# Question #d30a7

##### 1 Answer

You find *N* by identifying the non-equivalent sets of hydrogen atoms, and *M* by considering the shapes of the molecules. There are *N* = 4 isomers and *M* = 3 fractions.

#### Explanation:

WARNING: Long answer.

**Number of Isomers N **

The structure of 2-methylbutane is

There are four different sets of equivalent hydrogens:

**1**The three H atoms on C-4**2**The two H atoms on C-3**3**The one H atom on C-2**4**The six H atoms on C-3 and the methyl substituent

So there are four possible monochloro substitution products:

**1:** 1-Chloro-3-methylpentane

**2:** 2-Chloro-3-methylpentane

**3:** 2-Chloro-2-methylpentane

**4:** 1-Chloro-2-methylpentane

**Number of fractions, M **

**3** has four groups attached to the same carbon atom.

The molecules will have a roughly spherical shape.

They will have little contact with each other and therefore small dipole-dipole and London dispersion forces.

They will have the lowest boiling point.

**2** has a chain of four atoms with groups on two different carbon atoms.

The molecules should have better contact with each other and therefore stronger dipole-dipole and London dispersion forces.

**2** will have a higher boiling point than **3**.

**1** and **4** each have a chain if five atoms with only one substituent.

The molecules should have the best contact with each other and therefore the strongest dipole-dipole and London dispersion forces.

**1** and **4** should have the highest boiling points, and they should not differ much from each other.

**Prediction**:

- The lowest boiling Fraction 1 contains
**3**. - Fraction 2 contains
**2**. - The highest boiling Fraction 3 contains
**1**and**4**.