Oxidation of Alkenes!

[Zishi]

Hello. I'm a bit confused on one thing, that when we oxidize an alkene like propene we first get a secondary alcohol, and then on further heating we can get an aldehyde and then an acid. And for 2-methyl-prop-1-ene, firstly we get a tertiary alcohol, and then a ketone. Just wanted to ask that ain't primary alcohols oxidized to aldehydes, and secondary alcohols oxidised to ketones? Please explain it fully! =s

 

[beacon_of_light]

Okey! that is easy. you need to know some rules. See the attachment!

These are the two rules. When the C double bond is bonded to two alkyl groups, you get a ketone. when it is bonded to an alkyl group and a hydrogen atom, you get an aldehyde. Propene has an alkyl group and a hydrogen atom so you'll get an aldehyde while 2-methyl-prop-1-ene has 2 methyl groups on the same carbon(double bonded) atom which finally cleavages to give ketone!

And a simple rule is that a carbon atom attached to two hydrogen atoms will give carbon dioxide and water on oxidation

hope that helps

 

[Zishi]

Well, I know these rules but I'm only asking that ain't primary alcohols oxidised to aldehydes and secondary alcohols oxidised to ketones, OR THIS rule doesn't apply when oxidising alkenes? Thanks btw. =)

 

[beacon_of_light]

I just don't get what rules you're talking about ...The oxidation rules remain the same whether it is an aldehyde, a ketone or an alkene.

 

[Zishi]

See the attachment.

 

[soumayya]

Hello. I'm a bit confused on one thing, that when we oxidize an alkene like propene we first get a secondary alcohol, and then on further heating we can get an aldehyde and then an acid. And for 2-methyl-prop-1-ene, firstly we get a tertiary alcohol, and then a ketone. Just wanted to ask that ain't primary alcohols oxidized to aldehydes, and secondary alcohols oxidised to ketones? Please explain it fully! =s

When we oxidise alkenes, we 1st obtain a diol, then the molecule breaks up at the place where the double bond was situated...further oxidation follows as normal...

 

[MW24595]

Hmm...I'm pretty sure it has to do with the conditions. If it's in the cold, then you get a di-ol and the reaction stops there.
It it's warm, then you get an aldehyde or a ketone depending on the groups attached to the carbon atom with the double bond. (Aldehyde for 1 H and 1 R, Ketone for 2 R groups attached.) Also, you must know, that only primary and secondary alcohols are oxidised, (Primary alcohols into aldehydes, Secondary alcohols into Ketones). Tertiary alcohols do not get oxidized at all! Hope this helps.