Organic Chemistry Flashcards
Homologous series
Same general formula
Similar chemical properties
Gradation in their physical properties
Differ by a CH2 unit
What is a hydrocarbon
A compound/molecule consisting of hydrogen and carbon only
Alkanes
General formula: CnH2n+2, at room temperature and pressure; all colourless gasses (meth/eth/propl/but - ane)
Functional group
Reactive group in a molecule
Complete Combustion (Alkanes)
Products: Carbon dioxide + Water + Heat. Test: For CO2, bubble combustion products through colourless lime water- becomes milky white -CO2 present, for H2O condense the vapour by cooling- add white anhydrous copper(II) sulfate - becomes blue (H2O present)
Incomplete Combustion for alkanes
(Limited oxygen)Products: Carbon Monoxide + water
Problems Carbon dioxide, carbon monoxide, soot, sulfur dioxide (leading to acid rain)
Carbon dioxide: Greenhouse gas- absorbs IR given off by the earth - causes earths surface to warm- sea level rises, flooding, climate change
Carbon monoxide: Toxic gas (as combines with haemoglobin in the blood- reducing capacity to carry oxygen)
Soot: Carbon particles pollute the air- causes lung damage and respiratory problems
Sulfur dioxide: Acid rain- damages buildings ( especially limestone ones), damages vegetation, kills fish in lakes and rivers
Alkenes
General formula: CnH2n
Functional group: Carbon- Carbon double bond (C=C)
At room temp and pressure all colourless gases (eth/prop/but-1/but-2 ene)
Complete combustion of Alkenes
Products- Carbon dioxide + Water ( burns with an orange flame)
Incomplete combustion of Alkenes
(Limited oxygen) Products- carbon monoxide + water (sometimes soot, but don’t put in equation)
Unsaturated
The molecule contains one or more carbon-carbon double bonds
Addition reaction
Two molecules react to form one product
Addition reaction of Alkenes with bromine
Bromine adds across the double bond
Condition: room temp
This reaction is to test for the presence of a C=C bond- If organic substance is a liquid- shake with bromine water. If a gas- bubble the gas into bromine water
Orange bromine water changes to colourless in presence of a C=C bond
Addition reaction with Alkenes and hydrogen
Hydrogen adds across the C=C double bond
Conditions: Temperature 150 degrees Celsius, catalyst of nickel
Reaction called hydrogenation
Addition reactions of Alkenes with steam
Called hydration as water is being added across the C=C double bond
Conditions: Catalyst and high temperatures
What is a Polymer
Is a long chain molecule made from joining small molecules together
What is a monomer
A small molecule that combines with other monomers to make a polymer
What is Addition polymerisation
The process of joining monomer molecules together to form a long chain molecule
Chemical equation to form poly(ethene) from ethene monomers
H. H. —H. H —
|. |. | |. | |
n C = C. —————> -— |- C. C -|—-
|. |. |. |. |. |
H. H. —H. H—. n
Definition of a biodegradable material
A biodegradable material is one which is not decomposed by natural bacteria in the environment
Advantages and disadvantages of Landfill and Incineration
Landfill- Advantages- cheap(waste transported to a local site/ not much money for transport).
Disadvantages- wastes land(used for building and agriculture) -eyesores causes visual pollution
Incineration- Advantages- Heat energy produced during incineration- can be used to generate electricity.
Disadvantages- polluting gases released(CO2- can cause global warming) - High costs to buy an incinerator
Alcohols
General formula: CnH2n+1OH
Functional group- hydroxyl group(-OH)
At room temp and pressure- all colourless liquids (methanol/ethanol/propan-1-ol /propan-2-ol)
Complete combustion of alcohols
Products- Carbon dioxide and water
Clean(non smoky) blue fame with an orange tip
Incomplete combustion of alcohols
Limited oxygen products- carbon monoxide and water (and soot)
Oxidation of alcohols by air
*Propan -2-ol can be oxidised but a carboxylic acid is not formed but methanol, ethanol, and propan -1-ol can be oxidised by air to form carboxylic acids
Oxidation of alcohols by acidified potassium dichromate
This is an oxidising agent which oxidises some alcohols(methanol, ethanol, propan -1-ol) to carboxylic acids, on warming.
Observations: Acidified potassium dichromate solution changes from orange to green
Condition: warm in a water bath
Propan -2-ol is the same but a carboxylic acid is not formed
Fermentation and the conditions
The breakdown of sugars to produce ethanol and carbon dioxide
Conditions - sugars are dissolved in solution
- in the presence of yeast
- at a warm temperature (not above 37 degrees Celsius)
- in the absence of air
Carboxylic Acid
Functional group: carboxyl (-COOH)
At room temp and pressure all colorless liquids(meth/eth/prop/but anoic acid)
Salts of carboxylic acid
These are weak acids
They react with bases, metals and carbonates
Methanoate HCOO-
Ethanoate CH3COO-
Propanoate C2H5COO-
Butanoate C3H7COO-
Reactions of carboxylic acids with carbonates
Equation: Carbonate + acid —> salt + water + carbon dioxide
Test: As releases carbon dioxide turns colourless limewater to milky
Reactions of carboxylic acids with metals
Equation: Metal + acid —> salt + hydrogen
Test: gives a pop when tested with a lighted splint
Reactions of carboxylic acids with bases
Equation: Base + acid —> salt + water
Crude oil (petroleum)
A mixture containing mainly alkane hydrocarbons
Petrochemicals
Chemicals made from petroleum and natural gas
Finite resource
A resource that once used, cannot be replaced in a human lifetime
Is searlait a bitch
Yes
Fraction
A mixture of molecules with similar boiling points
4 steps in fractional distillation
- crude oil is heated and vaporised
- the vaporised crude oil enters a fractionating tower which is hotter at the bottom and cooler at the top
- the hydrocarbons cool as they rise up the tower and condense at different heights because they have different boiling points
- hydrocarbons with large molecules are collected near the bottom of the tower while those with small molecules are collectedd at the top
All different fractions and there uses
- Refinery gas for bottled gases
- Petrol used as a fuel for cars
- Naptha for manufacture of chemicals and plastics
- Kerosene as a fuel for aircraft
- Diesel as a fuel for cars and trains
- Fuel oils used for fuels for ships
- Bitumen used to surface roads and roofs
Cracking
The breakdown of larger saturated hydrocarbons (alkanes) into smaller more useful ones, some of which are unsaturated (alkenes)
Carried out be heating, it is a thermal decomposition reaction because alkanes are broken down into smaller molecules using heat
