Playbook
Basic Principles of Organic Chemistry
72 q - 1.15/paper - 10% HARD, the hardest chapter of any size. Functional-group priority, electronic effects and isomer counting.
- Questions in the bank
- 72
- q/paper (2025–26 papers)
- 1.15
- Tagged HARD
- 10%
- Subtopics
- 3
Strand: Reactions
When you’ll see it
A functional group to name or rank, an isomer to count or classify, a chiral carbon, or which effect or carbocation is the more stable.
How this chapter is tested
72 q at 1.15 a paper, 10% HARD: the hardest chapter of any size, and a playbook since 2026, when it rose from 0.85 a paper (2025) to 1.31. Its three pages are close to equal: naming, functional groups and homologous series (25 q, 8% HARD), electronic effects and intermediates (24 q, 8%), and isomerism and stereochemistry (23 q, 13%).
Isomerism holds the most HARD: counting chiral carbons, telling metamers from functional isomers, and what enantiomers share. The electronic-effects page is the ranking every reaction chapter reuses: alkyl groups (+I) and resonance stabilise a carbocation, so 3° > 2° > 1° > methyl, and benzylic and allylic cations are steadier still.
The sub-skills
The distinct skills inside the chapter, in the order to learn them.
Functional-group priority
Carboxylic acid > anhydride > ester > acid halide > amide > nitrile > aldehyde > ketone > alcohol > amine. The highest-priority group takes the suffix.
Homologous series
Successive members differ by CH₂, 14 u in molar mass, with the same functional group and a gradation in physical properties.
Electronic effects
+I: alkyl groups. −I: –NO₂, –CN, halogens. +R: –OH, –OR, –NH₂ donate by resonance even though O and N are electronegative.
Isomerism
Chain, position, functional group and metamerism (different alkyl groups either side of the same group); a chiral carbon carries four different groups.
Traps to expect
Distractor shapes this chapter reuses. The Traps page covers the patterns that cut across chapters.
Ester against acid halide
In the priority order the ester ranks ABOVE the acid halide. Reversing them names the compound from the wrong group.
Metamers against functional isomers
Ethanol and dimethyl ether differ in functional group: they are functional isomers, not metamers. Metamers keep the group and move the alkyl groups around it.
Learn it before you drill it
This chapter has full teaching notes — foundations, worked examples, self-checks and a per-subtopic mastery checkpoint. Read the notes once, then drill subtopic by subtopic below.
Basic Principles of Organic Chemistry notesDrill every basic principles of organic chemistry question
72 questions from the bank, scoped to 3 bundled subtopics.
Drill one subtopic at a time
The 3 subtopics this playbook covers, in catalog order.
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