Grignard reagent does not react with alkene bcoz it doesn't have acidic hydrogen..

Introduction

2-butene is an unsaturated hydrocarbon belonging to the alkene family. It consists of four carbon atoms and contains a double bond between two adjacent carbon atoms. On the other hand, Grignard reagents are organometallic compounds that contain a carbon-metal bond. They are commonly used for the formation of carbon-carbon bonds through nucleophilic addition reactions. However, 2-butene does not react with Grignard reagents due to several reasons.

Steric Hindrance

One of the primary factors that prevent the reaction between 2-butene and Grignard reagents is steric hindrance. The double bond in 2-butene has restricted rotation, causing the two substituents on each carbon atom to be fixed in a specific orientation. This results in the formation of a rigid structure that does not allow sufficient space for the bulky Grignard reagent to approach and undergo nucleophilic addition.

Reactivity of Grignard Reagents

Grignard reagents are highly reactive nucleophiles, capable of attacking electrophilic sites in various organic compounds. However, the reactivity of Grignard reagents is primarily focused on the carbon atom bearing the electrophilic site. In the case of 2-butene, the electrophilic carbon atom is the one involved in the double bond, which is relatively unreactive due to the presence of pi bonds. Thus, the Grignard reagent does not find a suitable electrophilic site to react with, hindering the formation of a new carbon-carbon bond.

Formation of an Enolate

Another reason for the lack of reactivity between 2-butene and Grignard reagents is the formation of an enolate intermediate. Grignard reagents are strong bases and can deprotonate acidic hydrogen atoms. In the case of 2-butene, the alpha carbon atoms adjacent to the double bond are acidic due to the presence of the electron-withdrawing pi bonds. The Grignard reagent can abstract one of these acidic hydrogens, resulting in the formation of an enolate intermediate. However, the presence of a double bond in 2-butene stabilizes the negative charge on the enolate, making it less reactive towards nucleophilic attack.

Conclusion

In conclusion, 2-butene does not react with Grignard reagents due to steric hindrance, the lack of a suitable electrophilic site, and the stabilization of the enolate intermediate. These factors hinder the formation of a new carbon-carbon bond and prevent the desired reaction from occurring.