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Chemistry Unit 1 Area of Study 2 (Organic Compounds (Hydrocarbons (ALKANES…
Chemistry Unit 1 Area of Study 2
Properties of Molecular Substances
Physical Properties:
Generally low boiling points
No electrical conductivity
Covalent Bonding
Sharing of electrons
Can be unequal share
DRAWING
Valence shell diagram
Electron dot diagram
Shows single, double and triple bonds
VSEPR
Valence Shell Electron Pair Repulsion
Shapes that can be formed
Linear: HCl
Bent: H2O
Tetrahedral: CH4
Trigonal Pyramidal: NH3
Trigonal Planar: BF3
Intermolecular Forces
Polarity
Due to Uneven sharing of electrons or lone pairs
EG: HCl (H slightly positive, Cl slightly negative).
It is dipole because it has a slightly pos. end and a slightly neg. end)
EG: NH3 (H3 slightly pos. and N slightly neg.)
Types
Hydrogen Bonding
Either O/N/F and H
EG: NH3, H2O, HF
Dipole-Dipole
Permanent Dipole
EG: HCl, CO
Dispersion forces
Instantaneous Dipole
Occurs in Non-Polar molecules
EG: CH4, CO2
Strength
Hydrogen > Dipole-Dipole > Dispersion Forces
Effect on Physical Properties
Boiling Point
H2O has abnormally high BP for its molecular weight due to the strength of Hydrogen Bonds
Compounds of Carbon
Allotropes
Amporphous
Has no long range order in bonding
EG: Charcoal
Giant Covalent Lattice
Highly ordered tetrahedral carbon atoms
EG: Diamond
Hard, does not conduct electricity because no free electrons
Hexagonal Stacked Lattice
Hexagonal 2D Layers stacked (intermolecular forces between layers)
EG: Graphite
Soft, conducts electricity
Nanostructures
Fullerenes (buckyballs)
Nanowires
Graphene
An allotrope is the same element with different structures
Organic Compounds
Crude Oil
Comes from dead marine organisms
Fossils come from long time, lots of heat and high pressure under the sea
Separates with fractional distillation (based on BP)
Homologous Series
Family where members differ by a single unit
Hydrocarbons
Molecules that only contain Hydrogen and Carbon
ALKANES
CnH2n+2
Structural Formula
CH3-CH2-CH2-CH3
Semi-structural Formula
CH3(CH2)2CH3
Meth, Eth, Prop, But, Pent, Hex, Hept, Oct, Non, Dec
ALKENES
CnH2n
Unsaturated
ALKYNES
CnH2n-2
Unsaturated
Alcohols
R-OH
Suffix is -ol
Carboxylic Acids
R-COOH
EG: Ethanoic Acid
Esters
R-COOH-R'
Suffix is -anoate
Name the alcohol first
EG: Ethyl Ethanoate
Isomers
Chain Isomers
Position of a branch
EG: 2-methylpentane vs 3-methylpentane
Positional Isomers
Position of functional group
EG: but-1-ene vs but-2-ene
EG:Propan-1-ol vs propan-2-ol
Polymers
A polymer is many units
A monomer is one unit
Named after monomer
EG: polyethene (made from ethene)
Additives: change physical properties
Additional Polymerisation
Tacticity
Isotactic: same side
Atactic: Random
Syndiotactic: Alternating