H2 Chemistry Notes: EXTENSION TOPICS, Topic 11 - Organic Chemistry

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12 Feb 2025, 00:00 Z

Q: What does H2 Chemistry Notes: EXTENSION TOPICS, Topic 11 - Organic Chemistry cover?
A: Map the 2026 H2 Organic Chemistry toolkit: functional groups, stereochemistry, reaction mechanisms, synthetic planning, and spectroscopy interpretation.

Organic chemistry commands significant weight in Paper 3; questions interleave mechanisms, spectroscopy, and synthesis.

This guide structures the knowledge for the 2026 syllabus, with cross-references to practice drills at https://eclatinstitute.sg/blog/h2-chemistry-notes.

Status: SEAB H2 Chemistry (9729, first exam 2026) syllabus and Chemistry Data Booklet last checked 2025-11-29 (syllabus PDF last modified 2024-07-17; booklet last modified 2024-12-17). Extension Topic 11 scope remains unchanged.

1 Functional Group Map

Family	Key reactions	Notes
Alkanes	Radical substitution (halogenation), combustion.	Initiation-propagation-termination steps.
Alkenes	Electrophilic addition ( $\ce{HX}$ , $\ce{X2}$

Feature	S_N1	S_N2
Substrate	Tertiary > secondary.	Primary > methyl.
Rate law	rate = $k [\ce{RX}]$	rate = $k [\ce{RX}][\ce{Nu^-}]$
Mechanism	Carbocation intermediate, racemisation.	One-step backside attack, inversion.
Solvent	Polar protic stabilises carbocation.	Polar aprotic favours nucleophile.

Conversion	Reagent/conditions	Observation
Primary alcohol → aldehyde	$\ce{K2Cr2O7/H^+}$ , heat and distil.	Orange to green solution; collect distillate.
Primary alcohol → carboxylic acid	$\ce{KMnO4/H^+}$ , reflux.	Purple to colourless/brown precipitate.
Aldehyde → carboxylic acid	Tollens' or Fehling's.	Silver mirror or brick-red ppt.
Carbonyl → alcohol	$\ce{NaBH4}$ (aqueous) or $\ce{LiAlH4}$
Carboxylic acid → alcohol	$\ce{LiAlH4}$ , dry ether, followed by water.	Powerful reducing agent (dangerous, exothermic).

Functional group	Stretch	Approx. wavenumber $\pu{cm-1}$
O-H (alcohol)	Broad	$\pu{3200-3550 cm-1}$
O-H (acid)	Very broad with tail	$\pu{2500-3300 cm-1}$
C=O	Strong sharp	$\pu{1680-1750 cm-1}$ (ketone at lower end, acid higher)
N-H (amine)	Medium	$\pu{3300-3500 cm-1}$ (one or two peaks)

H2 Chemistry Notes: EXTENSION TOPICS, Topic 11 - Organic Chemistry

1 Functional Group Map

2 Stereochemistry

3 Mechanism Templates

3.1 Electrophilic Addition to Alkenes

3.2 S_N1 vs S_N2

3.3 Electrophilic Aromatic Substitution

4 Oxidation and Reduction Summary

5 Spectroscopy Checklist

5.1 Infrared (IR)

5.2 Proton NMR

5.3 Carbon-13 NMR

5.4 Mass Spectrometry

6 Worked Synthesis Problem

7 Exam Strategies

8 Common Pitfalls

9 Quick Drills

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