I made a guess that the OH- group cannot do a backside attack on the carbon because the C double bond with O and the 5 carbon ring may act as steric hindrance and prevent it from forming a bond but I'm not really sure.organic chemistry reaction

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    $\begingroup$ Carbonyls undergo addition-elimination. SN2 reactions at sp2-hybridized carbons are extremely rare (I only know of one report in the literature for a contrived case), so much so that you should never propose them. $\endgroup$
    – Zhe
    Oct 19, 2020 at 14:49
  • $\begingroup$ Maybe it does. Take a look at this earlier SE Chem question, Nucleophilic attack at a carbonyl - angle of attack. $\endgroup$
    – ron
    Oct 19, 2020 at 16:05
  • $\begingroup$ when hydroxide ion attacks , there is a chance of negative electromeric effect at carbonyl group carbon atom, so backside attack is possible but backside to C double bond O $\endgroup$
    – maverick
    Oct 20, 2020 at 5:47

1 Answer 1


The substrate in this reaction is an Acyl Chloride, which is highly susceptible to nucleophilic acyl substitution, more so than other carboxylic acid derivatives, so SN2 attack (as mentioned in the comments) is highly improbable. The mechanism for this nucleophilic acyl substitution is as follows:


With equilibrium constant $K_c >> 1$ favouring the products on the right.


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