Seite - (000046) - in Biomedical Chemistry: Current Trends and Developments

2. For each bond to more electronegative atoms, such as oxygen atoms, count as + 3. Bonds between carbon atoms do not affect the oxidation state, unlike other elements. Figure 1.1.6: Compounds with the oxidation state of the highlighted carbon indicated below each structure. In order: methane, ethane, methanol, ethyl phosphate, formaldehyde, (R)-1- aminoethane-1-thiol, 1,1-dichloroethan-1-ol, acetic acid and carbamic acid. The simplest redox reaction in a biological system is the oxidation of an alcohol to a carbonyl compound. In a laboratory, a metal in a high oxidation state is usually used as oxidant, where it attaches to the oxygen of the alcohol then acts as a leaving group with an E2-like mechanism (Scheme 1.1.31). Scheme 1.1.31: General mechanism for the oxidation of an alcohol to a carbonyl compound with a metal or its complex (M). Note that the M leaves in a lower oxidation state. In the case of an aldehyde, the carbonyl group may be oxidized to carboxyl by nucleophilic attack of water generating a hydrated aldehyde, in which one of the hydroxyl groups is then oxidized to carbonyl yielding the carboxyl group. In biological systems however, the majority of the hydroxyl/carbonyl redox reactions involve the coenzyme NAD+ (oxidized nicotinamide adenine dinucleotide) or NADP+ (oxidized nicotinamide adenine dinucleotide phosphate) in lieu of a metal catalyst (Fig. 1.1.7). The