To determine the total number of chiral compounds, we must identify every possible monochlorinated product and check for the presence of chiral centers (a carbon atom bonded to four different groups).

The Structure of 2-Methylbutane

2-methylbutane consists of four types of chemically distinct hydrogen atoms. Substituting one chlorine atom at each of these positions yields the following results:

1. Substitution at the C1 position

Substituting a hydrogen on one of the two equivalent methyl groups at the second carbon results in 1-chloro-2-methylbutane. In this molecule, the second carbon (C2) becomes a chiral center because it is attached to four different groups: a hydrogen atom, a methyl group, a chloromethyl group, and an ethyl group. Because it contains a chiral center, this product exists as a pair of enantiomers (the 'd' and 'l' forms).

Count: 2 chiral compounds

2. Substitution at the C2 position

Substituting the hydrogen on the tertiary carbon results in 2-chloro-2-methylbutane. In this case, the second carbon is attached to two identical methyl groups. Since it does not have four different groups attached, the molecule is achiral.

Count: 0 chiral compounds

3. Substitution at the C3 position

Substituting a hydrogen on the secondary carbon results in 2-chloro-3-methylbutane. Here, the third carbon (C3) becomes a chiral center because it is bonded to a hydrogen atom, a chlorine atom, a methyl group, and an isopropyl group. This results in another pair of enantiomers.

Count: 2 chiral compounds

4. Substitution at the C4 position

Substituting a hydrogen on the terminal methyl group of the ethyl chain results in 1-chloro-3-methylbutane. This molecule does not possess any carbon atom bonded to four different groups, making it an achiral compound.

Count: 0 chiral compounds

By adding the chiral products from each possible substitution site, we get 2 (from C1) + 2 (from C3), resulting in a total of 4 chiral compounds.