Carboxylic derivs., reactions electronic effects

Carboxylic derivs., reaction, 230-244 acid hydrolysis, 240, base hydrolysis, 238 electronic effects in, 237 Grignard reagents, 238... 

Nucleophilic addition to C=0 (contd.) ammonia derivs., 219 base catalysis, 204, 207, 212, 216, 226 benzoin condensation, 231 bisulphite anion, 207, 213 Cannizzaro reaction, 216 carbanions, 221-234 Claisen ester condensation, 229 Claisen-Schmidt reaction, 226 conjugate, 200, 213 cyanide ion, 212 Dieckmann reaction, 230 electronic effects in, 205, 208, 226 electrons, 217 Grignard reagents, 221, 235 halide ion, 214 hydration, 207 hydride ion, 214 hydrogen bonding in, 204, 209 in carboxylic derivs., 236-244 intermediates in, 50, 219 intramolecular, 217, 232 irreversible, 215, 222 Knoevenagel reaction, 228 Lewis acids in, 204, 222 Meerwein-Ponndorf reaction, 215 MejSiCN, 213 nitroalkanes, 226 Perkin reaction, 227 pH and, 204, 208, 219 protection, 211... 

Electrochemical oxidation of some catecholamines such as dopamine, L-dopa, and methyldopa has been studied using cyclic voltammetry. The catecholamines undergo intramolecular cyclization to form the corresponding o-quinone derivatives. The significant differences in the electrochemical behaviour of the catecholamines have been attributed to the effects of the side-chain carboxyl group.253 Electron-transfer reactions of 2,-deoxyguanosine-5,-monophosphate (dGMP) in phosphate buffers by cyclic... 

Many carboxy derivatives are available by primary syntheses. Otherwise the best route to simple pyrimidinecarboxylic acid derivatives is oxidative. This statement is even more applicable to our present situation with readily available acyl-, alkenyl-, or alkynylpyrimidine substrates from the coupling procedures, which serve as excellent substrates for oxidative reactions. The normal carboxylic acid reactions are observed ester formation, ester hydrolysis, aminolysis, acid chloride formation and reactions. A carboxy group in an electrophilic position may readily be lost when the pyrimidine ring is further depleted of 7t-electrons by its substitution pattern selective decarboxylation can be effected in pyrimidinedicarboxylic acids. 

Zeaxanthin (C ) has been incorporated in DMPC and egg lecithin vesicles. This a,(D-bipolar carotenoid reinforces the DMPC vesicle with respect to mechanical stability and water permeability but has no effect on fluid egg lecithin membranes (Lazrak et al.,1987). Electron-poor derivatives with electron-withdrawing carboxyl or pyridinium end groups should reversibly take up electrons in a type of reversible Michael reaction and then act as organic wires. There are, however, no reports on stable anion radicals of such chro-mophores in the literature. Claims of electron transport through vesicle membranes are very probably erroneous. It has been shown by reduction of an entrapped indigo dye that bixin derivatives in DPPC vesicle membranes favor the transport of borohydride and dithionite ions through the membrane rather... 

In Summary The relative electronegativity and the size of L in RCL controls the extent of resonance of the lone electron pair(s) and the relative reactivity of a carboxylic acid derivative in nucleophilic addition-elimination reactions. This effect manifests itself structurally and spectroscopically, as well as in the relative acidity and basicity of the a-hydrogen and the carbonyl oxygen, respectively. 

---