Organic Chemistry Flashcards
(71 cards)
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.
