[Lo.Lee.Ta.]

Okay, so I was looking at the reaction of 4-phenol-3-buten-2-one with H2, Pd, and ethanol.

At STP, only the double bond on the side chain gets reduced. The ketone that is on the very end stays a ketone... It does not get reduced.


Then, I saw the reaction of propiophenone with H2/Pd at STP. They said it would turn into propylbenzene.
For this reaction, the ketone's double bond to O was reduced to only a C with 2 hydrogens bonded to it.
They noted that this reaction ONLY reduces the carbonyl because it is an aryl alkyl ketone.


Now, I used to think that "aryl" just meant that there was an aromatic ring that had some random R group attached to it.
But when they say it has to be an "aryl ketone," does this mean that the ketone must be DIRECTLY attached to the aromatic ring?


I was under the assumption that the 4-phenyl-3-buten-2-one was also an aryl ketone, which would mean that the carbonyl SHOULD also have been reduced.
But it wasn't...

So would you please clarify the difference between an aryl ketone and an aromatic ring containing a ketone?

Thanks SO much!

[discodermolide]

Your compound is

 That is a carbon chain with a phenyl substituent,
Propiophenone is

 That is an aryl ketone, an aromatic ring with a carbonyl substituent.
Aryl is a generic name for aromatic rings. So an aryl ketone is a benzene ring with a ketone hanging off as a substituent. Like propiophenone, or acetophenone.

[Lo.Lee.Ta.]

Thanks for drawing it out!

For the first molecule, the double bond makes the carbon chain the parent chain, right?
I see how that would be would not be an aryl ketone.


For the 2nd molecule, the benzene is the parent chain. So it is an aryl ketone.

Even if (for the 2nd molecule) the ketone was 1 or 2 carbons away from the benzene, it would still be an aryl ketone, right? Because the benzene is still the parent chain?

Thanks SO much!

[discodermolide]

Even if (for the 2nd molecule) the ketone was 1 or 2 carbons away from the benzene, it would still be an aryl ketone, right? Because the benzene is still the parent chain?

Thanks SO much!
[/quote]

No it would not be an aryl ketone, to be the famous aryl ketone the C=O must be directly attached to the aromatic ring.  In the case you mentioned if it is 1 or 2 carbons away from the ring, the ring is once again a phenyl substituent on a carbon chain.