chemical test for carbocation

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 ^o)
with ketone ---> turned yellow

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

Thanx :smile:

Reply 1

vinny221

with the ketone you are forming an acetal. i'm not sure how 2 alcohols would react under acid catalyst.

Reply 2

ChemistBoy

vinny221

with the ketone you are forming an acetal. i'm not sure how 2 alcohols would react under acid catalyst.

Acid catalysed dehydration to the alkene probably.

Reply 3

Cool_Engineer

Thanks guys :smile:

in terms of chemical tests... does that mean that the ketone is supposed to give the postive result? as its intermediate is gonna be the carbocation? (and i guess the yellow is the postive result)

but with alkene no carbocations involved

thanx