alkenes + their uses Flashcards
What is an alkene?
Unsaturated hydrocarbon. Contains a C=C bond.
General formula for alkenes is: CnH2n.
What is the test for alkenes?
Add bromine water. Colour change occurs from orange to colourless
Describe the combustion of
alkenes
They burn with smoky flames due to incomplete combustion
Describe addition reactions
of alkenes
atoms are added across the carbon-carbon double bond so that the double bond becomes a single carbon-carbon bond.
a) With hydrogen - hydrogenation; requires a higher temperature and a nickel
catalyst
b) With steam - hydration; requires high temperature, pressure, and phosphoric acid as a catalyst (reversible)
c) With Br2/Cl2/I2 - addition of halogens
What is an alcohol and what is it’s functional group?
An organic compound that contains an -OH functional group
State characteristics of
methanol, ethanol, propanol
and butanol
- Dissolve in water to form a neutral solution.
- React with sodium to form hydrogen.
- Burn in oxygen.
- React with carboxylic acids in presence of acid catalyst to form esters.
Oxidation of the alcohols
leads to…?
Carboxylic acids
What are some uses of
alcohols?
- Fuels
- Solvents
- Drinks
State the conditions required for
fermentation of glucose and state the
equation of the reaction
30 degrees Celsius, aqueous solution of the glucose, absence of air (because it’s an anaerobic reaction), yeast added;
C6H12O6 → 2 CH3CH2OH + 2 CO2
What are carboxylic acids?
Organic compounds that contain a COOH functional group, -anoic
State characteristics of
carboxylic acids
- Dissolve in water to form an acidic solution (contains H+ ions)
- React with metal carbonates to form carbon dioxide
- React with alcohols with an acid catalyst to produce esters
- React with metals to give off hydrogen gas
- Weak in water, because they only partially ionise
- reversible reaction if placed in water
- high pH
What type of acid is
carboxylic acid?
It is a weak acid.
Explain why carboxylic
acids are weak acids?
They are partially dissociated in water, thus the pH of a carboxylic acid in solution is not as low as a solution of a strong acid of the same
concentration.
What is an ester and how is it formed? What is characteristic about this class of compounds?
An organic compound containing a -COO- functional group, formed from
carboxylic acid and alcohol in the presence of a sulfuric acid catalyst.
They have a fruity smell.
What are some ways to make ethanol? (explain in detail)
By hydrating ethene to produce high yields of ethanol
- req high temp, alot of energy, ethene is crude oil, non renewable
By fermentation, start w a sugar solution such as glucose, mix w yeast, it converts the solution to an ethanol solution
- co2 gas also produced, temp should be around 30 degrees, must be taken place in anaerobic conditions.
- low temp, not alot of E required, renewable as sugar is from plants
- product is in aqueous solution of ethanol, dissolved in water, purify the ethanol through distillation, req energy.
