Alcohols

• These have the ending -ol and if necessary the position number for the OH group is added between the name stem and the –ol.
• If the compound has an –OH group in addition to other functional groups that need a suffix ending then the OH can be named with the prefix hydroxy.
• If there are two or more -OH groups then di, tri are used. Add the ‘e’ on to the stem name though e.g. propane-1,2,3-triol

• All the H-C-H bonds and C- C-O are 109.5o (tetrahedral shape), because there are 4 bond pairs of electrons repelling to a position of minimum repulsion.
• The H-O- C bond is 104.5o (bent line shape), because there are 2 bond pairs of electrons and 2 lone pairs repelling to a position of minimum repulsion.
• Lone pairs repel more than bond pairs so the bond angle is reduced. 

The alcohols have relatively low volatility and high boiling points due to their ability to form hydrogen bond between alcohol molecules.

• Primary alcohols are alcohols where 1 carbon is attached to the carbon adjoining the oxygen
• Secondary alcohols are alcohols where 2 carbon are attached to the carbon adjoining the oxygen
• Tertiary alcohols are alcohols where 3 carbon are attached to the carbon adjoining the oxygen 

• Reaction: primary alcohol --> aldehyde
• Reagent: Acidified potassium dichromate (VI) solution 
• Conditions: (use a limited amount of dichromate) warm gently and distill out the aldehyde as it forms: 
• Observation: the orange dichromate ion (Cr2O7 2-) reduces to the green Cr 3+ ion

An aldehyde’s name ends in –al. It always has the C=O bond on the first carbon of the chain so it does not need an extra number.

Write the oxidation equations in a simplified form using [O] which represents O from the oxidising agent 

CH3CH2CH2OH + [O] ----> CH3CH2CHO + H2O

         Propanol                        Propanal       

When writing the formulae of aldehydes in a condensed way write CHO and not COH e.g.CH3CH2CHO not CH3CH2COH

In general used as separation technique to separate an organic product from its reacting mixture. Need to collect the distillate of the approximate boiling point range of the desired liquid.

Note the bulb of the thermometer should be at the T junction connecting to the condenser to measure the correct boiling point

Note the water goes in the bottom of the condenser to go against gravity. This allows more efficient cooling and prevents back flow of water.

Reaction: primary alcohol ---> carboxylic acid
Reagent: potassium dichromate(VI) solution and dilute sulphuric acid
Conditions: use an excess of dichromate, and heat under reflux: (distill off product after the reaction has finished)
Observation: the orange dichromate ion (Cr2O7 2-) reduces to the green Cr 3+ ion

Reflux is used when heating organic reaction mixtures for long periods.The condenser prevents organic vapours from escaping by condensing them back to liquids.

Never seal the end of the condenser as the build up of gas pressure could cause the apparatus to explode. This is true of any apparatus where volatile liquids are heated including the distillation set up.

 Anti-bumping granules are added to the flask in both distillation and reflux to prevent vigorous, uneven boiling by making small bubbles form instead of large bubbles

• Don’t draw lines between flask and condenser.
• Don’t have top of condenser sealed
• Condenser must have outer tube for water that is sealed at top and bottom
• Condenser must have two openings for water in and out that are open

Reaction: secondary alcohol ----> ketone
Reagent: potassium dichromate(VI) solution and dilute sulphuric acid.
Conditions: heat under reflux
Observation: the orange dichromate ion (Cr2O7 2-) reduces to the green Cr 3+ ion

Ketones end in -one.

When ketones have 5C’s or more in a chain then it needs a number to show the position of the double bond. E.g. pentan-2-one

There is no further oxidation of the ketone under these conditions. 

Tertiary alcohols cannot be oxidised at all by potassium dichromate: This is because there is no hydrogen atom bonded to the carbon with the OH group

The fact that aldehydes can be further oxidised to carboxylic acids whereas ketones cannot be further oxidised is the chemical basis for two tests that are commonly used to distinguish between aldehydes and ketones.

Tollen’s Reagent

• Reagent: Tollen’s Reagent formed by mixing aqueous ammonia and silver nitrate. The active substance is the complex ion of [Ag(NH3 )2 ]+ .
• Conditions: heat gently 
• Reaction: aldehydes only are oxidised by Tollen’s reagent into a carboxylic acid and the silver(I) ions are reduced to silver atoms 
• Observation: with aldehydes, a silver mirror forms coating the inside of the test tube. Ketones result in no visible change.

