GCSE OCR GATEWAY CHEMISTRY ORGANIC CHEMISTRY REVISION

This page contains the detailed and easy notes for AQA GCSE Chemistry Organic Chemistry for revision and understanding Organic Chemistry.

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 GCSE OCR Chemistry Complete Revision Summary

ORGANIC CHEMISTRY

Organic Chemistry

  • Hydrocarbons and Crude Oil
  • Alkanes
  • Fractional Distillation
  • Properties of Hydrocarbons
  • Cracking
  • Alkenes
  • Reaction of Alkenes
  • Alcohols
  • Carboxylic Acid
  • Addition Polymerization
  • Condensation Polymerization
  • Amino Acids
  • DNA

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CRUDE OIL

  • It is a black thick liquid which takes millions of years to form.
  • It is the mixture of hydrocarbon.
  • Hydrocarbon are the compounds made up of carbon and hydrogen only.
  • The components of the crude oil are important and the crude oil is separated by the process of fractional distillation.

HYDROCARBON PROPERTIES


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FRACTIONAL DISTILLATION OF CRUDE OIL

  • Separating the mixtures on the basis of boiling points.
  • It is separated in fractionating column with different substances of similar boiling points

LIQUIFIED GASFUEL
GASOLINE/PETROLCAR FUEL
KEROSENEAIRCRAFT FUEL
DIESEL OILFUEL IN DIESEL ENGINES
RESIDUEMAKING ROADS




L – Look

G – Great

K – Kid

D – Doing

R – Roll

 CRACKING –Thermal decomposition of longer chain hydrocarbon into a shorter chain alkane and alkenes

Thermal Cracking                                               Catalytic Cracking

It is done at a very high temperature                     It is done using a catalyst


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ORGANIC CHEMISTRY (2)

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WHY CRACKING

  • Shorter chain alkanes are more in demand as they are more efficient fuel which fractional distillation alone cannot meet.
  • Alkenes are required for polymerization and synthesize other hydrocarbons which fractional distillation cannot meet.

ALKANES – Saturated Hydrocarbon

Carbon-carbon single bond                    made up of carbon and hydrogen

General Formulae  CnH2n+2

Methane – CH4

Ethane – C2H6

Propane – C3H8

Butane – C4H10

Pentane – C5H12

Homologous Series – Members of the same family have similar functional group similar chemical properties and general formulae but different physical property and each members differs from successive by CH2.

COMBUSTION

COMPLETE

INCOMPLETE

  
FUEL IS COMPLETELY BURNED

FUEL IS PARTIALLY BURNED DUE TO LIMITED SUPPLY OF OXYGEN

 

PRODUCES CARBON DIOXIDE AND WATER

PRODUCES CARBON MONOXIDE AND WATER

 

IT IS NOT TOXIC

CARBON MONOXIDE IS TOXIC AS IT DECREASES. THE OXYGEN CARRYING CAPACITY OF RED BLOOD CELLS

 

PRODUCTS OF COMBUSTION

Carbon Dioxide Test   

    Limewater Test     Carbon Dioxide will turn limewater milky

    Water Test

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FUNCTIONAL GROUPS
Groups of atoms that give special properties and reactions to the organic molecule

 Functional GroupsExamplesFormation
ALKENES      =Ethene, propene, butene, penteneCracking of crude oil
ALCOHOLS-OHmethanol, ethanol, propanol, butanol, pentanolReaction of alkene with water
CARBOXYLIC ACIDmethanoic acid, ethanoic acid, propanoic acid, butanoic acid.Oxidation of alcohols
ESTERSmethyl ethanoate, ethyl ethanoateReaction of alcohols and carboxylic acid

ALKENES




Unsaturated Hydrocarbon

  • Compounds which have carbon-carbon double bond
  • Compounds made up of carbon and hydrogen only

