C7 - Organic Chemistry Flashcards
Define a hydrocarbon
a compound containing carbon and hydrogen only
What happens as you increase the chain length of a hydrocarbon?
- becomes more viscous
- higher boiling points
- less flammable
- dark in colour
- less volatile
- less useful
Describe how fractional distillation works
- oil is heated and evaporated until most of it is a gas
- the gas rises through a fractionating column
- the long hydrocarbons have high boiling points so they condense back to liquids near the bottom
- the shorter hydrocarbons have lower boiling points so they condense higher in the column where it’s cooler
- crude oil mixture will be separated into different fractions
Define a saturated hydrocarbon
single carbon bonds only
(C-C)
Define alkanes
they are a group of saturated hydrocarbons - the simplest type of hydrocarbon
What is the general formula of an alkane?
C(n) H (2n+2)
Name the first 4 alkanes
1) methane
2) ethane
3) propane
4) butane
What happens to the flammability as the length of the hydrocarbon chain increases?
the flammability decreases because smaller molecules evaporate easily and the vapour burns
What happens to the volatility as the length of the hydrocarbon chain increases?
the volatility decreases because the intermolecular forces are stronger so it requires more energy to break which means they have higher boiling points making them less volatile
What happens to the viscosity (thickness) as the length of the hydrocarbon chain increases?
the viscosity increases because the intermolecular forces are stronger and longer chain hydrocarbons get more tangled which means more viscous
Define an alkene
a hydrocarbon that has 1 double covalent bond (C=C) between two carbon atoms - they are unsaturated
What is the general formula for alkenes?
C (n) H (2n)
Name the first 4 alkenes
1) ethene
2) propene
3) butene
4) pentene
How do you test if a substance is an alkane or an alkene?
add bromine water
- if it remains orange = alkane
- if it becomes colourless = alkene
Define cracking
breaking down a long hydrocarbon chain into an alkane and alkene
Describe the process of cracking
- vaporise them
- mix them with steam
- heat them to a very high temperature
(called steam cracking)
What are the 2 things you need for cracking?
- heat (to vaporise the hydrocarbons)
- catalyst (to increase the rate of the reaction)
What is the word equation for the complete combustion of hydrocarbons?
hydrocarbon + oxygen –> carbon dioxide + water
What is the word equation for the incomplete combustion of hydrocarbons?
hydrocarbon + oxygen –> carbon monoxide + water
When would complete/incomplete combustion occur?
complete - in a high oxygen supply
incomplete - in a low oxygen supply
Define a monomer
a small molecule that can be joined together to form a polymer
Define a polymer
long chain molecule made up of lots of monomer molecules
Define an addition reaction
when a double carbon bond (C=C) breaks and new atoms add to each carbon atom
Define polymerisation
a reaction where lots of small monomer molecules join together in a long chain
Name the 4 reactions alkenes can do
- hydrogenation
- hydration
- halogenation
- combustion (incomplete)
Describe hydrogenation
alkenes react with hydrogen ( + catalyst) to make an alkane
requires very high temperature
Describe hydration
alkene reacts with steam (+ catalyst) to form alcohol
Describe halogenation
alkenes react with the halogens to form a dihalide alkane
Describe combustion of alkenes
alkenes react with the oxygen in the air and form carbon monoxide and water
it’s incomplete which results in a smoky yellow flame and less energy being released
Define alcohols
organic compounds that contain the OH functional group
What is the general formula for alcohol?
C (n) H (2n+1) OH
Name the first 4 alcohols
- methanol
- ethanol
- propanol
- butanol
Describe the solubility and pH of alcohol
- alcohols are soluble
- they have a neutral pH
Describe what happens when alcohols react with sodium
- sodium sinks - more dense than ethanol
- hydrogen is produced
- mixture goes alkali
Describe the 2 ways to make alcoholic drinks
- fermentation uses an enzyme in yeast to convert sugars into ethanol and carbon dioxide
- reacting ethene with water vapour in the presence of a catalyst (hydration)
What are some pros and cons of fermentation to produce ethanol?
+ renewable
+ requires less energy
+ cheaper
- don’t get pure ethanol
- slower
What are some pros and cons of hydration to produce ethanol?
+ no waste products
+ faster
- non-renewable
- requires more energy
- more expensive
What is the functional group for carboxylic acids?
COOH
What is the general formula for carboxylic acids?
C (n) H (2n-1) COOH
Name the first 4 carboxylic acids
- methanoic acid
- ethanoic acid
- propanoic acid
- butanoic acid
Carboxylic acids are …… acids so they ……………… in solutions.
- weak
- partially ionise
Carboxylic acids form salts that end in ………
-anoate
What is the equation to make esters?
carboxylic acid + alcohol (+catalyst) –> ester + water
What is the functional group for esters
COO
What are the purpose of esters?
- they are volatile
- have unique fragrances / tastes
Define a diol
a monomer with 2 hydroxyl (functional) groups
Explain how a polyester is formed through condensation polymerisation
- react a dicarboxylic acid with a diol - use lots of each
- water is produced as a byproduct
- polyester will be a product
How many types of monomers are needed for condensation polymerisation?
- two monomer types, each containing two of the same functional group
OR - one monomer type with two different functional groups
Give 3 examples of naturally occurring polymers
- proteins
- starch / cellulose
- DNA
What are polypeptides?
- amino acids form polymers known as polypeptides
- polypeptides form proteins
What are the bonds between amino acids (formed in a condensation reaction) called?
(3 names)
- amide link
- peptide bond
- amide bond
What type of reaction takes place when amino acids combine to form a polypeptide?
condensation reaction
Which functional groups does an amino acid have?
(3)
- a carboxylic acid group
- an amino group
- an ‘R’ group
Which monomers combine to form DNA?
nucleotides
What are the three elements that make up carbohydrates?
- carbon
- oxygen
- hydrogen
What is a feedstock?
a raw material used to provide reactants for an industrial reaction
What is a petrochemical?
a substance made from crude oil via chemical reactions
