Carboxy/carboxylic acid groups

Another class of hydrocarbon binders used in propints are the carboxy-terminated polybutadiene polymers which are cross-linked with either tris[l-(2-methyl)aziridinyl] phosphine oxide (MAPO) or combinations with phenyl bis [l -(2-methyl)aziridinyl] phosphine oxide (Phenyl MAPO). Phenyl MAPO is a difunctional counterpart of MAPO which makes possible chain extension of polymers with two carboxylic acid groups. A typical propint formulation with ballistic properties is in Table 11 (Ref 83) Another class of composites includes those using hydroxy-terminated polybutadienes cross-linked with toluene diisocyanate as binders. The following simplified equations illustrate typical reactions involved in binder formation... 

Carboxy includes carboxy (carboxylic acids), alkoxycarbonyl (esters), carbamoyl (amides), thiocarbamoyl, hydrazinocarbamoyl (hydrazides), guanidinocarbonyl, azidocarbonyl (azides), chlorocarbonyl (acid chlorides), amidino, C-hydrazino-C-iminomethyl, C-alkoxy-C-iminomethyl (imino ethers), C-alkylthio-C-iminomethyl (iminothioethers), cyano (nitriles), C-formyl(aldehydes), dialkoxymethyl (acetals of aldehydes), C-acyl (ketones), isocyanato, and thiocyanato groups. 

The lithiation of isophthalic acid can be achieved either at 2- or 4- position after conversion of the carboxylic acid groups to oxazole derivatives or N,N -butylamide derivatives respectively. Conversion to N-methyl amide derivative leads to the precipitation of the N-lithio salt on treatment with BuLi which fails to lithiate further. The N-lithio salt of the N-butylamide, however, remains in solution under the experimental conditions. It may be noted that the two lithiation reactions furnish two different carboxydihydroisocoumarins. The 5-carboxy dihydroisocoumarin can be converted to erythrocentaurine, which is naturally occurring... 

Decarboxylation reactions in pyrimidines with a carboxylic acid group in electrophilic positions have received considerable attention since the carboxylic acid group may be an important group in a primary synthesis. Alkyl groups in electrophilic positions can also be removed by oxidation to a carboxylic acid followed by decarboxylation. Conditions for thermal decarboxylation vary considerably according to the compound. In the highly electrophilic positions, decarboxylation occurs very readily (Scheme 70). Thus the 4-carboxy-2-pyrimidinone (420) is decarboxylated at 40°C [Pg.182]

Enantioselective cleavage of non-peptide amide bonds is also important in the production of optically active amino acids (Scheme 3.12). Carboxy-peptidases often are the enzymes of choice in this area of work these enzymes catalyse the hydrolysis of an amide function which is close to a carboxylic acid group. The rate of hydrolysis is usually increased if R (Scheme 3.12) is an aromatic unit or a large aliphatic moiety. For example, thrco-jS-phenylserine R = PhCH(OH) has been resolved by incubation of the racemic JV-trifluoroacetate with carboxypeptidase-A, with the optically pure (L)-enantiomer being obtained in a good yield. 

In nearly all derivatives, this ligand is di-anionic with both the aryloxide and carboxy-late oxygen atoms bound to the metal centre (Table 6.7). In one structurally determined example, the carboxylic acid group remains protonated and chelates to the metal... 

R1NH2) were subjected to a formal [3 + 2] cycloaddition reaction with anhydrides in the presence of 4A molecular sieves, producing a series of resin-bound carboxy-y-lactams and carboxy-2-quinolones. The carboxylic acid group was converted into an amide by coupling with various primary amines (R2NH2) to increase molecular diversity. As the last step, the resin was treated with HF/pyridine-releasing carboxy-y-lactams 161 and 162 and carboxy-2-quinolones... 

Crini et al., 2002 proposed the synthesis of cyclodextrin-carboxy-methyl cellulose gels. Results obtained with these gels showed that effective and efficient extraction of beta-naphtol is achieved. The presence of carboxyl groups in the polymer networks permit to increase significantly the sorption properties. The carboxylic acid groups present in the adsorbents plays an important role in the adsorption of Cu, Pb and Ni [94]. 

---