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This is a question from my book, as stated in the title:

How will you convert benzaldehyde to benzophenone in no more than two steps?

I can do it in three steps - first using $\ce{PhMgBr}$ on benzaldehyde to get $\ce{Ph_2CH(OMgBr)}$ (sorry for this symbolic mess, I don't know how to format organic synthesis) followed by hydrolysis to $\ce{Ph_2CHOH}$ which is oxidised to $\ce{Ph_2CO}$.

I tried thinking of other ways, but really couldn't find anything. Hints would be appreciated. Thanks!

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    $\begingroup$ Hydrolysis is generally done one pot as a follow-up to the Grignard reaction. It's not usually considered a separate step. $\endgroup$
    – Zhe
    May 9, 2022 at 16:49
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    $\begingroup$ I agree with @Zhe $\endgroup$
    – Waylander
    May 9, 2022 at 17:19
  • $\begingroup$ @Zhe: I thought of that, but like still does there exist some synthesis without this "follow-up" thing? $\endgroup$ May 10, 2022 at 0:34
  • $\begingroup$ Pretty much all reactions need some kind of follow-up to remove excess reagents/side product and isolate the desired product $\endgroup$
    – Waylander
    May 10, 2022 at 7:12
  • $\begingroup$ In practice, no, because reactions are never as clean in glassware as on paper. Generally, for best results, you must use an excess of at least one reagent and reactions don't go to completion, so you'll need to follow-up the reaction with isolation and purification of the desired product. $\endgroup$
    – Zhe
    May 10, 2022 at 13:42

1 Answer 1

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I could give you a satisfactory answer, but I don't say that this is the best method.

  1. Conversion of benzaldehyde to benzoyl chloride:
    You can achieve this by adding $\ce{Cl2}$ or $\ce{SO2Cl2}$ (or other suitable chlorinating agents) to benzaldehyde. For more details refer this.
  2. By Friedel-Crafts acylation:
    Reaction between benzene and the above obtained benzoyl chloride in presence of Lewis acids like $\ce{AlCl3}$ gives you benzophenone.
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