1
$\begingroup$

Is it the double bond attacking the $\ce{X+}$ ion or the other way around?

Also, does it form a cyclic transition state if it isn't bromine or chlorine?

Eg. cyclohexene $+ \,\ce{Cl+ ->}$ cyclic transition state

But would the same thing happen if I put any other electrophile?

$\endgroup$
0
$\begingroup$

These kind of reactions are called Electrophilic addition reactions. These are usually given by alkenes and alkynes. In your example, the electrophile is $\ce{Cl+}$. The alkene will act as a source of π electrons and will donate it to the electrophile which is in need of electrons. So, alkene is called as nucleophile in this reaction.

Is it the double bond attacking the X+ ion or the other way around?

It depends on how you look at it. We can say that alkene polarizes the $\ce{Cl-Cl}$ bond by pushing electrons into the anti-bonding molecular orbital. This weakens the bond and hence electrophile is getting generated. In the next step,the electrophile attacks the double bond [or double bond attacks the electrophile] and hence electrophile gets added across across the double bond

Why does the 3-membered cyclic transition state form?

The cyclic transition state is just a temporary relief for the electrophile that's just been added. The π molecular orbital donates electrons to the electrophile.

While the p-orbitals in the π-bond overlap with the electrophile, each p-orbital forms a σ-bond.

But would the same thing happen if I put any other electrophile?

Generally,electrophilic addition reactions take place through carbocation intermediate. But this reaction can take place through cyclic 3-membered intermediate,if the electrophile has a lone pair.

Apart from $\ce{Cl+,Br+}$ even $\ce{Hg^2+}$ (when the reagent is $\ce{Hg(OAc)2/H3O+}$) and $\ce{NO+}$ (when the reagent is $\ce{NOCl}$) can form the 3-membered cyclic intermediate.

| improve this answer | |
$\endgroup$
  • 1
    $\begingroup$ This is my first answer.Can anyone verify whether what I have written is correct? Please suggest some tips on answering and tell what I can improve on,so that I can write better answers in the future.Thanks :) $\endgroup$ – Chem-Learner May 22 at 8:40
  • 1
    $\begingroup$ Include references if you have them $\endgroup$ – Waylander May 22 at 9:17
  • 1
    $\begingroup$ thanks at lot actually this helped :) $\endgroup$ – ganuwoahh May 22 at 14:55
  • $\begingroup$ @Waylander,Thanks for the suggestion.Unfortunately,I don't have any such references for this.If you have them, you can add them so that the answer is complete.Thanks $\endgroup$ – Chem-Learner May 22 at 18:41
  • $\begingroup$ @ganuwoahh Thanks for the feedback.It's nice to hear that it helped you :) $\endgroup$ – Chem-Learner May 22 at 18:42

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.