1 Classification reactions Imides

The imides, primaiy and secondary nitro compounds, oximes and sulphon amides of Solubility Group III are weakly acidic nitrogen compounds they cannot be titrated satisfactorily with a standard alkaU nor do they exhibit the reactions characteristic of phenols. The neutral nitrogen compounds of Solubility Group VII include tertiary nitro compounds amides (simple and substituted) derivatives of aldehydes and ketones (hydrazones, semlcarb-azones, ete.) nitriles nitroso, azo, hydrazo and other Intermediate reduction products of aromatic nitro compounds. All the above nitrogen compounds, and also the sulphonamides of Solubility Group VII, respond, with few exceptions, to the same classification reactions (reduction and hydrolysis) and hence will be considered together. 

This classification is illustrated in Scheme 300. The annelation of o-phenylenediamines with carboxylic acid derivatives is the most common method for the syntheses of benzimidazoles. As discussed in CHEC(1984) and CHEC-II(1996), either Br0nsted or Lewis acids can be used to promote the cyclization (e.g.. Scheme 301 also see Section 4.02.9.1(i)) <1998TA2245>. Carboxylic acids and their derivatives, such as acid chlorides, imidates, and phosgene iminium chloride, have been used in these reactions <2005JME8289, 2006BML4994>. 

Classification by Decomposition Behavior. The decomposition mechanism is a reasonable way to classify polymers. They can either depolymerize upon irradiation, for example, poly(methylmethacrylate), or decompose into fragments such as poly-imides or polycarbonates. This method of classification is closely related to the synthesis of polymers. Polymers that are produced by radical polymerization from monomers, which contain double bonds, are likely to depolymerize into monomers, while polymers that have been formed by reactions like polycondensation will not depolymerize into monomers upon irradiation, but will be decomposed into different fragments. The second group cannot be used to produce films with the same structure or molecular weight as the original material with methods such as PLD. 

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