Question

The pKapKa of cyclopentane is > 60, which is about what is expected for a hydrogen that is bonded to an sp3sp3 carbon. Explain why cyclopentadiene is a much stronger acid (pKapKa of 15), even though it too involves the loss of a proton from an sp3sp3 carbon. Match the words in the left column to the appropriate blanks in the sentences on the right. Make certain each sentence is complete before submitting your answer.

Answer 1

Answer and explanation:

cyclopentadiene is more acidic than cyclopentane

hydrocarbon compound are weak acid in nature

This relative acidity is explained by the stability of

cyclopentadienyl anion which is aromatic in nature

(check the attached image file 1)

To answer this question we must look at the stability of the anions that are formed when the compound lose proton.

All the electron in the cyclopentyl anion are localized.

In contrast, the aromatic cyclopentadienyl anion is a stable carbanion as a result of its aromaticity therefore making its conjugate acid a very strong acid compare to other compounds with hydrogen attached to sp³ carbons