2-Methylhexane
2-Methylhexane (C7H16, also known as isoheptane, ethylisobutylmethane) is an isomer of heptane. It is structurally a hexane molecule with a methyl group attached to its second carbon atom. It exists in most commercially available heptane merchandises as an impurity but is usually not considered as impurity in terms of reactions since it has very similar physical and chemical properties when compared to n-heptane (straight-chained heptane).
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