Alkanes Flashcards
Molecular formula
The actual number of each type of atom.
Empirical formula
The simplest whole number ratio of atoms of elements in a formula.
General formula
Of a homologous series, can be used to calculate the molecular formula of any member of a series by substituting n for the number of C atoms.
Alkanes: CnH2n+2
Alkenes: CnH2n
Structural formula
Of a compound shows how the atoms are arranged in a molecule &, in particular, shows which functional groups are present.
Displayed formula
Completely drawn out, showing all bonds.
Skeletal formula
A simplified organic formula with H2 atoms removed from any ‘alkyle’ chains, leaving just the C skeleton & functional groups.
Homologous series
A series of organic compounds with the same functional group, but with each successive member differing by CH2.
Functional group
A part of the molecule responsible for its chemical reactions.
Isomers
Molecules with the same molecular formula, but in which the atoms are arranged in a different way.
Structural isomers
Different structural formulae.
Three types: chain isomerism, positional isomerism, & functional group isomerism.
Hydrocarbon
A compound containing C & H only.
Saturated
Single C-C bonds only in a molecule.
Unsaturated
The molecule has at least 1 C=C bond.
Aliphatic
Hydrocarbon molecules with the C atoms joined together in straight/branched chains.
Alicyclic
Hydrocarbon molecules with the C atoms joined together in a ring structure.
Free radical
A reactive species with an unpaired e- which is formed as a covalent bond breaks.
Homolytic fission
The breaking of a covalent bond equally with 1 of each of the bonded e- going to each atom ie. creating free radicals.
Heterolytic fission
The breaking of a covalent bond with 1 of the C atoms taking both e- from the bond. Form ions (+ & -)
Substitution reactions
When an atom/group is replaced by another.
Radical substitution
A type of substitution where a radical replaces an atom/group.
Mechanism
A sequence of steps showing a suggested path taken by a reaction.
Initiation
The 1st step of radical substitution. It involves generating free radicals using UV radiation energy.
Propagation
2 or more steps.
1stly, alkane reacts with the Cl’, breaking its C-H bond homolytically, forming a ‘CH3 & H-Cl.
2ndly, ‘CH3 + Cl2 react to form, for eg CH3Cl & a new Cl’ to be used in further propagation.
Termination
The end of the reaction, when 2 free radicals combine to form a molecule.
Nb. Lots of possible termination steps.
