Organic Chemistry Definitions Flashcards
What are hydrocarbons?
Molecules made up of hydrogen and carbon atoms only
What is a homologous series?
A group of organic compounds with similar chemical properties due to them having the same functional group.
What are alkanes?
Hydrocarbons with only single bonds between carbon and hydrogen atoms. They are saturated as all carbon-carbon bonds are single covalent bonds so no atoms can be added.
What is the general formula for alkanes?
CnH2n+2
What does it mean if a molecule is saturated?
No atoms can be added to the molecule
What changes in properties are there as alkane chain-length increases?
-Melting and boiling point increases (short-chain gaseous RT)
-Volatility decreases (short-chain more volatile so evaporate more easily)
-Viscosity increases (short-chain less viscous)
-Flammability decreases (short-chain more flammable)
What is the general reaction for complete combustion of a hydrocarbon?
hydrocarbon + oxygen –> carbon dioxide + water
-Also releases a lot of energy so is an exothermic reaction
What is crude oil?
-A fossil fuel that is a mixture of a very large number of compounds, namely hydrocarbons
-It is a finite, non-renewable resource
How is crude oil formed?
It is formed from plants and animals (mainly plankton) that have decayed over millions of years buried in mud under high pressures and temperatures
What is feedstock?
A raw material used to provide reactants for an industrial reaction. The products of fractional distillation can be used as raw materials to make solvents, detergents, lubricants, polymers etc.
What is a petrochemical?
A substance made from crude oil via chemical reactions
What are kerosene, petrol and diesel used for?
Kerosene- aircraft fuel
Petrol- car fuel
Diesel- lorry or train fuel
What is cracking?
A thermal decomposition reaction in which longer chained alkanes are broken down into shorter chained alkanes and an alkene
What are the steps of catalytic cracking?
-Long chained hydrocarbons heated and vaporised
-Hydrocarbon vapour passed over hot powdered aluminium oxide (catalyst)
-As the hydrocarbons come into contact with the catalyst, they split into smaller alkane and an alkene
What are the steps of steam cracking?
-Long chained hydrocarbons heated and vaporised
-Hydrocarbon vapour mixed with steam and heated to very high temperature, causing long chained alkane to split apart into short chained alkane and an alkene
What are alkenes?
Hydrocarbons with carbon-carbon double bond. They are unsaturated because there is a double bond which can open up to form two new bonds.
They can be added together to form polymers as the double bond can break to form two new bonds
What is the test for alkenes?
Bromine water test. Bromine water added to alkene solution, bromine reacts with alkenes which decolourises the bromine water, changing it from orange to colourless.
What are the differences between alkanes and alkenes?
-Alkanes saturated while alkenes are unsaturated due to their carbon-carbon double bond.
-Alkenes are more reactive due to the C=C bond and can be added together to form polymers
-Alkenes can undergo addition reactions in which atoms are ‘added’ to the alkene across the C=C bond
What is a hydrogenation reaction?
-When alkenes react with hydrogen (addition reaction) to form an alkane
-Conditions: 60°C, nickel catalyst
-The C=C bond breaks apart, so two hydrogen atoms are added to the alkene to make an alkane
What is the addition reaction with steam?
- alkene + water –> alcohol
-Conditions: catalyst, high pressure and temperature
-Ethanol, unreacted ethene and water vapour are cooled so ethene condenses, ethanol and water separated using fractional distillation (used in industry for alc. bev.)
What is a halogenation reaction?
-alkene + halogen –> halogenoalkane
(eg ethene + bromine –> dibromoethane)
-When alkenes react with halogens (eg bromine) in which the halogen atoms are added across the C=C bond
-Does not require catalyst but shake solution
How do alkenes react with oxygen?
-Alkenes react with oxygen in combustion reacts like other hydrocarbons but often burn in air with smoky flames due to incomplete combustion
What is addition polymerisation?
-A reaction in which alkenes can be used to make polymers. -Many small monomers (alkenes) join together to form very large molecules (polymers) such as poly(ethene)
-Conditions: catalyst and high pressure
What are alcohols?
A homologous series with the -OH functional group
What is the general formula for alcohols?
CnH2n+1 OH
What are properties of the first four alcohols?
-Methanol, ethanol, propanol, butanol
-Flammable, soluble and can be oxidised to form carboxylic acids
What happens when alcohols are combusted?
Undergo complete combustion, react with O2 to form carbon dioxide and water
What happens when alcohols are added to water?
Dissolve in water forming a solution with a neutral pH
What happens when alcohols are oxidised?
Form a carboxylic acid with a -COOH functional group
What are the uses of alcohols?
-Used as fuels (release lots of energy when burned as fuel)
-Used as solvents in industry (can dissolve things which water cannot)
-Used in alcoholic beverages
What are the uses of ethanol?
-As a chemical feedstock to produce other organic compounds.
-As a biofuel (ethanol can be burned like petrol).
-Used in alcoholics drinks such as beer, wine, and spirits.
What are the adv. and disadv. of production of ethanol using ethene and steam?
-Adv: ethene cheap and reaction is cheap and efficient
-Disadv: ethene is made from crude oil which is a non-renewable resource, so if it starts to run out it will become expensive
What are the conditions of production of ethanol using fermentation?
-Fermentation tanks, requires yeast cells with enzymes to catalyse the reaction.
-30-40°C (optimum temp. for enzyme). Must be anaerobic respiration so ethanol doesn’t oxidise to ethanoic acid
What are adv. and disadv. of production of ethanol using fermentation?
-Adv: glucose is renewable resource, yeast easy to grow
-Disadv: slow process. Ethanol produced not pure so must be distilled
What are carboxylic acids?
A homologous series of organic compounds with the functional group -COOH
What happens when carboxylic acids react with a metal carbonate?
carboxylic acid + metal carbonate –> salt + carbon dioxide + water
What is the general formula for carboxylic acids?
CnH2n+1 COOH
What happens when carboxylic acids react with alcohols?
-carboxylic acid + alcohol –> ester + water
eg ethanoic acid + ethanol –> ethyl ethanoate
-Use an acid catalyst
What is a condensation polymerisation reaction?
-A reaction that involves at least two different monomers with two functional groups.
-When these types of monomers react they join together,they usually lose small molecules such as water.
-Formation of polyester involves dicarboxylic acid monomers (2 COOH groups) and diol monomers (2 OH groups)
What functional groups do amino acids have?
-Amino acids have one amino group (NH2) and one carboxyl group (COOH)
-They react by condensation polymerisation to produce
polypeptides
What monomers are starch and cellulose made of?
-Starch is made up of glucose
-Cellulose is made up glucose
