Organic Chemistry Flashcards
What is crude oil?
Crude oil is a mixture of compounds; a fossil fuel consisting of the remains of ancient biomass. Finite resource - cannot be replaced as it is used up.
What is hydrocarbon?
a compound made of hydrogen and carbon atoms only
What are alkanes?
Saturated hydrocarbons with the general formula CnH2n+2
What is a homologous series?
A series of compound with same general formula, same functional groups and similar chemical properties
Describe the combustion of hydrocarbons
- Exothermic reaction occurring when hydrocarbons are reacted with oxygen.
- Complete combustion produces carbon dioxide and water (carbon and hydrogen atoms are completely oxidised).
- Incomplete combustion produces carbon or carbon monoxide and water.
Describe the physical properties of alkanes
- First few in series are gases, then change to liquids, then to solids.
- In general, boiling points and viscosity increase as molecules get bigger.
- Volatility and flammability decrease as molecules get bigger.
- Poor reactivity.
Explain how fractional distillation of crude oil takes place
- Crude oil is heated and vaporised.
- Vapor rises up the fractionating column (tower).
- The column is hotter at the bottom and cooler at the top.
- Hydrocarbons cool as they go up the column and condense at different heights, as they have different boiling points.
- Large molecules, high boiling points - collected at the bottom.
- Small molecules, low boiling points - collected at the top.
- This gives fractions, which can be used in various ways.
What is cracking?
When large hydrocarbons are thermally broken down into smaller and useful molecules
Why type of reaction is cracking?
Thermal decomposition
What are the conditions for cracking?
Reactant heated to vapor, passed over a hot catalyst (catalytic cracking) or heated to vapor, mixed with steam and heated to high temperatures (steam cracking)
How are the products of cracking used?
The products are alkanes and alkenes - used as polymers and starting materials for synthesis.
What is an alkene?
an unsaturated hydrocarbon with a carbon-carbon double bond
What is the test for alkenes?
Add bromine water. Colour change occurs from orange to colourless.
Describe the combustion of alkenes
They burn with smokey flames due to incomplete combustion
Describe addition reactions of alkenes
Addition atoms across the carbon-carbon double bond so that the double bond becomes a single carbon-carbon bond.
a) With hydrogen - hydrogenation; requires a higher temperature and a nickel catalyst
b) With steam - hydration; requires high temperature, pressure, and concentrated phosphoric acid (H3PO4) as a catalyst
c) With Br2/Cl2/I2 - addition of halogens
What is an alcohol?
An organic compound that contains an -OH functional group
State characteristics of methanol, ethanol, propanol and butanol
- Dissolve in water to form a neutral solution.
- React with sodium to form hydrogen.
- Burn in oxygen.
- React with carboxylic acids in presence of acid catalyst to form esters.
What does oxidation of the alcohols lead to?
carboxylic acids
What are some uses of alcohols?
Fuels, solvents, drinks
State the conditions required for fermentation of glucose and state the equation of the reaction
30 degrees Celsius, aqueous solution of the glucose, absence of air, yeast added;
C6H12O6 → 2 CH3CH2OH + 2 CO2
What are carboxylic acids?
Organic compounds that contain a COOH functional group
State characteristics of carboxylic acids
- Dissolve in water to form an acidic solution (contains H+ ions)
- React with metal carbonates to form carbon dioxide
- React with alcohols with an acid catalyst to produce esters
- React with metals to give off hydrogen gas
What type of acid is carboxylic acid?
it is a weak acid
Explain why carboxylic acids are weak acids
They are partially dissociated in water, thus the pH of a carboxylic acid in solution is not as low as a solution of a strong acid of the same concentration.
What is an ester and how is it formed?
An organic compound containing a -COO- functional group, formed from carboxylic acid and alcohol in the presence of a sulfuric acid catalyst.
They have a fruity smell.
What is a polymer? How do molecules containing C=C bond form polymers?
A polymer is a long chain molecule which is made by lots of smaller molecules joining together.
C=C bonds open up and many smaller molecules (monomers) join together to form a chain (a polymer). No other products are made.
It is called an “addition polymerisation”
Give 3 examples of addition polymers and their uses
Polyethene - plastic bags
(Poly)tetrafluoroethene (PTFE) - teflon surfaces, for use in non-stick kitchenware
(Poly)chloroethene (polyvinylchloride, PVC) - water pipes
What is a repeating unit of a polymer?
