3.3.5 alcohols

• in dehydration of alcohols alkenes are formed from alcohols
• conditions for dehydration of alcohols:

  • concentrated sulphuric acid
  • hot
• markpoints for dehydration of alcohols:

  m1: curly arrow from middle of e- on O to H+

  m2: positively charged O formed, curly arrow from bond between C and O to show bond breaking

  m3: carbocation intermediate formed, curly arrow from one C and H bond to form a C=C bond
• primary tertiary and secondary alcohols are tested with warm acidified potassium dichromate and H2SO4
• observation if a primary alcohol reacts with warm acidified potassium dichromate

  orange solution to green solution
• observation if secondary alcohol reacts with warm acidified potassium dichromate

  orange solution to green solution
• observation if a tertiary alcohol reacts with warm acidified potassium dichromate

  no visible change or remains an orange solution
• what is formed if a primary alcohol is distilled

  aldehyde
• what is formed if a primary alcohol is heated under reflux

  carboxylic acid
• what is formed if a secondary alcohol is heated under reflux

  ketone
• why are anti bumping granules used

  to increase surface area so small bubbles are produced to prevent glassware breaking
• why is it important that the water direction in the condenser is correct

  so that the water fully fills to cool the tube and make sure all the product condenses
• why is distillation needed when making aldehydes

  to remove aldehydes from the reaction as soon as it’s formed to prevent further oxidation
• why is reflux needed when making carboxylic acid

  to ensure complete oxidation
• when making ketones which heating method would you choose and why

  reflux , gives a higher yield and is a simpler lab process
• oxidation equation for primary alcohols with distillation and gentle heat

  alcohol + [O] ——> aldehyde + water
• if an aldehyde is further reacted with excess oxidation agent and under reflux what is the oxidation equation

  aldehyde + [O] ——> carboxylic acid
• if an alcohol is refluxed with warm acidified potassium dichromate what is the oxidation equation

  alcohol + 2[O] ——> carboxylic acid + water
• oxidation equation for secondary alcohols

  alcohol + [O] ——> ketone + water
• what two reagents are use to test between aldehydes and ketones

  tollens reagent and fehlings solution
• observation if aldehyde is present and reacts with tollens reagent

  silver mirror
• observation if ketone is present and reacts with tollens reagent

  no visible change
• observation if aldehyde is present and reacts with fehlings solution

  blue solution to brick red precipitate
• observation if ketone is present and reacts with fehlings solution

  no visible change