Organic Chemistry Flashcards
Crude oil
Finite resource formed over millions of years from the remains of plankton which were buried in mud. Mixture of hydrocarbons (molecules made up of only hydrogen and carbon atoms).
Alkanes
General formula - CnH2n+2.
Saturated molecules as carbon atoms are fully bonded to hydrogen atoms, only single bonds, used as solvents and fuels.
Alkenes
General formula - CnH2n.
Unsaturated molecules because they have 2 fewer hydrogen than the equivalent alkane, contain a double bond, used to make polymers, burn in air with a smokey flame, more reactive than alkanes.
Viscosity
Thickness of a fluid. As size of hydrocarbon molecule increases, viscosity increases.
Flammability
How easily a hydrocarbon burns. As size of hydrocarbon molecule increases, flammability decreases.
Boiling point
Temperature at which hydrocarbon turns into gas. As size of hydrocarbon molecule increases, boiling increases.
Combustion
Hydrocarbon fuels release energy when combusted. During combustion, carbon and hydrogen atoms in the fuel react with oxygen (they are oxidised). In complete combustion, oxygen is unlimited and carbon dioxide and water is produced
Fractional distillation
- Crude oil is heated to high temperatures so all hydrocarbons evaporate.
- Crude oil vapour rises up the fractionating column where it is cooler at the top.
- Hydrocarbons condense when they reach their boiling point.
- The liquid fractions are removed and the remaining hydrocarbons continue moving up until they reach their boiling points and condense.
Long chain hydrocarbons condense at the bottom. Very short chain hydrocarbons do not condense and are removed from the top as gases.
Feedstock
A chemical that is used to make other chemicals.
Some fractions are used as feedstock in petrochemical industry.
Cracking
High demand for short-chain hydrocarbons to be used as fuels.
Long-chain alkane is broken down to produce a short-chain alkane and an alkene.
Testing for alkenes
Orange bromine water turns colourless.
Functional group
Part of a molecule that determines how it reacts.
Homologous series
A group of chemicals which have similar properties with the same functional group/with the same general formula.
Hydrogenation
Reaction of alkenes with hydrogen. Requires 150°C and nickel catalyst.
Carbon-carbon double bound coverts into a carbon-carbon single bond and 2 hydrogens are added. Produces an alkane.
Hydration
Reaction of alkenes with water in the form of steam. Requires 300°C, 70 atm and phosphoric acid as a catalyst.
Carbon-carbon double bond is converted into a carbon-carbon single bond and OH is added across.
Reversible reaction that produces an alcohol.
Reaction with halogens
Alkenes react with halogens.
Carbon-carbon double bond is converted to carbon-carbon single bond and the halogen atoms add across.
Produces di-(halogen)(alkane equivalent of alkene) e.g. ethene + bromine -> dibromoethane.
Hydration of ethene
PROS: produces high yield of ethanol
CONS: requires high temperature + energy, comes from crude oil and is non-renewable.
Alcohols
not rlly a general formula but add C-O-H to the alkanes displayed formula.
Used as fuels, solvents and found in alcoholic drinks.
Fermentation
Glucose mixed with yeast, converts the glucose to a solution of ethanol and also produces CO₂.
Conditions: 30°C, anaerobic.
PROS: low temp so not a lot of energy, comes from plants so renewable
CONS: ethanol produced is aqueous so needs to be purified by distillation which requires energy.
Solubility of alcohols
Soluble in water, form neutral solutions. As the number of carbon atoms increases, the solubility (ability to dissolve in water) decreases.
Reaction of alcohol and sodium
Produces a sodium (alcohol)oxide and hydrogen. e.g. methanol + sodium -> sodium methoxide + hydrogen.
Combustion of alcohols
Alcohols release energy when combusted. Combusting an alcohol in air produces carbon dioxide and water.
Reaction of alcohol and oxidising agent
e.g. acidified potassium dichromate. Produces a carboxylic acid and water.
Carboxylic acids and water
Carboxylic acids only partially ionise in aqueous solutions so are weak acids.
Reaction of carboxylic acids and metal carbonate
Produces a salt, carbon dioxide and water e.g. propanoic acid + potassium carbonate -> potassium propanoate + water + carbon dioxide
Reaction of carboxylic acids and alcohols
Produces an ester and water e.g. ethanoic acid + ethanol -> ethyl ethanoate + water: a reversible reaction, uses sufuric acid catalyst.
Esters have a pleasant smell so are useful in foods and perfumes.
Addition polymers
The monomer is an alkene. The double carbon-carbon bonds in the monomer is converted to single carbon-carbon bonds in the polymer. Name = poly(alkene).
Condensation polymers
Made from two different monomers, each with two of the same functional group e.g. ethane diol (has 2 alcohol groups) and hexanedioic acid (2 carboxylic acid groups).
Forms a polyester and water.
Amino acids
Have two different functional groups - amine group and carboxylic acid group.
React with each other to form water and a condensation polymer called a polypeptide since it’s from only 1 type of amino acid.
DNA
Consists of two polymer chains made from monomers called nucleotides (A,T, C, G), which wrap around each other to form a double helix.
Naturally occurring polymers
Starch and cellulose are polymers of glucose, proteins are polymers of amino acids.
