organic chemistry (2) Flashcards
What are alkanes
What are the first four examples
saturated hydrocarbon- each carbon atom forms 4 single c-c covalent bonds
general formula CnH2n + 2
undergo complete combustion
methane, ethane, propane, butane
What is fractional distillation
- crude oil is evaporated and enters a fractionating column, the excess liquid (bitumen) is drained off
- there is a temperature gradient in the column
- longer chain hydrocarbons have higher boiling points so they condense and are collected quicker than shorter chain length hydrocarbons
Why are short-chain hydrocarbons better fuels
they are less viscous, more flammable, and can be stored under pressure
What is cracking
Steam-
Catalytic-
cracking is splitting up long-chain hydrocarbons into more useful shorter-chain hydrocarbons
Steam- Mixing vaporised hydrocarbons with steam at a high temperature
Catalytic- vaporising hydrocarbons then pass the gas over hot powdered aluminium oxide catalyst
Alkenes (general formula and functional group)-
What type of combustion-
What are the first four examples
unsaturated hydrocarbons with c=c double bond that can open to allow alkenes to be reactive
general formula CnH2n
undergo incomplete combustion: alkene + oxygen -> carbon + carbon monoxide + carbon dioxide + water
ethene, propane, butene, pentene
Reactions of alkenes:
Addition reaction-
Hydrogenation-
Halogens (test)-
Steam-
Addition reaction- c=c bond opens to allow other atoms to bond
Hydrogenation- hydrogen reacts with double-bonded carbons in the presence of a catalyst
Halogens- alkenes react with halogens. They can be tested for with bromine which turns orange bromine water clear
Steam- reacting alkenes with steam forms alcohols in the presence of a catalyst
Addition polymers-
how to draw diagrams-
lots of monomers (alkanes) join together to form a polymer chain
draw the repeated formula in brackets and write ‘n’ on the outside to show the repetition
Alcohols (formation and properties)-
General formula and functional group
First four examples-
Their uses-
general formula- CnH2n+1OH
functional group -OH
they are formed by alkenes reacting with water
they are highly flammable and soluble in water
methanol, ethanol, propanol, butanol
Used as solvents, fuels and used for fermentation
fermentation reaction-
optimum conditions-
sugar -> ethanol + carbon dioxide
fermentation uses an enzyme in yeast to convert sugars into ethanol
happens fastest at 37*c in anaerobic conditions
Naturally occuring polymers:
Amino acids and protein-
DNA molecules-
Simple sugars-
Amino acids and protein- an amino acid contains two functional groups. Proteins are polymers of amino acids
DNA molecules- made from nucleotide polymers
Simple sugars- form larger polymers like starch and cellulose
Carboxylic acids
examples
functional group- COOH
general formula- CnH2n+1COOH
carboxylic acids dissolve in water but don’t fully ionise so form weak acids
methanoic acid, ethanoic acid etc
Esters and formation-
examples
Functional group- COO
formed when an alcohol and carboxylic acid react
an acid catalyst is used to create them
they have pleasant smells
(ethyl ethanoate)
Condensation polymers
A type of polymerisation where monomers join together, losing small molecules like water or hydrogen chloride as by-products.
Monomers: Usually have two different functional groups, allowing them to link in long chains.
Functional Groups:
Carboxylic acids (-COOH)
Alcohols (-OH)
How do you test for alkenes
mix with bromine water
turns clear in the presence of an alkene
