Positional isomerism differs in what aspect?

Positional isomerism specifically refers to isomers that differ in the position of a functional group or substituent within the same molecular framework. This type of isomerism arises when a particular structural component, such as a functional group, is attached at different locations on a carbon chain.

For example, in the case of butanol, the functional group (–OH) can be situated at either the first or the second carbon of a four-carbon chain, resulting in different isomers: 1-butanol and 2-butanol. Although the molecular formula remains the same, the specific positions of the functional groups lead to distinct compounds with varying physical and chemical properties.

The other aspects mentioned are not the focus of positional isomerism. While the type of chemical bonds and the arrangement of atoms are important in chemistry, they do not capture the essence of positional isomerism, which is fundamentally about the location of functional groups. Likewise, the overall molecular weight is constant in positional isomers due to the same molecular formula, making it irrelevant to the definition of this type of isomerism.