what's acid got to with this? got to do, go to do w/ it...

[SaintJude]

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So kaplan lists rx of secondary alcohol ---> ketone with sodium dichromate salt with sulfuric acid.

In fact, I've seen this referred to as a "well known 'chromic acid mixture' of dichromate and sulfuric acid"

What is the role of the sulfuric acid? Basically, why does the sodium dichromate have to be acidified in solution?

(anyone get the tina turner reference ? awww yeah)

 

[chiddler]

i've never heard of sodium chromate + h2so4. but i'm sure you've heard of chromic acid which is just a strong oxidizer.

so my guess is that it's just a strong oxidizer. do you have a sample reaction to verify?

 

[MedPR]

I'd guess it's a catalyst.

 

[SaintJude]

 

[chiddler]

yeah!

 

[SaintJude]

wiki says:

...this step solubilizes the chromium and allows it to be extracted into hot water. At this stage, other components of the ore such as aluminium and iron compounds, are poorly soluble. Acidification of the resulting aqueous extract with sulfuric acid or carbon dioxide affords the dichromate, which is isolated at the dihydrate by crystallization.

Not sure what this means, but this reaction could also be written as " NaCr2O7/ CO2 " then? (I ask b/c variations are common on FL)

 

[syoung]

the acid is to protonate the dicromate ion into chromic acid, and then the chromic acid is attacked by the lone pairs on O in the 2nd ROH, and follows normal mechanism to completion.
http://www2.chemistry.msu.edu/faculty/reusch/VirtTxtJml/alcohol2.htm