Understanding the reaction mechanism of Kolbe electrolysis on Pt anodes

Kolbe electrolysis has been proposed an efficient electrooxidation process to synthesize (un)symmetrical dimers from biomass-based carboxylic acids. However, the reaction mechanism of Kolbe electrolysis remains controversial. In this work, we develop a DFT- based microkinetic model to study the reaction mechanism of Kolbe electrolysis of acetic acid (CH3COOH) on both pristine and partially oxidized Pt anodes. We show that the shift in the rate-determining step of oxygen evolution reaction (OER) on Pt(111)@α-PtO2 surface from OH* formation to H2O adsorption gives rise to the large Tafel slopes, i.e., the inflection zones, observed at high anodic potentials in experiments on Pt anodes. The activity passivation as a result of the inflection zone is further exacerbated in the presence of Kolbe species (i.e., CH3COO* and CH3*). Our simulations find the CH3COO* decarboxylation and CH3* dimerization steps determine the activity of Kolbe reaction during inflection zone. In contrast to the Pt(111)@α-PtO2 surface, Pt(111) shows no activity towards Kolbe products as the CH3COO* decarboxylation step is limiting throughout the considered potential range. This work resolves major controversies in the mechanistic analyses of Kolbe electrolysis on Pt anodes: the origin of the inflection zone, and the identity of the rate limiting step.

Decarboxylation 2'-dicarboxy-5-(methyl-5'-indolyl-3')- indolyl-3-acetic acid with use of salts of copper

In this article a decarboxylation method based on the use of quinoline with a copper salt is discussed. Decarboxylation is the elimination of CO2 from the carboxylic group of carboxylic acids or the carboxylate group of their salts. The process is used to produce a large number of organic compounds, such classes as alkanes, alkenes, alcohols, ketones, ethers and esters. Decarboxylation plays an important role in the metabolism of living organisms, namely in the decarboxylation of amino acids. From this we can conclude that the process is important to study. Decarboxylation proceeds in different ways. The most common methods of decarboxylation includes heating in various conditions. For example, such as heating in the presence of acids and alkalis, under severe conditions with quinoline, thermal oxidation in the presence of transition metal salts, Kolbe reaction. In the procces of the CO2 removal group in relation to amino acids there are several types: α-decarboxylation, decarboxylation, associated with the trans-amination reaction and the condensation reaction of molecules. In the synthesis of substituted auxin 2'-dicarboxy-5-(methyl-5'indolyl-3')-indolyl-3-acetic acid, the yield of the product was not high. The usual heating in the presence of alkali output was less than 5%, and in this work it was decided to use other methods of decarboxylation to increase the yield of the product. The aim of the work is to improve the method of decarboxylation of carboxyindolyl substrates for increasing product yield and to compare with the result obtained by ordinary heating of this substances in the presence of alkali. At the end of the work summed up. Found the optimal conditions for the process of decarboxylation of investigated substrates. Optimal conditions chosen based on product yield. To confirm the chemical structures of the substances, 1H NMR, IR spectroscopy, and elemental analysis were used.

Catalyst-free electrochemical decarboxylative cross-coupling of N-hydroxyphthalimide esters and N-heteroarenes towards C(sp3)–C(sp2) bond formation

We formed C(sp3)–C(sp2) bonds under electrochemical conditions by using NHP esters and N-heteroarenes without any catalysts. Our approach could be a complement to the Kolbe reaction and a promising strategy for finding more new reactions.

Electrochemical Functionalization in Wavefunction Engineering of Epitaxial Graphene

ABSTRACTChemical modification of graphene web has attracted strong interest in engineering a band gap in graphene and in altering its magnetic and solubility properties. Electrochemical methods to functionalize graphene have emerged as attractive protocols to covalently modify graphene. Kolbe reaction, which involves the electrochemical oxidation of arylacetates (generation of α-naphthylmethyl radicals, in our present case), allows reversible grafting of radicals to graphene surface; the electro-erasing of the functional groups leads to graphene at its nearly pristine state. The surface coverage can be controlled from densely-packed (ideal as organic dielectrics) to sparsely functionalized surface (ideal for introducing reasonable band gap in graphene) with well-ordered structural patterning of the functional groups on EG surface by fine adjustment of electrochemical conditions. Such a control of the layer structure and packing of the functional groups over the graphene surface is an essential issue in the development of graphene chemistry.