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What are the products obtained on oxidising primary, secondary and tertiary alcohols using potassium dichromate? I am reading conflicting accounts. My book says that it oxidises all three to carboxylic acids but another book and a site i visited say that primary alcohol is oxidised to carboxylic acid, secondary alcohol to ketone and there is no reaction with tertiary alcohol. Could anyone tell me which is the correct version?enter image description here

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  • $\begingroup$ I believe you've got the words oxidized and reduced mixed up, you might want to correct that. $\endgroup$ – William R. Ebenezer Apr 9 at 13:45
  • $\begingroup$ Tertiary alcohol cannot be oxidised (short of forcing conditions which blow the molecule apart) - this is why tBuOH is sometimes used as solvent $\endgroup$ – Waylander Apr 9 at 13:52
  • $\begingroup$ @Waylander my book explicitly states that acidified KMnO4 and acidified K2Cr2O7 can oxidise tertiary alcohols (I have added a photo regarding this). Is it impossible in both cases or only for potassium dichromate? $\endgroup$ – Aryan Apr 9 at 14:03
  • $\begingroup$ As I said in my comment, this represents forcing conditions that cleave C-C bonds. With control of temperature and reagent quantities, it is routinely possible to oxidise primary and secondary alcohols in the presence of tertiary alcohols. I believe this is what the online source is referring to. $\endgroup$ – Waylander Apr 9 at 14:23
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In a sense both are correct. With control of temperature and reagent quantities primary and secondary alcohols can be oxidised in the presence of tertiary alcohols. Indeed acetone and t-BuOH are both used as solvents for such reagents see Jones oxidation.

However it is also true that with concentrated reagents and elevated temperature less activated C-C and C-H bonds can be broken, further reading here. Under strongly acidic conditions tertiary alcohols undergo dehydration and the resulting alkene is oxidised by permanganate across the double bond via the diol to carbonyl compounds more here

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I have also studied the same thing that when tertiary alcohols are oxidized, no reaction takes place in the presence of sulfuric acid and Potassium Dichromate(VI). As no colour change of Potassium dichromate(VI) is seen. Which should become green if the tertiary Alcohol was oxidized.

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