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Question
Which of the following reagents can be used to oxidise primary alcohols to aldehydes?
(i) \[\ce{CrO3}\] in anhydrous medium.
(ii) \[\ce{KMnO4}\] in acidic medium.
(iii) Pyridinium chlorochromate.
(iv) Heat in the presence of Cu at 573 K.
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Solution
(i) \[\ce{CrO3}\] in anhydrous medium.
(iii) Pyridinium chlorochromate.
(iv) Heat in the presence of Cu at 573 K.
Explanation:
Strong oxidising agents such as acidified potassium permanganate are used for getting carboxylic acids from alcohols directly. \[\ce{CrO3}\] in anhydrous medium is used as the oxidising agent for the isolation of aldehydes.
\[\ce{RCH2OH ->[CrO3] RCHO}\]
A better reagent for the oxidation of primary alcohols to aldehydes in good yield is pyridinium chlorochromate (PCC), a complex for chromium trioxide with pyridine and HCl.
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