Normal hydrocarbons have a pka value of 30-50 making them very weak acids. Cyclo

Question

Normal hydrocarbons have a pka value of 30-50 making them very weak acids. Cyclopentadiene is more acidic with a pka value of 15. Identify the acidic hydrocarbons and explain why cyclopentadiene is so much more acidic than normal hydrocarbons. Use structures to support your explanation

Clyclopentadiene structure:

http://upload.wikimedia.org/wikipedia/commons/b/bc/Cyclopentadiene.png

Normal hydrocarbons have a pka value of 30-50 making them very weak acids. Cyclopentadiene is more acidic with a pka value of 15. Identify the acidic hydrocarbons and explain why cyclopentadiene is so much more acidic than normal hydrocarbons. Use structures to support your explanation Clyclopentadiene structure:

Explanation / Answer

Cyclopentadiene is a non aromatic compound but cyclopentadiene anion is aromatic in nature due to,

1) six pi electrons

2) process of resonance

so to stabilized itself as the aromatic anion the cyclopentadiene removes on hydrogen ion and behaves like an acid.

From the figure you provided, the hydrogen at top vertex is acidic. If it is lost, a negative charge is formed and resonance exists in the compound. So The compound tries to lose that Hydrogen easily, making it more acidic than others

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