Q.60. - Organic Chemistry

Question

Question: Rizatriptan (trade name Maxalt) is a prescription drug used for the treatment of migraines. 

a. How many aromatic rings does rizatriptan contain? 

b. Determine the hybridization of each N atom. 

c. In what type of orbital does the lone pair on each N reside? 

d. Draw all the resonance structures for rizatriptan that contain only neutral atoms. 

e. Draw all reasonable resonance structures for the five-membered ring that contains three N atoms.

Step-by-Step Solution

Answer

Answer

e.

Step 1: Aromaticity

The aromatic compound is determined by the “Huckle rule.” The Huckle rule explains that if the compound satisfies the $\mathbf{4}\mathit{n}\mathbf{+}\mathbf{2}$ number, then the compound is aromatic, where $\mathit{n}\mathbf{=}\mathbf{0}\mathbf{,}\mathbf{1}\mathbf{,}\mathbf{2}\mathbf{,}\mathbf{3}\mathbf{,}\mathbf{4}\mathbf{.}\mathbf{.}\mathbf{.}\mathbf{.}\mathbf{.}$

Step 2: Nitrogen

The nitrogen atom belongs to the fifteenth group. Therefore, it has five electrons in its valence shell. If the atom forms the double bonds, then the hybridization is $s{p}^2$ . If the atom forms the single bonds, then the hybridization is $s{p}^3$ .

Step 3: Explanation

a.

 

The compound has three aromatic rings with six electrons in each and it obeys the $4n+2$ rule.

Aromatic rings

  

b.

 

The hybridization of nitrogen is shown in the given picture as:

Hybridization on nitrogen

 

c.

 

The double-bonded nitrogen has sp2  bonding. Therefore, the lone pair exists in the sp2 . The single-bonded nitrogen has sp3  bonding. Therefore, the lone pair exists in the sp3  . 

Lone pairs

 

d.

 

The resonating structure of the given compound is shown as:

Resonating structure

 

e.

 

The nitrogen-containing compounds have five-membered rings. The resonance structure is shown as:

Resonating structures