Chemistry of Cooking and
Oxidation
Higher Supported Study
Week 3 – Part 2
Chemistry of Cooking – Key Areas
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Shapes of Proteins
Denaturing of Proteins
Flavour and Aroma Molecules
Aldehydes and Ketones
Tests to differentiate between Aldehydes and
Ketones
• Effect of functional groups and properties
Shapes of Proteins
• Spirals, Sheets, complicated shapes
• Held in these shapes by intermolecular
bonding
Heating Proteins (Cooking)
• Intermolecular bonds are broken allowing the
proteins to change shape (denature).
• These changes alter the texture of foods.
• New intermolecular forces form
Flavour and Aroma Molecules
• Many flavour and aroma molecules are
ALDEHYDES
Aldehydes
Functional Group  Carbonyl (C=O)
END OF MOLECULE
- al endings
Naming Aldehydes
Ketones
Functional Group  Carbonyl (C=O)
Ketone  C=O found in middle of molecule
-one ending
Aldehydes and Ketones
• Can be named from structural formulae.
• Structural formulae can be drawn from names
• Molecular formulae can be written from
names
• Isomers can be drawn
Aldehyde Tests
Three possible tests to determine if substance is
aldehyde or ketone
Oxidising Agents
1) Fehling’s Solution ( Blue  brick red precipitate)
2) Acidified potassium dichromate (orange green)
3) Tollen’s Reagent (colourless  a silver mirror)
Must be warmed in a water bath
Aldehydes Oxidise (Ketones don’t)
Intermolecular Forces
Properties
High boiling points
• STRONG INTERMOLECULAR FORCES
High Volatility (how easily it evaporates)
• WEAK INTERMOELCULAR FORCES
• SMALL MOLECULAR SIZE
SOLUBILITY
• LIKE DISSOLVES LIKE
32. C7H6O2 → C7H8O
Which line in the table is correct
for the above conversion?
Reaction type
A reduction
B reduction
C oxidation
D oxidation
H:O ratio
increases
decreases
increases
decreases
27. The compound
structure
CH2CHCH2CHO
is
A
B
C
D
with
a saturated ketone
a saturated aldehyde
an unsaturated ketone
an unsaturated aldehyde.
the
6. The molecules shown below are isomers
A
B
a) Name each of the isomers.
A - butanal
B – butanone
b) Which isomer can be oxidised using Tollens’ reagent and what
would be observed?
Isomer A (butanal) is oxidised using Tollens’ reagent
A silver mirror forms (since the silver ions are reduced
to silver atoms)
8. Which type of bond is broken when a protein is
denatured?
A
B
C
D
Ionic
Polar covalent
Hydrogen
Non-polar covalent
C
Oxidation of Food
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Naming branched chain alcohols
Primary, secondary and tertiary alcohols
Isomeric alcohols
Hydrogen bonding of alcohols
Diols and Triols
Oxidation of alcohols
Naming branched chain carboxylic acids
Reactions of carboxylic acids.
Antioxidants in foods.
From an ion-electron equation recognise that a
substance is acting as an antioxidant.
Naming branched chain alcohols
• Functional Group (hydroxyl) always gets first
priority when numbering longest carbon chain
What SQA expect you to be able to do:
• Can be named from structural formulae
• Structural formulae can be drawn from names
• Molecular formulae can be written from
names
Primary, secondary and tertiary alcohols
Primary – Carbon to which hydroxyl group
attached is bonded to 2 or more hydrogens or is
bonded to 1 carbon
Primary, secondary and tertiary alcohols
Secondary – Carbon to which hydroxyl group
attached is bonded to 1 hydrogen or is bonded
to 2 carbons
Primary, secondary and tertiary alcohols
Tertiary – Carbon to which hydroxyl group
attached is bonded to 0 hydrogen or is bonded
to 3 carbons
10.a) Name the following alcohols and decide whether they are
primary, secondary or tertiary alcohols.
10.a) Name the following alcohols and decide whether they are
primary, secondary or tertiary alcohols.
Pentan-2-ol 2ry
Pentan-3-ol
Note: These alcohols are all
ISOMERS
2-methylbutan-2-ol 3ry
2ry
2,2-dimethylpropan-1-ol
1ry
Isomers
Draw the structural formula for,
and name isomeric alcohols,
including primary secondary and tertiary alcohols
Question
Name each of these alcohols.
State for each whether it is Primary, secondary
or tertiary
Which type of chemical reaction could be used
to distinguish which was which?
Diols and Triols
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The more hydroxyl groups
• The Stronger the H-Bonding
• The Higher the Boiling Point
• The Lower the volatility (doesn’t evaporate easily)
• The Higher the Viscosity(the thicker the liquid appears)
• More Viscous – less likely to dissolve in H2O (immiscible)
11. The alcohols shown below have similar molecular mass,
considering their structure comment on the viscosity and
boiling point of the molecules
pentan-1-ol
butane-2,3-diol
propane-1,2,3-triol
Increasing the level of hydrogen bonding will make the
molecule have a higher boiling point and more viscous.
Propane-1,2,3-triol will have the highest boiling point
and greatest viscosity, then butane-2,3-diol and lastly
pentan-1-ol.
Oxidation of alcohols
Aldehydes Oxidise (Ketones don’t)
27. Which of the following would not
react with acidified potassium
dichromate solution?
A
B
C
D
Methanol
Methanal
Butanone
Butan-2-ol
Naming branched chain carboxylic acids
Reactions of carboxylic acids.
• reduction in terms of products and effect on
the oxygen to hydrogen ratio
• reactions with bases to form salts
• reaction with alcohols to form esters
Reduction of Carboxylic Acids
Reactions with bases to form salts
Bases include
Metal Oxides
Metal Hydroxides
Metal Carbonates
12. (i) Name the functional group circled below.
carboxyl
(ii) Draw a structural formula for the organic compound
formed when the above compound reacts with NaOH(aq).
(zero)
Antioxidants in foods
Oxygen reacts with edible oils giving the food a
rancid flavour.
Antioxidants are molecules which will prevent
these oxidation reactions taking place.
Making Food Last Longer
Potatoes are typically fried under an
atmosphere of steam and packaged under
nitrogen.
15. Vitamin C, C6H8O6 is an antioxidant.
(i)What is the purpose of adding antioxidants to food?
To increase shelf life (stop it going off)
(ii) Complete the ion-electron equation for the oxidation of
vitamin C.
C6H8O6(aq)
C6H6O6(aq)
+2H+ + 2e-