AQA CHEMISTRY

• What is the reagent in the electrophilic addition of water to an alkene?


  Water with strong acid (sulfuric or phosphoric acid)
• What two species are added to the carbons either side of the double bond when water is electrophilically added to an alkene?


  H and OH
• What is the product when water is electrophilically added to an alkene?


  An alcohol
• What is the general formula of an alcohol with no carbon rings?


  CnH2n+1OH
• Where is the OH attached in aromatic alcohols?


  Directly to the ring
• What are aromatic alcohols known as?


  Phenols
• What is a primary alcohol?


  One which is attached to a carbon which is attached to 1 other carbon
• What is a secondary alcohol?


  One which is attached to a carbon which is attached to 2 other carbons
• What is a tertiary alcohol?


  One which is attached to a carbon which is attached to 3 other carbons
• What is the C-O-H angle in an alcohol and why?


  ~105° because the oxygen has two lone pairs which makes the functional group a V-shaped molecule
• Why do alcohols have a much higher boiling point than alkanes with a similar molecular mass?


  Because they can form hydrogen bonds, which are not present in alkanes
• Why do the boiling points of alcohols increase as chain length increases?


  Increased chain length leads to an increase in van der waals' forces
• Why do the boiling points of alcohols decrease as branching increases?


  Because this weakens their van der waals' forces
• Which types of alcohols are soluble in water and why?


  Those with short hydrocarbon chains because this allows the hydrogen bonding from the alcohol group to water molecules to dominate
• Why aren't alcohols with long hydrocarbon chains soluble in water?


  Because unlike in short chain hydrocarbons the long, non-polar hydrocarbon chain dominates over the hydrogen bonding
• What is the reagent in the dehydration of an alcohol?


  Concentrated sulfuric/phosphoric acid
• What are the conditions of the dehydration of an alcohol?


  Reflux at 180°C
• What is the product of the dehydration of an alcohol?


  Alkene
• What is an alternative method to reflux with strong acid to dehydrate an alcohol?


  Pass vapour over a heated alumina (aluminium oxide) catalyst
• Why can some alcohols not be dehydrated?


  Lack of an adjacent hydrocarbon
• What is oxidation of alcohols used to differentiate between?


  Primary, secondary or tertiary alcohols
• What is the usual reagent in the oxidation of alcohols?


  Acidified potassium (VI) dichromate
• What are primary alcohols oxidised to?


  Easily to aldehydes, and then carboxylic acids
• What are secondary alcohols oxidised to?


  Easily to ketones
• What are tertiary alcohols oxidised to?


  Not oxidised under normal conditions, only break down under very vigorous oxidation
• What is potassium dichromate usually oxidised with?


  Dilute sulfuric acid
• What is it essential to do when making aldehydes from alcohols?


  Distill off the aldehyde before it is further oxidised to a carboxylic acid
• What colour change do primary or secondary alcohols cause in potassium dichromate?


  Orange to green
• What colour change do tertiary alcohols cause in potassium dichromate?


  None
• What change in apparatus must be made to produce carboxylic acids instead of aldehydes?


  The Liebig condenser must be placed directly above the pear-shaped flask instead of to the side, so that any distilled aldehyde returns to the flask for further oxidation
• What is the composition of methylated spirits?


  Ethanol, along with a small amount of poisonous methanol and a purple dye
• What is an elimination reaction?


  One in which a small molecule leaves the parent molecule
• What smell do most aldehydes and ketones have?


  A pleasant one
• Are the physical properties of aldehydes and ketones similar?


  Yes
• What 3 reactions suggest that burning ethanol is carbon neutral and why?


  Photosynthesis, fermentation and combustion of ethanol, because overall 6 carbon dioxides go in and 6 carbon dioxides come out
• What is ethanol used as?


  A biofuel or as a solvent
• What are 2 ways of producing ethanol?


  Hydration of ethene or fermentation of glucose
• What are the reaction conditions of the hydration of ethene to make ethanol?


  Concentrated phosphoric acid catalyst, 300°C, 60 atm
• How is over 90% of ethanol made?

  Fermentation using yeast
• How is ethanol made using yeast?


  The yeast produces ethanol during anaerobic respiration, using glucose as its food