According to HSAB (hard-soft acid-base) concept, a soft nucleophile preferentially reacts with soft electrophile and a hard nucleophile with a hard electrophile.

Since $\ce {R2CuLi}$ is a soft nucleophile it should react with ketones or aldehydes rather than acyl chlorides since acyl chloride should have higher positive charge density due to combined effect of chloride and oxygen.

I still don't understand HSAB completely as I don't know much about concept of orbitals. But I think acyl halides should have higher positive charge density at the carbonyl carbon.

  • $\begingroup$ You are making a mistake in applying HSAB. You have to compare the hardness and softness of the site of nucleophilic attack. Does it make sense now? $\endgroup$ – YUSUF HASAN Jan 2 at 12:34
  • $\begingroup$ Here site of nucleophilic attack is the carbon attached with oxygen. Isn't the partial positive charge on the acyl carbon more than partial positive charge on carbonyl of ketone? Shouldn't then hardness of RCOCl>RCOR? Please reply to correct me. $\endgroup$ – user215736 Jan 2 at 12:42
  • 1
    $\begingroup$ HSAB is a concept, not a law. Use it with discretion. $\endgroup$ – user55119 Jan 2 at 21:09

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