AS Organic

General formula

Algebraic formula that can be applied to chemicals in the ‘family’

Molecular formula

Actual number of atoms in a molecule or element

Empirical formula

Simplest whole number ratio of atoms in a compound

Structural formula

Arrangements of atoms in a molecule without showing all the bonds

Skeletal formula

Shows bonds of carbon skeleton only, H and C atoms are not shown but functional groups are

Displayed formula

Shows the arrangement of atoms showing all the bonds and atoms in the molecule

Homologous series

Group of compounds that have the same functional group and general formula

• Successive members of a homologous series increase by CH₂

Prefix of alkanes

-ane

Suffix of branched alkanes

alkyl-

Suffix of alkenes

-ene

Suffix of alcohols

-ol

Suffix of aldehydes

-al

Suffix of ketones

-one

Suffix of carboxylic acids

-oic acid

Prefix of halogenoalkanes

fluoro-/chloro-/bromo-/iodo-

Prefix and suffix of cycloalkanes

cyclo-, -ane

Stem name for 1 carbon

meth-

Stem name for 2 carbons

eth-

Stem name for 3 carbons

prop-

Stem name for 4 carbons

but-

Stem name for 5 carbons

pent-

Stem name for 6 carbons

hex-

Method for naming compounds using IUPAC

1. Find the length of the stem by counting the longest continuous chain of carbons

2. Functional group on molecule normally tells you its suffix

3. Number the carbon chain so the functional group sits on the lowest possible carbon

4. Make a note of the carbon number of the functional group and place it before suffix

5. Any side chains and less important functional groups are written as prefixes in alphabetical order

6. If there is more than 1 identical functional group/side chain, put di(2), tri(3) or tetra(4)

Chemical mechanism

Shows movement of electrons during a chemical reaction

Curly arrows

Movement of a pair of electrons e.g., a double bond or lone pair

Structural isomer

Have the same molecular formula but a different structural formula

Chain isomer

Same molecular formula but different arrangement of carbon skeleton

Position isomer

Same molecular formula but different position of functional group on carbon skeleton

Functional group isomer

Same molecular formula but different functional group

Stereoisomer

Have the same structural formula but a different arrangement of atoms in space

How E/Z isomerism forms

Atoms cannot rotate around C=C bond + is rigid so E/Z isomerism occurs

E isomer

Same groups opposite the double bond

Z isomer

Same groups on same side of double bond

Cahn-Ingold-Prelog rules

Decides when we have 4 different groups around double bond:

1. Label carbons with double bond as carbon 1 and carbon 2

2. Calculate atomic number of first element directly bonded to C=C

3. Atoms with highest atomic number is given a higher priority

Alkanes

Saturated hydrocarbons with general formula C_nH_2n+2

General formula of cycloalkanes

C_nH_2n

Fractional distillation of crude oil

Column has temperature gradient - cooler at top, hotter at bottom

• Allows for vapour to rise + some parts to condense because of different carbon chain lengths

  • Longer chain = condense

Uses of crude oil

Gas (stove), kerosene (jet fuel), bitumen (roofing), diesel oil, petrol, fuel oil

Purpose of cracking

Heavier fractions can be cracked to higher demand, lighter fractions (lighter fractions e.g., petrol, is more valuable)

Thermal cracking

1000^oC and 70 atm of pressure - products are usually alkenes (used to make polymers e.g., plastics)

Catalytic cracking

450^oC and slight pressure with zeolite catalyst (lowers temperature + pressure needed so lowers costs and speeds up process) - products are usually aromatic hydrocarbons (useful for fuels)

Complete combustion of alkanes

• Alkanes burn in oxygen to form CO₂ and H₂O

• Alkanes are good fuels as they burn readily to produce large amounts of energy

• Used to power vehicles + most electricity

Incomplete combustion of alkanes

Alkanes burn in limited oxygen supply to form CO and C (soot)

Risks of carbon monoxide and soot

Carbon monoxide - poisonous, binds to haemoglobin in blood which prevents oxygen binding

Soot - can cause breathing problems

Creation of nitrogen oxides

Nitrogen and oxygen in air combine under high pressure and temperature e.g., from car engines

Photochemical smog

Ozone can cause photochemical smog at lower levels (exists as sunlight, hydrocarbons and NO₂)

Harms respiratory system + is toxic

Acid rain

Acidic gas (SO₂) reacts with water in atmosphere to form H₂SO₄ which falls as acid rain

Damages plants, kills fish + causes erosion of buildings

Wet scrubbing

Can remove SO₂ by neutralising it with an alkali (dissolving CaCO₃ in water and spraying)

3 steps of free radical chain reactions

Initiation, Propagation, Termination

Initiation in chain reactions

Radicals are produced normally using visible light/UV

Bond breaks, producing 2 radicals

Propagation in chain reactions

A radical reacts with a non-radical - new radicals are created which react with more non-radicals

Termination in chain reactions

2 radicals react - they form non-radical molecule which ends chain reaction