Alcohol Flashcards
Why alcohols polar?
Alcohols have a polar O-H bond because of the difference in electronegativity of the oxygen and hydrogen atoms.
Why are alcohols completely soluble in water?
Hydrogen bonds form between the polar -OH group of the alcohol and the water molecules.
What happens to the solubility as the chain increases?
The influence of the -OH group becomes smaller and the solubility decreases.
Primary Alcohols
OH group is attached to a carbon atom that is attached to 2 hydrogen atoms and one alkyl group.
Secondary alcohols
OH group is attached to a carbon atom that is attached to one hydrogen and two alkyl groups.
Tertiary alcohols
OH group is attached to a carbon atom that is attached to no hydrogen atoms and three alkyl groups.
How are primary and secondary alcohols oxidised?
Oxidised with potassium dichromate(VI) K2Cr2O7, with sulphuric acid, H2SO4
What colour change happens to alcohol if oxidised?
The orange solution containing dichromate (VI) ions is reduced to a green solution containing chromium (III) ions.
What can primary alcohols be oxidised to?
Aldehydes or carboxylic acids. Depends on reaction conditions because aldehydes also oxidised to carboxylic acids.
Why do you distill aldehyde as it forms?
Prevents any further reaction with the oxidising agent.
How is a carboxylic acid formed? What does heating under reflux ensure?
Primary alcohol is heated strongly under reflux, with an excess or acidified potassium dichromate (VI). Heating under reflux ensures that any aldehyde formed initially in the reaction also undergoes oxidation to the carboxylic acid.
What are secondary alcohols oxidised to?
To ketones heated under reflux to make sure reaction goes to completion.
Orange to Green
Primary + secondary
Orange to Orange
Tertiary
How do you decrease the risk of explosion when using reflux?
Anti bumping granules reduces bubbling - decreases risk
