Question: How many optically active products are
obtained when the given compound is treated with ozone followed by Zn in
acetic acid?
Solution: At first look the question seems very complex.
But there is nothing like that. This question is a combination of two different
topics, one is ozonolysis and another is optical active compound. We can solve
this problem by applying simple basics of the topics. So let us start.
The given compound is an alkene (due to presence of double bonds). When
ozone (O3) reacts with alkene, it breaks the double bond and form an
intermediate compound called ozonide. This ozonide on treatment with reducing
agent gives aldehyde or ketone while on treatment with oxidizing agent it gives
carboxylic acid.
In the given question, Zn in acetic acid is used during ozonolysis which is a reducing agent. Thus the
given compound on complete ozonolysis gives:
Now the next step of question: To check whether the obtained products
are optically active or not, for this let us check their chirality.
Compounds that are optically active contain molecule that are chiral. A chiral molecule is not superimposable on its
mirror image.
Molecule 1 is not superimposable on its mirror image and therefore is chiral and optically active.
Molecule 3 is superimposible on its mirror
image and therefore is achiral and optically inactive.
Now let us check products obtained after ozonolysis.
Thus, all the obtained products during ozonolysis are achiral. Means there is no optically active compound is formed.
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