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Topic: chemical test for carbocation  (Read 8564 times)

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engineer

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chemical test for carbocation
« on: February 23, 2006, 06:51:49 PM »
i never knew there's a test for carbocation  ???

in the lab we did the following to "test for carbocation"
we dissolved the sample in minimal methanol then add conc H2SO4 dropwise... the samples were alcohol and ketone.

alcohol ---> yellow then white then colourless   :-\
with ketone ---> turned yellow

i dont recall seeing such a chemical test. anyone know this? and what the +ve result is?

Thanx  :)

Offline arnyk

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Re:chemical test for carbocation
« Reply #1 on: February 23, 2006, 07:57:16 PM »
Alcohol + Alcohol -> Ether
Alcohol + Ketone -> Acetal

Both dehydration synthesis requiring conc. sulphuric acid.

A carbocation is an ion with a positively-charged carbon atom.
« Last Edit: February 23, 2006, 07:59:42 PM by arnyk »

Offline Alberto_Kravina

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Re:chemical test for carbocation
« Reply #2 on: February 24, 2006, 08:21:38 AM »
Quote
Alcohol + Alcohol -> Ether

Beware: An alkene could be a byproduct

R-OH + HO-R1 --H2SO4-->R-O-R1 + H2O
R-CH2OH ----H2SO4 ---> R-CH=CH2 + H2O

engineer

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Re:chemical test for carbocation
« Reply #3 on: February 24, 2006, 10:41:59 AM »
Thanks everyone  :)

in terms of chemical tests... do u know if the yellow colour formed with ketone is referred to as a positive result for this test? so any ketone under this test will form yellow? or not necessarily

thank you  :happy:

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