Question

An alkene X undergoes ozonolysis and gives two compounds Y and Z of molecular formula C3H6O. Y and Z are functional isomers of each other.

i. Write the two-steps chemical equation for the conversion of X into Y and Z. [2]

ii. Write the structural formula of Y and Z. Why are they called functional isomers? [3]

iii. What happens when hydrogen gas in the presence of nickel catalyst is passed over X? [1]

iv. What is the application of ozonolysis in the organic reaction mechanism? [1] v. How can you prove chemically the compound X is unsaturated? [1]​

Answer 1

1. $(CH_{3})_{2}-C=CH-CH_{2}-CH_{3} \rightarrow ozonide\\\\ozonide+Zn \rightarrow CH_{3}-CO-CH_{3}+CH_{3}-CH_{2}-CHO$
2. Y is $CH_{3}-CO-CH_{3}$ and Z is $CH_{3}-CH_{2}-CHO$.
3. $(CH_{3})_{2}-C=CH-CH_{2}-CH_{3} +H_{2}\rightarrow (CH_{3})_{2}-CH-CH_{2}-CH_{2}-CH_{3}$
4. It is used for production of pharmaceuticals.

Explanation:

1. The given compound X is 2-methyl pent-2-ene. When it is reacted with ozone it forms an ozonide in the first step. In the second step the reductive workup it forms acetone and propanal.
2. The formulas of Y is $CH_{3}-CO-CH_{3}$ and Z is $CH_{3}-CH_{2}-CHO$.They are functional isomers as they have same molecular formula but different functional groups - ketons and aldehyde.
3. When alkenes undergo catalytic hydrogenation, they form alkanes, X will form 2 methyl petane on reaction with hydrogen gas in presence of Ni.
4. The ozonolysis is used for the industrial-scale synthesis of pharmaceuticals.
5. The unsaturation of compound X can be proved by the bromine water test. As on reaction with it, the brown colour of bromine water becomes colourless due to the formation of dibromo alkane.

   

Answer 2

Answer:

The given questions regarding alkanes and ozonolysis of alkenes can be answered as follows.

Explanation:

• The given alkene X, that is subject to ozonolysis would be 2-methyl-2-pentene. Upon exposure to ozone, an ozonide is initially formed, after which it is broken down into 2 products - acetone and propanal, both with the molecular formula C₃H₆O.
  $(CH_3)_2-C=CH-CH_2-CH_3 \rightarrow ozonide\\Ozonide+Zn \rightarrow CH_3-CO-CH_3-CH_3-CH_2-CHO\\CH_3-CO-CH_3-CH_3-CH_2-CHO \rightarrow CH_3-CO-CH_3 + CH_3-CH_2-CHO$
• Structurally, Y (acetone) can be written as $CH_3-CO-CH_3$ and Z (2-methyl-2-pentene) can be written as $CH_3-CH_2-CHO$, implying that they're functional isomers.
• Alkenes, upon catalytic hydrogenation, form alkanes. This will occur in the presence of Nickel as the catalyst.
• The process of ozonolysis is useful in the field of pharmaceutics.
• The test of unsaturation can be performed by passing a compound through Bromine water. Upon reaction, the colour of the bromine water changes from brown to colourless, indicating the formation of dibromoalkane.

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