Micellar promoted photoreduction of ethylenediaminetetraacetato cobaltate(III) by 1-benzyl-1,4-dihydronicotinamide

Abstract

The photoreduction of ethylenediaminetetraacetato cobaltate(ii1) ([Co(edta)] -) by 1 -benzyl-I ,4dihydronicotinamide (BNAH) has been studied in the presence of the surfactants cationic dodecyltrimethylammonium chloride (DTAC) and anionic sodium dodecylsulphate (SDS). Cationic DTAC accelerates the photoreduction of [Co(edta)] -, while anionic SDS suppresses the reaction. The micellar effects on the reaction rates have been analysed by distribution of the reactants between an aqueous phase and a micellar phase and monitoring the difference in rate. In the DTAC micellar system, cationic micelles promote the reaction significantly by concentrating the photoexcited BNAH and [Co(edta)] -through hydrophobic and electrostatic interactions in spite of the smaller rate constant in the micellar phase compared with that in the aqueous phase. On the other hand, anionic SDS hinders approach of the anionic [Co(edta)]to the photoexcited BNAH in the SDS micelles, so as to retard the reaction rate.

Ab Initio Emulsion and Miniemulsion Polymerization of Styrene Mediated by a Cyclohexenyl-Functionalized Amphiphilic RAFT Agent

“…Ohkubo and others suggested that, in the micellelike nanoreactors, the organic reactions between hydrophobic reactants and functionalities at the hydrophobic tails of surfactant molecules could be significantly enhanced. − Besides the high local concentrations of functionalities and reactants within the micelles, two more possible reasons are responsible for this kinetic enhancement: (1) The hydrophobic cores limit the penetration of water into the reaction locus and eliminate the side reactions involving the reactants or the functionalities. This could be excluded by the observation of maintenance of cyclohexenyl groups during miniemulsion polymerization experiment 7 described below.…”

“…This could be excluded by the observation of maintenance of cyclohexenyl groups during miniemulsion polymerization experiment 7 described below. (2) The micelles could regulate the preorientation of the functionalities and the reactants within the cores and cause rate enhancement, for example, by holding them together for a longer period of time than homogeneous solutions …”

Nanoreactors for Polymerizations and Organic Reactions

“…As the microviscosity of the micelles is much greater than in homogeneous solutions, the reactants have a lower degree of translational freedom, which controls the regioselectivity. 116 Preorientation of the reactants at or close to the stern layer of the ionic micelle has allowed the formation of products with regioselectivity through photochemical reactions. In organic solvents, anthracene photocoupling reactions gave 91% head-to-tail addition in benzene and 50% head-to-head in methanol.…”

“…The hydrophobic attractive forces between reactants allow the reactants to be in contact for longer periods of time than in solution, resulting in kinetic enhancement of the rate. As the microviscosity of the micelles is much greater than in homogeneous solutions, the reactants have a lower degree of translational freedom, which controls the regioselectivity . Preorientation of the reactants at or close to the stern layer of the ionic micelle has allowed the formation of products with regioselectivity through photochemical reactions.…”

Oxidation of benzaldehyde in films by Oxo-Cr(V) salen derivatives at solid/liquid interface

“…It is well established that, in many cases, rates and pathways of a number of chemical reactions can be altered by performing the reaction either in pure bulk solvents, or at the air/water interface, at the solid/liquid interface, and in micellar media [22][23][24]. A number of studies of interaction of macromolecules with metal ions at solid/solution interfaces have been reported recently [25][26][27][28].…”