aroma princess
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prepration of 1,6-dibromohexane
Dear all... I am a newbie here...I am trying to synthesize 1,6-dibromohexane
using 1,6-hexanediol and hydrobormic acid (48%). The procedure I am following is,
1) Charge 1 mol 1,6-hexanediol to reactor followed by 8 equivalents of aq. HBr (48%) and heating the mass to reflux for 4 Hr.
2)Cool the mass to RT ,extract with benzene wash benzene layer with aq.NaOH followed by aq.HCl and distill off benzene on Rotavap. The product
obtained shows 95% purity on GC (area%) is it 1,6-dibromohexane?
I have plenty of aq HBr lying at my end so im not planning to use any other reagents for that. Can somebody guide me....
please
Thanks for reading
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Nicodem
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Thread Moved
25-8-2014 at 21:26 |
blogfast25
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Compare peak position on GC with a certified sample of 1,6-dibromo hexane.
Determine BP, MP and density of your product, compare to lit values.
Take IR spectrum and compare to database spectrum of 1,6-dibromo hexane.
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Paddywhacker
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Quote: Originally posted by aroma princess  | Dear all... I am a newbie here...I am trying to synthesize 1,6-dibromohexane
using 1,6-hexanediol and hydrobormic acid (48%). The procedure I am following is,
1) Charge 1 mol 1,6-hexanediol to reactor followed by 8 equivalents of aq. HBr (48%) and heating the mass to reflux for 4 Hr.
2)Cool the mass to RT ,extract with benzene wash benzene layer with aq.NaOH followed by aq.HCl and distill off benzene on Rotavap. The product
obtained shows 95% purity on GC (area%) is it 1,6-dibromohexane?
I have plenty of aq HBr lying at my end so im not planning to use any other reagents for that. Can somebody guide me....
please
Thanks for reading |
If that is all of the information that you have then the answer is "not necessarily", as it might be unchanged starting material.
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aroma princess
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Dear Blogfast,
I have taken IR and mass spectrum but its kinda confusing...the spectrum matches with 1,5 dibormohexane instead of 1,6 dibromohexane and it seems
unlikely that i will end up with 1,5-dibromohexane when i am using 1,6-hexanediol as starting material.
thanks for reading guys..
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kavu
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Well the IR and MS are doomed to be very similar. You really need to have a 1H and 13C NMRs done on the sample. 1H NMR is always the first thing you
check once you have a crude product. Also it would be highly advisable to run a fractional distillation or a column on the crude product as it's most
likely contaminated with at least some monobromination product and/or diol. What literature procedure did you follow?
[Edited on 27-8-2014 by kavu]
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smaerd
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1,5-dibromo is definitely possible. All it would take is a sigmatropic rearrangement if one of the substitution reactions went via SN1 rather then
SN2. Granted this seems highly unlikely to me, but I've heard of weirder things happening.
I'm sure you know this, but just in case. Make sure the FT-IR spectra you are comparing were run in the same conditions IE: neat, vs nujol mull,
whatever solvent. The relevant bands are probably all in the fingerprint region though which can be a scary place to be.
Please post a literature precedence, but yes an 1H-NMR would really make things easy. Or the FT-IR spectra, I might have time to take a look at it
tonight.
[Edited on 27-8-2014 by smaerd]
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unionised
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Does the product dissolve in water? (The diol does, so you can rule out the starting material)
Also, since you have GC, are you familiar with this trick?
http://en.wikipedia.org/wiki/Kovats_retention_index
where you can get retention time estimates by comparison with alkanes.
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aga
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If the products and byproducts and reagents are similar, i suppose all the IR and MS are going to be similar.
I suppose that's why so many routes to a product are worked out, just to be able tell if the product was what was expected.
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