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

The presence of a carboxylic acid can be tested by addition of sodium carbonate. It will fizz and produce carbon dioxide.

The fact that aldehydes can be further oxidised to carboxylic acids whereas ketones cannot be further oxidised is the chemical basis for two tests that are commonly used to distinguish between aldehydes and ketones.

Fehling’s solution

• Reagent: Fehling’s Solution containing blue Cu 2+ ions.
• Conditions: heat gently Reaction: aldehydes only are oxidised by Fehling’s solution into a carboxylic acid and the copper ions are reduced to copper(I) oxide . 
• Observation: Aldehydes = Blue Cu 2+ ions in solution change to a red precipitate of Cu2O. Ketones do not react.

CH3CHO + 2Cu2+ + 2H2O ---> CH3COOH + Cu2O + 4H+

The presence of a carboxylic acid can be tested by addition of sodium carbonate. It will fizz and produce carbon dioxide.

Dehydration Reaction: removal of a water molecule from a molecule

• Reaction: Alcohol ---> Alkene
• Reagents: Concentrated Sulphuric or Phosphoric acids 
• Conditions: warm (under reflux) Role of reagent: dehydrating agent/catalyst 
• Type of reaction: acid catalysed elimination

Some 2ry and 3ry alcohols can give more than one product when the double bond forms between different carbon atoms 

Mechanism

Glucose --->         ethanol          +    carbon dioxide
C6H12O6 --->    2 CH3CH2OH     +     2 CO2

Conditions needed: 
•Yeast
•No air because it oxidises the ethanol produced to ethanoic acid (vinegar)
•Temperatures 30 –40oC The optimum temperature for fermentation is around 38oC At lower temperatures the reaction is too slow. At higher temperatures the yeast dies and the enzymes denature.

Advantages
•Sugar is a renewable resource
•Production uses low-level technology / cheap equipment

Disadvantages
•Batch process which is slow and gives high production costs
•Ethanol made is not pure and needs purifying by fractional distillation
•Depletes land used for growing food crops 

Reagent: ETHENE - from cracking of fractions from distilled crude oil 
CH2=CH2 (g) + H2O (g) ----> CH3CH2OH (l)

Essential Conditions:

• high temperature 300 °C
• high pressure 70 atm
• strong acidic catalyst of conc H3PO4
• Type of reaction: Hydration/addition Definition: Hydration is the addition of water to a molecule

Advantages:
•faster reaction
•purer product
•continuous process (which means cheaper manpower)

Disadvantages:
•High technology equipment needed (expensive initial costs)
•ethene is a non-renewable resource (will become more expensive when raw materials run out)
•High energy costs for pumping to produce high pressures

• A biofuel is a fuel produced from plants.
• Ethanol produced from fermentation is a biofuel.
• It can be argued that ethanol produced from this method is classed as carbon–neutral as any carbon dioxide given off when the biofuel is burnt would have been extracted from the air by photosynthesis when the plant grew. There would be no net CO2 emission into the atmosphere.
• The term carbon neutral refers to “an activity that has no net annual carbon (greenhouse gas) emissions to the atmosphere 

Removal of CO2 by photosynthesis:    6CO2 + 6H2O --> C6H12O6 + 6O2
6CO2 molecules are removed from the atmosphere when the plants grow by photosynthesis to produce one molecule of glucose.

Production of CO2 by fermentation and combustion

Fermentation: C6H12O6 ---> 2 CH3CH2OH + 2 CO2 
Combustion: 2CH3CH2OH + 6O2  4CO2 + 6H2O

When 1 molecule of glucose is fermented 2 molecules of CO2 is emitted. The two ethanol molecules produced will then produce 4 molecules of CO2 when they are combusted

• Overall for every 6 molecules of CO2 absorbed , 6 molecules of CO2 are emitted. There is no net contribution of CO2 to the atmosphere. The process is therefore carbon neutral.

The term carbon neutral refers to “an activity that has no net annual carbon (greenhouse gas) emissions to the atmosphere”.

The equations showing why it is carbon neutral do not take into account any energy needed to:irrigate plants, fractionally distill the ethanol from the reaction mixture or process the fuel. If the energy for this process comes from fossil fuels then the ethanol produced is not carbon neutral 

1.Irrigate plants
2.Fractionally distill the ethanol from the reaction mixture
3.Process the fuel. 
4.Transport the biofuel