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    I had a go at a question which was asking to talk about the structural differences between benzene and the benzene intermediate formed during electrophilic substitution. One thing It asked specifically was to deduce the number of electrons that are involved in the pi-bonding, I thought that since the delocalised ring of electrons donated a pair of electrons then 4 electrons would be in the ring in the intermediate spread over 6 carbons but I have read that it is 5 electrons, which is true?

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    (Original post by Xenilbohl)
    I had a go at a question which was asking to talk about the structural differences between benzene and the benzene intermediate formed during electrophilic substitution. One thing It asked specifically was to deduce the number of electrons that are involved in the pi-bonding, I thought that since the delocalised ring of electrons donated a pair of electrons then 4 electrons would be in the ring in the intermediate spread over 6 carbons but I have read that it is 5 electrons, which is true?

    Thanks
    personally,i don't think knowing how to count the electrons help you in understanding the concept of electrophilic substitution. anyway, a pi bond in the double bond in benzene consists of 2 electrons in pi bonding molecular orbitals.

    then, as the pi bond is broken to initiate attack on the electrophile, you get the intermediate which, if shown as kekule structure, would show two double bonds left. => that means you only have how many pi bonds? hence how many electrons actually get delocalised then?

    also in nucleophilic/electrophilic reaction, these are heterolytic fission right? how many electrons are involved per one of those curly arrows?
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    (Original post by shengoc)
    personally,i don't think knowing how to count the electrons help you in understanding the concept of electrophilic substitution. anyway, a pi bond in the double bond in benzene consists of 2 electrons in pi bonding molecular orbitals.

    then, as the pi bond is broken to initiate attack on the electrophile, you get the intermediate which, if shown as kekule structure, would show two double bonds left. => that means you only have how many pi bonds? hence how many electrons actually get delocalised then?

    also in nucleophilic/electrophilic reaction, these are heterolytic fission right? how many electrons are involved per one of those curly arrows?
    If two double bonds left then you have 4 'pi' electrons so only 2 get delocalised. And one curly arrow represents the movement of a pair of electrons so 2 electrons are being transferred, therefore there will only be 4 electrons in the delocalised ring of electrons of the intermediate?
 
 
 
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