Esters

1
Esters
05/11/2009

• L.O.
• I know that cosmetics can be made naturally and
  synthetically.
• I know how an ester is made.
• I can carry out an experiment to compare
  different solvents.

2
Starter

• In backs of books name 10 things that have
  perfume added to them

Air freshener
Shampoo
Deodorant
Disinfectant
Washing up liquid
Candles
Body spray
Fabric Conditioner
Hair spray
Conditioner
3
What Makes a Good Perfume
Non-toxic
Does not poison
Does not irritate the skin
Can be put directly on the skin
Does not react with water
Does not react with perspiration
Evaporates easily - volatile
Perfume particles can reach the nose
Cannot be washed off easily
Insoluble in water
4
Volatility

• We can smell an ester because particles leave the
  ester, diffuse through the air and stimulate
  sensors in our nose.
• The volatility (ease of evaporation) of perfumes
  (esters) can be explained using ideas about
  moving particles.

Movement of particles
DIFFUSION
low concentration
high concentration
5
How are Cosmetics and Perfumes Made?

• Cosmetics and perfumes can be made
• from natural sources. (can you name any?)
• For large scale cosmetic production perfumes are
  more commonly made synthetically ( made by human
  action)

e.g. roses, lavender and pine trees
6
Making Esters - Esterification

• To make a perfume a chemical called an ester is
• made. An alcohol mixed with an acid makes an
  ester.
• Alcohol Acid Ester Water
• This reaction is reversible (it goes both ways).

ethanol
propanoic
ethyl propanoate
butanol
butyl ethanoate
ethanoic
propyl butanoate
butanoic
propanol
methanol
ethanoic
methyl ethanoate
7
Uses of Esters

• Esters can be used for-
• Food flavourings
• Solvents
• Perfumes

8
Comparing Solvents

• Aim To find the best solvent to dissolve nail
• polish.
• Method
• A strip of nail polish was painted onto a
• wooden spill and put into these solvents.

Write up the results and a conclusion for this
experiment
hot water
ethanol
propanone
9
Homework

• Complete the sheet
• Solutions definitions to learn
• to recap for a quick test next lesson

10
Explaining the results

• Water does not dissolve nail varnish. This is
• because the force of attraction between two water
  molecules is stronger than that between a water
  molecule and a molecule of nail varnish.

Weak forces of attraction between water molecule
and nail varnish molecule.
Strong forces of attraction between nail varnish
molecules.
Strong forces of attraction between water
molecules.
11
Making a Perfume

• ESTERS Ethyl ethanoate, an ester,  is formed by
  the reaction of ethanoic acid with ethanol e.g.
• ethanoic acid ethanol ethyl ethanoate water
  
• H2O
• Its an equilibrium, and starting with the pure
  acid plus pure alcohol you get about 2/3rds
  conversion to the ester, and the reaction is
  catalysed by a few drops of concentrated
  sulphuric acid.
• This means a yield of about 67 in the 'atom
  economy'.
• If the ester is warmed with water or any dilute
  acid (faster), it changes back into the original
  acid and alcohol. This reverse reaction is called
  hydrolysis i.e.
• ethyl ethanoate water gt ethanoic acid
  ethanol
• whereas esterification is
• ethanoic acid ethanol gt ethyl ethanoate
  water
• (more on reversible reactions and chemical
  equilibrium)
• Esters are usually sweet smelling and widely used
  as fragrances (e.g. perfumes) and food
  flavourings