Alexthelion_Lee
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#1
Report Thread starter 7 years ago
#1
We did an identifying organic compounds practical and there were some compounds that were positive for more than one group.
An alcohol decolourised bromine water?
A carboxylic acid decolourised bromine water?

I dont understand why they were positive for the alkene test when there are no C=C bonds...
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username1253260
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#2
Report 7 years ago
#2
It replaces the OH group via nucleophillic substitution.
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EierVonSatan
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#3
Report 7 years ago
#3
Simple chemical tests are prone to giving false positives, that's why we don't use them very often.

It's hard to say why without knowing the exact chemicals; for example if the alcohol was aromatic, like phenol, then that would react with bromine via electrophilic aromatic substitution. The carboxylic acid could react with bromine to give off HBr gas.

Or the bromine water wasn't the in the best condition to start with.
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username1253260
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#4
Report 7 years ago
#4
(Original post by EierVonSatan)
Simple chemical tests are prone to giving false positives, that's why we don't use them very often.

It's hard to say why without knowing the exact chemicals; for example if the alcohol was aromatic, like phenol, then that would react with bromine via electrophilic aromatic substitution. The carboxylic acid could react with bromine to give off HBr gas.

Or the bromine water wasn't the in the best condition to start with.
How does bromine gas react with a carboxylic acid to give off HBr?
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EierVonSatan
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#5
Report 7 years ago
#5
(Original post by n00bfi)
How does bromine gas react with a carboxylic acid to give off HBr?
The bromine is in solution, but it can do something called alpha-substitution under acidic conditions:

RCH2COOH + Br2 ---> RCHBrCOOH + HBr

It's not very effective though - but I offer it as a possibility :p:
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Pittitani
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#6
Report 3 years ago
#6
Can bromine water React with aliphatic alcohol
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