What is a hydrogen bond?

A hydrogen bond is a strong intermolecular attraction between a hydrogen atom that is bonded to a very electronegative atom and a lone pair of electrons on the electronegative atom of a neighbouring molecule.

Compare the boiling points of ethanol and ethane.

Ethanol boils at about 78 °C whereas ethane boils at about −89 °C, so the alcohol boils very much higher despite the similar size of the molecules.

How does the boiling point of an alcohol change as the carbon chain gets longer?

The boiling point rises, because the larger molecules have more electrons and therefore stronger van der Waals' forces adding to the hydrogen bonding that is already present.

CCEA AS-Level Chemistry 1110

Formulae, Equations and Amounts of Substance

Topic overview Ionic charges and the formulae of compound ions Writing and balancing full and ionic equations The mole, molar mass and Avogadro's constant Reacting masses and reactants in excess Hydrated salts and water of crystallisation

Atomic Structure

Topic overview Protons, neutrons and electrons Atomic number, mass number and the composition of ions Isotopes and relative isotopic mass Relative atomic, molecular and formula mass Mass spectra and relative atomic mass calculations Mass spectra of diatomic elements Electronic configuration and the building up principle Orbitals, electron spin and orbital shapes The s-, p-, d- and f-blocks of the Periodic Table Ionisation energies and their equations Trends in ionisation energy as evidence for shells and subshells

Bonding

Topic overview Ionic bonding and electron transfer Dot and cross diagrams for ionic compounds Covalent bonding and the shared pair Lone pairs and co-ordinate bonding Dot and cross diagrams for covalent molecules and ions The octet rule and its limitations Electronegativity and bond polarity Metallic bonding

Intermolecular Forces and Structure

Topic overview Van der Waals' forces and permanent dipole-dipole attractions Hydrogen bonding, boiling points and solubility Giant ionic, metallic and giant covalent structures Molecular covalent structures and melting points across Period 3

Shapes of Molecules and Ions

Topic overview Electron pair repulsion and VSEPR theory Shapes and bond angles up to four electron pairs Shapes with five and six electron pairs Polar bonds and polar molecules

Redox

Topic overview Rules for assigning oxidation states Oxidation states in peroxides, hydrides and Roman numeral names Oxidation, reduction and electron transfer Oxidising agents, reducing agents and disproportionation Half-equations and combining them into redox equations

The Halogens

Topic overview Colours, physical states and solubility of the halogens Chlorine with water and the treatment of drinking water Disproportionation of the halogens with sodium hydroxide Oxidising ability and displacement reactions Solid halides with concentrated sulfuric and phosphoric acid

Acid-Base Titrations

Topic overview Strong and weak acids and bases Concentration, molarity and units Preparing a standard solution Titration technique, mean titres and uncertainty Indicators and the end point Titration calculations

Qualitative Tests

Topic overview Chemical tests for the gases Flame tests for metal cations Testing for the ammonium ion, sulfate and carbonate Distinguishing the halides, and the starch test for iodine

Formulae and Amounts of a Substance

Topic overview Empirical and molecular formulae Calculating formulae from composition data Molar gas volume and reacting gas volumes Percentage yield Atom economy

Nomenclature and Isomerism in Organic Chemistry

Topic overview Homologous series and functional groups IUPAC rules for naming organic compounds Structural, displayed and skeletal formulae Structural isomerism Geometrical isomerism and E–Z notation

Alkanes

Topic overview Alkanes as saturated hydrocarbons Boiling points of alkanes and van der Waals' forces Boiling points of branched isomers Complete and incomplete combustion of alkanes Pollutants from alkane fuels and the atmosphere Catalytic converters Radicals, homolytic fission and heterolytic fission Free radical substitution of alkanes

Alkenes

Topic overview Unsaturated hydrocarbons and the bromine water test Sigma and pi bonds in the carbon–carbon double bond Electron density at C=C, reactivity and catalytic hydrogenation Addition of chlorine and bromine to alkenes Addition of hydrogen chloride and hydrogen bromide Electrophiles, heterolytic fission and the addition mechanism Carbocation stability and Markovnikov addition Addition polymerisation of alkenes

Halogenoalkanes

Topic overview Classification and boiling points of halogenoalkanes Laboratory preparation of a halogenoalkane from an alcohol Nucleophiles and hydrolysis with aqueous alkali Reactions with ammonia and with potassium cyanide Relative rates of hydrolysis and carbon–halogen bond enthalpy Elimination using ethanolic potassium hydroxide CFCs and the ozone layer

Alcohols

Topic overview Hydrogen bonding, boiling point and solubility of alcohols Classifying alcohols and preparing them from halogenoalkanes Combustion of alcohols and their use as fuels Reactions with sodium, hydrogen bromide and phosphorus pentachloride Oxidation with acidified potassium dichromate(VI)

Infrared Spectroscopy

Topic overview Molecular vibrations and the absorption of infrared radiation Characteristic absorptions and the wavenumber scale Identifying functional groups from infrared spectra Distinguishing compounds and following reactions by infrared

