How Many Structural Isomers are Possible for Heptane

How Many Structural Isomers are Possible for Heptane

Edited By Team Careers360 | Updated on Apr 20, 2023 05:21 PM IST

Introduction

Heptane has 9 different structural isomers. Structural isomers are compounds with the same elemental composition but distinct bonding arrangements. These isomers are also referred to as constitutional isomers in IUPAC nomenclature. The term "metamer" used to be used for this concept.

Structural equivalence

The requirement for distinct bonding applies to complex bonds too, such as in aromatic compounds like benzene. For two molecules to be considered structural isomers, each atom in molecule A must correspond to an atom in molecule B of the same element and same bonding. In certain cases, the atoms must also have the same isotope. If the structure of two molecules is the same, they are structural isomers (or structural isotopomers if isotopes are considered).

Structural symmetry and equivalent atoms

A molecule's structural symmetry refers to the atom permutation that preserves its structure. If a symmetry operation connects two atoms, they're considered structurally equivalent.

Examples:

  • Methane: all four hydrogens are structurally equivalent due to any permutation maintaining bonds.

  • Ethane: all six hydrogens are equivalent due to swapping two atoms or swapping two carbons and each hydrogen in one methyl group with a different hydrogen.

  • Propane: not all hydrogens are equivalent, but the 6 linked to the first and third carbons and the 2 attached to the middle carbon are equivalent.

Similar applies to other compounds like cyclopentane, allene, 2-butyne, hexamethylenetetramine, prismane, cubane, dodecahedrane, etc.

Conclusion

In the realm of chemistry, it is a noteworthy point that isomers can have distinct structures despite possessing the same chemical composition. Of the 9 isomers of heptane, each has a different arrangement of carbon atoms in their parent chain. As per IUPAC nomenclature, these isomers are named n-Heptane, 2-Methylhexane, 3-Methylhexane, 2,2-Dimethylpentane, 2,3-Dimethylpentane, 2,4-Dimethylpentane, 3,3-Dimethylpentane, 3-Ethylpentane, and 2,2,3-Trimethylbutane.

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