Unit 2 - Nature's Chemistry Flashcards
What is the functional group for an ester
Ester link
What does an ester’s name end in
-yl -oate
How are esters made
Condensation or esterification reaction
What is the word equation for esterification
Alcohol + carboxylic acid ester + water
Why is a wet paper towel used in a condensation reaction
To catch any gases that escape from the reaction
What is the catalyst used in a condensation reaction
Concentrated sulphuric acid
What is used to heat the reactants during a condensation reaction
Hot water bath - since alcohol flammable
How can you tell if an ester has been produced
Oily layer and a sweet smell
Why is sodium hydroxide used in a condensation reaction
To neutralise the acid catalyst
What are some uses for esters
- fragrances
- flavourings
- nail polish
- solvents for car paint
What is hydrolysis
The breaking up of a substance using water
What are fats and oils example of
Esters
Why do we need fats and oils
Give our body energy
Is a fat saturated or unsaturated
Saturated (c-c singles bonds)
Why do fats have higher melting points than oils
Molecules pack closer together, stronger Van Der Waal forces between them, higher melting points
Will a fat decolourise bromine solution
No it is a saturated molecule
Is an oil saturated or unsaturated?
Unsaturated (c=c double bonds)
Will an oil decolourise bromine solution
Yes - unsaturated molecule
What happens when oils react with oxygen
Turns rancid
What is the chemical reaction used to produce fats and oils
Condensation/ esterification
What molecules are needed to make a fat/oil
Glycerol + 3 fatty acids
What is hydrogenation
The addition of hydrogen to an unsaturated molecule
How is an alkane produced
When an alkene is reacted with hydrogen in a hydrogenation reaction
What happens when an oil reacts with hydrogen
Turns into margarine (hardening)
What term is used to describe an amino acid that must be obtained from our diet
Essential amino acid
What type of link is found in proteins
Amide/peptide link
What type of reaction is used to form proteins
Condensation
What are proteins made from
Amino acids
What produces amino acids during digestion
Enzyme hydrolysis of dietary proteins
What type of reaction is used to break down proteins to form amino acids
Hydrolysis
Between what elements in the protein do the bonds break between during hydrolysis
Carbon with double bonded oxygen and nitrogen
What are the two types of protein structure
Fibrous and globular
What is the structure of a fibrous protein
Polypeptide chains interwoven, held together by hydrogen bonds
What kind of properties do fibrous proteins have
Toughness, insolubility, resistance to changes in pH
What is the structure of globular proteins
Polypeptide chains are coiled together in spherical shapes
What happens to the structure of a protein when heated
Structure changes (eg heating an egg)
What happens to polarity and flammability as the carbon chain increases
Both decrease
Why does polarity and flammability decrease as the carbon chain increases?
There is less hydrogen bonding between molecules
If an alcohol ends in -triol how many hydroxyl groups are present
Three hydroxyl groups
What happens to the properties of a molecule as there is an increase in hydrogen bonding
- higher boiling points
- increased viscosity
- increased solubility in water
What makes an alcohol primary
The carbon that is attached to the hydroxyl group is surrounded by 1 other carbon
What makes an alcohol secondary
The carbon attached to the hydroxyl group is surrounded by 2 carbons
What makes an alcohol tertiary
The carbon attached to the hydroxyl group is surrounded by 3 carbons
What type(s) of alcohols oxidise
Primary and secondary
How do you know when an alcohol has been oxidised
The oxygen to hydrogen ratio increases
What is the colour change when an alcohol is oxidised using acidified potassium dichromate
Orange to green
What is the colour change when an alcohol is oxidised using copper dioxide
Black solid to brown solid
Where is the functional group of an aldehyde
End of molecule
When naming an aldehyde what does it end in
-al
When naming a ketone what does it end in
-one
Where is the functional group in a kentone
Middle of a molecule
Which oxidises, an aldehyde or a ketone
Aldehyde
What does a primary alcohol oxidise into
Aldehyde
What does a secondary alcohol oxidise into
Ketone
What does an aldehyde oxidise into
Carboxylic acid
Name 3 oxidising agents
- acidified potassium dichromate
- fehlings solution
- tollen’s reagent
What is the colour change for fehling’s solution
Blue to orange/red
What oxidising agent forms a silver mirror when oxidised
Tollen’s reagent
What happens to the oxygen to hydrogen ratio in a reduction reaction
O:H ratio decreases
In a neutralisation reaction what is produced as a by-product
Water
What can be used for a neutralisation reaction
Titration
What are antioxidants
Molecules which can prevent oxidation reactions taking place
Why are antioxidants good reducing agents
Oxidises itself so that it can prevent other compounds from oxidation
Give an example of a common antioxidant
Vitamin C
When answering a question on “chemistry of cooking” what are some factors to consider
- volatility
- boiling point
- solubility
- heating proteins
- oxidation
What is volatility
How easily food vaporises
Do flavour molecules have strong or weak intermolecular forces
Weak
When a molecule water soluble
If the functional group can hydrogen bond with water
When is a molecule oil soluble
If the functional group cannot hydrogen bond with water
What is a molecule with a long hydrocarbon chain most likely to be soluble in
Oil
What happens when a protein is heated
Intermolecular forces broken, changes shape (denatures), alters texture
What are salts of fatty acids
Soaps
How are soaps formed
Alkaline hydrolysis of fats/oils
What reactions/molecules are involved in alkaline hydrolysis
Fat/oil -hydrolysis-> glycerol + fatty acids
Fatty acids + sodium hydroxide - neutralisation-> soap + water
What part of the soap structure is non-polar
Covalent hydrocarbon chain (tail)
What part of the soap molecule is hydrophilic
Carboxylate head
Is the carboxylate head polar or non-polar
Polar
What part of the soap molecule is hydrophobic
Covalent hydrocarbon chain (tail)
What results in an emulsion being formed
The repulsion of negative charges
After agitation of the soap and grease molecules what are formed
Micelles
During the cleansing action of soap what part of the soap molecule attaches to the grease
The hydrocarbon tail
Define an emulsion
Small droplets of one liquid dispersed in another liquid
Name some examples of emulsions
- mayonnaise
- milk
- butter
- margarine
What can be added to prevent oil and water components separating
Emulsifier
How is an emulsifier formed
By reacting glycerol and 2 fatty acids together in a condensation reaction
What are essential oils
Concentrated extracts of the volatile non-water soluble aroma compounds from plants
What are some common uses of essential oils
- perfumes
- cosmetic products
- cleaning products
- flavourings in food
What are key compounds in essential oils
Terpenes
How are essential oils extracted
Steam distillation
What are terpenes
Unsaturated compounds formed by joining isoprene units together
What is the systematic name for an isoprene unit
2-methylbuta-1,3-diene
How many carbons are present in an isoprene unit
5 carbons
Draw an isoprene unit
(See notes)
What does a terpene form when it is oxidised
Terpenoids
What do terpenoids contain
Hydroxyl or carbonyl functional group
When UV light breaks bonds what are formed
Free radicals
What are free radicals
Highly reactive unpaired electrons
What are the 3 steps in a free radical chain reaction
- initiation
- propagation
- termination
How does the chain reaction stop during termination
Stable molecules formed
What are free radical scavengers
Molecules which can react with free radicals and form stable product to prevent chain reactions
What are free radical scavengers often found in
Cosmetic products (eg sun cream)
