META Group

META Group, Worldwide IT Benchmark Report 2004, Vol. 1 2004 IT Spending Staffing Analysis Pharmaceuticals Medical Equipment. 2003 p.2. 

Nitration of p-chlorobenzoic acid gives the desired product, because the directing effects of the chlorine (ortho, para) and the carboxyl (meta) groups reinforce each other. 

Kricheldorf has reported the synthesis of lyotropic poly(amide-imide)s and poly(benzoxazole-amide)s. These were prepared by the polycondensation of N,N-bis(trimethylsilyl)-p-phenylenediamine or N,AT -bis(trimethylsilyl)-3,3 -dim-ethylbenzidine with the diacyl chloride of trimellitimide of p-aminobenzoic acid, or the imide formed from p-amino benzoic acid and terephthalic acid. Lyotropic behaviour was observed in cone, sulphuric acid solution [38]. A series of thermotropic poly(imide-amide)s was prepared based on trimellitimides formed from trimellitic anhydride and an a, -bis(4-aminophenoxy) alkane with carbon chain lengths 9-12. Melting points were in the range 250-300 °C. They formed smectic A phases and tended to degrade around the isotropisation temperatures (around 350 °C). Pendant methyl groups or occupied meta- groups tended to prevent mesophase formation [39]. Novel LC poly(imide-amides) have also been synthesised from new diamine spacers derived from linear diaminoalkanes and 4-nitrophthalic anhydride. A smectic and nematic phase were observed when 4,4 -biphenyl dicarboxylic acid was used as co-monomer [40]. 

The resonance of a para group can induce a charge nearer to the acidic group than the resonance of a meta group can, and the effect of the resonance of a group is greater when the group is para than... 

In Figures 37 and 38 the points for meta substitution are not shown. Instead, the straight lines are those drawn for meta groups alone and shown in Figure 36. The line in Figure 37 is that for... 

The points for meta groups and those para groups that do not resonate very strongly with the benzene ring fall as close to the line... 

The alkylation of mefa-substituted aryUcetimines shows that meta substituents protect the neighbouring ortho C-H bond by steric hindrance. By contrast, if this meta group is an electron-withdrawing group such as fluorine its neighbouring ortho C-H bond is preferentially activated and then alkylated [109]. 

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