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Organic Chemistry II - Summary of Preparations

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    Study Guide Organic Chemistry II – Summary of Preparations 1. Preparations: Aryl Halides 1. Halogenation of Benzene • What happens? Benzene undergoes halogenation in the presence of a halogen (X ₂ ) and a Lewis acid catalyst (such as AlCl ₃ ). This leads to the substitution of a hydrogen atom on the benzene ring with a halogen atom. • What’s used? A halogen (X ₂ ) such as chlorine (Cl ₂ ) or bromine (Br ₂ ), and an AlCl ₃ catalyst. • Reaction:

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    Study Guide 2. Sandmeyer Reaction • What happens? In the Sandmeyer reaction, an amino group ( - NH ₂ ) on a benzene ring is converted to a halogen (usually bromine or chlorine) by first diazotizing the amine group with sodium nitrite (NaNO ₂ ) and hydrochloric acid (HCl), followed by treatment with a copper halide (CuX). • What’s used? Sodium nitrite (NaNO ₂ ), hydrochloric acid (HCl), copper(I) halide (CuX), and the appropriate halogen. • Reaction: (with CuBr as the catalyst for bromine substitution) 2. Preparations: Ethers 1. Sulfuric Acid Process • What happens? The sulfuric acid process involves the dehydration of alcohols to form ethers. Alcohol undergoes an acid - catalyzed elimination reaction with sulfuric acid (H ₂ SO ₄ ), resulting in the formation of an ether and water.

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    Study Guide • What’s used? Alcohol (R - OH) and concentrated sulfuric acid (H ₂ SO ₄ ). • Reaction: 2. Williamson Synthesis • What happens? The Williamson synthesis is an important method for forming ethers through an SN2 reaction. It involves the reaction of an alkoxide ion (RO ⁻ ) with a primary alkyl halide (RX), leading to the formation of an ether. • What’s used? An alkoxide ion (RO ⁻ ), an alkyl halide (RX), and heat ( Δ). • Reaction: 3. Preparations: Alcohols 1. Williamson Synthesis

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    Study Guide • What happens? The Williamson synthesis is used to prepare alcohols via the reaction of an alkoxide ion (RO ⁻ ) with a primary alkyl halide (RX) in a nucleophilic substitution reaction. This leads to the formation of an ether, which can be converted into an alcohol if water is added. • What’s used? Alkoxide ion (RO ⁻ ), alkyl halide (RX), and water (H ₂ O). • Reaction: 2. Hydroboration - Oxidation • What happens? In the hydroboration - oxidation reaction, an alkene reacts with borane (BH ₃ ) to form a trialkylborane intermediate, which is then oxidized using hydrogen peroxide (H ₂ O ₂ ) to form an alcohol. • What’s used? Borane (BH ₃ ), hydrogen peroxide (H ₂ O ₂ ). • Reaction:

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    Study Guide 3. Reduction of Aldehydes and Ketones • What happens? Aldehydes and ketones can be reduced to alcohols using lithium aluminum hydride (LiAlH ₄ ) as a reducing agent. • What’s used? Lithium aluminum hydride (LiAlH ₄ ) and water (H ₂ O). • Reaction: 4. Reduction of Carboxylic Acids

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    Study Guide • What happens? Carboxylic acids can be reduced to alcohols using lithium aluminum hydride (LiAlH ₄ ). • What’s used? Lithium aluminum hydride (LiAlH ₄ ) and water (H ₂ O). • Reaction: 5. Reduction of Esters • What happens? Esters can be reduced to alcohols using lithium aluminum hydride (LiAlH ₄ ), producing a primary alcohol and an alcohol derived from the ester group. • What’s used? Lithium aluminum hydride (LiAlH ₄ ) and water (H ₂ O). • Reaction:

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    Study Guide 6. Grignard Reagent with Aldehydes and Ketones • What happens? Grignard reagents (RMgBr) react with aldehydes or ketones to form alcohols through nucleophilic addition. The intermediate product is then treated with acid to form the alcohol. • What’s used? Grignard reagent (RMgBr), acid (H ⁺ ). • Reaction (Aldehyde): Key Takeaway • Williamson Synthesis: Alcohols can be synthesized by nucleophilic substitution between an alkoxide and an alkyl halide. • Hydroboration - Oxidation: Alkenes undergo hydroboration followed by oxidation to form alcohols. • Reduction of Aldehydes, Ketones, Carboxylic Acids, and Esters: LiAlH ₄ reduces carbonyl compounds to alcohols. • Grignard Reagent: Grignard reagents add to aldehydes and ketones, forming alcohols upon acid work - up.

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    Study Guide 4. Preparations: Aldehydes 1. Oxidation of Primary Alcohols • What happens? Primary alcohols can be oxidized to aldehydes using an oxidizing agent like pyridinium chlorochromate (PCC). The reaction occurs in the presence of a solvent like dichloromethane (CH ₂ Cl ₂ ). • What’s used? Pyridinium chlorochromate (C ₆ H ₅ N ⁺ HCrO ₃ Cl ⁻ ) and dichloromethane (CH ₂ Cl ₂ ). • Reaction: 2. Reduction of Acyl Halides • What happens? Acyl halides (R - CO - Cl) are reduced to aldehydes using lithium tri - tert - butoxyaluminum hydride (LATB - H) at low temperatures. • What’s used? Lithium tri - tert - butoxyaluminum hydride (LATB - H) and water (H ₂ O).

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    Study Guide • Reaction: 3. Reduction of Esters • What happens? Esters can be reduced to aldehydes using diisobutylaluminum hydride (DIBAL - H) at low temperatures followed by hydrolysis. • What’s used? Diisobutylaluminum hydride (DIBAL - H) and water (H ₂ O). • Reaction: 4. Reduction of Nitriles • What happens? Nitriles (R - C≡N) can be reduced to aldehydes using diisobutylaluminum hydride (DIBAL - H) followed by hydrolysis. • What’s used? Diisobutylaluminum hydride (DIBAL - H) and water (H ₂ O).

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