Energetics

Topic overview Exothermic and endothermic changes Standard conditions and the standard enthalpy change Enthalpy level diagrams Standard enthalpies of combustion and formation Standard enthalpy of neutralisation Measuring enthalpy changes by experiment Enthalpy calculations using q = mcΔT Hess's Law and enthalpy cycles Indirect enthalpy calculations using Hess's Law Average bond enthalpies and their limitations

Kinetics

Topic overview Reaction rate and the factors that change it Collision theory and activation energy The Maxwell–Boltzmann distribution of molecular energies Catalysts and the activation energy barrier

Equilibrium

Topic overview Reversible reactions and dynamic equilibrium Changing conditions and the position of equilibrium The equilibrium constant Kc and its units The magnitude of Kc and the extent of reaction Industrial processes and compromise conditions

Group II Elements and Their Compounds

Topic overview s-block character and electronic configuration Trends in atomic radius and first ionisation energy Reactions of the elements with oxygen, water and dilute acids The oxides and their reactions with water and dilute acids Thermal stability of the carbonates and hydroxides Uses of magnesium oxide, calcium carbonate and lime Solubility trends and solubility curves

Alcohols

5 subtopics
15 things to know
Unit AS 2

What Alcohols covers

Alcohols is examined in Unit AS 2, Further Physical and Inorganic Chemistry and an Introduction to Organic Chemistry, and drawn on again in Unit AS 3, Basic Practical Chemistry. It covers hydrogen bonding, boiling point and solubility of alcohols, Classifying alcohols and preparing them from halogenoalkanes, combustion of alcohols and their use as fuels, reactions with sodium, hydrogen bromide and phosphorus pentachloride and oxidation with acidified potassium dichromate(VI).

Where it is assessed

Unit AS 2

Further Physical and Inorganic Chemistry and an Introduction to Organic Chemistry, and again in Unit AS 3, Basic Practical Chemistry.

Check the CCEA specification ↗

The 5 subtopics

Each one has its own page. CCEA AS Chemistry students sit this topic in the first year.

What you need to know

Answer each one before you reveal it.

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Key term

Explain why alcohol molecules are able to form hydrogen bonds with one another.

Key term

Explain the large difference in boiling point between an alcohol and the alkane of similar relative molecular mass.

Key term

How is an alcohol classified as secondary?

Key term

Which products are formed when an alcohol burns completely?

Key term

What is observed when a small piece of sodium is added to ethanol?

Key term

Name the oxidising mixture used to oxidise alcohols and state the colour change seen.

Key term

How is an alcohol classified as tertiary?

Key term

Write the equation for the complete combustion of ethanol.

Key term

Write the equation for the reaction of ethanol with sodium.

Key term

Which species is responsible for the green colour produced during the oxidation of an alcohol?

Key term

Which functional group do all alcohols contain?

Key term

Classify propan-2-ol as primary, secondary or tertiary.

Key term

Write the equation for the complete combustion of methanol.

Key term

Name the two products formed when sodium reacts with ethanol.

Key term

Which products can be obtained by oxidising a primary alcohol?

Take Alcohols further

The same content, four other ways.

Questions from this topic

Each one with the model answer underneath.

1
Which functional group do all alcohols contain?
Model answer
All alcohols contain the hydroxyl group, –OH, joined to a carbon atom of the chain.
2
What is a hydrogen bond?
Model answer
A hydrogen bond is a strong intermolecular attraction between a hydrogen atom that is bonded to a very electronegative atom and a lone pair of electrons on the electronegative atom of a neighbouring molecule.
3
Explain why alcohol molecules are able to form hydrogen bonds with one another.
Model answer
The O–H bond is highly polar because oxygen is far more electronegative than hydrogen, and the oxygen atom also carries lone pairs, so each molecule provides both parts that a hydrogen bond needs.
4
Compare the boiling points of ethanol and ethane.
Model answer
Ethanol boils at about 78 °C whereas ethane boils at about −89 °C, so the alcohol boils very much higher despite the similar size of the molecules.
5
Explain the large difference in boiling point between an alcohol and the alkane of similar relative molecular mass.
Model answer
The alcohol molecules are held together by hydrogen bonds as well as by van der Waals' forces, and hydrogen bonds need considerably more energy to overcome, while the alkane has only the weak van der Waals' forces.
6
How does the boiling point of an alcohol change as the carbon chain gets longer?
Model answer
The boiling point rises, because the larger molecules have more electrons and therefore stronger van der Waals' forces adding to the hydrogen bonding that is already present.

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Alcohols revision questions

Is Alcohols examined at AS in CCEA Chemistry?: Yes. It sits in Unit AS 2, which you take in the first year, so it is on the AS paper as well as counting towards the full A level.
What does Alcohols cover in CCEA AS-Level Chemistry?: 5 subtopics: hydrogen bonding, boiling point and solubility of alcohols, classifying alcohols and preparing them from halogenoalkanes, combustion of alcohols and their use as fuels, reactions with sodium, hydrogen bromide and phosphorus pentachloride and oxidation with acidified potassium dichromate(vi). Each one has its own page with questions and model answers.
How is Alcohols organised?: By the CCEA 1110 specification, subtopic by subtopic, so it matches the order you are taught it in.

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