GOC allylic,vinylic, benzylic positions, carbocation stability

Carbo-cations may be stabilized by:  

(a) π-bonds only at allylic position
  

(b) π-bonds only at vinylic position
  

(c) π-bonds at allylic and benzylic position also
(d) -I effect
  
  



  
  
  

The question has been taken from ADVANCED PROBLEMS IN ORGANIC CHEMISTRY by HIMANSHU PANDEY




* [allylic position explanation](http://web.chem.ucla.edu/~harding/IGOC/A/allylic_position.html)
* [benzylic position explanation](http://web.chem.ucla.edu/~harding/IGOC/B/benzylic_position.html)
* [vinylic position explanation](http://web.chem.ucla.edu/~harding/IGOC/V/vinylic_position.html)


For carbocation stability, think about which case has opportunity for electron resonance, i.e., which case(s) allows the positive charge to be delocalized to adjacent pi bonds. This [resource](http://web.chem.ucla.edu/~harding/tutorials/cc.pdf) might help.


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Allylic position is the same as allylic carbon....similarly for vinylic and benzylic...so the stability of carbocations goes as 


benzylic > allylic > vinylic
vinyl carbocations moreover are highly unstable...whereas the other two are rather stable ones...and the answer is (C) [![enter image description here](https://i.stack.imgur.com/ySePO.jpg)](https://i.stack.imgur.com/ySePO.jpg)
[![enter image description here](https://i.stack.imgur.com/zzeTu.png)](https://i.stack.imgur.com/zzeTu.png)


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