Textbook Question
Starting with an alkyl halide, how could the following compounds be prepared?
c. butylmethylamine
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7. Substitution Reactions
SN2 Reaction
3:48 minutesProblem 15c,d
Textbook Question
Show how you might use SN2 reactions to convert 1-chlorobutane into the following compounds.
c. 1-iodobutane
d. CH3—(CH2)3—CN
Verified step by step guidance1
Step 1: Understand the SN2 reaction mechanism. SN2 reactions involve a single-step nucleophilic substitution where the nucleophile attacks the electrophilic carbon and simultaneously displaces the leaving group. This reaction is favored in primary alkyl halides like 1-chlorobutane.
Step 2: For part c (conversion to 1-iodobutane), select an appropriate nucleophile. Use iodide ion (I⁻) as the nucleophile because it is a strong nucleophile and can replace the chlorine atom in 1-chlorobutane. The reaction can be carried out in a polar aprotic solvent like acetone to favor the SN2 mechanism.
Step 3: Write the reaction for part c. The iodide ion attacks the carbon bonded to chlorine in 1-chlorobutane, displacing the chloride ion (Cl⁻) and forming 1-iodobutane. The reaction can be represented as: CH₃(CH₂)₃Cl + I⁻ → CH₃(CH₂)₃I + Cl⁻.
Step 4: For part d (conversion to CH₃—(CH₂)₃—CN), select an appropriate nucleophile. Use cyanide ion (CN⁻) as the nucleophile because it is a strong nucleophile and can replace the chlorine atom in 1-chlorobutane. Again, use a polar aprotic solvent like acetone to favor the SN2 mechanism.
Step 5: Write the reaction for part d. The cyanide ion attacks the carbon bonded to chlorine in 1-chlorobutane, displacing the chloride ion (Cl⁻) and forming CH₃—(CH₂)₃—CN. The reaction can be represented as: CH₃(CH₂)₃Cl + CN⁻ → CH₃(CH₂)₃CN + Cl⁻.
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3mKey Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
SN2 Reaction Mechanism
The SN2 (substitution nucleophilic bimolecular) reaction is a type of nucleophilic substitution where a nucleophile attacks an electrophile, resulting in the simultaneous displacement of a leaving group. This mechanism involves a single concerted step, where the nucleophile approaches the electrophile from the opposite side of the leaving group, leading to inversion of configuration. Understanding this mechanism is crucial for predicting the outcomes of reactions involving alkyl halides like 1-chlorobutane.
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Nucleophiles and Electrophiles
In organic chemistry, nucleophiles are species that donate an electron pair to form a chemical bond, while electrophiles are electron-deficient species that accept electron pairs. In the context of SN2 reactions, the nucleophile attacks the electrophilic carbon atom of the alkyl halide, displacing the leaving group. Identifying strong nucleophiles, such as iodide ions (I-) or cyanide ions (CN-), is essential for successfully converting 1-chlorobutane into the desired products.
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Leaving Groups
A leaving group is an atom or group that can depart from the parent molecule during a chemical reaction, facilitating the formation of new bonds. In SN2 reactions, the quality of the leaving group significantly affects the reaction rate; better leaving groups, such as iodide (I-) compared to chloride (Cl-), enhance the reaction's efficiency. Understanding the role of leaving groups is vital for predicting the feasibility of converting 1-chlorobutane into 1-iodobutane and butanenitrile.
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