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Glossary#

addition reaction - a type of reaction in which two molecules combine to form a large molecule. At least one of the molecules must be unsaturated.

addition polymerization – a type of polymerization in which unsaturated monomers (e.g. alkenes) undergo addition reactions with themselves to form polymers.

alkenes - a homologous series of unsaturated hydrocarbons with the general formula CnH2n

alkyl group – a homologous series of hydrocarbon molecules, with the general formula CnH2n+1

bromine water – an aqueous solution of bromine that can be used to test for the presence of unsaturation.

carbocation – an ion-containing a positively charged carbon atom. Carbocations are intermediates in electrophilic addition reactions of alkenes.

degree of polymerization – the number of monomers in a polymer, represented by the letter n. (Note that this ‘n’ is distinct from the ‘n’ used in a general formula).

electrophile – a species that takes part in a reaction by accepting a lone pair of electrons from a nucleophile.

electrophilic addition – an addition reaction in which an electrophile attacks a double bond and becomes bonded to one of the atoms that formed the double bond by a single covalent bond. One example is the formation of halogenoalkanes from alkenes, in which a halogen (X2) or hydrogen halide (HX) attacks a carbon–carbon double bond.

electrophilic addition reactions of alkenes - making halogenoalkanes, dihalogenoalkanes and alcohols.

homologous series – a group of compounds that all have the same functional group but a different number of carbon atoms. Examples include alkanes, alkenes, alcohols, amines and halogenoalkanes.

hydration – the addition of water across a carbon–carbon double bond.

hydrogenation – the addition of hydrogen across a carbon–carbon double bond.

monomer – the repeating unit from which a polymer is made. For example, the monomer of polypropene is propene.

Markownikoff ’s rule – the more electronegative part of the electrophile will usually attach itself to the more highly substituted carbon atom.

pi bond – a covalent bond formed by the sideways overlap of atomic orbitals. It is involved in double bonds, and prevents rotation about the bond. Represented by the symbol π.

polymerization – the formation of a long chain molecule (polymer) consisting of many monomer molecules joined together.

positional isomerism – a category of structural isomerism in which molecules have the same molecular formula but in which the functional group is attached to a different carbon atom. Alkenes with more than three carbon atoms can form positional isomers.

sigma bond – the strongest type of covalent bond, formed by the end-to-end overlap of atomic orbitals. Represented by the symbol σ.

unsaturated – a hydrocarbon, such as an alkene, that contains one or more carbon–carbon multiple bonds.

unsymmetrical – an alkene (such as propene) in which the atoms or groups of atoms attached to opposite ends of the carbon–carbon double bond is not the same. This means that when they undergo addition reactions, unsymmetrical alkenes create a mix of different products.