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Author: Subject: Need help with eugenol reaction
pharmastudent
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[*] posted on 29-11-2016 at 19:45
Need help with eugenol reaction


Hi,

I have a lab tomorrow but I'm confused about the reaction and what the chemical equation will be.

We're reacting eugenol with 4-chlorobenzoyl chloride and pyridine...I know we're trying to make a eugenol derivative and I think eugenol benzoate will be formed. But I'm not sure what the chemical equation would be, or really understand the mechanism.

Can anyone help? :)

[Edited on 30-11-2016 by pharmastudent]
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JnPS
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[*] posted on 29-11-2016 at 20:34


Yup, pretty sure eugenol 4-chlorobenzoate will be formed

Pyridine just serves as a base to pull the proton off the hydroxyl group on eugenol, forming the alkoxide ion which will then attack the electrophilic carbonyl carbon on the 4-chlorobenzoyl chloride forming a tetrahedral intermediate. The chlorine will then leave when the electrons on the original carbonyl carbon come back down to reform the C-O double bond.

I attached a picture of the overall reaction. Let me know if you need a diagram showing the mechanism in addition to me writing it out in words



[Edited on 30-11-2016 by JnPS]

Eugneol_BenzoylChloride .jpg - 10kB
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DraconicAcid
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[*] posted on 29-11-2016 at 20:38


It's not going to be eugenyl benzoate unless the reaction is with benzoyl chloride. Eugenol is an alcohol (a phenol, IIRC, but still an alcohol). Alcohols react with acyl chlorides to give esters. You should be able to find the general mechanism in your text, and come up with the specific one for your set of compounds.



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pharmastudent
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[*] posted on 29-11-2016 at 20:39


Quote: Originally posted by JnPS  
Yup, pretty sure eugenol 4-chlorobenzoate will be formed

Pyridine just serves as a base to pull the proton off the hydroxyl group on eugenol, forming the alkoxide ion which will then attack the electrophilic carbonyl carbon on the 4-chlorobenzoyl chloride forming a tetrahedral intermediate. The chlorine will then leave when the electrons on the original carbonyl carbon come back down to reform the C-O double bond.

I attached a picture of the overall reaction. Let me know if you need a diagram showing the mechanism in addition to me writing it out in words



[Edited on 30-11-2016 by JnPS]


Thank you so much! :)
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JnPS
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[*] posted on 29-11-2016 at 20:40


@Draconic Acid, Damn it I thought I had this one, so my lovely drawn picture is wrong?
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pharmastudent
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[*] posted on 29-11-2016 at 20:40


Quote: Originally posted by DraconicAcid  
It's not going to be eugenyl benzoate unless the reaction is with benzoyl chloride. Eugenol is an alcohol (a phenol, IIRC, but still an alcohol). Alcohols react with acyl chlorides to give esters. You should be able to find the general mechanism in your text, and come up with the specific one for your set of compounds.


Thank you!
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DraconicAcid
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[*] posted on 29-11-2016 at 20:46


Quote: Originally posted by JnPS  
@Draconic Acid, Damn it I thought I had this one, so my lovely drawn picture is wrong?


No, it's correct. I just wanted to guide Pharmastudent to the right answer instead of giving it to him.




Please remember: "Filtrate" is not a verb.
Write up your lab reports the way your instructor wants them, not the way your ex-instructor wants them.
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JnPS
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[*] posted on 29-11-2016 at 20:51


Ahh........., true.........guess I got overexcited, haven't been able to do any organic in a while
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[*] posted on 29-11-2016 at 20:53


Thank you guys...I was on the right track but I wasn't 100% sure tbh, now its all fallen into place :)
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[*] posted on 29-11-2016 at 21:37


Pyridine is more than a base here. It catalyzes the nucleophilic acyl substitution. I'm having trouble uploading the file, but google "Lies My Sophomore Organic Professor Told Me" "Christopher R Jamison" and "Princeton" and you should find a helpful PDF. The first third of it discusses the analogous acylation with dimethylaminopyridine (DMAP).

Pyridine is more nucleophilic than phenol, so Pyr first attacks the acyl chloride to displace Cl- and form an intermediate [acyl pyridinium]+[Cl]- ion pair. This ion pair is setup to assist the phenol in the subsequent nucleophilic attack: a concerted deprotonation/substitution. In other words, Cl- is the base. Not what you'd expect on the basis of pKa, but it agrees with computations and experiment. Pretty cool, yeah?




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[*] posted on 29-11-2016 at 21:47


@DDTea is this the link you're talking about?
http://www.princeton.edu/chemistry/macmillan/group-meetings/...

That is pretty cool! Why do you think they keep teaching the old mechanism then? (I'm definitely bringing this up to my organic prof XD)
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30-11-2016 at 00:12
NitratedKittens
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[*] posted on 30-11-2016 at 00:18


Quote: Originally posted by JnPS  
Ahh........., true.........guess I got overexcited, haven't been able to do any organic in a while


I know how you feel, I'm on an A-level chem course just waiting for organic chemistry to come around.




Basket of kittens for you ........BOOM
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