A2 Module 4

Further Physical and Organic

Chemistry

Introduction

This module develops the concepts of physical chemistry introduced

in the foundation modules. Kinetics and equilibria are both treated

quantitatively. Acids, bases and buffer solutions and the changes in

pH during titrations are considered.

The study of organic chemistry is extended to include compounds

containing the carbonyl group, aromatic compounds, amines, amino

acids and polymers. The final section examines the way in which

spectroscopic techniques are used to determine the molecular

formulae and structures of organic compounds. The emphasis is on

problem solving rather than on spectroscopic theory.

Wherever possible, candidates should carry out experimental work to

illustrate the theoretical principles included in this module.

Candidates should:

13.1 Kinetics

13.1.1 Simple rate equations understand and be able to use rate equations of the

form Rate = k[A]m [B]n where m and n are the orders of reaction with respect to reactants A and B (m, n restricted to values 1, 2 or 0).

13.1.2 Determination of rate be able to derive the rate equation for a reaction from

equation data relating initial rate to the concentrations of the

different reactants.

be able to explain the qualitative effect of changes in temperature on the rate constant k.

13.2 Equilibria

13.2.1 Equilibrium constants K c and know that K c is the equilibrium constant

K p for homogeneous systems calculated from equilibrium concentrations for

a system at constant temperature.

know that K p is the equilibrium constant calculated from partial pressures for a system at constant temperature (the relationship between K c and K p is not required).

be able to derive partial pressures from mole fractions and total pressure.

be able to construct an expression for K c or K p for an homogeneous system in equilibrium; be able to perform calculations involving such expressions.

13.2.2 Qualitative effects of be able to predict the effects of changes of

changes of pressure, temperature, pressure and concentration on the temperature and position of equilibrium and on the value of the

concentration equilibrium constant.

know that a catalyst does not affect the value of the equilibrium constant.

13.3 Acids and Bases

13.3.1 Brønsted-Lowry acid�base know that an acid is a proton donor.

equilibria in aqueous know that a base is a proton acceptor.

Solution know that acid�base equilibria involve the transfer of

protons.

13.3.2 Definition and know that pH = �log10 [H+], where [ ] represents the

determination of pH concentration in mol dm-3 .

be able to convert concentration into pH and vice-versa.

be able to calculate the pH of a solution of a strong acid from its molar concentration.

13.3.3 The ionic product of water, know that water is weakly dissociated.

Kw know that Kw = [H+][OH-] = 10-14 mol2 dm-6 at 25�C

be able to calculate the pH of a strong base from its molar

concentration.

13.3.4 Weak acids and bases know that weak acids and weak bases dissociate only

partially in aqueous solution.

13.3.5 Ka for weak acids be able to construct an expression, with units, for the dissociation constant Ka for a weak acid.

know that pKa = �log10 Ka

be able to calculate the pH of a weak acid from the dissociation constant, Ka , and the molar concentration.

be able to perform calculations relating pH to pKa for weak acids.

13.3.6 pH curves, titrations and understand the typical shape of pH curves for acid�

indicators base titrations in all combinations of weak and strong

monoprotic acids and bases; be able to perform calculations for these titrations.

understand the shape of the pH curves for the titration of sodium carbonate with monoprotic acids, e.g. HCl, and of diprotic acids, e.g. ethanedioic acid, with NaOH and be able to perform calculations for these titrations.

know that indicators change colour over a narrow pH range; be able to select an appropriate indicator by consideration of the pH curve.

13.3.7 Buffer action be able to explain the action of acidic and basic buffers

both qualitatively and quantitatively.

be able to calculate the pH of buffer solutions.

13.4 Nomenclature and

Isomerism in Organic

Chemistry

13.4.1 Naming organic compounds be able to apply IUPAC rules for nomenclature

to simple organic compounds, limited to chains with up to 6 carbon atoms and the functional groups listed in this module and in AS3.

13.4.2 Isomerism know and understand the meaning of the term structural

isomerism.

know that geometrical isomerism and optical isomerism are forms of stereoisomerism.

understand that geometrical isomers exist in cis and trans forms due to restricted rotation about the C=C bond.

know that an asymmetric carbon atom is chiral and gives rise to optical isomers which exist as mirror images and differ only in their effect on plane-polarised light.

understand the meaning of the terms enantiomer and racemate.

understand why racemates are formed.

be able to draw the structures of isomers.

13.5 Compounds Containing the

Carbonyl Group

13.5.1 Aldehydes and ketones recall that aldehydes are readily oxidised to carboxylic

acids and that this forms the basis of a simple chemical test to distinguish between aldehydes and ketones (e.g. Fehling�s solution or Tollen�s reagent).

recall that aldehydes can be reduced to primary alcohols and ketones to secondary alcohols using reducing agents such as NaBH4.

Mechanisms showing H- are required; (equations showing [H] as reductant are acceptable).

understand the mechanism of the reaction of carbonyl compounds with HCN as a further example of nucleophilic addition producing hydroxynitriles.

