Alcohols, carboxylic acids and esters Flashcards
What are the names and molecular formula of 3 main alkanes?
Methane (CH4), ethane (C2H6) and propane (C3H8)
What happens when an alkane burns in plenty of air?
It produces carbon dioxide and water
Do alkanes dissolve or react in water? why?
They do not dissolve in water and usually don’t react with aqueous substances, this is because they have single C-C bonds which are hard to break and therefore unreactive
What are saturated and unsaturated bonds? how does their presence affect the chemical?
Saturated molecules contain only single bonds between two carbon atoms, they are unreactive,
Unsaturated molecules contain one or more double bond between carbon atoms, they are reactive
Which of alkanes and alkenes have unsaturated and saturated molecules?
Alkanes have have saturated molecules while alkenes have unsaturated molecules
What is the general formula for alkanes and alkenes?
Alkanes- CnH(2n+2)
Alkenes- CnH(2n)
What are the two smallest and most common alcohols? and what is their structural formula?
The smallest alcohol is methanol - CH3OH
The second smallest is ethanol - C2H5OH
What is the general formula and functional group for alcohols?
The functional group is -OH
So the general formula is CnH(2n+1)OH
What does the presence of the -OH functional group do to the properties of alcohols?
It means unlike alkanes they are all soluble in water, and compared to an alkane with the same number of carbon atoms, they have higher melting and boiling points
What the presence of a hydrocarbon chain do to the affect of an alcohol when put under a flame?
It means that the alcohol is flammable and that when burnt they produce carbon dioxide and water
How does ethanol react with sodium?
Sodium fizzes as hydrogen gas is made,
It produces hydrogen and for example sodium ethoxide, it reacts because of -OH presence
How does fermentation work?
Yeast uses sugar as food to make energy and when it respires anaerobically it produces ethanol and carbon dioxide
Why does fermentation stop?
Fermentation can only be used to male dilute ethanol solution as fermentation stops when ethanol becomes more concentrated as higher concentrations kills the yeast that cause fermentation
How do we use dilute solutions of ethanol?
Distillation is a process that is used to make ethanol solutions more concentrated, it is used to make fuel and spirits like whisky
How does the distillation process work?
Dilute solutions of ethanol are heated to just above ethanol’s boiling point, ethanol boils off leaving water, ethanol vapour cools and condenses to form a liquid
How does genetically modified E. coli bacteria convert waste biomass into ethanol?
Plant material from a range of sources is dissolved in acids and solvents, the bacteria use cellulose in plants as food and produce ethanol. Process works at just above room temp.
How is ethane from oil converted into ethanol?
Ethane is an alkane in crude oil that can be converted into ethene.
Ethene reacts with steam to produce ethanol, a catalyst is required and distillation separates and purifies the ethanol
What are the disadvantages to making ethanol from crude oil and how sustainable is it?
Crude oil is not renewable,
The process requires high temperatures (300*C) which uses lots of energy
What are the advantages to making ethanol from crude oil?
It has high atom economy as only hydrogen is made,
hydrogen is an excellent by product as it has many uses,
the process is much faster than fermentation
What are the two main carboxylic acids and what are their formula?
Methanoic acid - HCOOH
Ethanoic acid - CH3COOH
What is the structural formula for ethanoic acid?
H
| = O
H--C--C
| \
H O -- HWhat properties do carboxylic acids have?
They have a sharp, unpleasant taste, many have an unpleasant smell
What is the functional group of carboxylic acids and what does it do?
-COOH
It gives them their acidic properties
How do carboxylic acids react with metals, alkalis and carbonates?
Carboxylic acid + metal = salt + hydrogen
Carboxylic acid + alakli = salt + water
Carboxylic acid + metal carbonate = salt + water
All salts made by carboxylic acids end with ‘-oate’
What kind of acids are carboxylic acids?
They are weak acids, they are used to make vinegar and are only corrosive in high concentrations
What makes an acid strong or weak?
Strong acids have lower pH than weak acids as they produce a higher concentration of H+ ions when they dissolve in water
What happens to acids when dissolved in water?
Strong acids completely ionise in water whereas weak acids do not ionise and most molecules stay as complete molecules
How are esters produced?
When carboxylic acids react with alcohols in the presence of a strong acid catalyst
What properties do esters have and how are they used as such?
Esters have distinctive smells, often fruity. Natural esters give fruits and flowers their smell. They are also used as food flavourings, solvents and plasticizers, and in perfumes
What are the techniques used in making an ester?
Heating under REFLUX,
distillation,
purification using a TAP FUNNEL,
drying
How is the name of an ester formed? eg. What does ethanoic acid and methanol produce?
The carboxylic acid gives the first part of the name -thyl and the alcohol gives the second part -anoate.
Ethyl methanoate is produced.
What are fats and oils and where do they usually come from?
Fats are solids at room temperature and usually come from animals,
Oils are liquids at room temperature and usually come from plants.
They are esters of glycerol and fatty acids
Why do living organisms make fats and oils?
They make them as energy stores
What do most animal fats contain?
Most animal fats contain fatty acids with saturated hydrocarbon chains, this means all of the carbon atoms in the chain are joined by single c-c bonds
What do most vegetable oils contain?
Most vegetable oils contain fatty acids with unsaturated hydrocarbon chains, this means some of the carbon atoms in the chain are joined by double c=c bonds
How can we test for unsaturation?
Bromine water can be used to test, unsaturated compounds turn bromine water from orange-brown to colourless where saturated compounds don’t react, this can be used to test for alkanes and alkenes
