DAT Destroyer OChem #245 (2011 version)

[DentistDMD]

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On the solution manual, it says choice A cannot be reduced. But when 2-pentanol is treated with potassium dichromate, it becomes 2-pentanone, right? I thought ketones could be reduced by either sodium borohydride or lithium aluminum hydride? Thanks in advance.

 

[fujindesu]

Right, but what you're describing is oxidation, not reduction. so Choice A can be oxidized but not reduced

 

[OUDent88]

This problem is kinda tricky...If you oxidize choice A you do get a ketone but remember that aldehydes are very easy to oxidize (they are strong reducing agents) and ketones dont have that hydrogen so they are resistant to oxidation. Ketones would need a really strong oxidizing agent like potassium mangenate to react and potassium dichromate isnt strong enough to oxidize the ketone. So choice A would not be favorable. Since you start with an aldehyde in choice D and you know it will readily react with potassium dichromate because the presence of the hydrogen on the aldehyde makes it easy to oxidize and ketones dont have that hydrogen.

hope this helps!

 

[DentistDMD]

Please disregard this thread. I have misunderstood the question. 2-pentanol clearly cannot be reduced by sodium borohydride or lithium aluminum hydride. I initially misunderstood the problem as "which of the following choices can be oxidized and sequentially be reduced?"