See image — IUPAC and Nomenclature Chemistry Question

💡 Solution & Explanation

Concept: IUPAC nomenclature of ketones where one substituent is an aryl group. Step 1: Identify the structure. The molecule shown is acetophenone: a benzene ring attached to a -C(=O)-CH3 (acetyl) group. Step 2: Identify the principal characteristic group. The carbonyl (C=O) of a ketone is the principal characteristic group, given the suffix '-one'. Step 3: Select the parent chain. The longest carbon chain containing the carbonyl carbon is two carbons: C(=O)-CH3, which is 'ethan-1-one' (ethanone). Step 4: Name the substituents. The benzene ring attached to C-1 of the ethanone chain is a 'phenyl' group. Step 5: Assign the locant. The phenyl group is on carbon 1 of ethanone (the carbonyl carbon is C-1), giving '1-phenylethan-1-one', commonly written as '1-Phenyl ethanone'. Step 6: Evaluate the options. - (a) 2-Phenyl ethanone: incorrect locant; C-2 is the methyl end, not where phenyl is attached. - (b) 1-Phenyl ethanone: correct — phenyl on C-1 of ethanone. - (c) 1-(Oxoethyl)benzene: treats benzene as parent and oxoethyl as substituent; non-standard and incorrect preferred IUPAC name. - (d) 1-(Ethyaloxo)-benzene: not a valid IUPAC name. Therefore, the correct answer is B.