Question

Are amides nucleophiles?

Answer 1

Definition of nucleophile:

1. It is a chemical species that is capable of donating lone pair of electrons to the electron-deficient center like a proton$\left({\mathrm{H}}^{+}\right)$.
2. Example: Ammonia$\left({\mathrm{NH}}_3\right)$, Water$\left({\mathrm{H}}_2\mathrm{O}\right)$.

Definition of electrophile:

1. These are chemical species that are electron deficient and have a tendency to accept electrons from electron-rich species.
2. Example: Aldehyde$\left(\mathrm{RCHO}\right)$, Alkyl Chloride$\left(\mathrm{RCl}\right)$.

Explanation:

1. In the case of amides, there occurs delocalization of lone pair on N towards carbonyl carbon, so lone pair of nitrogen is not freely available for donation and hence amides cannot act as nucleophiles.
2. But, carbonyl carbon in amides is electron deficient because it is bonded with an electronegative oxygen atom.
3. So, such carbon is highly susceptible to nucleophilic attack.
4. Also, due to the delocalization of the lone pair of electrons on N towards carbonyl carbon in amide, the electrophilicity of the carbonyl carbon gets somewhat reduced (that is ${\mathrm{\delta }}^{+}$ charge on carbonyl carbon gets reduced), thus making it less reactive towards nucleophiles.
5. But still carbonyl carbon is electron deficient, so nucleophiles can attack over it.
6. So, amides are not nucleophiles.