It is a smallest structure which, upon numerous translations, yields the structure of the polymer.
In addition polymers: to draw it, take a monomer, change C=C to C-C and show additional single bonds extending away from these carbons.
What is a condensation polymer?
It is a polymer made in condensation polymerisation.
In this reaction, many molecules join together; the polymer is formed, but also a small molecule is released, e.g. H2O, HCl.
Polyesters, e.g. terylene.
What is an amide bond?
An amide bond is similar to the ester bond, with O replaced by N, e.g.
(C=O)-NH2
Just like an ester, it contains the C=O group.
What is an amino acid?
It is an organic compound that contains both a carboxylic acid functionality (COOH) and an amine functional group (-NH2).
How do amino acids make proteins?
By numerous condensation polymerisation reactions; proteins are polymers made of amino acids (monomers).
What are polypeptides?
long chains of amino acids but are shorter than protein.
What are carbohydrates?
They are organic molecules made of C,H, and O. They are biologically relevant,
e.g. starch and cellulose.
Both of these are polymers made of glucose (other carbohydrate) monomers.
Their structures differ in the way the glucose molecules are joined together.
What is DNA? Describe its role and structure.
DNA (deoxyribonucleic acid) is a material that makes up chromosomes - cell structures that store genetic information.
DNA is made of two polymer chains that are held together in a double helix.
Each polymer chain can be made from 4 different monomers - nucleotides.
What is cracking of hydrocarbons?
Breaking apart long hydrocarbons into shorter more useful hydrocarbons
What is catalyst cracking?
Vaporise hydrocarbon and pass gas over a hot powered aluminium oxide catalyst
What is steam cracking?
Vaporise hydrocarbon, mix with steam and heat to a very high temperature
What is the reactant in cracking?
Long alkane molecules
What are the products of cracking?
Shorter chain alkaline and alkenes
What are the uses of alkenes
- making polymers
- making other chemical
What is a double covalent bond?
A bond in which two atoms share two pairs of electrons
What is a molecular formula?
A chemical formula that shows the number and kinds of atoms in a molecule, but not the arrangement of the atoms
What is the display formula?
Shows all of the atoms in a molecular and their arrangements
What is a saturated hydrocarbon?
A hydrogen in which all the bonds between carbon atoms are single bonds
What trends does hydrocarbon have?
- boiling point -> the longer the hydrocarbon, the higher the boiling point
- viscosity -> the longer the hydrocarbon, the more viscous it is
- flammability-> the shorter the hydrocarbon, the more flammable it is
What is complete combustion?
A combustion reaction in the presence of plenty of oxygen and producing carbon dioxide and water
What is incomplete combustion?
Combustion with insufficient oxygen, producing water, carbon particulates and carbon monoxide
Why isn’t a crude oil useful?
It is a mixture of lots of hydrocarbons of a huge range of lengths
What is the composition of crude oil?
Mainly hydrocarbons, with a few impurities such as sulfur
What is the fractional distillation of crude oil?
The separation of crude oil into fractions
What is hydrocarbon fraction?
A group of hydrocarbons with similar boiling points and numbers of carbon atoms
What are some of the common hydrocarbon fractions?
Petrol, diesel oil, kerosene, fuel oil and LPG
What are carboxylic acid?
Organic compounds that are weak acids
What pH does a carboxylic acid have?
pH of less than 7
What is the combustion of alcohols?
Burn completely in oxygen to form carbon dioxide and water
What is plastics?
Synthetic polymers that can be milder or shaped
What are monomers?
A small molecule that can join together with other small molecules to form polymers
What is addition polymers?
Alkenes (monomers) join up and the double bond is removed
What are condensation polymers?
Polymers containing different functional groups forming a long chain and a small molecule (usually water)
What is polyester?
A synthetic polymer linked by ester groups
What are amino acids?
Monomers of proteins
What are proteins?
Biological condensation polymers made of different amino acids and more than one polypeptide chains
What is polypeptide?
A single polymer chain made of amino acids
What is the monomer of DNA?
Nucleotide
What is DNA?
A condensation polymer which encodes instructions for development and functioning of living organisms
What is a double helix?
Shape of DNA; made of two polynucleotide chains wound around each other
What is polysaccharide?
Polymers of sugars
What is starch?
A storage polysaccharide in plants
What is glucose?
Monomer of starch, cellulose and glycogen
What is cellulose?
A polysaccharide that is common in the cell walls of plants and many other organisms
