Predicting Organic Chemistry Reactions: Products and Mechanisms
What are the possible products and mechanisms of the following reactions?
a. Isobutyl chloride + AgNO₃ in ethanol/water
b. 1-bromo-1-methylcyclopentane + NaOEt/ethanol
c. 2-chloro-2-methylbutane in ethanol
d. 1-bromo-1-methylcyclopentane heated in methanol
Answers:
a. Isobutyl Chloride + AgNO₃ in Ethanol/Water:
b. 1-Bromo-1-methylcyclopentane + NaOEt/Ethanol:
c. 2-Chloro-2-methylbutane in Ethanol:
d. 1-Bromo-1-methylcyclopentane Heated in Methanol:
a. Isobutyl Chloride + AgNO₃ in Ethanol/Water:
Products: The formation of a white precipitate of silver chloride (AgCl) and isobutyl nitrate ((CH₃)₂CHCH₂ONO₂).
Mechanism: Nucleophilic substitution occurs where Ag⁺ from AgNO₃ reacts with Cl⁻ of isobutyl chloride to form AgCl. It's important to note that nucleophilic substitution might not occur due to the weak nucleophilic character of NO₃⁻ in ethanol/water. However, isobutyl nitrate could still form by reacting with AgNO₃, substituting NO₃⁻ for Cl⁻.
b. 1-Bromo-1-methylcyclopentane + NaOEt/Ethanol:
Product: The probable product is 1-ethylcyclopentene.
Mechanism: The reaction follows an elimination mechanism (E2) where the ethoxide ion (OEt⁻) abstracts a proton from the β-carbon adjacent to bromine, leading to the formation of the most substituted alkene (Zaitsev's rule). There might be a competing E1 mechanism that could form a carbocation intermediate and yield a mixture of products.
c. 2-Chloro-2-methylbutane in Ethanol:
Product: The expected product is 2-methyl-2-butanol.
Mechanism: Nucleophilic substitution takes place where ethanol acts as a nucleophile, attacking the electrophilic carbon (C2) bearing chlorine. The reaction follows the S_N1 mechanism due to tertiary carbocation formation.
d. 1-Bromo-1-methylcyclopentane Heated in Methanol:
Product: The anticipated product is methylcyclopentene.
Mechanism: The reaction follows an elimination mechanism (E1) where methanol acts as a weak base, abstracting a proton from the β-carbon, resulting in the formation of the most substituted alkene. E2 mechanism might also occur, and high temperature favors E1 mechanism.