Alcohols Flashcards
Are alcohols polar and if so why?
Alcohols are polar due to the O-H bond. The electronegativity of oxygen and hydrogen are different, resulting in a polar bond which results in an overall polar molecule.
Why do alcohols have a low volatility compared to alkanes?
Alcohols have strong hydrogen bonding between the molecules which require a large amount of energy to break, to change it from a liquid to a gas ( vaporisation). Resulting in a low volatility compared to alkanes which require little energy to break their london bonding between molecules leading to a higher volatility.
How does the solubility of alcohols in water compare to that of alkanes?
Alcohols have a high solubility in water due to their polarity and as they can hydrogen bond with water molecules.
Whilst alkanes have no/little polarity and do not hydrogen bond with water resulting in little solubility.
What happens to alcohols solubility as chain length increases?
As chain length increases the solubility of the alcohol decreases, since the infleunce of the -OH group on the molecule becomes smaller.
Define primary alcohols
Alcohols in which the -OH group is attaches to a carbon which has two hydrogens and one alkyl group also attached.
Define secondary alcohols
Alcohols in which the -OH group is attaches to a carbon which has one hydrogen and two alkyl group also attached.
Define tertiary alcohols
Alcohols in which the -OH group is attaches to a carbon which has three alkyl group also attached.
What is created in alcohol combustion?
Water and carbon dioxide.
As well as heat the reaction is always exothermic.
What oxidising agent is used for the oxidation of alcohols?
Solution of potassium dichromate and sulfuric acid, K2Cr2O7 and H2SO4.
What colour change occurs as alcohols are oxidised and why?
Orange to green as the Dichromate ions (orange) react to form Chromium ions (green).
What are porduced when primary alchols are oxidised?
Aldehydes or Carboxylic acids.
With water as the second product!
What type of alcohol is oxidised to aldehydes and how?
A primary alcohol is gentely heated with acidified potassium dichromate and distilled off to prevent any further reaction.
What type of alcohol is oxidised to carboxylic acids and how?
A primary alcohol is heated strongly under reflux with excess acidified potassium dichromate, forming a carboxylic acid.
What is produced when secondary alcohols are oxidised?
ketones
what type of alcohol is oxidised to ketones and how?
Secondary alcohols are heated under reflux with acidified potassium dichromate.
