Chemistry - Organics

crude oil

crude oil is a fossil fuel that can be extracted from the ground and processed to make fuels and feedstock

crude oil is formed from decomposed plants and plankton and heated under pressure for millions of years

Fractional distillation -process of separating different hydrocarbons in crude oil into more useful fractions

fractional distillation process

1. crude oil is heated

2. enters distillation column

3. hot at bottom, cools towards top

4. this causes the various factions to separate based on their boiling point

order of factions= petroleum gases, petrol, kerosene, diesel, fuel oil and bitumen

petroleum gases have the shortest chain length, lowest boiling point, lowest viscosity

bitumen has the longest chain length, the highest boiling point, the highest viscosity

petroleum can be used for barbecues, and domestic heating

petrol can be used for car fuel and farming equipment

kerosene can be used for planes and domestic cooking

diesel can be used for heavy machinery and various vehicle fuel

fuel oil can be used for heating and farming.

bitumen can be used for tarmac, roofing and water proofing

hydrocarbons- are molecules containing hydrogen and carbon ONLY

functional group = part of molecule that determines how the molecule will react

Alkanes

• type of hydrocarbon

• alkanes are saturated

• unreactive

• all conform to general formula of CnH2n+2

Alkane examples - methane (CH4), ethane (C2H6), propane (C3H8), butane (C4H10)

Alkenes

• formed by cracking larger alkanes into smaller ones

• unsaturated (has a double bond)

• important in formation of polymers and feedstock

• very reactive known as addition reactions

• test for alkenes is to add bromine water (+’ive results is colour change to colourless)

• all conform to general formula of CnH2n

Alkene examples - ethene (C2H4), propene (C3H6), butene (C4H8), pentene (C5H10)

Combustion

Complete combustion of an alkene: alkane + oxygen —> carbon dioxide + water

Incomplete combustion of an alkene: alkane + oxygen —> carbon monoxide + water

note: carbon monoxide is toxic (binds to haemoglobin better than oxygen and suffocates)

complete combustion of an alcohol: alcohol + oxygen —> carbon dioxide + water

Alcohols

functional group = O-H

general formula = CnH2n+2O

(alcohols have the same numbering system as alkenes and alkanes)

1. ethanol - (CH4O) can be used for cleaning products, drinking, and combustion

when alcohols are oxidised it becomes carboxylic acid

production of alcohols

method 1: fermentation

• yeast respires anaerobically using a sugar solution and produces ethanol and carbon dioxide

• C6H12O6 —> 2C2H5OH+2CO2

• advantages - sugar is renewable resource, occurs at atmospheric pressure, cheaper, carbon neutral

• disadvantages- labour is intensive as it is a batch process, slow reaction

method 2: hydrolysis of ethene

• ethene reacts with steam and it forms and alcohol

• C2H4+H2O —> C2H5OH

• advantages- faster and less intensive labour

• disadvantages- specific conditions needed, more expensive, uses non-renewable resources

carboxylic acids

properties

• functional group: OH-C=O + r

• dissolves in water

• 3-5 Ph

• reacts with Na

alcohol + carboxylic acid —> esters + water (condensation reaction)

Polymers!

monomer - single molecule used to make a polymer

polymer - molecule made from many monomers

repeating unit - unit that repeats in polymer chain

overall process

crude oil is extracted —> fractional distillation —> cracking —> polymers

addition polymers

• alkenes under heat pressure and a catalyst (triggers double bond to break open and add molecules together

condensation polymers

• dicarboxylic acid and di-ol

HDPE and LDPE

• HDPE - pack chains close together, increases points of surface contact and results in stronger intermolecular forces and higher melting points

• LDPE - chains are randomly arranged so few point of surface contact weaker forces of attraction so lower melting point

thermosetting and thermosoftening

• thermosetting - strong cross links, so strong covalent bonds. high melting point

• thermosoftening - weak forces so weaker intermolecular forces - low boiling point

amino acids

follows this arrangement : H2N-C-C=O. (and a -O off the second C)

Quiz on Crude Oil and Hydrocarbons

1. What is crude oil?A fossil fuel that is extracted and processed to make various fuels and feedstock.

2. How is crude oil formed?From decomposed plants and plankton subjected to heat and pressure over millions of years.

3. What is fractional distillation?A process that separates hydrocarbons in crude oil into more useful fractions based on their boiling points.

4. List the order of fractions from crude oil based on boiling points.Petroleum gases, petrol, kerosene, diesel, fuel oil, bitumen.

5. What are alkanes?Saturated hydrocarbons that conform to the general formula CnH2n+2.

6. What is the functional group of alcohols?O-H. The general formula is CnH2n+2O.

7. What happens during complete combustion of an alkane? Alkane + oxygen → carbon dioxide + water.

8. What does fermentation produce?Ethanol and carbon dioxide from yeast and sugar.