Topic 7: Organic Chemistry Flashcards
What is crude oil?
- Crude oil is a mixture of compounds; a fossil fuel consisting of the remains of ancient biomass.
- It is a finite resource - cannot be replaced as it is used up.
What is a hydrocarbon?
A compound made up exclusively of hydrogen and carbon atoms
What are alkanes?
Saturated hydrocarbons of a general formula CnH2n+2
What is a homologous series?
Series of compounds 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
What type of reaction is cracking?
Thermal decomposition
What are the conditions for cracking?
-
Catalytic Cracking:
- Reactant heated to vapor.
- Passed over a hot catalyst.
-
Steam Cracking:
- Reactant heated to vapor.
- Mixed with steam.
- Heated to high temperatures.
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?
Unsaturated hydrocarbon. Contains a C=C bond. General formula for alkenes is: CnH2n.
What is the test for alkenes?
Add bromine water. Colour change occurs from orange to colourless.
Describe the combustion of alkenes
They burn with smoky flames due to incomplete combustion
Describe addition reactions of alkenes
Addition atoms cross 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.
Oxidation of the alcohols leads 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 (chemical + word)
30 degrees Celsius, aqueous solution of the glucose, absence of air, yeast added:
Word: Glucose → ethanol + carbon dioxide
Chemical: 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? What is characteristic about this class of compounds?
- 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?
- Polymer: long chain molecule made from many smaller molecules (monomers).
- C=C bonds open up, allowing monomers to join and form a polymer chain.
- No other products are produced.
- This process is called “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?
- Smallest structural unit
- Repeated many times
- Forms 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? How is it made? There are 2 main groups - name them and give industrially relevant examples.
- 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.
a) Polyesters, e.g. terylene.
b) Polyamides, e.g. Nylon.
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? What are polypeptides?
- Proteins are polymers made of amino acids through condensation polymerisation.
- Polypeptides are shorter chains of amino acids formed by condensation polymerisation.
- Proteins consist of multiple bonded polypeptide chains.
What are carbohydrates?
- Organic molecules composed of carbon (C), hydrogen (H), and oxygen (O).
- Biologically relevant examples: starch and cellulose.
- Both starch and cellulose are polymers of glucose monomers.
- Differ in the arrangement of glucose molecules.
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.
