Organic chem question about Jones reagent...
Jones reagent is a mixture of potassium dichromate, sulfuric acid, water, and acetone that produces chromic acid in situ. It is useful for many alcohol oxidations, but explain why it can't be used to oxidize 1-pentanol to pentanal.
This is actually a fairly easy one to answer. As you stated, Jones reagent is basically chromic acid in acetone and is a very strong oxidizing agent. It can readily be used to convert secondary alcohols to ketones but primary alcohols like 1-pentanol will be converted to carboxylic acids, not aldehydes. A primary alcohol can be oxidized up one oxidation state to an aldehyde (like pentanal) with a mild oxidizer but a strong oxidizer like Jones reagent will take it up two oxidation states to the carboxylic acid (pentanoic acid in this case). If you wanted to convert 1-pentanol to pentanal, a mild oxidizing reaction like a Swern oxidation or PCC (pyridinium chlorochromate) would be a better choice.