Question:

An alkene X on ozonolysis gives a mixture of Propan-2-one and methanal. What is X?

Updated On: Apr 11, 2025
  • Propene

  • 2-Methylpropene

  • 2-Methylbut-1-ene

  • 2-Methylbut-2-ene

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The Correct Option is B

Solution and Explanation

To solve the problem, we need to determine which alkene (X) gives a mixture of Propan-2-one (acetone) and Methanal (formaldehyde) upon ozonolysis.

1. Understanding Ozonolysis:
Ozonolysis cleaves the double bond in alkenes and forms carbonyl compounds (aldehydes or ketones) at the positions where the double bond was present.

2. Analyze the products:
- Propan-2-one: $CH_3COCH_3$ (a ketone with 3 carbon atoms)
- Methanal: $HCHO$ (an aldehyde with 1 carbon atom)

3. Work backwards to deduce the structure of X:
To get these two products, the double bond must be between a carbon with two methyl groups (to give acetone) and a terminal CH₂ group (to give methanal).

4. Structure of X:
The correct structure is that of 2-Methylpropene ($CH_2=C(CH_3)_2$)
Upon ozonolysis:
$CH_2=C(CH_3)_2 \rightarrow CH_3COCH_3$ (Propan-2-one) + $HCHO$ (Methanal)

Final Answer:
The correct alkene X is 2-Methylpropene.

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Concepts Used:

Alkenes

Alkenes

In organic chemistry, an alkene is a hydrocarbon containing a carbon-carbon double bond.[1]

Alkene is often used as synonym of olefin, that is, any hydrocarbon containing one or more double bonds.

Read More: Ozonolysis

IUPAC Nomenclature of Alkenes

  1. An alkene or cycloalkene is indicated by the suffix (ending) ene.
  2. For the root name, the longest chain must include both carbon atoms of the double bond.
  3. The root chain must be numbered beginning at the end closest to a double bond carbon atom. If the double bond is in the chain's centre, the nearest substituent rule is used to determine where the numbering begins.
  4. If the compound contains more than one double bond, it is named with a diene, triene, or equivalent prefix indicating the number of double bonds, and each double bond is assigned a locator number.

Read More: Unsaturated Hydrocarbon