Module 4 Chapter 14
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What are the uses of alcohols
Sanitisers Perfumes Solvents -> mixtures Cooking Fuel -> combustion Drink -> ethanol
What are the two ways to make ethanol
Through yeast fermentation. Or by the hydration of ethane
What is required for the hydration of ethene
Water is required to be added as steam and a phosphoric acid catalyst
What do alcohols contain and what determines their physical and chemical properties
-OH functional groups = hydroxyl group Physical and chemical properties of alcohols are due to the -OH
How are alcohols named
Suffix-ol added to the stem of the longest carbon chain And its position is indicated with a number of
What are the physical properties of alcohols
Alcohols are less volatile (compared to alkenes) They have a high melting point Greater water solubility As carbon chain length increases alkanes and alcohols become more similar Differences are due to the polarity present in alkanes and alcohols
What are alcohols molecules therefore (polar) and what are the intermolecular forces that are present therefore
They are therefore polar And the intermolecular forces will be very weak London forces but there will also be much stronger hydrogen bonds between the polar O-H groups.
What is volatility
The tendency of a substance to evaporate at normal temperatures.
What happens when going from liquid to gas and the relative energy to make it do so compared to an alkane
All the intermolecular forces are broken to go from a liquid to gas and because hydrogen bonds are present more energy is required than a weak London forces in an alkane
What is the solubility of alcohols
Alcohols can form hydrogen bonds with water And therefore they are very soluble in water (hydrophilic)
What is the solubility of alkanes
Alkanes are non-polar and they can’t form hydrogen bonds with water
What is the difference in solubility between small alcohols compared to large
Small alcohols are completely soluble in water, hydrogen bonds form between polar - OH groups of alcohol and therefore water molecules As HC chain increases in size, the power of the -OH group become smaller and solubility decreases.
What are the different types of alcohols and what classifies each of the alcohols
Primary, second and tertiary It depends on the number of H atoms and alkyl groups attached to the carbon with the alcohol group.
What are primary alcohols
They -OH group is attached to two hydrogen atoms and one alkyl group (except for methanol)
What are secondary alcohols
The -OH group is attached to a carbon that is attached to one hydrogen and two alkyl groups
What is a tertiary alcohol
An alcohol with an OH group that is attached to a carbon that has three alcohols attached to it
Uses of Methanol
High performance fuel (efficient combustion), chemical feedstock ,converted to polymers, paints, etc.
What are the uses of ethanol
Alcoholic drinks, fuels, solvent, feedstock
What are the two combustion reactions that alcohols can undergo
Complete combustion making water and carbon dioxide Incomplete combustion producing water and carbon monoxide or water and carbon (soot)
As the number of carbon atoms in the alcohol increases what occurs
The more heat per mole is released
What can primary alcohols be oxidised by and what is this usually
They can be oxidised by an oxidising agent And this is usually a mixture of potassium dichromate (VI), K2Cr2O7, acidified with dilute sulphuric acid.
What happens if the alcohol is oxidised (colour)
The orange dichromate (VI) ions are reduced to a green solution containing chromium ions.
What can alcohols be oxidised to
Either aldehydes or carboxylic acids
What does the product of an oxidation of an alcohol depend on
The reaction conditions used, and aldehydes can also be oxidised to carboxylic acids.