OCR A Chemistry UNIT 2 definitions

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  • Created by: DJT
  • Created on: 05-04-13 19:51
hydrocarbons
organic compounds that contain carbon and hydrogen only.
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saturated hydrocarbon
a hydrocarbon with single bonds only.
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unsaturated hydrocarbon
a hydrocarbon containing carbon-to-carbon multiple bonds.
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aliphatic hydrocarbon
a hydrocarbon with carbon atoms joined together in straight or branched chains.
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alicyclic hydrocarbon
a hydrocarbon with carbon atoms joined together in a ring structure.
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functional group
the part of the organic molecule responsible for its chemical reactions.
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homologous series
a sereis of organic compounds with the same functional group but with each successive member differing by CH2.
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Alkanes
the homologous sereis with the general formula CnH2n+2.
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Nomenclature
a system of naming compounds.
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alkyl group
an alkane with a hydrogen atom removed, e.g. CH3, C2G5; any alkyl group is often shown as 'R'.
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general formula
the simplest algebraic formula of a member of a a homologous series. For example, the general formula of the alkanes is CnH2n+2.
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displayed formula
shows the relative positioning of all the atoms in a molecule and bonds between them.
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structural formula
shows the minimal detail for the arrangement of atoms in a molecule. e.g CH3CH2CH3
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skeletal formula
a simplified organic formula with hydrogen atoms removed from alkyl chains, leaving just the carbon skeleton and associated functional groups.
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structural isomers
molecules with the same molecular formula but with different structural arrangements of atoms.
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Stereisomers
compounds with the sane structural formula, but with a different arrangement of the atoms in space.
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E/Z isomerism
a type of stereoisomerism in which different groups attached to each carbon of a C=C double bond many be arranged differently in space because of the restricted rotation of the C=C bond.
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cis-trans isomerism
a special type of E/Z isomerism in which there is a non-hydrogen group and a hydorgen on each C of a C=C double bond: the cis isomer (Z isomer) has the H atoms on each carbon on the same side; the trans isomer (E isomer) has the H atoms on opposite.
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Homolytic fission
the breaking down of a covalent bond, with one of the bonded atoms going to each atoms, forming two radicals.
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radical
a species with and unpaired electron.
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Heterolytic fission
the breaking of a covalent bond with both of the bonded electrons going to one of the atoms, forming a cation (+ ion) and an anion (- ion)
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nucleophile
an atom (or group of atoms) that is attracted to an electron-deficient centre or atom, where it donates a pair of electrons to form a new covalent bond.
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electrophile
an atom (or group of atoms) that is attracted to an electron-rich centre or atom, where it accepts a pair of electrons to from a new covalent bond.
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addition reaction
a reaction in which a reactant is added to an unsaturated molecule to make a saturated molecule.
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substitution reaction
a reaction in which an atom or group of atoms is replaced with a different atom or group of atoms.
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elimination reaction
refers to the removal of a molecule from a saturated molecule to make an unsaturated molecule.
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fractional distillation
the seperation of the components in a liquid mixture into fractions which differ in boiling points (and hence chemical composition) by means of distillation, typically using a fractioning column.
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Cracking
the breaking down of long-chained saturated hydrocarbons to from a mixture of shorter-chained alkanes and alkenes.
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catalyst
a substance that increases the rate of a chemical reaction without being used up in the process.
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Radical substitution
a type of substitution reaction in which a radical replaces a different atom or group of atoms.
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Mechanism
a sequence of steps showing the path taken by electrons in a reaction.
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Initiation
the first step in a radical substitution in which the free radicals are generated by ultraviolet radiation.
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Propogation
the two repeated steps in radical substitution that build up the poducts in a chain reaction.
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Termination
the step at the end of radical substitution when two radicals combine to form a molecule.
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pi bond
the reactive part of a double bond formed above and below the plane of the bonded atoms by sideways overlap of p-orbitals.
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Electrophilic addition
a type of addition reaction in which an electrophile is attracted to an electron-rich centre or atom, where it accepts a pair of electrons to form a new covalent bond.
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Carbocation
an organic ion in which a carbon atom has a positive charge.
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curly arrow
a symbol used in reaction mechanisms to show the movement of an electron pair in the breaking or formation of a covalent bond.
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polymer
a long molecular chain built up from monomer units.
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monomer
a sall molecule that combines with many other monomers to form a polymer.
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Addition polymeristaion
the process in whihc unsaturated alkene molecules (monomers) add on to a growing polymer chain one at a time, to form a very long saturated molecular chain (the addition polymer)
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addition polymer
a very long molecular chain, formed by repeated addition reactions of many unsaturated alkene molecules (monomers).
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repeat unit
a specific arrangement of atoms that occurs in the structure over and over again . Repeat units are included in brackets, outside of which is the symbol n.
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Biodegradable material
a material that is broken down naturally in the environment by living organisms
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Other cards in this set

Card 2

Front

a hydrocarbon with single bonds only.

Back

saturated hydrocarbon

Card 3

Front

a hydrocarbon containing carbon-to-carbon multiple bonds.

Back

Preview of the back of card 3

Card 4

Front

a hydrocarbon with carbon atoms joined together in straight or branched chains.

Back

Preview of the back of card 4

Card 5

Front

a hydrocarbon with carbon atoms joined together in a ring structure.

Back

Preview of the back of card 5
View more cards

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Sonal Chakraborty

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