ALCOHOLS

• What state are alcohols in at room temperature and why?

  Liquids because they have many strong IMF's (H-bonding)
• What's the trend in melting points and boiling points of alcohols?


  As the carbon chain length increases the melting point and boiling point also increases
• Are alcohols soluble in water and why?

  yes, because they have a polar O-H bond
• What's the trend in solubilities of alcohols and why?

  Solubility decreases as the carbon chain length increases because there's a larger portion of the carbon chain length that's non-polar.
• What are primary alcohols oxidised to ?

  Aldehydes
• What can aldehydes be further oxidised to?

  carboxylic acids
• What are secondary alcohols oxidised to?

  Ketones
• Which type of alcohols can be oxidised and which type of alcohols can't be oxidised?

  Primary and secondary alcohols can be oxidised whilst tertiary alcohols can't be oxidised.
• Why is distillation used for oxidising primary alcohols to aldehydes and not reflux?

  Because we don't want the aldehyde to oxidise further (to a carboxylic acid)
• When drawing the reflux apparatus, in which direction does the water flow/from what point does the water enter and from what point does the water leave?

  Water enters from bottom of condenser and water leaves from top of condenser
• What are the two shapes that the flask can be for the reflux apparatus?

  Either round bottomed or v-shaped
• What's one thing that you have to add between the condenser and the flask and what's it for?

  You must add a seal to ensure no organic vapours escape
• Do you put a stopper in the top of the condenser of the reflux apparatus and why?

  You don't because otherwise the build up of gas pressure may cause the apparatus to explode
• What are anti-bumping granules added for?

  To prevent bumping/uneven boiling
• Where should the bulb of the thermometer be in the distillation apparatus?

  At the junction where the condenser is connected
• What do you do to the collection flask to improve the yield of the distillate?

  Cool it in ice
• What do you do to improve the yield of the aldehyde obtained through distillation?

  Keep the temperature of the reaction mixture below the boiling point of the alcohol.
• how do you test between a primary, secondary and tertiary alcohol?

  Add acidified potassium dichromate to identify which alcohol is the tertiary alcohol because there'll be no colour change.

  Then add tollen's reagent to the samples and the one that's a primary alcohol will form a silver mirror as there'll be an aldehyde present (after oxidation with the potassium dichromate)

  The one that's a secondary alcohol will have no colour change because ketones don't react with tollen's reagent
• In the conversion of an alcohol to alkene what's the reagent needed and what's the role of the reagent?

  Reagent is concentrated sulfuric acid

  The role of the reagent is a catalyst
• what are the conditions needed for the conversion of an alcohol to an alkene?

  Heat, reflux
• What are the conditions for the conversion of alkene to alcohols?

  concentrated Phosphoric acid catalyst, 70 atm/6000 kPa pressure, 300℃
• What is the reagent for alkene to alcohol conversion?

  steam
• What are the two ways of producing ethanol?

  Hydration of ethene and fermentation of sugar
• What are the pros of producing ethanol via hydration of ethene?

  It's a faster process, continuous process, and has a higher atom economy
• What's the conditions for the fermentation of yeast to produce ethanol?

  no oxygen and a temperature of around 25-40℃
• How do you draw the apparatus for reflux?

  You first draw the reaction vessel/flask

  then draw the condenser going into the flask

  then connect the condenser and the flask using a seal

  Then draw the water cooler thing (that surrounds the condenser) with water entering from bottom and leaving from top

  don't seal the top of the condenser
• What are the pros of producing ethanol via fermentation?

  From renewable resources

  Cheaper equipment

  Lower temperature and pressures
• What are the cons of producing ethanol by hydration of ethene?

  More expensive

  from non-renewable resources

  has more energy costs
• What are the cons of producing ethanol by fermentation?

  Slower rate of reaction

  batch process

  lower percentage atom economy
• How many CO2's are released during fermentation

  2
• How many CO2's are used during photosynthesis?

  6
• How many CO2's are released during combustion?

  4
• Why might bioethanol not be carbon neutral?

  CO2 released during fertilisation or transportation or harvesting the plants to produce the sugar
• What's the definition of biofuel?

  fuel derived from/produced from renewable resources
• What does carbon neutral mean?

  There's no overall CO2 emission into the atmosphere.
• What's a byproduct of oxidation of alcohols that's always produced?

  Water
• What's the observation with aldehydes for Fehling's solution and what's the equation for this reaction with ethanal and in which order do you balance the equation?

  change in colour from Blue to red ppt (Cu^2+ ions reduced to Cu2O)

  Equation: CH3CHO + 2Cu^2+ + 2H2O- -> CH3COOH + Cu2O + 4H+

  First balance the copper by adding 2 to LHS

  then balance the oxygens by adding 2 H2O's to LHS

  Then balance H's by adding 4 H+ to RHS
• What's the observation for Tollen's reagent with aldehydes and what's the equation for this reaction with ethanal and in which order do you balance the equation?

  Silver mirror forms

  CH3CHO + 2Ag^+ + H2O --> CH3COOH + 2Ag + 2H+

  first balance the silver ensuring that there's 2Ag on both sides

  then balance the oxygens by adding 1 H2O to LHS

  then balance H's by adding 2H+ to RHS
• What does Tollen's reagent have in it?


  Aqueous ammonia and silver nitrate
• What does Fehling's solution have in it?

  Blue Cu^2+ ions