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Topic: THF ring opening  (Read 15317 times)

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Offline Archer

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THF ring opening
« on: August 10, 2013, 09:40:47 AM »
Hi All,

Just a quick question, out of general interest really, has anyone ever seen THF react with HCl to form 4-chlorobutanol?

I am doing a reaction with sodium nitrite and Conc. HClaq in THF at 20°C and the GCMS of the reaction mixture shows a small but significant peak which gives a NIST search of 4-chlorobutanol. I have no doubts about it as the MS matches and the isotope ratio of the molecular ion is as predicted.

I have never seen this before with THF so I was wondering whether it was due to the presence of nitrous acid or if anyone else had seen this type of ring opening with strong aqueous acid.

Best wishes

Archer
“ I love him. He's hops. He's barley. He's protein. He's a meal. ”

Denis Leary.

Offline rucik5

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Re: THF ring opening
« Reply #1 on: August 10, 2013, 04:14:28 PM »
Hi,
it did happen to me. Once a very long time ago during my Master's project, and once more relatively recently. I was deprotecting an acetal with excess aqueous HCl in THF. I don't remember the exact conditions (pretty sure it was room temp/overnight though) but I saw a lot of the chloro-alcohol being formed. 100% sure; from the NMR.
I can dig out my old NMR and the exact procedure if you want.

Maybe you'll find this interesting:

http://www.orgsyn.org/orgsyn/pdfs/CV2P0571.pdf

« Last Edit: August 10, 2013, 04:24:47 PM by rucik5 »

Offline Archer

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Re: THF ring opening
« Reply #2 on: August 10, 2013, 04:38:28 PM »
Thanks, no need for the conditions and NMR, I was just interested to see if it was the HCl alone.

Thanks for the link! Always something new to discover in organic chemistry :)
“ I love him. He's hops. He's barley. He's protein. He's a meal. ”

Denis Leary.

Offline opsomath

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Re: THF ring opening
« Reply #3 on: August 13, 2013, 12:53:53 PM »
Sounds like y'all have this one under control, but I was going to say that it is well known that Lewis acids cause a (sometimes dangerously exothermic) polymerization of THF. Very stable to base, not so much to acid.

Offline Babcock_Hall

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Re: THF ring opening
« Reply #4 on: August 13, 2013, 04:00:22 PM »
I don't have any direct experience.  The closest reaction to the one in which you are interested is one in which TMSI reacts with THF to make the silyl derivative iodobutanol.  One of the authors might have been Michael Jung.  It has been some time since I looked at this paper, and I may have something wrong, but if it is useful to you, I'll leaf through my photocopies.

Offline Archer

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Re: THF ring opening
« Reply #5 on: August 13, 2013, 06:00:59 PM »
Thanks for the offer, it is just a curious side reaction of the synthesis I am doing. It doesn't appear to interfere with the reaction or isolation of the product.

I was thinking about warming the reaction to reduce the 48 hour wait at room temp.

From the sounds of it this may be a bad idea! Will just have to exercise patients! Only two more substrates to do so better go with slow but sure rather than fast and potentially dangerous.
“ I love him. He's hops. He's barley. He's protein. He's a meal. ”

Denis Leary.

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