Download C3 Topic 5 Organic chemistry PP

Organic chemistry
C3 Topic 5
Making ethanol
• Most ethanol is made from carbohydrates (glucose) by
fermentation
glucose

ethanol
+
carbon dioxide
C6H12O6

2C2H5OH
+
2CO2
• The fermentation mixture is kept warm and under anaerobic
conditions (no oxygen)
• Yeast provides an enzyme for this reaction, breaking down
glucose into ethanol and carbon dioxide
Fermentation
Advantages
• Uses biofuels that are renewable (sugar cane
and sugar beet)
Disadvantages
• Produces ethanol at only 15% concentration
% ethanol
• Different percentages of ethanol are present
in different drinks
Effects of alcohol
• The ethanol in alcoholic drinks acts as a drug that can affect both the
brain and the body
• Small amounts:
- less self-conscious/more confident
- more talkative
•
-
Large amounts:
Slower reaction times
Violent/aggressive behaviour
Loss of balance/coordination
Vomiting/fainting
Dehydration (leading to a hangover)
Increased risk of accidents
Lowered inhibitions
Effects of alcohol
• Vitamin B deficiency causing skin damage, diarrhoea and
depression
• Decreased iron levels leading to anaemia
• Liver damage (will no longer make toxins safe)
• Destruction of brain cells
• Increased risk of cancer (mouth, larynx, oesophagus, liver, stomach,
colon, rectum and breast)
• Increased risk of heart disease and high blood pressure
• Inflammation and irritation of the intestinal and stomach lining
leading to ulcers and damage to the pancreas
• In men: inability to get an erection, reduced sperm count, shrinking
testes and penis
• In women: miscarriage and low birth weight or birth defect in
babies
Separating ethanol- fractional distillation
• At levels of 15%, ethanol kills the yeast cells
that made it, stopping fermentation
• Ethanol boils at lower temperatures than
water, so the fraction of the liquid that boils
first will contain a higher percentage of
ethanol (more concentrated)
• This vapour is condensed to produce stronger
drinks (spirits)
Fractional distillation of ethanol
Fractional distillation
Advantages
• Produces ethanol that is 95% pure
Preparing ethanol using fractional
distillation in the laboratory
Making ethanol from crude oil
• Ethanol can also be made by reacting ethene with
steam in the presence of a catalyst
• This is hydration
catalyst
ethene + steam → ethanol
C2H4 + H2O → C2H5OH
• Ethene is produced by the cracking of crude oil
fractions
Hydration of ethene
Advantages
• Product is nearly 100% pure, with little or no
waste
Disadvantages
• Uses crude oil, which is a non-renewable
resource
Making ethene from ethanol
• Heating ethanol to a high temperature in the
presence of a suitable catalyst produces
ethene and steam
• This is dehydration
catalyst
ethanol → ethene + steam
C2H5OH → C2H4 + H2O
Homologous series
• A series of compounds which:
- have the same general formula
- show a gradual variation in physical properties
as exemplified by their boiling points
- have similar chemical properties
General formula- CnH2n+2
Alkane
Formula
Methane
CH4
Ethane
C2H6
Propane
C3H8
Butane
C4H10
Alkanes
Chemical structure
Ball-and-stick
model
General formula- CnH2n
Alkene
Formula
Ethene
C2H4
Propene
C3H6
Alkenes
Chemical structure
Ball-and-stick
model
Alcohols
• End in – ol
• Contain the hydroxyl group (OH)
• General formula: CnH2n+1OH
Carboxylic acids
• Contain a carboxyl group (-COOH)
• General formula CnH2nO2
Methanoic acid- HCOOH
Ethanoic acid- C2H5COOH
• What would a molecule of propanoic acid look
like?
Oxidation of ethanol
• Ethanol can be oxidised to form ethanoic acid
• This reaction occurs in open bottles of wine
and in the production of ethanoic acid in
vinegar

+
ethanol
oxygen
+
ethanoic acid
water
Ethanoic acid- vinegar
• Vinegar is used as:
- a flavouring
- a preservative
• Turns litmus paper and
universal indicator red
Ethanoic acid- vinegar
Reactions of ethanoic acid
acid
ethanoic acid
+
+
+
acid
ethanoic acid
+
2CH3COOH(aq)
+
+
+
+
carbonate
water
potassium ethanoate
CH3COO-K+(aq)
oxide
→
salt
Ca2+O2-(aq)
+
→
+
→
metal
magnesium
2CH3COOH(aq)
+
salt
KOH(aq)
calcium oxide
acid
acid
→
potassium hydroxide
CH3COOH(aq)
ethanoic acid
alkali
→
→
→
salt
H2O(l)
calcium ethanoate
+
water
(CH3COO-)2Ca2+(aq)
+
H2O(l)
+
hydrogen
salt
+
hydrogen
magnesium ethanoate
+
water
water
→ (CH3COO-)2Mg2+(aq)
Mg(s)
→
→
+
+
+
carbon dioxide
+
H2(g)
+
water
ethanoic acid + sodium carbonate → sodium ethanoate + carbon dioxide + water
2CH3COOH(aq)
+
Na2CO3(aq)
→
2CH3COO-Na+(aq)
+
CO2(g)
+
H2O(l)
Reactions of ethanoic acid
acid
+
ethanol
ethanoic acid
+
ethanol
→
ethyl ethanoate
+
water
C2H5OH(l)
→
CH3COOC2H5(l)
+
H2O(l)
CH3COOH(l)
C2H4O2
+
→
ester
+
water
Esters
• Organic compounds that contain carbon,
hydrogen and oxygen
• Produced from the reaction between an
organic acid and an alcohol
• Used as flavourings and perfumes as they are
pleasant smelling
Polyesters
• Used as fibres to make fabric and as plastics
for making bottles
• Can be recycled to form fleece that is used to
make clothing
Ester group
Oils and fats
• Esters
• Oils are liquid at room temperature
• Fats are solid at room temperature
Making soap
• Oils and fats can be broken down by boiling with
concentrated alkali solution to produce soaps, which
are sodium or potassium salts of long chain
carboxylic acids
concentrated alkali + oil/fat → soap + glycerol
How does soap work?
• The head is hydrophilic (water-loving:
dissolves in water)
• The tail (long chain of carbon atoms) is
hydrophobic (water-hating: dissolves in
dirt/grease)
O- is an
anion
(hydrophilic)
How does soap work?
• The hydrophobic tails stick to the dirt/grease and
starts to lift it off the fabric
• The hydrophilic heads point towards the water and
allow the dirt/grease to mix
Turning oils into fats
• Vegetable oils are unsaturated (contain double bonds)
• Animal fats such as butter/lard are saturated (contain single
bonds only)
• Liquid oils can be turned into solid fats by catalytic
hydrogenation. This is done by bubbling hydrogen through
vegetable oils and removes the C=C unsaturation
• Catalytic hydrogenation is used to manufacture margarine