Chapter 14 Flashcards
What is the functional group of alcohols?
-OH, hydroxyl group
What is the suffix of alcohols?
-ol
What is the general formula of alcohols?
CnH2n+1OH or R-OH
When do positional isomers occur in alcohols?
In carbon chains of 3 or more
What is a polyhydric alcohol?
Alcohols that contain two or more -OH groups
What is the structure of phenol?
When an -OH group is attached directly to a benzene ring
What is an ether?
A structural isomer of alcohol
Are alcohols polar or non-polar?
Polar
Where are the partial charges on an alcohol molecule that cause it to be polar?
- Partial positive charge on the Carbon atom the -OH group is attached to.
- Partial negative charge on the Oxygen in the -OH group.
Why does the boiling point increase with chain length in alcohols?
Alcohols create hydrogen bonds with each other, so have higher boiling points than alkanes of similar Mr as more energy is needed to overcome the stronger intermolecular forces.
Define volatility?
A measure of the tendency of a substance to vaporise (the higher the boiling point the lower the volatility)
How does the volatility of alcohols compare to alkanes?
Alcohols are less volatile than alkanes of similar Mr.
What is the solubility of alcohols like?
They have -OH groups which can form hydrogen bonds with water. This makes the first three alcohols soluble in water but after that the long alkyl chain interferes with the Hydrogen bonds.
When are alcohols soluble in water?
The first three alcohols are soluble in water but after that the long alkyl chain interferes with the Hydrogen bonds.
What is ethanol and when is it used?
Ethanol is ‘alcohol’ in alcoholic drinks. Commonly used as a solvent in the form of methylated spirits.
What is methanol and when is it used?
Methanol is used as a petrol additive to improve combustion. Important feedstock in the production of organic chemicals.
What is ethane-1,2-diol and when is it used?
Used as antifreeze as it lowers the melting point of water from 0” to as low as -40” when mixed with water.
What are the 4 reactions alcohols can take place in?
- Combustion
- Oxidation
- Dehydration
- Substitution
What is produced in the complete combustion of alcohols?
Carbon Dioxide and water
Why do alcohols make good fuels?
The combustion of alcohols is exothermic
What does increasing the number of carbon atoms in the chain during combustion result in?
It increases the amount of heat energy released per mole.
What does the oxidation of alcohols produce?
Molecules with different functional groups
What functional group does Aldehydes and Ketones contain?
The CARBONYL GROUP
What is the Carbonyl Group ?
A carbon double bonded to the oxygen. -C=O
What is the suffix of an Aldehyde?
‘…al’
What is the suffix of a Ketone?
‘…one’
What functional group do Carboxylic acids contain?
The CARBOXYL GROUP
What is the Carboxyl Group?
-COOH
What is the suffix of a Carboxylic Acid?
‘….oic acid’
What is used to carry out the oxidation of alcohols?
Acidified potassium dichromate (VI) solution
What colour does the potassium dichromate solution change to during a reaction?
From orange to green
What is the equation for potassium dichromate?
Cr2O7 ^2-
What is the equation for the potassium dichromate after it turns green?
Cr ^3+
What are primary alcohols oxidised to?
Aldehydes and then to a carboxylic acid
How is a primary alcohol oxidised into a aldehyde?
Under distillation with H+/ Cr2O7 ^2-
How is a aldehyde oxidised into a carboxylic acid?
Under reflux with H+/Cr2O7 ^2-
How are ketones made?
Secondary alcohols are oxidised to ketones, under reflux with H+/Cr2O7 ^2-
What are tertiary alcohols oxidised into?
They are not oxidised, the reaction mixture stays orange.
Define dehydration?
A water molecule is removed from a starting reactant
Define an elimination reaction
A small molecule is removed from a single larger molecule leaving an unsaturated molecule.
What acid catalyst is used in the dehydration of alcohols?
Concentrated H2SO4/ Concentrated H3PO4
How is a dehydration of alcohols reaction carried out?
The alcohol is heated under reflux in with an acid catalyst
What does the dehydration of an unsymmetrical alcohol result in?
2 alkenes that are positional isomers
What occurs during the mechanism of the dehydration of alcohols?
The hydrogen atom is removed from the carbon atom bonded to the most number of carbon atoms.
Define a substitution reaction
When an atom/ group of atoms is replaced by another atom/ group of atoms.
