Organic Chemistry 1 Flashcards
Hydrocarbon definition
Compound containing carbon and hydrogen ONLY
Saturated definitions
Contains single covalent bonds between carbon atoms
Are alkanes saturated or unsaturated
Saturated hydrocarbons
What is the general formula of alkanes
CnH2n + 2
What is the empirical formula
simplest whole number ratio of atoms of each element in a compound
What is a molecular formula
number of atoms of each different element in a molecule (tells you nothing about the way they are joined)
What is the structural formula
shows how the atoms are joined (bonded)
What is the displayed formula
shows ALL bonds and ALL atoms in molecule
Name the alkanes in the order of the number of the carbons in the molecules
- Methane
- Ethane
- Propane
- Butane
-Pentane
What happens to the boiling point as the chain length increases
Boiling point increases
What are the characteristics of the homologous series
- Members differ by a CH2 group
- Similar chemical properties (i.e. reactivity)
- Gradual trend in physical properties
- Same functional group
Isomer definition
Isomers are compounds with the same molecular formula but different structural formulae
Are alkenes saturated or unsaturated
They are unsaturated hydrocarbons
Unsaturated definition
Contains at least one double covalent bond between carbon atoms
What is the general formula of alkenes
CnH2n
How are alkenes produced
By cracking alkanes
Why are alkenes more reactive then alkanes
The double bond can break to form 2 single bonds so add other atoms (addition reaction)
Describe a test to distinguish between butane and butene
- Add Bromine water into the samples
- If solution decolourises from orange it is butene
- If solution stays orange it is butane
What type of reaction happens with alkenes
Addition reactions
What type of reaction happens with alkanes
Substitution reaction
What will make alkanes react
UV light
Explain the process of fractional distillation
- Oil is heated to about 450 °C where it vaporizes then pumped into the bottom of a tall tower called a fractionating column.
- The column is very hot at the bottom but much cooler at the top. As the vaporized oil rises, it cools and condenses.
- Heavy fractions (containing large molecules) have a high boiling point and condense near the bottom of the column.
- Lighter fractions (containing small molecules) have a lower boiling point and condense further up the column.
- The different fractions are collected at different heights.
Compare and contrast the reactions of alkanes and alkenes with halogens using the reactions of ethane and ethene with bromine as examples. Include reaction condition, types of reactions and names of products.
Alkanes:
-Needs UV light
- Substitution reaction to produce - bromoethane + Hydrogen bromide
-Be able to name the products
-SUBSTITUTION reaction
Alkenes:
-No UV required – reaction occurs readily at room temp
- Addition reaction to produce 1,2-dibromoalkane
- Be able to name the product
- ADDITION reaction
Name the different fractions of crude oil from top to bottom
- Refinery gases
- Gasoline (Fuel for car engines)
- Kerosine (aeroplane fuel)
- Diesel (fuel for lorries)
- Fuel oil (ship fuel)
- Bitumen (road surfaces)
Explain the relationship between molecule size and boiling point
The larger the hydrocarbon, the higher its boiling point
- Intermolecular forces between large molecules are stronger than the intermolecular forces between small molecules.
- Therefore, more energy is needed to break the forces between large molecules, and so the boiling point is higher.
How do the colour of the fractions change with the size of the molecule
As the molecule gets SMALLER the colour of the fraction becomes lighter, from dark brown to light brown, orange/yellow and transparent
How does the size of the hydrocarbon affect the viscosity
The longer the hydrocarbon in a fraction the more viscous the fraction will be. This is because the longer chains of large hydrocarbon molecules have stronger intermolecular forces and are more easily entangled
How does the size of the hydrocarbon affect the volatility and flammability
Generally, the smaller the molecules in a fraction, the more volatile and flammable the fraction.
What are the reasons for cracking
- Produces shorter chain alkanes which are higher in demand than longer chain alkanes. e.g. we need far more octane (petrol) than actually get from crude oil and we have more bitumen than we have use for.
- Cracking also produces alkenes - used to make polymers and plastics
What are the conditions for catalytic cracking
- temperature 600-700oC
- Catalyst of silicon dioxide (SiO2, silica) or Aluminium Oxide (Al2O3, alumina)
What is a polymer
POLYMERS are long chains of molecules consisting of small repeating units called MONOMERS. The monomers are often ALKENES
What is a monomer
MONOMERS are small molecules that join together to make polymers
What is polymerisation
POLYMERISATION = the formation of long chain molecules from lots of small molecules joining together
