Reactivity patterns electrochemical reactions

Electrochemical techniques are a convenient means of studying one-electron oxidations of amines. The reaction pattern of the anodic oxidation of amines depends greatly on the reaction conditions, including the nature of the electrode and the nucleophilicity of the solvent [1-3]. A major drawback of electrode oxidations is that unwanted secondary electron-transfer reactions can occur at the electrode surface. Also in electrochemical processes the effective reaction volume is limited at the electrode surface, thereby creating a high local concentration of reactive intermediates which can lead to dimerization and disproportionation reactions. These factors have to some extent, limited the synthetic utility of the anodic oxidation of amines. Because of this the anodic oxidation of amines has been intensively studied, although mainly from a mechanistic standpoint. 

Since the SECM response is a function of the rate of the heterogeneous reaction at the substrate, it can be used to image the local chemical and electrochemical reactivity of surface features. A technique called reaction-rate imaging, which is unique to SECM, is particularly useful in imaging the areas on a surface where reactions occur. Membranes (5-7), leaves (8-10), polymers (11,12), surface films (13-17), and artificially patterned biological systems (7,18-20) have been imaged with SECM. 

Other methods have been developed that allow the detection of point mutations in non-hybridization based assays. An effective alternative electrochemical method harnesses differences in the kinetics of the reaction of Ru(bpy)3 with gnanine in the context of base mismatches to report base substitutions [47]. In addition, altered patterns of chemical reactivity have been detected in RNA-DNA hybrids containing 2-NH2 modifications in an RNA complement at mispaired positions [48]. Extension of this approach to an immobilized system has not yet been demonstrated, but it may hold pronfise for any applications where alterations in chemical, rather than electrochanical, reactivity are required. 

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