Mechanisms for electrophilic addition

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Chu 3J
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Joined: Fri Sep 25, 2015 3:00 am

Mechanisms for electrophilic addition

Postby Chu 3J » Mon Feb 29, 2016 1:25 am

In an electrophilic addition mechanism, how do we know which one is the nucleophile and which is the electrophile?

Mary Anastasi
Posts: 25
Joined: Fri Sep 25, 2015 3:00 am

Re: Mechanisms for electrophilic addition

Postby Mary Anastasi » Mon Feb 29, 2016 8:52 am

The nucleophile is electron dense and often (but not always) has a negative charge. Br- is an example of this. However, double and triple bonds can act as this source of electrons as well. Electrophiles do not have a lot of electrons and need more, often to complete their octet. An example of this is a carbon atom with 3 bonds and a lone pair; it has a positive charge, so it needs a nucleophile's electrons to gain four bonds. Electrophiles are often (but not always) positively charged. Basically, just determine which species is donating electrons and which is receiving them. Although it is important to remember that you are considering the transfer of electrons and not protons, so it is the electrophile that shares some of its electrons with the positive species.


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