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oa South African Journal of Chemistry - Reduction of -unsaturated ketones using a Zn/NiCl system in aqueous media in the presence of anionic and cationic surfactants : research article

 

Abstract

The reduction of aromatic and aliphatic -unsaturated ketones, namely acetophenone (1) and (-)-carvone (3) with a Zn/NiCl system in HO or HO/EtOH media in the absence or presence of anionic and cationic surfactants have been investigated and have shown remarkable results. The anionic sodium dodecyl sulphate (SDS), the cationic cetyltrimethylammonium bromide (CTAB) and the non-micelle-forming didodecyldimethylammonium bromide (DDAB) surfactants were utilized. The reduction of acetophenone in HO medium gave only a low yield of 1-phenyl ethanol (2) in comparison with the yields which resulted when a HO/EtOH medium was employed. The yields increased relatively in a HO medium in the presence of cationic surfactants which showed a gradual increase at low concentrations following different patterns and sharp increases at 60°C and pH9. The reduction of (-)-carvone (3) with the same system in HO medium gave relatively higher yields than that of acetophenone. In the presence of cationic surfactants CTAB and DDAB in aqueous medium the total reduction yield increased appreciably and sometimes reached 100 % in the presence of DDAB at a concentration of 0.98 x 10-2 mol L-1 at 60°C. The effects of pH, combined metallic salts and different surfactant concentrations on the reduction of (-)-carvone have been also investigated. This paper focuses on the application of surfactants in the reduction of -enones by metal/metallic chloride/HO systems in the absence of organic solvents. This method displays regioselectivity and stereoselectivity. This method may also be considered as a contribution to the antipollution process by means of the elimination of organic solvents from the chemical process.

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/content/chem/61/1/EJC24449
2008-01-01
2016-12-06
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