In actual form, a lot many molecules are aligned differently than what appears to be the case from their chemical formulae. These are the compounds that have the same molecular formula but different molecular structure. Theoretically, all the compounds can have structural isomers. This phenomenon is also known as isomorphism. Usually, the isomers have a prefix of “iso”, “neo”, etc.
For example, Butanol [H₃C–(CH₂)₃–OH],
Methyl Propyl Ether [H₃C–(CH₂)₂–O–CH₃], and
Diethyl Ether [(H₃C–CH₂–)2O]
have the same molecular formula C₄H₁₀O but are three distinct structural isomers.
Logically, in structural isomers, the number of atoms are same but their alignment and bonds are different. Due to this difference in bond linkage, it results in different chemical properties.
For example, n-pentane, neo-pentane and iso-pentane are isomers but have different boiling points, i.e., 36 °C, 30 °C & 9.5 °C respectively. this is a fairly wide boiling point range for C₅H₁₂ Clearly, the more branched the isomer, the less opportunity there are for chain-chain interactions, and the less intermolecular interaction, the lower the boiling point. And thus even for a short-chain hydrocarbon, isomerism affects volatility.
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