Cambridge International AS & A Level Chemistry: Organic Synthesis

Vocabulary flashcards covering organic synthesis reaction types, functional group tests, oxidising and reducing agents, and multi-step synthetic routes for A-Level Chemistry.

Hydrogenation

The addition reaction of alkenes with hydrogen using a $H_2$, $Pt$ / $Ni$ catalyst and heat to produce alkanes.

Cracking

The process in which large, less useful hydrocarbon molecules are broken down into smaller, more useful molecules in an oil refinery using an $Al_2O_3$ catalyst and heat to produce alkanes and alkenes.

Free-Radical Substitution

The reaction in which halogen atoms substitute for hydrogen atoms in alkanes under UV light and halogen, involving initiation, propagation, and termination steps to form halogenoalkanes.

Electrophilic Addition

The mechanism of the reaction in which an electrophile attacks the $C=C$ bond and addition across the double bond occurs using reagents such as $Br_2$, $HBr$, $H_2O$, and $H_2SO_4$.

Nucleophilic Addition

The mechanism of the reaction in which a nucleophile attacks the carbon atom in a carbonyl group ($C=O$) and addition across the bond occurs, using reagents such as $HCN$.

Electrophilic Substitution

The replacement of an atom by another atom or group of atoms after initial attack by an electron-deficient species (electrophile, e.g. $Br_2$).

Nucleophilic Substitution

The mechanism of the organic reaction in which a nucleophile attacks a carbon atom carrying a potential positive charge, resulting in the replacement of an atom carrying a partial negative charge by the nucleophile.

Oxidation

The loss of electrons or gain of oxygen of an atom, ion, or molecule, using oxidising agents such as acidified $K_2Cr_2O_7$ or $KMnO_4$.

Reduction

The gain of electrons or loss of oxygen of an atom, ion, or molecule, using reducing agents such as $NaBH_4$ or $LiAlH_4$.

Hydrolysis

The breakdown of a compound by water or by dilute acids or alkali, forming alcohol and carboxylic acid from esters, or alcohol from halogenoalkanes.

Condensation

A reaction in which two organic molecules join together and in the process eliminate a small molecule such as water or hydrogen chloride.

Acidified Potassium Dichromate ($K_2Cr_2O_7 / H_2SO_4$)

An oxidising agent that oxidises primary alcohols to aldehydes then carboxylic acids, secondary alcohols to ketones, and aldehydes to carboxylic acids, undergoing a colour change from orange to green.

Acidified Potassium Permanganate ($KMnO_4 / H_2SO_4$)

An oxidising agent that oxidises primary alcohols, secondary alcohols, aldehydes, and alkenes (to diols), undergoing a colour change from purple to colourless.

Sodium Borohydride ($NaBH_4$)

A reducing agent that reduces aldehydes to primary alcohols and ketones to secondary alcohols, but does not reduce carboxylic acids or alkenes.

Lithium Aluminium Hydride ($LiAlH_4$)

A reducing agent that reduces carboxylic acids to aldehydes then primary alcohols, aldehydes to primary alcohols, and ketones to secondary alcohols.

Fehling's Solution

A test reagent for aldehydes where a clear blue solution turns opaque red/orange as a precipitate is formed.

Tollens' Reagent

A test reagent for aldehydes that forms a silver mirror upon a positive test.

Bromine Water

A test reagent for alkenes that decolourises, changing from orange to colourless.

2,4-Dinitrophenylhydrazine (2,4-DNPH)

A reagent used to test for carbonyl compounds (aldehydes and ketones), producing an orange precipitate upon a positive test.

Iodoform Test

A test for the methyl ketone ($CH_3CO-$) group that produces a yellow precipitate of triiodomethane.

Silver Nitrate and Ammonia Test

A test for halogens in halogenoalkanes that forms silver halide precipitates: $AgCl$ (white), $AgBr$ (cream), and $AgI$ (yellow).

Carboxylic Acid Test

A functional group test where carboxylic acids react with carbonates to form $CO_2$ gas which turns limewater cloudy.

Amine Test

A functional group test where amines turn damp red litmus paper blue and turn universal indicator blue / purple.

Multi-Step Synthesis of 2-Hydroxybutanoic Acid from Propan-1-ol

A 3-step synthesis: Step 1: Oxidation of propan-1-ol to propanal using acidified $KMnO_4 / K_2Cr_2O_7$; Step 2: Nucleophilic addition of $HCN$ with $KCN$ and heat to form 2-hydroxybutanenitrile; Step 3: Hydrolysis with $2H_2O$ and $HCl$ to yield 2-hydroxybutanoic acid and ammonium chloride.

Multi-Step Synthesis of Sodium Propanoate Salt from Propan-1-ol

A 3-step synthesis: Step 1: Oxidation of propan-1-ol to propanoic acid using acidified $KMnO_4 / K_2Cr_2O_7$; Step 2: Condensation/esterification with ethanol to form ethyl propanoate; Step 3: Hydrolysis with $NaOH$ to yield sodium propanoate salt and ethanol.

Synthesis of Hexanoic Acid from 1-Chloropentane

A 2-step synthesis: Step 1: Nucleophilic substitution of 1-chloropentane with ethanolic $KCN$ under heat to form a nitrile intermediate; Step 2: Hydrolysis of the nitrile with concentrated hydrochloric acid to yield hexanoic acid and ammonium chloride salt.

Synthesis of Compound X from OHCCH2CHO

A 2-step synthesis: Step 1: Nucleophilic addition of $CN^-$ using $NaCN$ as a catalyst and heat to form a hydroxynitrile; Step 2: Refluxing the nitrile with dilute aqueous sulfuric acid causing hydrolysis to form compound X ($HO_2CCH(OH)CH_2CH(OH)CO_2H$).