I have two compounds..

How is the first one more stable?enter image description here As I have been taught that -I effect of Chlorine dominates its +R effect but to explain this case, My teacher is saying that because of the achievement of the complete octet, chlorine donates its electrons to the carbocation(showing +R effect). If that's the case then the nucleophilic addition of alkanoyl chloride should be the slowest but experimentally proven, they show the fastest nucleophilic addition reaction by increasing the electrophilicity of the carbon atom(showing -I effect). Moreover, on treatment of alkynes with HCl, we get gem dihalides(which also shows the +R effect of chlorine).

Please help me with this because I am really confused between the -I and the +R effect of halogens.

  • $\begingroup$ Don't relate stability with reactivity. Usually more stable means less reactive, but 'usually'. Also, Octet stabilization dominates other factors $\endgroup$
    – ba-13
    May 2, 2020 at 12:40
  • $\begingroup$ chemistry.stackexchange.com/questions/43751/… $\endgroup$
    – Mithoron
    May 2, 2020 at 15:10

1 Answer 1


some people say that its because of octet completion of the carbocation and the NS reactivity that you mentioned is due to the -I effect of chlorine which makes it the most reactive and not the least reactive


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