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Topic: 1,4-dioxane treated with HBr  (Read 6235 times)

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Offline thegreatguyokay

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1,4-dioxane treated with HBr
« on: January 27, 2014, 12:52:32 AM »
Hey everyone, I have another question. What would the product be if one were to treat a 1,4-dioxane with HBr?

Offline zsinger

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Re: 1,4-dioxane treated with HBr
« Reply #1 on: January 27, 2014, 01:49:35 AM »
You tell us…….dioxane is essentially a double ether…….are ethers usually reactive?  It may protonate and deprotonate, however I doubt it.  Don't think it will make dibromo-dioxane, but i may be mistaken.
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Offline thegreatguyokay

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Re: 1,4-dioxane treated with HBr
« Reply #2 on: January 28, 2014, 11:13:20 PM »
well I think the product made would look something like this although im not really sure if its possible

2XBr-Ch2-Ch2-Br- since the oxygen is broken and replaced by Br but that's where I get confused about. Would it be two Br or one? Since we only have one Br coming from HBr would it look more like this:

2X Br-Ch2-Ch3

Offline kriggy

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Re: 1,4-dioxane treated with HBr
« Reply #3 on: January 29, 2014, 11:03:23 AM »
This might be helful for you.
http://www.wikipremed.com/03_organicmechanisms.php?mch_code=030207_090
please note that in the 2nd bracket in mechanism they have 1 more carbon than there should be.
You will probably get mixture of products

Offline PhDoc

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Re: 1,4-dioxane treated with HBr
« Reply #4 on: February 08, 2014, 03:21:19 PM »
The pKa of HBr is -9; the pKa of a protonated ether is approximately -3.6 (diethyl ether). Note pKa information can change by approximately 1 unit depending upon your source.

http://evans.harvard.edu/pdf/evans_pka_table.pdf

If you combine anhydrous HBr (hydrogen bromide, not hydrobromic acid) with dioxane, on which side of the equation will the equilibrium lay? To determine this, you simply need a complete equation wherein you identify acidic and basic components, and then perform simple calculations.

When you have a species present to "drain off" the equilibrium, then you can expect it to happen. A protonated ether is an excellent leaving group when exposed to bromide as a nucleophile.

While "wikipremed" is cute, please read this article from the Canadian Journal of Chemistry:
http://www.nrcresearchpress.com/doi/pdf/10.1139/v51-090

Ethers are readily cleaved by strong acids such as HI and HBr under anhydrous conditions. Cleavage with HI is far more rapid than with HBr.

Also, consult Advanced Organic Chemistry by Jerry March:
chemistry-chemists.com/chemister/Mechanizms/march6ed.pdf‎
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