Question

The product of ozonolysis of an alkene is ethanal and methanal, then that alkene is
A.\[{\text{C}}{{\text{H}}_3} - {\text{C}} \equiv {\text{C}} - {\text{C}}{{\text{H}}_3}\]
B.\[{\text{C}}{{\text{H}}_3} - {\text{CH}} = {\text{CH}} - {\text{C}}{{\text{H}}_3}\]
C.\[{\text{C}}{{\text{H}}_3} - {\text{CH}} = {\text{C}}{{\text{H}}_2}\]
D.\[{\text{C}}{{\text{H}}_3} - {\text{C}} \equiv {\text{CH}}\]

Answer 1

Hint: In the above question we have been given the product of ozonolysis and we have to search for a reactant. Oxygen adds up in the unsaturation of alkenes and the total number of carbon remains same in reactant and product.

Complete step by step answer:
Ozonolysis is an organic reaction in which the ozone molecule is used for breaking the unsaturated bond and converting it into a carbonyl group.
We have been given two products that are formed by ozonolysis of an alkene. So the reactant species is an alkene that means it has a double bond in it. If we look at the above options, option A and D has triple bonds or are alkynes. Hence we can eliminate option A and D from here.
The ‘al’ function group refers to the aldehyde functional group.
The chemical formula for methanal is \[{\text{HCHO}}\]. The formula for ethanal is \[{\text{C}}{{\text{H}}_3}{\text{CHO}}\]. In ozonolysis oxygen gets added up in a double bond. Hence the number of carbon should remain constant in the product and reactant. In the two products forms have total 3 carbons, one carbon in \[{\text{HCHO}}\] and two carbon in \[{\text{C}}{{\text{H}}_3}{\text{CHO}}\]. According to this the reactant should have total tree carbon which is in option \[{\text{C}}{{\text{H}}_3} - {\text{CH}} = {\text{C}}{{\text{H}}_2}\]. The reaction occurs as follow:
\[{\text{C}}{{\text{H}}_3} - {\text{CH}} = {\text{C}}{{\text{H}}_2}\xrightarrow{{{\text{ozonolysis}}}}{\text{HCHO}} + {\text{C}}{{\text{H}}_3}{\text{CHO}}\]

Hence the correct option is C.

Note:
Ozone has a molecular formula as \[{{\text{O}}_3}\]. It is an allotrope of oxygen and is less stable than oxygen. It has formed a very thin layer on the earth’s atmosphere and most of its concentration lies in the stratosphere. It is colourless to pale blue in colour and is soluble in carbon tetrachloride.