a level chem question- organic

so_soon

which compounds are able to react with concentrated sulphuric acid give a product that will declorise acidic potassium manganate (VII)?
the answer is these two: (CH3)3OH and CH3CH2CH(OH)CH3. so this is a tertiary alcohol and a secondary alcohol... but what will the products be when they react with conc. sulphuric acid which will react with KMnO4...thats what i dont get.

Gives alkenes. Alkenes then react with acidified Manganate to give di-ols, hence the colour change from purple to colourless :smile:

Reply 2

OP

thanks!

Reply 3

so_soon

thanks!

No probs

I'm shocked as to how I remembered this stuff after 3 years :p:

Reply 4

EierVonSatan

21

Mustard-man

Gives alkenes. Alkenes then react with acidified Manganate to give di-ols, hence the colour change from purple to colourless :smile:

Not to be too picky but the colour change is from deep purple to brown :smile:

Reply 5

EierVonSatan

Not to be too picky but the colour change is from deep purple to brown :smile:

Nah, it's purple to colourless when the Manganate is in acidic conditions, which is the condition I stated. It's something else when it's in alkaline conditions, which is probably what you are referring to.

Edit: yeah, I was right. See chemguide :smile:

Reply 6

OP

heres another similar one: compund x on reaction with hot concentrated sulphuric acid gave a mixture of three alkenes.

a- butan-2-ol
b- propan-2-ol
c- 2-methylbutan-2-ol
d- 2-methylpropan-2-ol

according to the mark scheme, the answer is a, but how in the world was i supposed to figure that out?

Reply 7

so_soon

heres another similar one: compund x on reaction with hot concentrated sulphuric acid gave a mixture of three alkenes.

a- butan-2-ol
b- propan-2-ol
c- 2-methylbutan-2-ol
d- 2-methylpropan-2-ol

according to the mark scheme, the answer is a, but how in the world was i supposed to figure that out?

Well, draw the structure of each alcohol, then draw the possible resulting products of each one. You will find that butan-2-ol can give three alkene structures, two of which are cis and trans geometric isomers.

Reply 8

OP

ok but which bonds are supposed to be breaking/where does it attack?

Reply 9