# How many carbons does an alkane need to have an enantiomer?

How many carbon atoms does an alkane need before it is capable of existing in enantiomeric forms?

If we allow our substituents to be isotopes, then 2 is all that is really necessary:

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If we exclude such compounds from consideration, then cyclopropanes will give you smallest number of carbons at 5:

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As a side note, for a non-alkane, only 1 carbon is necessary:

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• If we were not confined to saturated compounds, I'd suggest 1,3-dimethyl allene. – Ivan Neretin Oct 4 '16 at 5:50
• Also, come to think of it, carbon is not necessary at all. – Ivan Neretin Oct 4 '16 at 5:59

If you are only looking for alkanes, of the form $\ce{C_nH_{2n+2}}$, with no isotopic substitution, then the most logical way is to think back to the definition of a chiral carbon. The IUPAC Gold Book writes:

The traditional name for a carbon atom that is attached to four different entities...