ORGO Oxidation Q

[flycd05]

---

Members do not see this ad.

There's a question in achiever where they give u a p-ethyltoluene reacting with K2Cr2O7/H+. The correct answer shows both the methyl and ethyl groups being oxidized into a carboxylic acid! so it looked like this HOOC--Benzene ring--COOH

Also, the carboxylic acid on the ethyl group showed only one carbon meaning when it got oxidized, one of the carbons disappeared HOW IS THIS RIGHT?

I always thought that only a methyl group on a benzene ring can be oxidized into a carboxylic acid. Can a ethyl group be oxidized into a carb acid too?? and if so, then where's the 2nd carbon on the ethyl group?

hope my wording wasn't confusing but just wanted to make sure that this isnt an error in achiever! thanks

 

[Orgodox]

Its correct, The way i learned it was as long as you have on H on that carbon next to the ring no mater how long the chain is the KcCr2O7 "burns it down" lol and leaves you with an acid on the ring

 

[klutzy1987]

There's a question in achiever where they give u a p-ethyltoluene reacting with K2Cr2O7/H+. The correct answer shows both the methyl and ethyl groups being oxidized into a carboxylic acid! so it looked like this HOOC--Benzene ring--COOH

Also, the carboxylic acid on the ethyl group showed only one carbon meaning when it got oxidized, one of the carbons disappeared HOW IS THIS RIGHT?

I always thought that only a methyl group on a benzene ring can be oxidized into a carboxylic acid. Can a ethyl group be oxidized into a carb acid too?? and if so, then where's the 2nd carbon on the ethyl group?

hope my wording wasn't confusing but just wanted to make sure that this isnt an error in achiever! thanks

Its correct. Any time benzene has a carbon group attached to it that has a hydrogen in the benzylic position, it will oxidize with CrO3 or KMnO4 etc.. and will form benzoic acid, cleaving off any additional carbons on the chain.

 

[klutzy1987]

Ugh i was beat to the punch again lol. I gotta learn to type faster.

 

[Orgodox]

Sorry kluzty lol

 

[flycd05]

ugh stupid exceptions again lol. thanks guys!

 

[wifi08]

it is correct. as long as you have excesss KMnO4 it will react with all alkanes. furthermore it creates a CAcid. even if ther is more than a metyyl group, i.e. ethyl propyl it will always make a CAcid alone attached to the ring

 

[td4azklz]

What if you are reacting the ring with, say, PCC? Will you get an aldehyde? ...I know that PCC only oxidizes primary Carbons.....right? So the answer is no?

 

[condoleezarice]

An important sidenote:

It must be HOT KMnO4 for an alkyl group off of a benzene to be oxidized into a carboxylic acid. All alkyl groups will turn into COOH. Cold KMnO4 will not react with alkyl groups, just alcohols and aldehydes I believe.

td4azklz:

I don't think anything will happen if you add PCC. PCC is a very weak oxidizing agent, and alkyl groups need very strong oxidizing agents in order to become carboxylic acids(someone check me on this, not totally sure). PCC will react with primary alcohols to become an aldehyde.

 

[klutzy1987]

Also note that a tertiary carbon will not oxidize on a benzene. There needs to be at least on H in the benzylic position.