Reactions, general classification compounds

Classification by Chemical Constitution Classification of solvents according to chemical constitntion allows certain qualitative predictions. In general, a compound dissolves far more easily in a solvent possessing related functional groups than in one of a completely different nature (see table 3.11). A proper choice of solvent, based on the knowledge of its chemical reactivity, helps to avoid undesired reactions between solute and solvent. 

The general classification outlined in Sections A to G covers the vast majority of the types of reaction whereby cationic metal carbonyl compounds are prepared. There remain, nevertheless, a few further reactions which, for the sake of completeness, are included in this survey, but which do not belong to a specific section. 

The reactivity of TAs may be considered in two ways. The first consists in describing all the reactions of each separate class of compounds. This was done in early reviews (79KGS291 86KGS3). The second approach—that of the present review—is based on the classification into types of reactions of different compounds. The latter approach allows one to focus on general and specific peculiarities of transformations and to compare the chemical behavior of various groups of TA derivatives. 

The 3-azido- 1,2,4-triazoles (230) exist in the azide form rather than the triazolotetrazole form.481-484 These compounds were obtained by cyclization of the hydrazonyl bromides (229, R = H) and by treating the 3-hydrazinotriazole (233) with nitrous acid482 (Scheme 26). The former reaction involves a preferential ring interconversion of tetrazole to triazble and presumably could be included in the general classification of Eq. (37) An alkyl substituent located in the tetrazole moiety appears to have a stabilizing influence on the triazolotetrazole ring system, since the bicyclic compounds (232), not azides (231), were obtained when the... 

It is obviously impossible to classify chemical reactions in a completely logical manner, and the editors have in general based their classification on types of chemical element, compound or reaction rather than on mechanisms, since views on the latter are subject to change. Some duplication is inevitable, but it is felt that this can be a help rather than a hindrance. 

This is the most common route, the reagent being a metal compound/solvent combination. Typical conditions call for the metal salt (e.g., acetate) in a buffer system (e.g., NaOAc/AcOH) and a co-solvent such as chloroform. Generally the reaction mixture is refluxed until the metal complex spectrum (see Section 9.22.5.6 and Table 4) is fully developed. Metal acetylacetonates and metal phenoxides have also been employed. The topic has been reviewed in detail by Buchler,51 who has also summarized the history and classification of metal complexes of this series, and the mechanisms of metalation.52... 

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