GENERAL FORMAULE  CnH2n

Useful to make polymers, alkanes, alcohols

MANUFACTURE OF ETHANOL

 FERMENTATIONHYDRATION OF ETHENE
REACTION

Glucose                      Ethanol + carbon dioxide

C6H12O6                        2C2H5OH + 2CO2

Ethene + Steam      Ethanol
REACTION CONDITIONSGentle temperature and pressure. Anaerobic conditionsNickel catalyst and high temperature and pressure
ADVANTAGESUses renewable resources like sugarcane. Less dependent on fossil fuels and due to less energy requirements do not harm the environment.It is a continuous process. It is rapid more efficient and have 100% atom economy. Produces more pure ethanol
DISADVANTAGESIt is a batch process. The ethanol has to be distilled from time to time as high concentration will kill the yeast. The reaction is slow and produces impure ethanol. Also the atom economy is not 100%Requires ethene which is dependent on crude oil. Uses non renewable resources.

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REACTIONS OF ALKENES

ALCOHOLS – Have functional Group –OH

General Formulae

CnH2n+1 OH

Formed by replacing hydrogen of alkane with OH group

Used as fuel, solvents, spirits

         

       

REACTIONS OF ALCOHOLS

COMBUSTION

  • It can undergo complete or incomplete combustion. Complete combustion produces carbon dioxide and water.
  • Ethanol + Oxygen = Carbon dioxide + water

C2H5OH + O2                                 CO2 + H2O

  •  Incomplete combustion produces carbon dioxide and water.
  • Ethanol + Oxygen = Carbon monoxide + water

 C2H5OH + O2                                 CO + H2O

OXIDATION

  • Alcohols are oxidised to carboxylic acid in the presence of oxidising agent.
  • Methanol   Methanoic Acid
  • Ethanol    Ethanoic Acid
  • Oxidising agent used is acidified potassium dichromate solution

METAL

Alcohols react with metals to form salt and hydrogen.

2C2H5OH + 2Ca                                 2C2H5OCa + H2

CARBOXYLIC ACID

Weak Acids

Carboxylic Acids are weak acids as they are partially dissociated in water to release H+ ions.

CH3COOH     CH3COO + H+




Metal oxides and Metal hydroxide

Carboxylic Acid reacts with metal oxides and metal hydroxide to form salt and water.

CH3COOH + NaOH                                 CH3COONa + H2O

Metal carbonate

Carboxylic Acid reacts with metal carbonate to form salt, water and carbon dioxide.

CH3COOH + Li2CO3                                 CH3COOLi + CO2 + H2O

                        
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ESTERS

  • Fruity smelling compounds
  • Used in the manufacture of perfumes, foods and cosmetics.

CARBOXYLIC ACID + ALCOHOLS               ESTERS + WATER

Alkyl alkanoate

Methanoic Acid + Methanol                           Methyl methanoate + Water

ADDITION POLYMERIZATION

  • The individuals unit that polymerizes to form a polymers is known as a monomers. Eg Ethene
  • The structure formed by the polymerization of the monomer is a polymers.

Polymers are materials made by linking up smaller repeating chemical units.

Some bend and stretch – rubber and polyester.

Some hard and tough – epoxies and glass.

ADDITION POLYMERS

  1. a) Formed by addition reaction.
  2. b) Require only one monomer generally an alkene
  3. c) Nothing is lost in the reaction.

eg Polyethene, polypropene

CONDENSATION POLYMERS

  1. a) Requires two monomers
  2. b) Requires two functional group
  3. c) Formed by condensation reaction.
  4. d) A small molecule of water is
  5. e) Example: Nylon a polyester

NATURAL POLYMERS

  1. a) They are found naturally
  2. b) All the complex biomolecules are polymers
MonomerPolymer
GlucoseStarch
ProteinsAmino Acid
NucleotideDNA

 DNA

  1. a) DNA is polynucleotide
  2. b) Nucleotide = Phosphate + Sugar + Nitrogenous Bases
  3. c) There are four bases present in the DNA
  • Adenine
  • Thymine
  • Guanine
  • Cytosine

KEY TERMS

Hydrocarbon – Hydrocarbon are the compounds made up of carbon and hydrogen only.

