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OCR A Level Chemistry Paper 2 definitions
complete combustion
the process that occurs upon burning a compound in a plentiful supply of oxygen
covalent bond
the strong electrostatic attraction between a shared pair of electrons and the nuclei of bonding atoms
delocalised electrons
electrons in a molecule, ion, or solid metal that are not associated with a single atom or covalent bond
dipole
a partial charge on an atom, or end of a molecule, caused by the differing electronegativities of the atoms in a covalent bond
displacement reaction
a reaction in which a more reactice element displaces a less reactive element from a compound containing the less reactive element
displayed formula
a formula showing the relative positioning of all the atoms in a molecule and the bonds between them
electronegativitity
a measure of the tendency of an atom to attract a bonding pair or electrons
electrophile
an electron pair acceptor
electron pair repulsion
the repulsion experienced by the pairs of electrons around a nucleus due to their like negative charged that results in the shape of a molecule (as it adopts the shape in which the electrons experience the least repulsion)
empirical formula
a representation of a compound that shows the simplest whole number ratio of the atoms of each element in its structure
isotopes
atoms of the same element with the same number of protons but different numbers of neutrons, and different atomic masses
Pauling electronegativity value
a value assigned as a measure of the relative attraction of a bonded atom for the pair of electrons in a covalent bond
relative atomic mass
the weighted mean mass of one atom of an element relative to one-twelfth of the mass of one atom of carbon-12
relative isotopic mass
the mass of one atom of an isotope relative to one-twelfth the mass of one atom of carbon-12
relative molecular mass
the weighted mean mass of one molecule of a compound relative to one-twelfth the mass of one atom of carbon-12
structural formula
a formula showing the minimal detail for the arrangement of atoms in a molecule
substitution reaction
a reaction in which an atom or group of atoms is replaced with a different atom or group of atoms, forming the same number of products as there were reactants
volatility
the ease with which a liquid turns into a gas (evaporates)
addition reaction
a reaction in which two or more reactant molecules combine to form a single product
addition polymerisation
formation of a very long molecular chain by repeated addition reactions of many unsaturated alkene monomers
alicyclic
organic compounds containing carbon atoms arranged in one or more non-aromatic rings
aliphatic
a compound containing carbon and hydrogen atoms joined in straight or branched chains, or non-aromatic rings
alkanes
a homologous series of hydrocarbons with single carbon-carbon bonds and a general formula of CnH2n+2
alkenes
a homologous series of hydrocarbons containing at least one double carbon-carbon bond and a general formula of CnH2n
alkyl group
a substituent of larger organic molecules formed by removing a hydrogen atom from an alkane parent chain
biodegradable
a substance that can be decomposed by bacteria or other living organisms
Cahn-Ingold-Prelog priority rules
a set of rules used to identify whether a stereoisomer is E or Z; atoms with a higher atomic number have higher priority
carbocation
an ion that contains a positively charged carbon atom
chain reaction
a reaction in which the products cause additional reactions to take place
Cis-trans isomerism
a type of E/Z isomerism in which two of the substituent groups attached to each carbon atom of the C=C group are the same
condensation reaction
a reaction in which two smaller molecules react together to form a larger product with the elimination of a small molecule such as water
dehydration reaction
an elimination reaction in which water is removed from a saturated molecule to form an unsaturated product
E/Z isomerism
a type of isomerism in which different groups attached to each carbon of a C=C bond are arranged differently due to the restricted rotation about the double covalent bond
electrophilic addition
a reaction in which a pi-bond is broken and two new sigma-bonds are formed as a result of the addition of an electron pair acceptor
electrophilic substitution
a type of substitution reaction in which an electrophile is attracted to a region of high electron density, where it accepts a pair of electrons to form a covalent bond, replacing an atom/group of atoms
elimination reaction
a reaction in which an atom or group of atoms is removed from a molecule to form a new product
fingerprint region
