Q18 P.
Question
Imidazole forms part of the structure of the amino acid histidine and can act as both an acid and a base.
Imidazole Histidine
(a) Look at the electrostatic potential map of imidazole, and identify the most
acidic hydrogen atom and the most basic nitrogen atom.
(b) Draw structures for the resonance forms of the products that result when
imidazole is protonated by an acid and deprotonated by a base.
Step-by-Step Solution
Verified(a) The nitrogen on the left is more electron-rich and more basic. The indicated hydrogen is most electron-poor (bluest) and is most acidic.
(b)
Resonance is a method of describing delocalized electrons within certain molecules or polyatomic ions where the bonding cannot be expressed by one single Lewis structure. A molecule or ion with such delocalized electron is represented by several contributing structure called resonance structure.
(a) The nitrogen on the left is more electron-rich and more basic. The indicated hydrogen is most electron-poor (bluest) and is most acidic. In an electrostatic potential map, the color red indicates regions of a molecule that are electron rich.
The resonance forms of the products that result when imidazole is protonated by an acid and deprotonated by a base.
Imidazole is protonated by an acid
Imidazole is deprotonated by a base.