KCET 2026 Chemistry Solved Paper

Concept:A primary alcohol can be selectively oxidised to an aldehyde using a mild oxidising agent.Explanation:$R-\mathrm{CH}_{2}\mathrm{OH}$ is a primary alcohol.To get $R-\mathrm{CHO}$, we must oxidise only up to the aldehyde stage without further oxidation to the carboxylic acid.PCC (Pyridinium Chlorochromate) is a mild oxidising agent that performs this conversion efficiently.The reaction is:$$R-\mathrm{CH}_{2}\mathrm{OH} \xrightarrow{\mathrm{PCC}} R-\mathrm{CHO}$$Alkaline $\mathrm{KMnO}_{4}$ is a strong oxidising agent and oxidises primary alcohols all the way to carboxylic acids.$$\mathrm{RCH}_{2}\mathrm{OH} \xrightarrow{\text{alkaline }\mathrm{KMnO}_{4}} R-\mathrm{COOH}$$LiAlH$_4$ and $\mathrm{Na}/\mathrm{C}_{2}\mathrm{H}_{5}\mathrm{OH}$ are reducing agents, so they cannot carry out this oxidation.Hence, the correct reagent is PCC.Answer:Option D: PCC (Pyridinium Chlorochromate)