In a set of reactions, bromoethane yielded a final product 'S'. The compound 'S' should be

Step-by-step solution

Bromoethane ( CH₃CH₂Br ) reacts with alcoholic KOH to undergo dehydrohalogenation, forming ethene ( P = CH₂=CH₂ ). Ethene reacts with Br₂/CCl₄ to undergo electrophilic addition, forming 1,2-dibromoethane ( Q = BrCH₂CH₂Br ). 1,2-dibromoethane reacts with excess KCN to undergo nucleophilic substitution, replacing both bromine atoms with cyano groups to form succinonitrile ( R = NC-CH₂CH₂-CN ). Succinonitrile undergoes acid-catalyzed hydrolysis ( H₃O⁺ ) to convert the cyano groups into carboxylic acid groups, yielding