Organic Synthesis

Carbonyls and Optical Isomerism Worksheet

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1. Synthesis from Simple Precursors

Carbonyl compounds can be synthesised from a variety of compounds in multi-step processes. For each of the following reagent and target, draw out the steps, showing any organic molecules produced along the way; state the reactants and conditions required for each step; and state the name of the process.

a) The formation of ethanal from ethene.

Step 1: Hydration
Reagent: Steam (H₂O)
Conditions: H₃PO₄ catalyst, high temp/pressure
Product: Ethanol

Step 2: Partial Oxidation
Reagent: Acidified Potassium Dichromate (K₂Cr₂O₇/H⁺)
Conditions: Warm and Distil
Product: Ethanal

b) The formation of ethanal from bromoethane.

Step 1: Nucleophilic Substitution
Reagent: Aqueous Sodium Hydroxide (NaOH)
Conditions: Warm
Product: Ethanol

Step 2: Oxidation
Reagent: Acidified Potassium Dichromate (K₂Cr₂O₇/H⁺)
Conditions: Warm and Distil
Product: Ethanal

c) The formation of ethanedial from ethene.

Step 1: Electrophilic Addition
Reagent: Bromine (Br₂)
Conditions: Room temperature
Product: 1,2-dibromoethane

Step 2: Nucleophilic Substitution
Reagent: Aqueous NaOH
Conditions: Warm / Reflux
Product: Ethane-1,2-diol

Step 3: Oxidation
Reagent: Acidified K₂Cr₂O₇/H⁺
Conditions: Distil (to prevent further oxidation to the acid)
Product: Ethanedial

2. Complex Synthesis Pathways

Carbonyls are frequently used as part of a multistep process. For each of the following reagent and target, draw out the steps, showing any organic molecules produced along the way; state the reactants and conditions required for each step; and state the name of the process.

a) The formation of 2-hydroxy-2-methylpropanenitrile from propan-2-ol.

Step 1: Oxidation
Reagent: Acidified K₂Cr₂O₇
Conditions: Heat under reflux
Product: Propanone

Step 2: Nucleophilic Addition
Reagents: NaCN and dilute acid (H⁺)
Conditions: Room temperature
Product: 2-hydroxy-2-methylpropanenitrile

b) The formation of propenenitrile from chloroethane (Carefully note the name of the product).

Step 1: Nucleophilic Substitution
Reagent: Aqueous NaOH
Conditions: Warm / Heat under reflux
Product: Ethanol

Step 2: Oxidation
Reagent: Acidified K₂Cr₂O₇
Conditions: Heat and Distil
Product: Ethanal

Step 3: Nucleophilic Addition
Reagents: NaCN/H⁺
Conditions: Room temperature
Product: 2-hydroxypropanenitrile

Step 4: Dehydration
Reagent: Conc. H₂SO₄
Conditions: Heat
Product: Propenenitrile (CH₂=CH-CN)

Synthesis of Propenenitrile from Chloroethane

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