Crude Oil – It is a black thick liquid which takes millions of years to form. It is the mixture of hydrocarbon.

Fractional Distillation – Separating the mixtures on the basis of boiling points.

Alkanes – Saturated Hydrocarbon. Carbon-carbon single bond. Made up of carbon and hydrogen only

Saturated hydrocarbon – Saturated Hydrocarbons have only carbon-carbon single bonds.

Unsaturated hydrocarbon – Unsaturated Hydrocarbons have carbon-carbon double bonds and triple bonds.

General Formula – It applies to families of compounds; provides a way to predict the molecular formula of the molecule, based on the number of carbon atoms it contains.

Viscosity – movement of flow. A fluid with low viscosity flows easily

Flammable – Flammable materials are combustible materials that can easily ignite at room temperature

Complete Combustion – Fuel is completely burned. Produces Carbon dioxide and water.

Incomplete Combustion – Fuel is partially burned due to limited supply of oxygen. Produces Carbon Monoxide and Water.

Cracking – Thermal decomposition of longer chain hydrocarbon into a shorter chain alkane and alkenes

Alkenes – Unsaturated Hydrocarbon. Compounds which have carbon-carbon double bond. Compounds made up of carbon and hydrogen only

Functional Group – Groups of atoms that give special properties and reactions to the organic molecule

Homologous Series – Members of the same family have similar functional group similar chemical properties and general formulae but different physical property and each members differs from successive by CH2

Alcohols – Have functional Group –OH. The General Formulae of Alcohols is CnH2n+1 OH. Used as fuel, solvents, spirits

Carboxylic Acid – Carboxylic Acids are weak acids as they are partially dissociated in water to release H+ ions.

Esters – Fruity smelling compounds. Used in the manufacture of perfumes, foods and cosmetics.

Fermentation – Fermentation is a metabolic process that produces chemical changes in organic substrates through the action of enzymes.

Weak Acid – Weak acids are only partially ionized in their solutions.

Monomers – The individuals unit that polymerizes to form a polymers is known as a monomers. Eg Ethene

Polymers – The structure formed by the polymerization of the monomer is a polymers. Polymers are materials made by linking up smaller repeating chemical units.

Some bend and stretch – rubber and polyester.

Some hard and tough – epoxies and glass.

Addition Polymerization – It is the process of repeated addition of monomers with double or triple bonds to form polymers. There is no loss of an atom or a molecule. Ex – PVC, polyethene, Teflon.

Condensation Polymerization – It is a process that involves repeated condensation reactions between two different monomers. There is a loss of a molecule of water, ammonia etc as a by-product. Ex – Nylon, bakelite, silicon.

Monosaccharide – Simplest carbohydrates (single units). They cannot be hydrolyzed into smaller units. Ex – Glucose, fructose.

Polysaccharide – Formed of numerous monosaccharide units. Ex – starch, cellulose

Starch – It is the reserve food material of plant cells. It consists of two components- amylose and amylopectin, both glucose polymers.

Cellulose – Main structural polysaccharide of plants. It is a long, unbranched chain of about 6,000 glucose units with molecular weight between 0.5 to 2.5 million.

Proteins – The proteins are linear unbranched polymers of Amino acids. The proteins are composed of carbon, hydrogen, oxygen, nitrogen, and Sulphur.

DNA – It is a long, double chain of deoxyribonucleotide units. DNA is the genetic material and forms molecular basis of heredity in all organisms.

Disclaimer:

I have tried my level best to cover the maximum of your specification. But this is not the alternative to the textbook. You should cover the specification or the textbook thoroughly. This is the quick revision to help you cover the gist of everything. In case you spot any errors then do let us know and we will rectify it.

References:

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