• Question: how do you make a double bond

    Asked by Ifeoluwa.A to Anne, Arthur, Rose, Ruhina, Thomas on 16 Jun 2015.
    • Photo: Rose Simnett

      Rose Simnett answered on 16 Jun 2015:

      That depends on what you’re starting from. You can make a double bond from an alcohol by dehydration. Or from a carbonyl (a double bond between a carbon and an oxygen) by a wittig reaction. You can even make a new double bond from two existing double bonds by a metathesis reaction.

    • Photo: Ruhina Miller

      Ruhina Miller answered on 19 Jun 2015:

      In addition to Rose’s points – which are all very good/useful reactions, if you are looking to make an alkene double bond specifically you can:
      – Start with an alkyne and use a specific catalyst so you have cis- or trans- directionality depending on which you want
      – Dehydrogenation at high temperatures with a catalyst, but you end up with a mixture of products and sometimes more than one double bond in the molecule
      – Eliminate alkyl halides (as well as alcohols)

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