Draw the major organic product of the reaction between CH
3
−C≡CH and NaNH
2
followed by 1−chloro−3−methylbutane.
The Correct Answer and Explanation is :
To determine the major organic product of the reaction between 1-butyne (( \text{CH}_3\text{C} \equiv \text{CH} )) and sodium amide (( \text{NaNH}_2 )), followed by the reaction with 1-chloro-3-methylbutane, we need to analyze the reaction mechanism and the structure of the products formed.
Step 1: Deprotonation
The first step involves the deprotonation of 1-butyne by sodium amide. 1-butyne contains an acidic hydrogen atom attached to the terminal alkyne carbon (the carbon connected to the methyl group). Sodium amide is a strong base and will effectively remove this acidic hydrogen, generating a terminal alkyne anion:
[
\text{CH}_3\text{C} \equiv \text{CH} + \text{NaNH}_2 \rightarrow \text{CH}_3\text{C} \equiv \text{C}^- \text{Na}^+ + \text{NH}_3
]
Step 2: Nucleophilic Substitution
The next step involves the nucleophilic substitution reaction between the resulting alkyne anion (( \text{CH}_3\text{C} \equiv \text{C}^- )) and 1-chloro-3-methylbutane (( \text{CH}_3\text{C}(\text{CH}_3)\text{CH}_2\text{Cl} )). The anion acts as a nucleophile and attacks the electrophilic carbon attached to the chlorine in the alkyl halide, leading to the substitution of the chlorine atom.
Product Formation
The nucleophilic attack results in the formation of a new carbon-carbon bond between the terminal carbon of the alkyne and the carbon attached to the chlorine in 1-chloro-3-methylbutane. The chlorine is displaced as chloride ion (( \text{Cl}^- )).
The overall reaction yields the product 2-heptyne (( \text{CH}_3\text{C} \equiv \text{C}\text{CH}_2\text{C}(\text{CH}_3)\text{CH}_2\text{CH}_3 )), as the reaction extends the carbon chain by two carbons:
[
\text{CH}_3\text{C} \equiv \text{C}^- + \text{CH}_3\text{C}(\text{CH}_3)\text{CH}_2\text{Cl} \rightarrow \text{CH}_3\text{C}(\text{C}\text{C}(\text{CH}_3)\text{CH}_2\text{CH}_3) + \text{Cl}^-
]
Conclusion
The major organic product of this reaction sequence is 3-methyl-1-heptyne. This product results from the nucleophilic substitution of the alkyne anion with 1-chloro-3-methylbutane, illustrating how a terminal alkyne can be utilized to form larger carbon frameworks through nucleophilic substitution reactions.