Organic Chemistry and Polymers

functional group

part of an organic molecule where most of its chemical reaction occur

homologous series

a series of compounds that belongs to the same functional group that differs by -CH

substituent

an atom or group of atoms attached to a chain or ring of carbon atoms

alkyl group

the group of atoms that would be obtained by removed a hydrogen atom from an alkane

locants

numbers that tell us where substituents/functional groups are located on the main chain

structural isomers

compounds that have the same molecular formula but differ in the way that atoms are arranged

physical properties of alkanes are related to

• size of molecule

• degree of branching

solubility

measured as the mass of solute that can dissolve 100g of solvent at a specific temperature

Density

mass per unit volume

• impacted by how closely molecules pack together

Viscocity

a measure of the resistance of a liquid to flow

• larger molecules, more viscous, stronger inter forces, molecules cant move as easily

• greater branching, less viscous, molecules not packed at tightly, weaker disp. forces, molecules move past each other more readily

Volatility

how easily liquids evaporate (significant when considering use of hydrocarbon fuel)

• larger molecules, lower volatility

• greater branching, more volatile, weaker disp. forces, require less energy to overcome

combustion reaction

chemical reaction between a substance and oxygen that proceeds with the evolution of heat and light

complete and incomplete combustion

complete: sufficient oxygen present

incomplete: limited supply of oxygen

haloalkanes physical properties

• solubility decreases with increasing chain length (non-polar)

alcohols (ol)

an organic compound in which a hydroxyl group -OH is bonded to a carbon atom

alcohols physical properties

solubility decreases in water as length of hydrocarbon chain increases

• hydrogen bonding

• dispersion forces

aldehydes (al)

an organic compound whose functional group is the carbonyl functional group

ketones (-one)

has alykl groups on either side of carbonyl function group (in the middle)

carboxylic acids (oic acid)

an organic compound whose functional group is the carboxyl group

carboxylic acids physical properties

• form more H bonds than hydroxyl groups

• two carboxyl groups hydrogen bonds the molecules forms a dimer

• greater H bonds = more energy required to overcome

• higher melting/boiling point and viscosity

• lower volatility

• hydrogen bonding, dispersion, covalent

esters (oate)

carboxylic acid derivative, -OH portion of carboxyl group replaced with -OR group

esterification reactions

condensation reaction: carboxylic acids react fairly readily with alcohols to form esters

• catalyst used

crude oil

• non-renewable, used up at a far faster rate than its generated

plant sources

sugar cane, corn

• can fic c02 from atmosphere into glucose via photosynthesis

• glucose extracted + fermented into ethanol - bioethanol

barriers to replacing crude oil w more renewable resources

• large area of land needed to grow plants

• very high cost

polymers

large covalent molecules made by joining together smaller molecules called monomers (formed through polymerisation)

they have a carbon backbone

addition polymers

formed from unsaturated monomers where C=C can reaction to form new sngle covalent bonds between monomer molecules

monomers can simply add together

NO other products formed

prefix ‘poly’

condensation polymerisation

polymers formed by reaction between the functional groups of two different monomers

monomers must contain at least two functional groups

small molecules such as water will be eliminated

High Density Polyethene

• produced at low pressures in presence of a catalyst

• polymer chains have very few side branches

• able to pack closely together

• high density + hard and rigid

• white water piping, containers

Low Density Polyethene

• produced at high pressures in the presence of catalyst

• polymer chains have frequent branches

• unable to pack closer together

• low density + soft and flexible

• garbage bags, cling wrap

Thermoplastic Polymers

• weak intermolecular forces

• softens when heated

• no crosslinks

Thermosetting polymers

• strong covalent bonds

• covalent bonds between polymers called crosslinks (makes them rigid and heat resistant)

• chars when heated as covalent bonds broken

Uses + choices of polymers

advantages:

• non reactive

• cheaper raw materials

• low density

• good insulation of electricity

disadvantages:

• take a long time to decompose

• difficult to recycle

• releases toxins when burnt

• cause pollution

recycling

• compostable polymers

• break down naturally

• leave no harmful substances