3.4 alcohols

• what is the suffix added to the iupac name of an alcohol?

  -OH
• when do you add the prefix hydroxy-

  when theres another functional group with a suffix ending
• what is the boiling point like for alcohols and volatility?

  they have high boiling points and low volatility due to their ability to form hydrogen bonds between alcohol molecules
• what is the solubility like for alcohols?

  smaller alcohols can dissolve in water because they form hydrogen bonds to water molecules
• what is the oxidising agent used to oxidise alcohols?

  k2Cr2O7 - pottassium dichromate
• what are the observations when a K2Cr2O7 is reduces?

  orange Cr2O7^-2 is reduced to a green Cr^3+ ion
• what are the PRODUCTS during the PARTIAL oxidation of a PRIMARY alcohol, what is the REAGENT and what are the CONDITIONS?

  1. products: aldehyde and water
  2. reagent: potassium dichromate and dilute sulfuric acid
  3. condition: warm gently with limited dichromate and distil out aldehyde as it forms
• what are the PRODUCTS during the FULL oxidation of a PRIMARY alcohol, what is the REAGENT and what are the CONDITIONS?

  1. products: carboxylic acid and water
  2. reagent: potassium dichromate and dilute sulfuric acid
  3. condition: excess dichromate, heat under reflux
• what are the PRODUCTS during the PARTIAL oxidation of a SECONDARY alcohol, what is the REAGENT and what are the CONDITIONS?

  1. products: ketone and water
  2. reagent : potassium dichromate and dilute sulfuric acid
  3. heat under reflux
• why cant tertiary alcohols be oxidised?

  the carbon with the -OH doesn't have a hydrogen bonded to it
• when is distillation used?

  to separate an organic product organic product from its reacting mixture
• how do i maximise yield whilst using distilation?

  only collect the distilate at the approximate boiling temperature of the aldehyde and not higher
• draw the distillation set up

  label the set up

  A) thermometer

  B) condenser

  C) water out

  D) water in

  E) round bottom flask

  F) heat

  G) collection flask

  
• why might an electric heater be used in distilation instead of a bunsen burner?

  because the organic chemicals are flammable and cant be exposed to naked flames
• when do you use reflux?

  used when heating organic reaction for long periods
• why do you use a condenser?

  to prevent organic vapours from escaping by condensing them back to liquids
• why dont we seal the reflux condenser ?

  the build up of gas pressure could cause the apparatus to explode
• why are anti-bumping granules added to the flask in distilation and reflux?

  to prevent vigorous bubbles by making smaller bubbles
• what are two tests used to distinguish aldehydes from ketones?

  tollens reagent and fehlings solution
• what is the REAGENT , CONDITION and what is the REACTION when using TOLLENS REAGENT?

  1. reagent: mixing aqeuous ammonia and silver nitrate
  2. condition: heat gently
  3. reaction : aldehydes are oxidised to carboxylic acids and silver ions are reduced to silver atoms so you observe a silver mirror
• what is the REAGENT , CONDITION and what is the REACTION when using FEHLINGS SOLUTION ? and OBSERVATION

  1. reagent : fehlings solution contains cu+2 ions
  2. conditions: heat gently
  3. reaction : aldehydes are oxidised to carboxylic acids and copper (ll) ions are reduced to copper (l) oxide
  4. observation : blue Cu2+ ions turn to red ppt of Cu2O
• how do you test the presence of carboxylic acids?

  adding Sodium carbonate and observing fizzing and the production of co2
• what does the dehydration of alcohols produce?

  alkenes and water
• what are the PRODUCTS, REAGENT and what TYPE OF REACTION is the dehydration of alcohols?

  1. products : alkene + water
  2. reagent : concentrated sulfuric acid or phosphuric acid
  3. type of reaction : acid catalysed elimination
• in an acid catalysed elimination reaction ( dehydration of alcohols) what is the role of sulfuric acid or phosphuric acid?

  dehydrating agents and catalysts
• draw the mechanisms of an acid catalysed elimination of propanol

  draw the mechanism

  A) acid catalysed elimination

  
• the dehydration of alcohols provide an alternative route to produce polymers rather than using crude oil
• what are two ways to form ETHANOL?

  fermentation and hydration of ethene (acid catalysed addition)
• what is the REACTION of fermentation and condition?

  1. reaction : glucose → ethanol + carbondioxide
  2. conditions: yeast , no air ( no oxygen ) and temperatures from 30 degrees- 40 degrees
• what are the advantages and disadvanatages of fermentation?

  advantages

  + sugar is renewable

  + its cheap

  disadvantage

  -slow

  -needs to be purified

  -depletes land use for crops
• what is the PRODUCT produced by the hydration of ethene, the TYPE OF REACTION , the REAGENT and the CONDITIONS?

  1. ethene → ethanol
  2. acid catalysed ADDITION or hydration
  3. concentrated phosphuric acid
  4. high temperature (300), high pressure (70)
• what are the advantages and disadvantages ethene hydration?

  advantages

  + faster

  +purer products

  +continous process

  disadvantage

  • high tech equipment is expensive
  • ethene is non-renewable
  • high pressures mean high costs
• draw the mechanism for the acid catalysed addition of ethene

  draw it

  A) acid catalysed addition

  
• what type of fuel is the ethanol produced by fermentation?

  biofuel
• how is the production of the biofeul carbon neutral?

  because the same amount of co2 taken in by the plant from the air will be burnt and returned to the air
• what does carbon neutral mean?

  no net annual carbon to the air
• what are the equations to show that biofuel is carbon neutral?

  Photosynthesis, combustion.

  
• what is not considered when saying ethanol produced by fementation is carbon neutral?

  energy needed for irrigation and other things icba
• describe the bond angles in alcohols:

  • the C-C-O and H-C-H are tetrahedral and have a bond angle of 109.5
  • the H-O-C bond is bent because the oxygen has 2 lone pairs and 2 bonding pairs so has a bond angle of 104.5
• what are the boiling points of alcohols?

  high