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Module 4: Core organic chemistry (4.2.1 Alcohols)

6 dot points across 6 inquiry questions. Click any dot point for a focused answer with worked past exam questions where available.

How do primary, secondary and tertiary alcohols differ in their reactions?

Classification and properties of alcohols (hydrogen bonding), combustion, oxidation by acidified dichromate (primary to aldehyde and carboxylic acid, secondary to ketone, tertiary not oxidised), dehydration to alkenes, and substitution to haloalkanes.
An OCR H432 module 4 answer on alcohols: classification and hydrogen bonding, combustion, oxidation by acidified potassium dichromate to aldehydes, ketones and carboxylic acids, dehydration to alkenes, and conversion to haloalkanes.
11 min answer →

Why are alkanes unreactive, and how do they burn and react with halogens?

Structure and bonding of alkanes (sigma bonds, tetrahedral carbon), boiling-point trends, complete and incomplete combustion, pollutants, and free-radical substitution with halogens (initiation, propagation, termination).
An OCR H432 module 4 answer on alkanes: sigma bonding and tetrahedral shape, boiling-point trends from London forces, complete and incomplete combustion and pollutants, and the free-radical substitution mechanism with halogens.
11 min answer →

Why is the carbon-carbon double bond so reactive, and what does it react with?

Structure and bonding of alkenes (sigma and pi bonds, trigonal planar carbon), E/Z isomerism, electrophilic addition (hydrogen, halogens, hydrogen halides and steam), Markownikoff's rule, and addition polymerisation.
An OCR H432 module 4 answer on alkenes: pi bonding and trigonal planar shape, electrophilic addition with hydrogen, halogens, hydrogen halides and steam, Markownikoff's rule via the more stable carbocation, and addition polymerisation.
12 min answer →

How do we name organic compounds and represent the different ways their atoms can be arranged?

Formulae (empirical, molecular, general, structural, displayed and skeletal), homologous series and functional groups, IUPAC nomenclature, and isomerism (structural and E/Z stereoisomerism with Cahn-Ingold-Prelog priority).
An OCR H432 module 4 answer on the basics of organic chemistry: the six types of formula, homologous series and functional groups, IUPAC nomenclature, and structural and E/Z stereoisomerism using Cahn-Ingold-Prelog priority rules.
11 min answer →

Why do haloalkanes react with nucleophiles, and how does the carbon-halogen bond control the rate?

Polarity of the carbon-halogen bond, nucleophilic substitution (with hydroxide, cyanide and ammonia), the trend in hydrolysis rate with carbon-halogen bond enthalpy, elimination to alkenes, and the role of CFCs in ozone depletion.
An OCR H432 module 4 answer on haloalkanes: the polar carbon-halogen bond, nucleophilic substitution with hydroxide, cyanide and ammonia, the hydrolysis-rate trend with bond enthalpy, elimination to alkenes, and CFCs and ozone depletion.
12 min answer →

How do we plan a route to a target molecule, and how do infrared and mass spectra reveal structure?

Planning multi-step synthesis routes between functional groups using practical techniques (reflux, distillation, purification), and the analytical techniques of infrared spectroscopy (functional-group absorptions) and mass spectrometry (molecular ion and fragmentation).
An OCR H432 module 4 answer on organic synthesis and analysis: building multi-step reaction routes between functional groups, practical techniques, infrared spectroscopy for functional groups, and mass spectrometry for relative molecular mass and fragmentation.
12 min answer →