Abstract

Background: Reduction is one of the major chemical processes that takes place in life and laboratory as observed in photosynthesis (carbohydrates) and addition of hydrogen atoms to unsaturated compounds (alkenes, alkynes and carbonyls) respectively. Objectives: A reaction mechanism is proposed for a new variant of “selective” reduction using sodium borohydride (NaBH₄) and iodine (I₂). Methodology: Three compounds namely; gallic acid, vanillin and caffeic acid were separately reduced by sodium borohydride in iodine and the obtained products identified. Results: The identities of the reduced products had been revealed to be 3,4,5-trihydoxycyclohexyl methanol, o-methoxy-p-methyl cyclohexan-1-ol and 1-(3, 4-dihydroxy phenyl)-2-propen-3-ol (3, 4-benzenediol-2-propen-3-ol respectively in previously documented studies. Expectedly, the first two start-up compounds had their carbonyl (-C=O) groups reduced. In addition the aromatic endocyclic double bonds (-Ar-C=C) were similarly reduced which introduced a new twist (variant) to this particular reduction hence the essence of the proposed reaction mechanism. However, the third compound had only its -C=O reduced while the double bonds (endocyclic and exocyclic) were left unreduced. Conclusion: The reaction mechanism for this variant of reduction shows that the associated electromeric and hyper-conjugation effects are resonancestabilized in the transfer of electrons and or bonds over the carbon atom positions in the gallic acid which also serves as a reference for vanillin. This reaction mechanism is given trivial appellation-Olawale reduction mechanism.

Keywords: Reduction, NaBH₄/iodine (I₂), Resonance, Electromeric, Hyper-conjugation