Question

An alkene that provides only Butanone-2 on ozonolysis is?
A. 3,4-dimethylhex-3-ene
B. 2,3-dimethylhex-2-ene
C. 3-methylhex-3-ene
D. 2,3-dimethylpent-2-ene

Answer 1

In organic chemistry, ozonolysis is a special reaction which not only breaks C-C pi bond but also breaks C-C single sigma bond as well. This cleavage is a type of oxidative cleavage with the help of ozone reaction.

Complete answer:
Ozone is a powerful oxidizing agent. In ozonolysis, ozone is used for the cleavage of alkenes which leads to the formation of alcohols, carbonyl compounds, or carboxylic acid. Ozone is a powerful oxidant.
In procedure, ozone gas is bubbled through the alkene solution at $- {78^ \circ }C$ until the solution becomes blue in color. The blue color indicates that the reaction is completed.
A simple conversion of alkenes to carbonyl compounds,
${R^1}{R^2}C = C{R^3}{R^4}\xrightarrow{{{O_3}}}{R^1}{R^2}C = O + O = C{R^3}{R^4}$
We break carbon-carbon double bonds and form a carbon-oxygen double bond on each of the carbons that are composed of alkenes originally. In the next step, we do reductive workup with the help of reducing agent which reduces the intermediate formed at the end of the ozonolysis reaction. In the oxidative workup (hydrogen peroxide) any aldehydes that have formed oxidize to carboxylic acid.
Here the first option is 3,4-dimethylhex-3-ene, ozonolysis of this will form only butan-2one. The reaction is as follows
$C{H_3}C{H_2}C(C{H_3}) = C(C{H_3})C{H_2}C{H_3}\xrightarrow{{{O_3}}}2C{H_3}C{H_2}C(C{H_3}) = O$
The compound is symmetric therefore will give only one type of product. And that is butan-2-one on ozonolysis.

**Hence the correct option is A. 3,4-dimethylhex-3-ene

Note:**
Ozonolysis of a compound having multiple double bond results in different products. Ozonolysis is used as a method for the structure determination of molecules. Analyzing these different products and then adding up those products by double bonds helps in the determination of structure of organic molecules.