Module 4 Flashcards
Define the term ‘Hydrocarbon’
A molecule that contains carbon and hydrogen only
What feature makes a hydrocarbon unsaturated?
One or more carbon-carbon double bonds
What is a homologous series?
A family of compounds with similar chemical structures and properties, whose successive members’ formulae differ by a constant group (e.g. +CH2)
Define structural isomer
A version of a compound with the same molecular formula but a different structural formula
What is the difference between homolytic and heterolytic fission?
Homolytic fission divides electrons equally, usually forming a radical (ORA)
What effect does
1) a longer chain length
2) more chain-branching
…have on the boiling point of a hydrocarbon?
1) Longer chains encounter more London forces and therefore have higher boiling points
2) More-branched molecules ‘tesselate’ less-well and therefore encounter less London forces, and have lower boiling points
What limitations does the halogenation of alkanes by UV light encounter?
- Further substitutions
- Position of substitutions varies
How does a double bond form?
The sideways overlap of p-orbitals above and below the plane of the sigma bonds
Explain the Khan-Ingold-Prelog nomenclature rules
Priority is assigned to groups to determine the isomer based on Atomic Number (Ar), at the first point of difference, the branch with the higher atomic number takes priority
Which are more reactive - alkanes or alkenes?
Alkenes: the double (pi) bond is weaker than the sigma bond, and alkanes themselves are relatively unreactive
What are the conditions required for hydration of an alkene?
Phosphoric acid and steam
What is an electrophile?
An electron pair acceptor
Summarise Markownikoff’s Rule
When a hydrogen-halide reacts with an alkene, the major product formed is the one where the hydrogen attaches itself to the carbon atom (in the former double bond) with the most other hydrogens attached. This is because alkyl groups ‘push’ electrons (also making tertiary carbocations most stable)
List the ways in which waste polymers can be disposed of
- Recycling
- PVC recycling using solvents
- Used as fuel
- Feedstock (reclaimation of raw materials)
(- Bio- and Photo- degradable)
What colour change does Potassium Dichromate show when it acts as an oxidising agent?
From orange to green
How is an aldehyde formed from a 1” alcohol?
1[Oxidation], using potassium dichromate and sulphuric acid under distillation
How is a carboxylic acid formed from a 1” alcohol?
2[Oxidation], using potassium dichromate and sulphuric acid under reflux
How is a ketone formed from a 2” alcohol?
1[Oxidation], using potassium dichromate and sulphuric acid under reflux
How do you dehydrate an alcohol?
Add phosphoric or sulphuric acid under reflux
What is a nucleophile?
Electron pair donor
What are the patterns in the rate of hydrolysis of Haloalkanes?
- Halogens lower-down the group hydrolyse fastest, (iodo-alkane fastest, then bromo- then chloro- etc.)
- Tertiary haloalkanes are hydrolysed fastest also, again due to the carbocation stability
How should the water inlet and outlet of a Liebig condenser be spatially orientated?
The water inlet should always be below the water outlet - to make sure that the entire jacket is flooded
How can you distinguish between the two layers in a separating funnel?
Add water, it will add to the aqueous layer
How can acid impurities be removed from a separating funnel?
Add sodium carbonate, swirl and invert, to vent any carbon dioxide evolved
What substances make good drying agents?
Anhydrous Inorganic Salts
- Calcium sulphate
- Magnesium sulphate
- Calcium chloride (for hydrocarbons)
What reagents and conditions are required to turn an alcohol into a haloalkane?
Sodium-halide and sulphuric acid
What reagents and conditions are required to turn a haloalkane (back) into an alcohol?
Sodium Hydroxide under reflux
What are the conditions and reagents required for hydrogenation (alkene to an alkane)?
Hydrogen and a Nickel catalyst
Why does a mass spectrum show a ‘M+1’ peak?
Because of the small amount of Carbon-13 present
