Organic chemistry Flashcards
Hydrocarbon
Compound made of only H and C
Homologous series
Series of organic compounds with the same functional group and general formula
Functional group
Group of atoms responsible for the reactions of a compound
Saturated
Contains only single bonds
or has max amount of hydrogens attached
Isomers
Molecules that share the same molecular formula, but have different atom arrangements
Chain isomers
Isomers with different positions and amounts of carbon chains
Position isomers
Isomers with different positions for functional groups
Functional group isomers
Isomers with different functional groups
Stereoisomers
Isomers formed by rotation about a double bond between two carbons (both carbons must have two different groups attached)
Methods of obtaining alkane fuels
- fractional distillation
- cracking
- reforming
Fractional distillation
- crude oil is vaporised
- it is then passed into a fractionating column
- the vapour is cooled as it rises
- hydrocarbons condense at different heights based on boiling points
- mixtures of similar fuels called fractions are collected
Cracking
- thermal decomposition of long chain hydrocarbons
- more useful, shorter chain fuels are formed
Reforming
- processing of straight chain hydrocarbons
- cyclic and branched fuels are produced for more efficient combustion
Pollutants formed from combustion
- carbon monoxide
- sulfur and nitrogen oxides
- carbon particulate
- unburned fuel
Problem with carbon monoxide
Toxic
Problem with sulfur and nitrogen oxides
Causes acid rain
How a catalytic converter works
- precious metal catalysts are spread over a large surface area
- exhaust fumes pass over the catalysts
- harmful gases are adsorbed and converted into less harmful gases
Pros and cons of biofuel (compared to fossil fuel)
Pros:
- renewable
- closer to carbon neutral
Cons:
- large amount of land needed
- lower fuel yield
Stages of radical substitution
- initiation
- propagation
- termination
Radical
A species with an unpaired outer shell electron (shown as a dot)
Initiation
- caused by UV light
- homolytic fission of the covalent bond in a halogen molecule
- two halogen radicals are produced
Propagation
- a radical reacts with a molecule
- a new radical and molecule are formed
- the cycle continues
Termination
- a radical reacts with another radical
- a molecule is formed
Limitations of radical substitution (to form a specific product)
- many different products formed because of the many propagation and termination reactions
- low atom economy
- desired product needs to be separated out
Types of bonds present in a double covalent bond
1 sigma, 1 pi
Electrophile
Electron pair acceptor
Hydrogenation
- electrophilic addition of hydrogen with an unsaturated molecule
- requires heat + nickel catalyst
- alkene»_space; alkane
- vegetable oil»_space; margarine
Production of dihalogenoalkanes / test for saturation
- electrophilic addition of halogens with alkenes
- combine at room temp
- goes from green / orange / brown to colourless
Production of halogenoalkanes (from alkenes)
- electrophilic addition of hydrogen halides
- bubble through at room temperature
Production of alcohols (from alkenes)
- electrophilic addition of steam
- requires acid catalyst
Production of diols (from alkenes)
- reaction with potassium manganate(vii) (oxidising agent) and water
- requires acidic conditions
Homolytic fission
- covalent bond is broken
- both atoms take one electron from the bond
- this forms two radicals
Heterolytic fission
- covalent bond is broken
- one atom takes both electrons from the bond
- this forms two oppositely charged ions
Uses of polymer waste
- recycled
- used as fuel (incinerated)
- turned into useful chemicals via cracking
How chemistry helps in polymer disposal
- polymers can be made biodegradable by using additives or by using plant based materials
- harmful pollutants from incinerators can be managed
What makes a functional group primary, secondary, or tertiary?
The number of chains attached to the same carbon as the functional group
Nucleophile
Electron pair donor
2 methods for production of alcohols (from halogenoalkanes)
Method 1:
- nucleophilic substitution with OH-
- uses aqueous potassium hydroxide under reflux
Method 2:
- nucleophilic substitution with water
- uses water mixed in ethanol (with silver nitrate to test for halide ions produced)
Production of nitriles (from halogenoalkanes)
- nucleophilic substitution with CN-
- uses ethanolic potassium cyanide
- remember that a carbon is added to the chain
Production of primary amines (from halogenoalkanes)
- nucleophilic substitution with ammonia
- uses ammonia in a sealed tube
- 2 ammonias are needed for the mechanism
Production of alkenes (from halogenoalkanes)
- elimination with OH-
- heat with ethanolic potassium hydroxide
Why ethanol is used in halogenoalkane reactions
- water / aqueous solutions do not mix with organic molecules
- ethanol can dissolve both the halogenoalkane and the other reactant, allowing them to react
Trend in reactivity of primary, secondary, and tertiary halogenoalkanes
Tertiary is most reactive
Trend in reactivity of halogenoalkanes if you change the halogen
- reactivity is highest for iodoalkanes (increases down the group)
- this is because bond enthalpy is lower
Production of chloroalkanes (from alcohols)
Add phosphorus(v) chloride
Production of bromoalkanes (from alcohols)
Add potassium bromide and sulfuric acid
Production of iodoalkanes (from alcohols)
Add red phosphorus and iodine
Production of aldehydes (from alcohols)
- use a primary alcohol
- oxidation using potassium dichromate(vi) with dilute sulfuric acid
- distill as product is formed
Production of carboxylic acids (from alcohols)
- use a primary alcohol
- oxidation using potassium dichromate(vi) and dilute sulfuric acid
- reflux then distill
Production of ketones (from alcohols)
- use a secondary alcohol
- oxidation using potassium dichromate(vi) with dilute sulfuric acid
- reflux then distill
Why tertiary alcohols cannot be oxidised
- oxidation in this case is a loss of hydrogen
- there are no hydrogens connected to the same carbon as the hydroxyl group
All tests for aldehydes (with positive results)
Heat with:
- potassium dichromate(vi) (orange to green)
- tollen reagent (grey precipitate)
- fehling solution (blue to red)
Production of alkenes (from alcohols)
Heat with a phosphoric acid catalyst
Distillation
- impure liquid is heated in a flask connected to a condenser
- the liquid with the lowest boiling point evaporates and passes into the condenser first, being collected in another flask
Extraction using a solvent
- find a solvent that does not mix with the reaction mixture’s solvent
- desired product must be more soluble in this second solvent
- add both liquids to a separating funnel and shake them together
- allow the contents to settle into two layers and separate them
- most of the desired product should now be in the second solvent
Removing water with drying agents
- add powdered drying agent to the liquid
- swirl, then leave it for a while
- drying agent goes from powder to crystals when absorbing water
- add more drying agent
- if no further water is absorbed, the liquid is dry
- filter out the crystals
