[sweetdaisy186]

Hey guys!

For our organic lab, we had to oxidize cyclododecanol to cyclododecanone. We had to use a 2.4 DNP test to see if a orange ppt would form; and it did. However, I want to know what it was testing for exactly. I don't know the full name of DNP, so I can't look it up in my text book. Would anyone happen to know the full name so that I can look it up. I can't find anything on google either, which was quite surprising. Thanks!

[Dude]

2,4-dinitrophenylhydrazine.
It reacts with aldehydes and ketones to give high boiling "derivatives", which were a means of characterizing materials prior to the advent of IR, NMR etc.

[sweetdaisy186]

oooooooooooooooooooooooo, but what do you mean when you say high boiling "derivatives?" So, if I end up with an orange ppt that means that a ketone is present correct? THANKS FOR YOUR *delete me*

[sweetdaisy186]

oooo, last question. Do we actually use something called a 2.4 DNP solution? Is that what the solution is called? Thanks again!

[Dude]

Yes, a precipitate indicates that either an aldehyde or ketone is present.  The DNP reacts to form an imine (if I remember correctly).  Prior to modern techniques, this was the preferred technique to confirm carbonyl structures.  For example, if a precipitate with a melting point of 150 C was formed, then this would be used as evidence that it was a 7 carbon linear aldehyde as opposed to an 8 carbon linear aldehyde which might have a melting point of 160 C(melting point # was made up, I don't know the actual values but there are extensive tables of data).  The DNP solution is probably just the DNP in a strong acid solution, which promotes the reaction.  The term derivative just means that the new imine material was derived from the original carbonyl material.  There are other materials that react similarly (ie hydroxylamine).  I was in error about high boiling, I meant to indicate high melting point derivatives since they are generally solids.

[sweetdaisy186]

oooooooo, okay! I understand now! Thanks a lot!

[movies]

Just one thing, the functional group of the derivative is called a hydrazone.  An imine is just like a carbonyl, but with nitrogen instead of oxygen and either an H or an alkyl group occupying the third bond from N.  So, a hydrazone is kind of like a special imine because the third bond goes to a nitrogen.

Also, the derivative you get from reacting a carbonyl compound with hydroxylamine is called an oxime, another kind of special imine.