Organic Chemistry: Substitution Reactions

A set of vocabulary flashcards covering the definitions, reagents, conditions, and observations for substitution reactions in organic chemistry, including alkanes, alcohols, haloalkanes, and amines.

Substitution Reaction

A chemical 'swap' where one atom or functional group is removed from a molecule and replaced by another atom or group, while the carbon chain remains unchanged.

Saturated Compound

A substance where all carbon-carbon bonds are single bonds ($C-C$); these compounds primarily undergo substitution because every carbon is already bonded to the maximum number of atoms.

Reagent

A substance or compound added to a system to cause a chemical reaction, or to test if one occurs.

Alkane to Haloalkane reagents

Bromine ($Br_{2}$) or Chlorine ($Cl_{2}$) water used in combination with $UV$ Light.

UV Light

A catalyst required in the substitution of alkanes to break halogen bonds and form radicals to initiate the reaction.

Alcohol to Haloalkane chlorinating agents

Year 12 laboratory reagents including Thionyl chloride ($SOCl_{2}$), Phosphorus trichloride ($PCl_{3}$), and Phosphorus pentachloride ($PCl_{5}$).

$SOCl_{2}$ (Thionyl chloride)

A reagent used to swap a hydroxyl group ($-OH$) for a chlorine atom ($Cl$); the reaction often produces misty fumes of $HCl$ gas.

Haloalkane to Alcohol reagents

Aqueous potassium hydroxide ($KOH(aq)$) or sodium hydroxide ($NaOH(aq)$) plus heat.

Aqueous KOH vs. Alcoholic KOH

Using $KOH(aq)$ leads to substitution (forming an alcohol), whereas using $KOH(alc)$ leads to elimination (forming an alkene).

Haloalkane to Amine reagent

Concentrated ammonia dissolved in alcohol ($\text{conc. } NH_{3}(alc)$).

Bromine Water Observation

Under $UV$ light, substitution is indicated by a slow decolourisation from orange to colourless.

Substitution of Alcohols vs. Alkanes

The substitution of alcohols is generally faster and more efficient than the substitution of alkanes.

$$PCl_{3}$$

Phosphorus trichloride; a reagent used to replace the $-OH$ group of an alcohol with a $-Cl$ atom.

$$PCl_{5}$$

Phosphorus pentachloride; a chlorinating agent used in substitution reactions to produce haloalkanes from alcohols.