Question

Question: In most amines, the nitrogen atom is sp³ hybridized, with a pyramidal structure and bond angles close to 109^o.In urea, both nitrogen atoms are found to be planer, with bond angles close to 120^o. Explain this surprising finding. (Hint: consider resonance forms and the overlap needed in them.)

Short answer

Answer

The structure of urea is planer with a bond angle close to . The Resonance structures of urea are as follows:

Resonance structures of urea

Step-by-step solution

Resonance structure

The Resonance structure is a set of Lewis structure helpful in showing the electron delocalization in a polyatomic ion or a molecule. In many cases, a single Lewis structure fails to explain the bonding in a molecule/polyatomic ion due to partial charges and fractional bonds in it.

Resonance forms of urea

The central carbon atom of urea is sp²hybridized, and the structure is planer. The Resonance structures of urea are as follows:

Resonance structures of urea

From the resonance structure, it’s clear that the lone pair is tied up in resonance, i.e., the lone pair is delocalized between carbon and nitrogen. The nitrogen–carbon bond has some double-bond character as shown in the resonance hybrid structure.