Is it possible to selectively halogenate a certain position on an alkane chain, and also get a good yield?

I understand that to form such haloalkanes, taking a different substrate other than alkane (like a substituted alkane with the substituent attached at that position) would be a good choice, but is there a favourable synthesis to convert an alkane, say, n-pentane to 3-chloropentane?

Free radical bromination works well for smaller alkanes (due to its selectivity for secondary and tertiary positions) but it would not make much good out of longer ones. One could distil out the desired product after the free radical halogenation, but that doesn't seem quite effective.

P.S. The question may sound silly but only intends to know whether such synthesis is possible or not.

  • 3
    $\begingroup$ A good way of making 3-Chloropentane from n-pentane - no. As you observe, a free radical halogenation produces a mixture of products and separating out 3-Cl-pentane from 2- and 1- chloropentane is not a job anyone would undertake lightly. If you need a clean sample of 3-Cl then start from something else (e.g. pentan-3-ol) and do the functional group interconversions. $\endgroup$
    – Waylander
    Mar 3 '20 at 13:13
  • 3
    $\begingroup$ Or from pent-1-ene - allylic chlorination and then hydrogenation. $\endgroup$
    – Mithoron
    Mar 3 '20 at 22:27

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