Module 4 Chapter 14 Flashcards
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.
What is the functional group of an aldehyde and a carboxylic acid
DRAW IT
How are aldehydes made
Gentle heating of primary alcohols with acidified potassium dichromate, forms an aldehyde.
Aldehyde is distilled out of the reaction mixture as it forms —> this is to stop it from oxidising further to a carboxylic acid with the oxidising agent
What is the colour change when aldehydes are made
Orange to green
DRAW THE REACTION WHEN butan-1-ol reacts with an oxidising agent to form butanal
DRAW IT
How are carboxylic acids made
Primary alcohols are heated strongly under reflux (which ensures that any aldehyde formed initially in the reaction also undergoes oxidation to carboxylic acid)
An excess of acidified potassium dichromate is used (ensuring all the alcohol is oxidised)
What are secondary alcohols oxidised to
They are oxidised to ketones, and no further oxidation is possible when using acidified dichromate (VI)
How are secondary alcohols oxidised to ketones and what is the colour change
They are heated under reflux with the oxidising agent
The dichromate ions change orange —> green
DRAW the reaction of propan-2-ol with an oxidising agent producing propanone
DRAW IT
What is the oxidation reactions of tertiary alcohols and what is the colour change
They do not undergo oxidation reactions
Dichromatae (VI) ions remain orange when added to a tertiary alcohol
Why ant tertiary alcohols not be oxidised
Because the carbon atom that carries the OH group does not have a hydrogen atom attached but it is instead bonded to other carbon atoms.
What is a dehydration reaction
Any reaction where a water molecule has been removed
What is required fr dehydration of an alcohol to take place and what type of reaction is it
An alcohol is heated under reflux in the presence of an acid catalyst (concentrated sulphuric acid/ phosphoric acid)
You will make an alkene
And it is an elimination reaction
What is the reaction of cyclohexanol to cyclohexane
What occurs when hydrogen halides are added to alcohols
Haloalkanes form
What is required for the substitution of alcohols
The alcohol is heated under reflux with sulphuric acid and sodium halide, hydrogen halide is formed in situ
Hydrogen halide reacts with alcohol to produce the haloalkane
DRAW THE TWO REACTIONS THAT TAKE PLACE IN THIS REACTION (substitution of alcohols to form a haloalkane)
