Carbon dioxide aqueous solutions, mechanisms

Brodzinski, R., S. G. Chang, S. S. Markowitz, and T. Novakov (1980). Kinetics and mechanism for the catalytic oxidation of sulfur dioxide on carbon in aqueous solution. J. Phys. Chem. 84, 3354-3358. 

Vassiliev YB, Bagotzky VS, Osetrova NV, Khazova OA, Mayorova NA (1985) Electroreduction of carbon-dioxide 1. The mechanism and kinetics of electroreduction Of CO2 in aqueous-solutions on metals with high and moderate hydrogen overvoltages. J Electroanal Qiem 189(2) 271-294... 

More recently Hand et al. (ref. 9) have studied the decomposition reaction of N-chloro-a-amino acid anions in neutral aqueous solution, where the main reaction products are carbon dioxide, chloride ion and imines (which hydrolyze rapidly to amine and carbonyl products). They found that the reaction rate constant of decarboxylation was independent of pH, so they ruled out a proton assisted decarboxylation mechanism, and the one proposed consists of a concerted decarboxylation. For N-bromoamino acids decomposition in the pH interval 9-11 a similar concerted mechanism was proposed by Antelo et al. (ref. 10), where the formation of a nitrenium ion (ref. 11) can be ruled out because it is not consistent with the experimental results. Antelo et al. have also established that when the decomposition reaction takes place at pH < 9, the disproportionation reaction of the N-Br-amino acid becomes important, and the decomposition goes through the N,N-dibromoamino acid. This reaction is also important for N-chloroamino compounds but at more acidic pH values, because the disproportionation reaction... 

The mechanism of carbon dioxide reduction in aqueous and nonaqueous solutions was investigated by several authors. It is now generally accepted that the reduction of carbon dioxide to formate ions is a multistep reaction with the intermediate formation of free radicals CO2 and HCO2 either in the solution or adsorbed on the electrode ... 

Mechanisms of carbon dioxide reduction in both aqueous and nonaqueous solutions have been studied mainly at metal electrodes. 

The amide functionality plays an important role in the physical and chemical properties of proteins and peptides, especially in their ability to be involved in the photoinduced electron transfer process. Polyamides and proteins are known to take part in the biological electron transport mechanism for oxidation-reduction and photosynthesis processes. Therefore studies of the photochemistry of proteins or peptides are very important. Irradiation (at 254 nm) of the simplest dipeptide, glycylglycine, in aqueous solution affords carbon dioxide, ammonia and acetamide in relatively high yields and quantum yield (0.44)202 (equation 147). The reaction mechanism is thought to involve an electron transfer process. The isolation of intermediates such as IV-hydroxymethylacetamide and 7V-glycylglycyl-methyl acetamide confirmed the electron-transfer initiated free radical processes203 (equation 148). 

Lu JM, Geimer J, Naumov S, Beckert D (2001) A Fourier transform EPR study of uracil and thymine radical anions in aqueous solution. Phys Chem Chem Phys 3 952-956 Lymar SV, Jiang Q, Hurst JK (1999) Mechanism of carbon dioxide-catalyzed oxidation of tyrosine by peroxynitrite. Biochemistry 35 7855-7861... 

Evidence has been obtained that the photodecarboxylation of benzannelated acetic acids in aqueous solution proceeds via carbanion intermediates 5H-dibenzo[a,d]cyclohepten-5-carboxyl-ic acid, for example, undergoes photodecarboxylation with a quantum efficiency of close to unity. The reactions of the -nitrobenzyl anion, generated by photochemically induced loss of carbon dioxide from -nitrophenylacetate anion, have been examined and a mechanism proposed to account for the formation of the corresponding bibenzyl derivative. Reductive decarboxylation of carboxylic... 

Reactions in a single phase are said to be homogeneous. Examples of experimentally observed homogeneous reaction rates in aqueous solution for carbon dioxide hydration, and ferrous iron oxidation in water are presented in Tables 9.2 and 9.3, respectively. The overall reaction is presented first, followed by the reaction rate equation and then some suggestions for a reaction mechanism that shows the connection between these two. The reaction mechanism is sometimes a h5T)othesis if it is not based on experimental evidence. 

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