Definitions for AS OCR chemistry A
Key definitions for organic chemistry
- Created by: Alyssa Tamburo
- Created on: 03-04-11 17:29
Functional Group
The part of the organic molecule responsible for its chemical reactions.
Homologous Series
A series of organic compounds with the same functional group but with each successive member differing by CH2.
Alkyl group
An alkane with a hydrogen atom removed. For example, CH3, C2H5 etc.
General Formula
The simplest algebraic formula of a member of a homologous series. For example, alkanes have the general formula of CnH2n+2, alkenes- CnH2n, alcohols- CnH2n+1OH.
Displayed Formula
Shows the relative positioning of all the atoms in a molecule and the bonds between them.
Structural Formula
The minimal detail for the arrangement of atoms in a molecule.
Skeletal Formula
- Simplified organic formula with hydrogen atoms removed from the alkyl chains
- leaving just the carbon skeleton and functional groups.
Structural Isomers
Molecules with the same molecular formula but with different structural arrangements of atoms.
Stereoisomers
Same structural formula but with a different arrangement of atoms in space.
E/Z isomerism
- Different groups are attached to each carbon of a carbon-carbon double bond.
- These may be arranged differently in space because of the restricted rotation of the carbon-carbon double bond.
cis-trans isomerism
- A special type of E/Z isomerism.
- There is a hydrogen and a non-hydrogen group on each C of the carbon-carbon double bond.
- The Cis isomer (Z) has hydrogens on the same side.
- The Trans (E) has hydrogens on different sides.
Homolytic Fission
The breaking of a covalent bond with one of the bonded electrons going to each atom to form two radicals.
Heterolyic Fission
The breaking of a covalent bond with both of the bonded electrons going to one of the atoms forming a cation and an anion.
Nucleophile
An atom that is attracted to an electron deficient atom where it donates a pair of electrons to form a new covalent bond.
Radical
A species with an unpaired electron.
Electrophile
An atom that is attracted to an electron rich atom where it accepts a pair of electrons to form a new covalent bond.
Addition Reaction
A reactant is added across an unsaturated molecule to make a saturated molecule. In other words...
- double bonds to single bonds
- 2 reactants to 1 product
Substitution Reaction
An atom is replaced with a different atom.
- 2 reactants to 2 products
Elimination Reaction
Removal of a molecule from a saturated to make an unsaturated.
- Single bonds to double bonds
- 1 reactant to 2 products
Fractional Distillation
Separation of components in a liquid mixture into fractions which differ in boiling points.
Cracking
Breaking down a long chained saturated hydrocarbon to form a mixture of short chained alkanes and alkenes.
Radical Substitution
A radical replaces a different atom.
Mechanism
A sequence of steps showing the path taken by electrons in a reaction.
Initiation
The FIRST step in radical substiution in which the free radicals are generated by UV radiation.
Termination
The LAST step in radical substitution when two radicals combine to form a molecule.
Pi bond
- The reactive part of the double bond.
- It is formed above and below the plane of bonded atoms by overlap of p-orbitals.
Carbocation
An organic ion where the carbon atom has a positive charge.
Curly Arrow
Shows the movement of an electron pair in the breaking and formation of a covalent bond.
Polymer
A long molecular chain built up from many small monomer units.
Addition Polymerisation
An unsaturated alkene (monomer) adds on to a polymer chain one at a time to form a long saturated molecular chain.
Addition Polymer
A very long molecular chain formed by repeated addition reactions of many unsaturated alkene molecules (monomers).
Repeat Unit
- A specific arrangement of atoms that occur in the structure over and over again.
- The repeat units will be in brackets outside of which is the symbol n.
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