Draw the conjugate bases of pyrrole and cyclopentadiene. Explain Why is the sp3 hybridized C―H bond of cyclopentadiene more acidic than the N―H bond of pyrrole?

The explanations are given in the section below

Explanation:

First step:

We need to understand the acid-base equilibrium of the reaction. Bear in mind that the conjugate acid-base pairs are species that differ by one proton. Furthermore, one is a Lewis acid (meaning the ability to protons) and the conjugate base (accepts protons)

A simple conjugate base is obtained by removing one proton from an acid as shown below:

HX ⇄ A⁻ + H⁺

The diagrams are as follows:

Tests for unsaturation involves addition across the multiple bonds in the unsaturated compound.

Explanation:

In organic chemistry, we define an unsaturated compound as any compound that contains a double or triple bond. These multiple bonds are also known as pi bonds.

There are two major tests for unsaturation which shall both be discussed here.

The first test for unsaturation is by the use of bromine water. The unknown sample is passed through a solution of bromine water which normally appears reddish brown. The bromine water becomes decolorized due to addition of bromine across the multiple bond. This is a standard test for unsaturation.

Secondly, unsaturated compounds decoulourize a solution of potassium permanganate when passed through it. This alone can not be used as a distinctive test for unsaturation.

Propenoic acid will give a positive test to the both reagents showing that it contains multiple bonds, in this particular instance, a double bond.