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Topic: Weird organic chemistry reaction...  (Read 4279 times)

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Offline 0rion

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Weird organic chemistry reaction...
« on: October 06, 2009, 01:42:43 AM »
Hi guys,

I have a question that I have no idea how to approach, its for a formative online quiz, and I have already used my first of 3 attempts, which is was certain was the correct answer, so now I'm stumped.

The question asks you to draw the major organic product of a reaction involving

a) acetyl chloride (which is just 1-chloroethane right?)
b) CH3(CH2)2CH2OH (which is just butanol right?)
c) Pyridine (which as i understand is a hexane right with a N in place of a single carbon)

I have no idea what the reaction could be, my first guess was that the Oxygen would 'attack' the carbon containing the chlorine and form an ester, with HCl as the leaving group. But that was wrong. (making the product 1-ethoxybutane)

I've read in my textbook that Pyridine can act as a base or a nucleophile, so which part does it play in this reaction??

Any help would be greatly appreciated!

Offline 0rion

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Re: Weird organic chemistry reaction...
« Reply #1 on: October 06, 2009, 03:51:42 AM »
Dont worry, i figured it out

Lack of sleep was the problem here people... acetyl chloride = CH3COCl not CH3CH2Cl

Its pretty simple for me from there, pyridine acts as a base, zaps the H+ from the OH group, O- becomes a nucleophile, and zaps the central carbon of acetyl chloride, Cl- breaks off and bonds with HCl, end products are HCl, Butyl-Methanoate and good old pyridine :)

Thanks anyway haha

Offline DrCMS

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Re: Weird organic chemistry reaction...
« Reply #2 on: October 06, 2009, 04:49:54 AM »
c) Pyridine (which as i understand is a hexane right with a N in place of a single carbon)

No pyridine is benzene with a N in place of a CH.
I think you might of confused it with piperidine which is cyclohexane with NH in place of a CH2

Offline Dan

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Re: Weird organic chemistry reaction...
« Reply #3 on: October 06, 2009, 07:45:43 AM »
pyridine acts as a base, zaps the H+ from the OH group

Pyridine acts as a base, but not at this stage. Butanol is not acidic enough to be significantly deprotonated by pyridine (pKa of the pyridinium ion is ~5, pKa of butanol is ~16). Acyl chlorides will still react very rapidly with alcohols in the absence of a base.
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Offline DrCMS

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Re: Weird organic chemistry reaction...
« Reply #4 on: October 06, 2009, 08:47:26 AM »
Its pretty simple for me from there, pyridine acts as a base, zaps the H+ from the OH group, O- becomes a nucleophile, and zaps the central carbon of acetyl chloride, Cl- breaks off and bonds with HCl, end products are HCl, Butyl-Methanoate and good old pyridine :)

Wrong mechanism wrong product, as Dan said acid chlorides are very reactive and the reaction is:
acid chloride + alcohol  :rarrow: ester + HCl

In this case the ester is butyl acetate or butylethanoate if you want.

Pyridine is used to mop up the HCl to give pyridine hydrochloride which can then be washed out of the finished product.

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