Alcohols

1
Alcohols

• AS Chemistry lesson 48
• Textbook reference p148-151
• Next lesson 152-155

2
Learning outcomes

• Describe the industrial production of ethanol
  from both sugars and ethene
• Outline the uses of ethanol and methanol
• Explain the terms hydrogen bonding, the water of
  solubility and the relatively low volatility of
  alcohols
• Classify alcohols into primary, secondary and
  tertiary alcohols

3
Making alcohol from ethene

1. What is an alcohol?
2. Write out the mechanism for the hydration of
   ethene using water
3. What are the reacting conditions?

4
Addition of a hydrogen halide (HBr)
5
Industrial alcohol

• Most alcohol that is made is made industrially
  from the hydration of ethene
• This is a REVERSIBLE reaction (so when some of it
  is being made some of it is also being converted
  back into its products)
• The reacting conditions
• 300C
• 60 atmospheres of pressure
• Using Phosphoric acid (H3PO4) catalyst

6
Phosphoric acid

• What is phosphoric acids conjugate base?

7
Alcohol from yeast

• The traditional way to make ethanol is through
  FERMENTATION of sugar using yeast
• This is how all alcohol that is in drinks is made
• Balance this equation
• C6H12O6 (aq) ? CH3CH2OH (l) CO2 (g)

8
Fermentation

• Relies on the enzyme ZYMASE in yeast
• Most concentrated it can make a solution is 14
  alcohol (afterwards the enzyme denatures)
• Reaction conditions
• 37C
• Yeast catalysed
• Anaerobic (no oxygen)

9
Using alcohol

• The best way to use ethanol is to drink it
• However, most ethanol that is made is used as
  FUEL (up to 10 of petrol in the US is ethanol)
• Ethanol has a high octane rating
• What is the octane rating scale? What 2 alkanes
  does it use in its comparison?
• Write out the equation for the combustion of
  ethanol

10
The octane ratings for different fuels
11
Methylated spirits

• Made mostly from ethanol with a small amount of
  methanol and dye
• Used as a solvent for removing non-polar stains
  like paint and ink

12
Methanol

• Highly toxic alcohol (but tastes and smells just
  like ethanol)
• Sometimes found in illegal versions of spirits
• Used as a fuel in high performance racing engines
• Also used as a starting point in industry for
  making other chemicals

13
Hydrogen bonding

• Draw two molecules of ethanol hydrogen bonding
  with each other with as much detail as possible

14

• What does volatile mean?

15
Volatility

• The more volatile something is the lower its
  boiling point is
• Alcohols have a much higher boiling point (are
  less volatile) then their alkane counterparts
  because of they can H-bond with each other

16
Solubility

• Alkanes are insoluble in water (because they are
  non-polar)
• The first three alcohols, however, because they
  can form hydrogen bonds, are soluble
• Longer chain alcohols are not soluble because too
  much of the molecule is non-polar

17
Classes of alcohols
18
Types of alcohol

• There are three classes of alcohol
• 1 (Primary) the OH is on a carbon that is
  attached to 1 other carbon
• 2 (Secondary) The OH is on a carbon attached
  to two other carbons
• 3 (Tertiary) The OH is on a carbon attached to
  three other carbons