Exothermic, generally reactions

Adequate heat removal facilities are generally important when controlling the progress of exothermic chemical reactions. Common causes of thermal runaway in reactors or storage tanks are shown in Figure 7.4. A runaway reaction is most likely to occur if all the reactants are initially mixed together with any catalyst in a batch reactor where heat is supplied to start the reaction. 

Pyrotechnics is the technology of utilizing exothermic chem reactions when these are, generally speaking, non-expl, relatively slow, self-sustaining and self-contained... 

Although the literature contains a very large number of research articles concerned with the kinetics and mechanisms of reactions involving solids, there are comparatively few authoritative, critical and comprehensive reviews of the formidable quantity of information which is available. Probably the most important general account of the field is the book Chemistry of the Solid State, edited by Gamer [63]. Chapters 7—9 are particularly relevant in the present context as they provide a systematic exposition of the kinetic equations applicable to the decomposition of single solids (Jacobs and Tompkins [28]) and their application to endothermic [64] and exothermic [65] reactions. 

The treatment of acyl halides with ammonia or amines is a very general reaction for the preparation of amides.The reaction is highly exothermic and must be carefully controlled, usually by cooling or dilution. Ammonia gives unsubstituted amides, primary amines give A-substituted amides, and secondary amines give N,N-disubstituted amides. Arylamines can be similarly acylated. In some cases aqueous... 

Alkylation Mildly exothermic, side reactions generally a problem Low... 

Koikov, L. N. et al J. Org. Chem. USSR, 1985, 21, 1564-1574 The general reaction of nitroso arenes with a-dimethylaminostyrenes in benzene or ether to produce ArCO.C(NMe2)=NC6H4R is vigorously exothermic, and with large quantities the reaction mixture may be ejected from the reaction vessel. 

For exothermic reversible reactions the situation is different, for here two opposing factors are at work when the temperature is raised—the rate of forward reaction speeds up but the maximum attainable conversion decreases. Thus, in general, a reversible exothermic reaction starts at a high temperature which decreases as conversion rises. Figure 9.5 shows this progression, and its precise values are found by connecting the maxima of the different rate curves. We call this line the locus of maximum rates. 

K. N. Houk, N. G. Rondan, and J. Mareda, Theoretical Studies of Halocarbene Cycloaddition Selectivities. A New Interpretation of Negative Activation Energies and Entropy Control of Selectivities, Tetrahedron 1985, 41, 1555. Calculations on carbene addition reactions led to a general explanation of why it is possible for very exothermic, bimolecular reactions to have negative activation enthalpies. 

The treatment of acyl halides with ammonia or amines is a very general reaction for the preparation of amides.843 The reaction is highly exothermic and must be carefully controlled,... 

From the observation that the generally exothermic addition reactions do not occur readily we may infer that they require appreciable activation energies. These latter range from 17 to 23 kcal. for the additions of HI to olefins53 to 30 to 40 kcal. for the additions of HBr or HC1 to olefins, f It has been demonstrated by Okabe and McNesby24 that if sufficient energy is available in the molecule (e.g., by vacuum UV photolysis) then direct elimination of CH4 or H2 is possible from alkanes. In these cases, isotopic labeling experiments have shown that the two H atoms may come from adjacent C atoms to form the olefin, or even from the same C atom to form the isomeric carbene ... 

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