Alcohols Flashcards
What is the simplest alcohol
Methanol
What are primary alcohols
The -OH group is attached to carbon that is attached to 2 hydrogens and one alkyl group
What are secondary alcohols
OH group attached to carbon atom to one Hydrogen and 2 alkyl groups
What are tertiary alcohols
OH attached to carbon atom that’s attached no hydrogen and three alkyl groups
What are physical properties of alcohols
Alcohols have polar O-H bonds because difference of electronegativity
Of oxygen and hydrogen
IM forces are weak London forces
Also much stronger Hydrogen bonds between the polar O-H bonds
What’s the volatility and boiling point of alcohols
In the liquid state IM hydrogen bonds hold the alcohol molecules together.These bonds must be broken in order to change the liquid alcohol to gas
What is alcohol solubility in water
Alcohols such as methanol and ethanol are completely soluble in water as hydrogen bond form between the polar -OH group of the alcohol and the water molecules
As the size of the hydrocarbon chain increases the influence of the -OH groups become relatively smaller and solubility of longer chain alcohols become like hydrocarbons
Solublility decreases
What type of alcohols can be oxidised
Primary and secondary
How can primary alcohols be oxidised
By potassium dichromate and acidified with sulphuric acid to produce aldehydes or carboxylic acid
Aldehydes are themselves oxidised to carboxylic acids
What’s the preparation for aldehydes
Gentle heating of primary alcohol with acidified potassium dichromate produce aldehyde
Aldehyde is distilled out of the reaction mixture as it’s formed
Prevents any further reaction with oxidising agent
What’s the preparation of carboxylic acids
Primary alcohols heated strongly under reflux with an excess of potassium dichromate a carboxylic acid is formed. Use of excess of the acidified potassium dichromate ensure that all the alcohol is oxidised. Heating under reflux ensures that any aldehyde formed initially in the reaction also undergoes oxidation to carboxylic acid
What the oxidation of secondary alcohols
Oxidised to ketones by heating under reflux with oxidising mixture
Do tertiary alcohols undergo oxidation
No
What is dehydration of alcohols
Alcohol heated under reflux in the presence of an acid catalyst such as concentrated sulfuric acid H2SO4 or concentrated phosphoric acid H3PO4 .Product of reaction is alkene
What is dehydration also known as
Elimination
