Hydrocarbons

Alkanes: Free-Radical Substitution and CombustionSign up

know the general formula of alkanes and cycloalkanes, and understand that they are hydrocarbons (compounds of carbon and hydrogen only) which are saturated (contain single bonds only) · understand the term 'structural isomerism' and be able to draw the structural isomers of organic molecules, given their molecular formula · be able to draw and name the structural isomers of alkanes and cycloalkanes with up to six carbon atoms · know that alkanes are used as fuels and obtained from the fractional distillation, cracking and reforming of crude oil, and be able to write equations for these reactions · know that pollutants, including carbon monoxide, oxides of nitrogen and sulfur, carbon particulates and unburned hydrocarbons, are emitted during the combustion of alkane fuels · understand the problems arising from pollutants from the combustion of alkane fuels, limited to the toxicity of carbon monoxide and why it is toxic, and the acidity of oxides of nitrogen and sulfur · be able to discuss the reasons for developing alternative fuels in terms of sustainability and reducing emissions, including the emission of CO2 and its relationship to climate change · be able to apply the concept of carbon neutrality to different fuels, such as petrol, bioethanol and hydrogen · understand the reactions of alkanes with: (i) oxygen in the air (combustion); (ii) halogens · understand the mechanism of the free radical substitution reaction between an alkane and a halogen: (i) using free radicals, which are species with an unpaired electron, represented by a single dot; (ii) showing the initiation step of the mechanism, with curly half-arrows for free radical formation; (iii) showing the propagation and termination steps of the mechanism; (iv) having limited use in synthesis because of further substitution reactions

Alkenes: Electrophilic Addition and OxidationSign up

be able to describe the reactions of alkenes, limited to: (i) the addition of hydrogen, using a nickel catalyst, to form an alkane; (ii) the addition of halogens to produce a di-substituted halogenoalkane; (iii) the addition of hydrogen halides to produce mono-substituted halogenoalkanes; (iv) the addition of steam, in the presence of an acid catalyst, to produce alcohols; (v) oxidation of the double bond by acidified potassium manganate(VII) to produce a diol · know the qualitative test for a C=C double bond using bromine or bromine water · be able to describe the mechanism (including diagrams), giving evidence where possible, of: (i) the electrophilic addition of bromine and hydrogen bromide to ethene; (ii) the electrophilic addition of hydrogen bromide to propene. Use of the curly arrow notation is expected — the curly arrows should start from either a bond or from a lone pair of electrons. Knowledge of the relative stability of primary, secondary and tertiary carbocation intermediates is expected.

Arenes: Benzene Structure, Reactions and Side-Chain vs Ring HalogenationSign up

be able to use thermochemical, X-ray diffraction and infrared data as evidence for the structure and stability of the benzene ring (students may represent the structure of benzene as the Kekulé or the delocalised form as appropriate in equations and mechanisms) · understand that the delocalised model for the structure of benzene involves overlap of p-orbitals to form pi-bonds · understand why benzene is resistant to bromination, compared to alkenes, in terms of delocalisation of pi-bonds in benzene compared to the localised electron density of the pi-bond in alkenes · know the following reactions of benzene, limited to: (i) oxygen in air (combustion to form a smoky flame); (ii) bromine, in the presence of a catalyst; (iii) a mixture of concentrated nitric and sulfuric acids; (iv) fuming sulfuric acid; (v) halogenoalkanes and acyl chlorides with aluminium chloride as catalyst (Friedel-Crafts reaction)