Electrochemical Cleavage of Carbon‐Chlorine Bonds in Multiply Bridge‐Chlorinated Bicyclo[1.1.1]pentane‐1,3‐dicarboxylic Acids

• Published in: ChemElectroChem Vol. 8; no. 17; pp. 3243 - 3249
• Main Authors: Kaleta, Jiří, Hromadová, Magdaléna, Pospíšil, Lubomír
• Format: Journal Article
• Language: English
• Published: 01-09-2021
• Subjects: bicyclo[1.1.1]pentane-1,3-dicarboxylic acids; C−Cl cleavage; protonation; reduction; voltammetry
• ISSN: 2196-0216; 2196-0216
• DOI: 10.1002/celc.202100372

Reduction of five derivatives of bicyclo[1.1.1]pentane‐1,3‐dicarboxylic acid containing one to four chlorine substituents on methylene bridges were investigated by cyclic voltammetry and electrochemical impedance spectroscopy. Electrochemical cleavage of C−Cl bonds and the reduction of H+ provided by dissociation of COOH groups are two competing processes characterized by different time constants. A concerted mechanism of C−Cl bonds cleavage is operative. The location of LUMO orbitals changes with increasing number of chlorine substituents from COOH sites to bicyclo[1.1.1]pentane. Carboxylic groups participate in the protonation of intermediates formed by the C−Cl bond rupture. The esterification of two derivatives eliminates the self‐protonation. Esters are reduced only at very negative potentials near the end of an available potential window.
Bond rupture: Derivatives of bicyclo[1.1.1]pentane‐1,3‐dicarboxylic acid containing one to four chlorine substituents on methylene bridges were investigated by electrochemical methods. A concerted mechanism of C−Cl bonds cleavage is operative. The location of LUMO orbitals changes with increasing number of chlorine substituents from COOH sites to bicyclo[1.1.1]pentane. The esterification eliminates the self‐protonation.