ippie said:
(CH3)2C=CH2 + hot KMnO4 --> (CH3)2C=O + CO2
right?
then,
(CH3)2C=CH2 + O3 / Zn ---> (CH3)2C=O + ???
A. CO2
B. formaldehyde
What's the answer? Please, help!!!
KMnO4 is a strong oxidizing agent. so when formaldehyde is formed initially, it is first oxidized to formic acid. subsequently formic acid will be then oxidized into bicarbonate.
as you should know, bicarbonate equilibrates with CO2 and aqueous content of bicarbonate is very low due to its low solubility in water. thus CO2 will bubble out of the solution.
Although ozone itself is strong oxidizing agent, using Zn (Zn 2+ ion has one of the lowest reduction potential, thus Zn is a very good reducing agent) along with ozone makes the reaction very mild, meaning not as oxidizing. Thus one of the initial product of the both reaction, which is formaldehyde, will not be oxidized further.
on the side note, in order for a typical transitional metal complex oxdizing agent to oxidize the carbonyl carbon, the carbonyl compound should have the alpha hydrogen(s).
The reason for this is that, usually it is the hemiacetal form the carbonyl compound that reacts with highly oxidized metal in the oxidizing compound. The metal-oxygen ligand bonding is quite strong(plz refer to hard-soft acid base principle)so its bond will be stable. To compensate for the shift of electron density in the metal-oxygen bond, oxygen shifts the electron density from adjacent carbon, which is the carbonyl carbon in this case.
The carbonyl carbon in turn withdraws from its adjacent bonds. Usually alpha hydrogen and carbonyl carbon bond is weak enough for this process to occur. On the contrary, C-C bond is not as weak as C-H bond.
[ozonolysis]