an area of an infrared spectrum below 1500 cm-1 that gives a characteristic pattern for different componds
fractional distillation
the separation of components in a liquid mixture by their different boiling points into fractions with different compositions
fragment ions
ions formed from the breakdown of the molecular ion in a mass spectrometer
fragmentation
the process in mass spectrometry that causes a positive ion to split into smaller pieces, one of which is a positive fragment ion
functional group
the part of the organic molecule responsible for its chemical reactions
general formula
the simplest algebraic formula of a member of a homologous series
heterolytic fission
the breaking of a covalent bond forming a cation and an anion
homologous series
a series of organic compounds with the same functional group but with each successive member differing by CH2
homolytic fission
the breaking of a covalent bond with one of the bonded electrons going to each atom, forming two radicals
hydrocarbon
a compound of hydrogen and carbon only
hydrolysis
a reaction with water that breaks a chemical compound into two compounds, the H and OH in a water molecule becomes incorporated into the two compounds
infrared spectroscopy
an instrumentation method of analysis that identifies bonds from absorption of the infrared radiation of different wavelengths
intermediate
a species formed during a reaction that reacts further and is not present in the final products
molecular formula
a formula that shows the number and type of each element present in a molecule
molecular ion
the positive ion formed in mass spectrometry when a molecule loses an electron
monomer
a small molecule that combines with many other monomers to form a polymer
nucleophile
an electron pair donor
nucleophilic substitution
a reaction in which a nucleophile is attracted to an electron-deficient carbon atom, and replaces an atom or group of atoms on the carbon atom
optical isomers
stereoisomers that are non-superimposable mirror images of each other
pi-bond
a bond formed by the sideways overlap of two p-orbitals, with the electron density above and below the plane of the bonding atoms
polymer
a large molecule formed from many thousands of repeat units of smaller molecules (monomers)
precipitation reaction
the formation of a solid from a solution during a chemical reaction
primary alcohol
an alcohol in which the OH group is attached to a carbon atom that is attached to two or three hydrogen atoms
radical
a species with an unpaired electron
retention time
in gas chromatography, the time for which a component to pass from the column inlet to the detector
sigma-bond
a bond formed by the overlap of orbitals in an end-to-end fashion, with the electron density concentrated between the nuclei of the bonding atoms
saturated
molecules in which all carbon-carbon bonds are single covalent bonds
secondary alcohol
an alcohol in which the -OH group is attached to a carbon atom that is attached to two carbon chains and one hydrogen atom
skeletal formula
the simplified organic formula, shown by removing hydrogen atoms from alkyl chains, leaving just a carbon skeleton and associated functional groups
spin-spin coupling
in an NMR spectrum, the interaction between spin states of non-equivalent nuclei that results in the splitting of a signal
stereoisomers
molecules with the same structural formula but with a different arrangement of atoms in space
structural formula
a formula showing the minimal detail for the arrangement of atoms in a molecule
structural isomers
molecules with the same molecular but different structural formulae
termination
the step at the end of a radical substitution reaction when two radicals combine to form a molecule
tertiary alcohol
an alcohol in which the -OH group is attached to a carbon atom that is attached to three carbon atoms and no hydrogen atoms
unsaturated
the presence of multiple carbon-carbon bonds
alkynes
the hydrocarbon homolgous series with at least one triple carbon-carbon bond and the general formula of CnH2n-2
aromatic
a compound containing one or more benzene rings
chiral carbon
a carbon atom attached to four different atoms or groups of atoms
chemical shift
a scale, in ppm, that compares the frequency of an NMR absorption with the frequency of the reference tetramethylsilane at 0ppm
chromatogram
a visible record showing the result of separation of the components of a mixture by chromatography
dehydration
an elimination reaction in which water is removed from a saturated molecule to make an unsaturated molecule
enantiomers
stereoisomers that are non-superimposable mirror images of each other
esterification
a condensation reaction in which a carboxylic acid reacts with an alcohol to form an ester and water
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