4.1 Flashcards
(30 cards)
what are aliphatic hydrocarbons?
when carbon atoms are joined together in either a straight or branched chain.
Alicyclic hydrocarbons
when the carbon atoms are joined together in a ring structure but are not aromatic
aromatic hydrocarbons
when there is at least one benzene ring in the structure
what is a homologous series
a series of organic compounds having the same functional group but with each successive member differing by ch2
what is an Isomer?
organic compounds with the same molecular formula but different arrangements if atoms
Alkanes general formula and facts
General formula- Cn H2n+2
Alkanes are saturated
cyclohexane has two fewer hydrogens.
Trend in boiling point from small to large alkanes
the bigger the alkane, the higher the bp is.
This is due to the longer chains having a stronger induced dipole attraction due to more electrons and surface area.
Takes more energy to overcome
Why do branched chains have lower boiling points?
They can’t pack as closely together and have small molecular surface areas so the induced dipole interactions are reduced.
What is the issue with carbon monoxide?
The carbon monoxide binds to the haemoglobin before the oxygen can meaning less oxygen can be carried around your body leading to oxygen deprivation
What is Heterolytic fission?
Where the bond breaks unevenly with one of the bonded atoms receiving both electrons from a bonded pair.
What is homolytic fission?
When the bond breaks evenly and each receives one electron from the bonded pair two radicals are formed.
What is a free radical?
A particle that has an unpaired electron and therefore very reactive.
Free radical substitution.
- Can happen with bromine or chlorine
- Initiation: sunlight(uv) breaks the Cl2 bond to form two free radicals (photodissociation)
- Propagation: free radicals are used up and created in a chain reaction.
- Termination: free radicals react together to form a stable molecule.
The issue with free radical substitution.
You don’t always get a particular product but a mixture of them.
Alkenes general formula and facts.
the General formula is An H2n
They are all hydrocarbons and are unsaturated.
What is a double bond made up of?
- A Sigma Bond is formed when two s orbitals overlap
* A pi bond is formed by the sideways overlap of two adjacent p orbitals
Why are Alkenes more reactive than Alkanes
- Alkanes only contain C-C bonds and C-H bonds which are hard to break due to high bond enthalpy and also non polar
- Alkenes have a double bond and as the pi bond sticks out it’s more likely to be attacked by electrophiles. also a low bond enthalpy in the pi bond.
What are Stereoisomers?
These have the same structural formula but a different arrangement in space.
This can occur due to lack of rotation about the double bond and cause E/Z isomerism
What do the Cahn-Ingold-Prelog rules say?
The atom with the higher atomic number on each carbon is given priority (in E/Z isomerism)
Electrophilic Addition reactions and why they happen.
- Happen to Alkenes
- the double bonds open up and atoms are added to the carbon atoms
*The double bond has lots of electrons so can be attacked by electrophiles.
What is an electrophile?
Electron pair acceptors.
Turning Ethene to Ethane
Reacts with hydrogen gas with a nickel catalyst and 150°c
How to test for double bonds
Bromine water goes from orange to colourless.
As bromine is added across the double bond to form colourless dibromoalkane
How to make Alcohols with Alkenes.
Hydrate with steam
300°c and a pressure of 60-70atm
conc Phosphoric(v) acid catalyst
Low yield but you can recycle unused alkenes
