Organic Chemistry structured questions · SEC G3 Pure Chemistry

Learning objectives

• name natural gas, mainly methane, and crude oil as non-renewable sources of energy
• describe crude oil as a mixture of hydrocarbons and its separation by fractional distillation to yield fractions which have competing uses as fuels and as a source of chemicals (see also 1.2(a))
• describe biofuel (exemplified by bioethanol from sugarcane) as a renewable alternative to natural gas and crude oil
• describe how biofuel, when compared to fossil fuels, can be more environmentally sustainable in terms of carbon dioxide emission (see also 12(g)).
• describe a homologous series as a group of compounds with a general formula, similar chemical properties and showing a gradation in physical properties as a result of increase in the size and mass of the molecules, e.g. melting and boiling points; viscosity
• describe the alkanes as a homologous series of saturated hydrocarbons with the general formula CnH2n+2
• draw the structures of branched and unbranched alkanes, C1 to C4, and name the unbranched alkanes methane to butane
• define isomerism and identify isomers
• describe alkanes (exemplified by methane) as being generally unreactive except in terms of combustion and substitution by chlorine
• describe the alkenes as a homologous series of unsaturated hydrocarbons with the general formula CnH2n
• draw the structures of branched and unbranched alkenes, C2 to C4, and name the unbranched alkenes ethene to butene
• describe the manufacture of alkenes and hydrogen by cracking hydrocarbons and recognise that cracking is essential to match the demand for fractions containing smaller molecules from the refinery process
• describe the difference between saturated and unsaturated hydrocarbons from their molecular structures and by using aqueous bromine
• describe the reactions of alkenes (exemplified by ethene) in terms of combustion, polymerisation (see also 11.4(b)), and the addition with bromine, steam and hydrogen
• state the meaning of polyunsaturated when applied to food products
• describe the manufacture of margarine by the addition of hydrogen to unsaturated vegetable oils to form a solid product.
• describe the alcohols as a homologous series containing the –OH group
• draw the structures of branched and unbranched alcohols, C1 to C4, and name the unbranched alcohols methanol to butanol
• describe the reactions of alcohols in terms of combustion and oxidation to carboxylic acids
• describe the formation of ethanol by the catalysed addition of steam to ethene and by fermentation of glucose
• describe the carboxylic acids as a homologous series containing the –CO2H group
• draw the structures of carboxylic acids, C1 to C4, and name the unbranched acids methanoic acid to butanoic acid
• describe the carboxylic acids as weak acids, reacting with carbonates, bases and some metals
• describe the formation of ethanoic acid by the oxidation of ethanol by atmospheric oxygen or acidified potassium manganate(VII).
• describe the reaction of a carboxylic acid with an alcohol to form an ester, e.g. ethyl ethanoate
• deduce the name and formula of an ester from the unbranched carboxylic acid, C1 to C4, and alcohol, C1 to C4, and vice versa.
• describe polymers as large molecules built up from small units (monomers), different polymers having different units and/or different linkages
• describe the formation of poly(ethene) as an example of addition polymerisation of ethene as the monomer (see also 11.2(j))
• state some uses of poly(ethene) as a typical plastic, e.g. plastic bags; clingfilm
• deduce the structure of the polymer product from a given monomer and vice versa
• describe nylon, a polyamide, and Terylene, a polyester, as condensation polymers, the partial structure of nylon being represented as and the partial structure of Terylene as (details of manufacture and mechanisms of these polymerisations are not required)
• state some typical uses of man-made fibres such as nylon and Terylene, e.g. clothing; curtain materials; fishing line; parachutes; sleeping bags
• describe the pollution problems caused by the disposal of non-biodegradable plastics
• describe two methods of recycling plastics as
• physical method (exemplified by melting small pieces of poly(ethene) waste into pellets)
• chemical method (exemplified by depolymerisation and cracking of plastic waste into chemical feedstock and fuel respectively) — describe depolymerisation as a process in which polymers are broken down into their monomers, exemplified by hydrolysis of polyesters using acid as a catalyst (details of mechanisms are not required)
• discuss the social, economic and environmental issues of recycling plastics.