Which of the following reagents can be used to oxidize primary alcohols to aldehydes?

I.  CrO3 in anhydrous medium

II.  KMnO4 in acidic medium

III.  Pyridinium chlorochromate

IV.  Heat in the presence of Cu at 573K

Choose the correct option
1. (I, II, III)
2. (II, III, IV)
3. (I, III, IV)
4. (I, II, IV)

CrO3 in anhydrous medium is used to oxidise primary alcohols to aldehydes.

                     RCH2OHCrO3anhydrous RCHO

Acidic KMnO4  is a very strong oxidising agent. It oxidizes primary alcohol into a carboxylic acid.
                    RCH2OHKMnO4RCOOH

Pyridinium chlorochromate C6H5N+HClCrO3- is a very good reagent for the oxidation of primary alcohols to aldehydes.

                   RCH2OHPCC RCHO
When the vapors of primary alcohols are passed over heated copper at 573K, dehydrogenation takes place and an aldehyde is formed.

                   RCH2OH 573KCuRCHO