Explanation:

To determine the number of open chain structures possible for N-Methlybutanamine that are referred to as metamers, we need to understand the concept of metamers.

Metamers:
Metamers are constitutional isomers that have the same molecular formula but differ in the position of the functional group or substituent. In this case, we are looking for metamers of N-Methlybutanamine, which means the position of the methyl group (-CH3) will change while keeping the rest of the molecule unchanged.

Structure of N-Methlybutanamine:
N-Methlybutanamine has the molecular formula C5H13N. It consists of a butane backbone (4 carbon atoms) with an amino group (-NH2) attached to one end and a methyl group (-CH3) attached to a different carbon atom.

Possible Metamers:
To determine the possible metamers, we need to consider the different positions where the methyl group (-CH3) can be attached to the butane backbone. Let's analyze each position:

1. Carbon 1: The methyl group can be attached to the first carbon atom of the butane backbone. This results in a metameric structure.

2. Carbon 2: The methyl group can be attached to the second carbon atom of the butane backbone. This results in a metameric structure.

3. Carbon 3: The methyl group can be attached to the third carbon atom of the butane backbone. This results in a metameric structure.

4. Carbon 4: The methyl group can be attached to the fourth carbon atom of the butane backbone. This results in a metameric structure.

5. Carbon 1 and 2: The methyl group can be attached to both the first and second carbon atoms of the butane backbone simultaneously. This results in a metameric structure.

6. Carbon 3 and 4: The methyl group can be attached to both the third and fourth carbon atoms of the butane backbone simultaneously. This results in a metameric structure.

Therefore, there are a total of 6 possible open chain structures for N-Methlybutanamine that are referred to as metamers.

Molecular formula of N-methyl butanamine is C₅H₁₃N. Primary, secondary and tertiary amines are different functional groups and metamerism cannot coexist with functional isomerism. Hence, we shall consider only those isomers of N-methyl butanamine which are secondary (2°) amines.