Can a bond be electrophilic or nucleophilic?


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> The indicated bond is:
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> [![enter image description here](https://i.stack.imgur.com/59exE.png)](https://i.stack.imgur.com/59exE.png)
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> **A**) Nucleophilic because it is electron-deficient.  
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> **B**) Electrophilic because it is electron-rich.  
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> **C**) Nucleophilic because it is electron-rich.  
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> **D**) Electrophilic because it is electron-deficient.
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The answer is **D**. I'm arguing with my friend because of this particular question.


I argued that there may be an error in this question. The arrow is pointing toward a carbon atom, so the question should be "The indicated carbon atom is:". But, if you take the question as it is, I answered **C** since I think that the "indicated bond" is the double bond, and is therefore nucleophilic and electron-rich. If it is not the double bond, then what is the indicated bond in this question? And is it possible for a single bond to be electrophilic?




Bonds can indeed be considered to be nucleophilic. For example, in the electrophilic aromatic substitution mechanism an electrophile interacts with benzene’s π system. By analogy, we can also see this as a nucleophilic electron pair (situated in the HOMO) interacting with the electrophile’s LUMO.


However, since bonds are considered to be the bonding electrons which by definition carry a negative charge, bonds can only be nucleophiles or non-nucleophilic; never electrophiles.


Bonds also cannot be electron-deficient. A bond in a Lewis structure is made up of two electrons, full stop. In MO theory, we may no longer consider the bond localised but we still have an electron pair in a certain bonding orbital and thus never electron-deficient.


I suspect the book made an error here and wanted to point at the carbon atom so the text should be as you suggest.


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