GAMSAT organic chemistry: topics, tips and practice
Organic chemistry is a substantial part of Section III and the topic many candidates find hardest. Here’s what to focus on, how to make it stick and two practice questions.
Functional groups and naming: alcohols, carbonyls, carboxylic acids, esters, amines and amides.
Isomerism: structural isomers, cis and trans, and conformations.
Stereochemistry: chirality, R and S, enantiomers, diastereomers and meso compounds.
Mechanisms: nucleophiles and electrophiles, substitution (SN1 and SN2), elimination and addition.
Acidity and basicity of organic molecules, and how structure affects them.
How to study GAMSAT organic chemistry
Draw everything. Sketch structures and mechanisms by hand; spatial questions are much easier on paper.
Learn principles, not lists. Steric hindrance and electron movement explain most reactions you’ll meet.
Drill stereochemistry. Assigning R and S quickly and spotting mirror planes saves real time.
Don’t skip it. It feels like memorisation, but it’s too large a share of the section to leave out. See our GAMSAT chemistry guide for the rest of the subject.
GAMSAT organic chemistry practice questions
Choose your answer, then open the explanation.
Section III / Stereochemistry
Which of these molecules is chiral?
A 2-chlorobutane
B 2-chloropropane
C 1-chlorobutane
D 2-chloro-2-methylpropane
Show the answer and explanation
A. A molecule with one carbon bonded to four different groups is chiral. In 2-chlorobutane, C2 carries H, Cl, CH₃ and CH₂CH₃. In 2-chloropropane the central carbon has two CH₃ groups (B). In 1-chlorobutane no carbon has four different groups (C). In 2-chloro-2-methylpropane the central carbon has three CH₃ groups (D).
Section III / Mechanisms
In an SN2 reaction, a nucleophile attacks the carbon bonded to the leaving group from the opposite side, in a single step.
Which alkyl bromide reacts fastest with hydroxide ions by SN2?
A CH₃Br
B CH₃CH₂Br
C (CH₃)₂CHBr
D (CH₃)₃CBr
Show the answer and explanation
A. The nucleophile has to reach the carbon from the back. Each methyl group added to that carbon crowds it further, so the rate falls from methyl to primary to secondary. Tertiary bromides like D are too hindered for SN2 and react by SN1 instead.
A substantial share of Section III’s chemistry questions. Organic units often combine structures, reaction schemes and stereochemistry, so they reward both content knowledge and spatial reasoning.
Do I need to memorise organic reactions for the GAMSAT?
Less than you might think. Learn why reactions happen, such as which atoms are electron rich or poor and how crowded the reacting carbon is. Passages often introduce unfamiliar reactions and expect you to apply those principles.
