Introduction: This unit develops the concepts of physical chemistry introduced at AS. 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.

3.4.1 Kinetics

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)

Determination of rate equation

• be able to derive the rate equation for a reaction from 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
• understand that the orders of reactions with respect to reactants can be used to provide information about the rate determining/limiting step of a reaction

3.4.2 Equilibria

Equilibrium constant Kc for homogeneous systems

• know that Kc is the equilibrium constant calculated from equilibrium concentrations for a system at constant temperature
• be able to construct an expression for Kc for an homogeneous system in equilibrium;
• be able to perform calculations involving such an expression

Qualitative effects of changes of temperature and concentration

• be able to predict the effects of changes of temperature on the value of the equilibrium constant
• understand that the value of the equilibrium constant is not affected by changes either in concentration or the addition of a catalyst

3.4.3 Acids and Bases

Bronsted.Lowry acid.base equilibria in aqueous solution

• know that an acid is a proton donor
• know that a base is a proton acceptor
• know that acid.base equilibria involve the transfer of protons

Definition and determination of pH

• know that pH = . log10[H+], where [ ] represents the 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 concentration

The ionic product of water, Kw

• know that water is weakly dissociated
• know that Kw = [H+][OH- ]
• be able to calculate the pH of a strong base from its concentration.

Weak acids and bases

Ka for weak acids

• know that weak acids and weak bases dissociate only slightly in aqueous solution
• 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 perform calculations relating the pH of a weak acid to the dissociation constant, Ka, and the concentration pH curves, titrations and indicators
• understand the typical shape of pH curves for acid.base titrations in all combinations of weak and strong monoprotic acids and bases
• be able to use pH curves to select an appropriate indicator
• be able to perform calculations for the titrations of monoprotic and diprotic acids with sodium hydroxide, based on experimental results

Buffer action

• be able to explain qualitatively the action of acidic and basic buffers
• know some applications of buffer solutions
• be able to calculate the pH of acidic buffer solutions

3.4.4 Nomenclature and Isomerism in Organic Chemistry

Naming organic compounds

• be able to apply IUPAC rules for nomenclature not only to the simple organic compounds, limited to chains with up to 6 carbon atoms, met at AS, but also to benzene and the functional groups listed in this unit

Isomerism

• know and understand the meaning of the term structural isomerism
• know that E-Z isomerism and optical isomerism are forms of stereoisomerism
• know that an asymmetric carbon atom is chiral and gives rise to optical isomers which exist as non super-imposable 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 structural formulae and displayed formulae of isomers
• appreciate that drug action may be determined by the stereochemistry of the molecule and that different optical isomers may have very different effects

3.4.5 Compounds Containing the Carbonyl Group

Aldehydes and ketones

• know 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 and Tollens' reagent)
• appreciate the hazards of synthesis using HCN/KCN
• know 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

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. in solvents, plasticizers, perfumes and food fl avourings)
• know that vegetable oils and animal fats are esters of propane-1,2,3-triol (glycerol)
• know that esters can be hydrolysed
• understand that vegetable oils and animal fats can be hydrolysed to give soap, glycerol and long chain carboxylic (fatty) acids
• know that biodiesel is a mixture of methyl esters of long chain carboxylic acids

Acylation

• know that vegetable oils can be converted into biodiesel by reaction with methanol in the presence of a catalyst
• know the reaction with ammonia and primary amines with acyl chlorides and acid anhydrides
• 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

3.4.6 Aromatic Chemistry

Bonding

• understand the nature of the bonding in a benzene ring, limited to planar structure and bond length intermediate between single and double

Delocalisation

• stability understand that delocalisation confers stability to the molecule
• be able to use thermochemical evidence from enthalpies of hydrogenation to illustrate this principle

Electrophilic substitution

• understand that electrophilic attack in arenes results in substitution; mechanisms limited to the monosubstitutions given below

Nitration

• understand that nitration is an important step in synthesis e.g. manufacture of explosives and formation of amines from which dyestuffs are manufactured
• understand the mechanism of nitration, including the generation of the nitronium ion

Friedel.Crafts acylation reactions

• understand that Friedel.Crafts acylation reactions are important steps in synthesis
• understand the mechanism of acylation using AlCl3 as catalyst

3.4.7 Amines

Base properties (Bronsted.Lowry)

• be able to explain the difference in base strength between ammonia, primary aliphatic and primary aromatic amines in terms of the availability of a lone pair on the N atom

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 that the latter can be used as cationic surfactants

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

3.4.8 Amino Acids

Acid and base properties

• understand that amino acids have both acidic and basic properties, including the formation of zwitterions

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
• know that mixtures of amino acids can be separated by

Chromotography

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

3.4.9 Polymers

Addition polymers

• be able to draw the repeating unit of addition polymers from monomer structures and vice versa

Condensation polymers

• understand that condensation polymers may be formed by reactions between dicarboxylic 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 and Kevlar)

Biodegradability and disposal of polymers

• understand that polyalkenes are chemically inert and therefore non-biodegradable
• understand that polyesters and polyamides can be broken down by hydrolysis and are, therefore, biodegradable (mechanisms not required)
• appreciate the advantages and disadvantages of different methods of disposal of polymers
• appreciate the advantages and disadvantages of recycling polymers

3.4.10 Organic Synthesis and Analysis

Applications

• be able to deduce how to sythese organic compounds using the reactions in this specification
• be able to identify organic functional groups using the reactions in the specification

3.4.11 Structure Determination

Data sources

• be able to use data from all the analytical techniques listed below to determine the structure of specified compounds

Mass spectrometry

• understand that the fragmentation of a molecular ion M+. X+ + Y. gives rise to a characteristic relative abundance spectrum that may give information about the structure of the molecule (rearrangement processes not required)
• know that the more stable X+ species give higher peaks, limited to carbocation and acylium (RCO+) ions

Infrared spectroscopy

• be able to use spectra to identify functional groups in this specification

Nuclear magnetic resonance spectroscopy

• understand that nuclear magnetic resonance gives information about the position of 13C or 1H atoms in a molecule
• understand that 13C n.m.r. gives a simpler sprectrum than 1H n.m.r.
• know the use of the
  scale for recording chemical shift
• understand that chemical shift depends on the molecular environment
• understand how integrated spectra indicate the relative numbers of 1H atoms in different environments
• understand that 1H 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
• 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

Chromatography

• know that gas-liquid chromatography can be used to separate mixtures of volatile liquids
• know that separation by column chromatography depends on the balance between solubility in the moving phase and retention in the stationary phase