of the normal reaction which produces 6-hydroxymellein. The Km value of 6-hydroxymellein synthase for acetyl-CoA in the normal reaction was estimated to be 22 pM, while in both the NADPH-depleted dimer and the monomer reactions the affinity of 6-hydroxymellein synthase protein for acetyl-CoA was markedly lower at 284 and 318 pM respectively. By contrast the Km values for malonyl-CoA in the normal and the two abnormal reactions were essentially the same (40 - 43 pM), indicating that the affinity of 6-hydroxymellein... 

Ribonuclease Ti is a stable enzyme. It is fairly resistant to heat (100° for 10 min at pH 6) and acid but somewhat unstable in alkaline solution (>pH9) (5, 19). It should be noted that the catalytic reaction by the enzyme cannot be stopped by simply heating the reaction mixture to 100°, and even at 100° an abnormal reaction might occur (K. Satoh, Y. Inoue, and F. Egami, unpublished). 

The resulting tetraethyl ester on hydrolysis and decarboxylation yields propane-1, 2,3-tricarboxylic acid.155 In this example the malonate anion is generated by using one molar proportion of sodium ethoxide this is Michael s original method. However, these conditions sometimes lead to competing side reactions and the formation of abnormal reaction products. Better yields of the required product are often obtained with small amounts of sodium ethoxide (the so-called catalytic method) or in the presence of a secondary amine (e.g. diethyl-amine, see below). 

Evidence is now accumulating to show that reactions involving metals might be the common denominator underlying AD and PD. In these disorders, an abnormal reaction between a protein and a redox-active metal ion (copper or iron) promotes the formation of ROS. It is especially intriguing how the antioxidant Cu/Zn-SOD activity can convert into a pro-oxidant activity, a theme echoed in the recent proposal that Ap and PrP, the proteins respectively involved in AD and prion diseases, possess similar redox properties [Bush, 2002],... 

Genetic disorders with abnormal reactions to environmental factors are no less treatable than many other disorders treated by physicians. These genetic disorders are treated by restricting access to, replacing and/or removing the toxic substance from the environment of the susceptible persons. Pharmacogenetic polymorphisms are invisible until their effects are revealed by exposure of individuals who harbor them to environmental toxins microarrays and allied technology provide the means to screen for these polymorphisms and to identify susceptible individuals before they are affected. 

A related isomerization, that of phenylacetylcobalt carbonyl to o-toluyl-cobalt carbonyl, has recently been studied (143). It also appears to proceed via a tricarbonyl but could not proceed via Eqs. (9) and (10). This rearrangement has much in common with the so-called abnormal reactions of benzyl Grignard and benzyllithium reagents to produce ortho-substituted products (13, 13f). It is possible that a cyclic intermediate similar to that postulated in the Grignard rearrangements may be involved, Eq. (87). 

Cornforth46 has severely criticized this scheme and stated that all claims in this paper should be accepted as fact after, but not before, verification by independent experiment. Amongst other points, he noted that the conversion of (151) into (152) requires (a) an abnormal reaction of a /S-keto-ester with a Grignard reagent, and (b) a so-called dehydration involving the wholly unexplained disappearance of a C-methyl group. 

In his comments on Van t Hoff s book, Semenov wrote "when one is reading this book one feels as if the author was much more interested in the reasons for the abnormal reaction course and the perturbation effect rather than in further extending his knowledge of the normal process, since he treated them as virtually evident... Van t Hoff s consideration of the abnormal behaviour of reactions is thrice as much [5, p. 7], To our mind this splendid principle suggested in Van t Hoffs book should be specially distinguished in modern chemical kinetics. It goes without saying that the sophisticated theory must be supported by accurate experiments. ... 

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