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ChemistryNEET 2024Alkanes: conformations and reactions

Hydrocarbons

Given below are two statements:

Statement I: The boiling points of the three isomeric pentanes follow the order n-pentane > isopentane > neopentane.

Statement II: When branching increases, the molecule attains the shape of a sphere. This results in a smaller surface area for contact, due to which the intermolecular forces between the spherical molecules are weak, thereby lowering the boiling point.

In the light of the above statements, choose the most appropriate answer from the options given below:

  1. A.Both Statement I and Statement II are incorrect
  2. B.Statement I is correct but Statement II is incorrect
  3. C.Statement I is incorrect but Statement II is correct
  4. D.Both Statement I and Statement II are correct✓

Solution

Branching makes a molecule more compact and spherical, reducing surface contact and hence the van der Waals forces, so boiling point falls from n-pentane to isopentane to neopentane. Both statements are correct and II explains I.

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