13.5.2 Carboxylic acids and esters know that carboxylic acids are weak acids but

will liberate CO2 from carbonates.

know that carboxylic acids and alcohols react, in the presence of a strong acid catalyst, to give esters.

know that esters can have pleasant smells.

know the common uses of esters (e.g. as solvents, plasticisers and food flavourings).

know that esters can be hydrolysed, including the production of soap, glycerol and higher fatty acids from naturally-occurring esters.

13.5.3 Acylation know the reactions of water, alcohols, ammonia and

primary amines with acyl chlorides and acid anhydrides.

understand the mechanism of nucleophilic addition�elimination reactions between water, alcohols, ammonia and primary amines with acyl chlorides.

understand the industrial advantages of ethanoic anhydride over ethanoyl chloride in the manufacture of the drug aspirin.

13.6 Aromatic Chemistry

13.6.1 Bonding understand the nature of the bonding in a benzene ring,

limited to planar structure and bond length intermediate between single and double.

13.6.2 Delocalisation stability understand that delocalisation confers stability to the

molecule.

be able to use thermochemical evidence from enthalpies of hydrogenation to illustrate this principle.

13.6.3 Electrophilic substitution understand that electrophilic attack in arenes results

in substitution; mechanisms limited to the monosubstitutions given below.

13.6.4 Nitration understand that nitration is an important step in synthesis

(e.g. explosive manufacture and formation of amines from which dyestuffs are manufactured).

understand the mechanism of nitration, including the generation of the nitronium ion.

13.6.5 Friedel�Crafts reactions understand that Friedel�Crafts alkylation and

acylation reactions are important steps in synthesis.

understand the mechanism of alkylation and acylation using AlCl3 as catalyst.

know that industrially ethylbenzene is manufactured from benzene and ethene using HCl/AlCl3 ; know that this is an important intermediate in the manufacture of polystyrene (details of processes not required).

13.7 Amines

13.7.1 Base properties be able to explain the difference in base strength between

(Brønsted�Lowry) ammonia, primary aliphatic and primary aromatic amines

in terms of the availability of a lone pair on the N atom.

13.7.2 Nucleophilic properties understand that the nucleophilic substitution reactions

(including mechanism) of ammonia and amines with haloalkanes form primary, secondary, tertiary amines and quaternary ammonium salts; know the use of the latter as cationic surfactants.

13.7.3 Preparation know that primary aliphatic amines can be prepared from

haloalkanes and by the reduction of nitriles.

know that aromatic amines are prepared by the reduction of nitro compounds.

13.8 Amino Acids

13.8.1 Acid and base properties understand that amino acids have both acidic and

basic properties.

13.8.2 Proteins understand that proteins are sequences of amino acids

joined by peptide links.

understand that hydrolysis of the peptide link produces the constituent amino acids.

understand the importance of hydrogen bonding in proteins (detailed structures not required).

13.9 Polymers

13.9.1 Addition polymers know that addition polymers may be formed directly from

compounds containing C=C bonds.

be able to draw polymer structures from monomer structures and vice versa.

understand that polyalkenes are chemically inert and therefore non-biodegradable.

13.9.2 Condensation polymers understand that condensation polymers may be

formed by reactions between dibasic acids and diols, between dicarboxylic acids and diamines and between amino acids.

know the linkage of the repeating units of polyesters (e.g. Terylene) and polyamides (e.g. nylon 6,6).

understand that polyesters and polyamides can be broken down by hydrolysis and are, therefore, biodegradable (mechanisms not required).

13.10 Organic Synthesis and

Analysis

13.10.1 Applications be able to use the organic reactions described above in synthesis and analysis, using the characteristic reactions of functional groups in this module and in AS3 (alkenes, haloalkanes and alcohols).

13.11 Structure Determination

13.11.1 Data sources be able to use data from all the analytical techniques listed below to determine the structure of specified compounds.

13.11.2 Mass spectrometry understand that mass spectrometry can be used to

determine the molecular formula of a compound from the mass of the molecular ion.

understand that the fragmentation of a molecular ion

M+. X+ + Y.

gives rise to a characteristic relative abundance spectrum

(rearrangement processes not required).

know that the more stable X+ species give higher peaks, limited to carbocation and acylium (RCO+ ) ions.

13.11.3 Infra-red spectroscopy understand that certain groups in a molecule absorb

infra-red radiation at characteristic frequencies.

understand that "fingerprinting" allows identification of a molecule by comparison of spectra.

be able to use spectra to identify particular functional groups and to identify impurities, limited to data presented in wave-number form.

13.11.4 Nuclear magnetic understand that nuclear magnetic resonance gives

resonance spectroscopy information about the relative number and position of hydrogen atoms in a molecule.

understand that proton n.m.r. spectra are obtained using samples dissolved in proton-free solvents (e.g. deuterated solvents and CCl4 ).

understand why tetramethylsilane (TMS) is used as a standard.

know the use of the d scale for recording chemical shift.

understand that chemical shift depends on the molecular

environment.

understand how integrated spectra indicate the relative numbers of protons in different environments.

be able to use the n +1 rule to deduce the spin�spin splitting patterns of adjacent, non-equivalent protons, limited to doublet, triplet and quartet formation in simple aliphatic compounds.