Question

What are the products obtained after ozonolysis of the following compounds: 2,4,4-trimethylpent-2-ene; 2-methylbut-1-ene; 1-methylclohexene?

Answer 1

Ketones, and aldehydes, depending on workup......

Explanation:

`R_1R_2C=CR_3R_4stackrel(O_3)rarrR_1R_2C=O + O=CR_3R_4`.

While aldehydes are unstable with respect to oxidation, you should be able to chop up an olefin to give a series of aldehydes and ketones. If you can individually identify each oxo-compound, you could evidence the structure of the original olefin by wet chemical methods.

Answer 2

The products depend on the nature of the workup.

Reducing workup

This involves reaction with ozone, then workup with `"Zn/acetic acid"` or `("CH"_3)_2"S"`.

The process cleaves the alkene into aldehydes and/or ketones.

(a) 2,4,4-Trimethylpent-2-ene

`("CH"_3)_3"CH=C"("CH"_3)_2 → underbrace(("CH"_3)_3"CH=O")_color(red)("2,2-dimethylpropanal") + underbrace("O=C"("CH"_3)_2)_color(red)("propanone")`

(b) 2-Methylbut-1-ene

`"CH"_3"CH"_2"C"("CH"_3)"=CH"_2 → underbrace("CH"_3"CH"_2"C"("CH"_3)"=O")_color(red)("butanone") + underbrace("O=CH"_2)_color(red)("methanal")`

(c) 1-Methylcyclohexene

Oxidative workup

This involves reaction with ozone, followed usually by workup with `"H"_2"O"_2`.

The process converts any potential aldehydes into carboxylic acids.

(a) 2,4,4-Trimethylpent-2-ene

`("CH"_3)_3"CH=C"("CH"_3)_2 → underbrace(("CH"_3)_3"C(OH)=O")_color(red)("2,2-dimethylpropanoic acid") + underbrace("O=C"("CH"_3)_2)_color(red)("propanone")`

(b) 2-Methylbut-1-ene

`"CH"_3"CH"_2"C"("CH"_3)"=CH"_2 → underbrace("CH"_3"CH"_2"C"("CH"_3)"=O")_color(red)("butanone") + underbrace("O=C(OH)H")_color(red)("methanoic acid")`

(c) 1-Methylcyclohexene