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Topic: Preparation of N-butyl bromide purpose of HCl Wash  (Read 9092 times)

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Offline GWashington1732

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Preparation of N-butyl bromide purpose of HCl Wash
« on: December 12, 2010, 06:55:04 PM »
In a lab, we prepared n-butyl bromide from n-butyl alcohol. I need to know the purpose of the HCl wash on the product. I know that the NaOH and Water washes were used to remove the leftover from the previous washes. But I can't figure out the reason for the HCl wash. I know it has something to do with the left over unreacted alcohol but I'm not sure where to go from there.   
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Offline Hybrid

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Re: Preparation of N-butyl bromide purpose of HCl Wash
« Reply #1 on: December 13, 2010, 01:29:25 AM »
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Offline GWashington1732

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Re: Preparation of N-butyl bromide purpose of HCl Wash
« Reply #2 on: December 13, 2010, 12:58:18 PM »
This makes no mention of the HCl wash. I knew that the other two washes were to remove the remaining acid, but I have no clue what the HCl wash has to do with removing the excess alcohol.
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Offline Doc Oc

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Re: Preparation of N-butyl bromide purpose of HCl Wash
« Reply #3 on: December 13, 2010, 04:20:20 PM »
What specific reaction conditions/reagents did you use to make the butyl bromide?
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Offline GWashington1732

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Re: Preparation of N-butyl bromide purpose of HCl Wash
« Reply #4 on: December 13, 2010, 04:56:20 PM »
We brought N-butyl alcohol together with HBr and H2SO4 in a reflux condenser. This was followed by a distillation.

THe distillate was then washed with 1 M HCl (for some reason)
This was followed by two  washes NaOH and HOH. (to remove excess acid)
It was then dried using anhydrous CaCl2 and Molecular seives.

The identity of the product was confirmed through chemical tests (Ceric nitrate+AgNO3, and IR and NMR Spectroscopy. 
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Offline Doc Oc

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Re: Preparation of N-butyl bromide purpose of HCl Wash
« Reply #5 on: December 13, 2010, 06:33:19 PM »
I agree, that wash doesn't seem to make any sense.  You should be able to get most of the impurities out with a base wash.
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Offline GWashington1732

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Re: Preparation of N-butyl bromide purpose of HCl Wash
« Reply #6 on: December 13, 2010, 07:20:42 PM »
The only hint he gave was that it had something to do with removing the unreacted N-Butyl Alcohol.
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Offline Hybrid

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Re: Preparation of N-butyl bromide purpose of HCl Wash
« Reply #7 on: December 14, 2010, 12:01:38 AM »
GWashington1732, as written in books i send to u he wash with H2SO4 to remove the unreacted  alcohol . i never found a method use HCl as catalyst or for wash so i give u the standard procedure with the part of sulfuric acid washing (P 190).
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Offline GWashington1732

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Re: Preparation of N-butyl bromide purpose of HCl Wash
« Reply #8 on: December 14, 2010, 12:33:13 AM »
I have found a few references to HCl being used in a wash but never any explanation as to why.
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