Answer:

The property that distinguishes between ( )2- Methylbutan- 1-ol and (-) 2- Methylbutan-1-ol is their specific rotation.

Explanation:

Specific rotation is a measure of the extent to which a substance rotates plane polarized light. It is dependent on the chemical structure of the molecule and the wavelength of light used. The specific rotation of a substance is a constant value that is independent of concentration, path length, and temperature.

( )2- Methylbutan- 1-ol and (-) 2- Methylbutan-1-ol are enantiomers, which means they are mirror images of each other and have the same physical and chemical properties except for their interaction with plane polarized light. The specific rotation of ( )2- Methylbutan- 1-ol is -10.5°, while the specific rotation of (-) 2- Methylbutan-1-ol is +10.5°. This means that when a beam of plane polarized light passes through a solution of ( )2- Methylbutan- 1-ol, it will rotate the plane of polarization to the left, while a solution of (-) 2- Methylbutan-1-ol will rotate the plane of polarization to the right.

Boiling point, relative density, and refractive index are physical properties that are dependent on the molecular weight, intermolecular forces, and density of the substance. Since ( )2- Methylbutan- 1-ol and (-) 2- Methylbutan-1-ol have the same molecular formula and structure, they have the same boiling point, relative density, and refractive index.

In conclusion, the property that differentiates between ( )2- Methylbutan- 1-ol and (-) 2- Methylbutan-1-ol is their specific rotation.

(+)2- Methylbutan- 1-ol and (-) 2- Methylbutan-1-ol have different values for boiling point.

Enantiomers differ in physical properties such as melting/ boiling point.

However, they have the same relative density, refractive index and specific rotation.

The magnitude of specific rotation is the same but their sign is opposite.

Hence the correct option is A.