RC+-0 Name as Substituent R On a molecule with a higher priority functional group,C=O is oxo-and -CHO is formyl. Aldehyde priority is higher than ketone. COOH CHO 3-methyl-4-oxopentanal 3-formylbenzoic acid => Chapter 18 8 Chapter 18 8 Name as Substituent • On a molecule with a higher priority functional group, C=O is oxo- and -CHO is formyl. • Aldehyde priority is higher than ketone. CH3 C CH CH3 CH2 C H O O COOH CHO 3-methyl-4-oxopentanal 3-formylbenzoic acid =>