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The indicated bond is:

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A) Nucleophilic because it is electron-deficient.
B) Electrophilic because it is electron-rich.
C) Nucleophilic because it is electron-rich.
D) Electrophilic because it is electron-deficient.

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?

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  • $\begingroup$ How does the arrow even indicate a bond? It seems to be pointing to a C atom that is involved in three bonds... $\endgroup$ – Curt F. Jan 21 '18 at 4:45
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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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