Unit 2 - Nature's Chemistry Flashcards
What is an alcohol?
A molecule containing a hydroxyl functional group, -OH group.
What can alcohols be classified as?
Primary, secondary or tertiary.
What is a primary alcohol?
Alcohols where the carbon atom of the hydroxyl group is attached to only one single alkyl group.
What is a secondary alcohol?
Those where the carbon atom of the hydroxyl group is attached to two alkyl groups on either side. The two alkyl groups present may be
either structurally identical or even different.
What is a tertiary alcohol?
Those which feature a hydroxyl group attached to the carbon atom which is connected to 3-alkyl groups.
What is a diol?
Alcohols containing two hydroxyl groups
What is a triol?
Alcohols containing three hydroxyl groups.
Polarity and bonding of hydroxyl groups.
Hydroxyl groups make alcohols polar and this gives rise to hydrogen bonding.
What is a carboxylic acid?
A molecule containing the carboxyl functional group -COOH.
What do carboxylic acids react with?
Bases
What happens in redox reactions with carboxylic acids?
The H+ ions are displaced from solution by metals higher up in the electrochemical series.
What is an ester?
A molecule containing an ester link -COO-
How are esters named?
The alcohol molecule gives the ester the first part of its name.
The carboxylic acid molecule gives the ester its second name.
Examples of ester names:
Ethanol and Propanoic Acid = ethyl propanoate.
Butanoic Acid and Ethanol = ethyl butanoate.
Methanol and Methanoic Acid = methyl methanoate.
What are esters used as in industry?
flavourings, fragrances, solvents for non-polar solutes, nail varnish, evaporate easily (volatile).
How are esters formed?
When a carboxylic (alkanoic) acid molecule reacts with an alcohol (alkanol) molecule in a condensation or esterification reaction.
What is the catalyst for an ester?
Concentrated sulfuric acid
What is a condensation reaction?
A reaction where a molecule of water is eliminated as two molecules join. (esterification)
What is Hydrolysis?
The splitting of a molecule by reaction with water.
Is esterification a reversible or non-reversible reaction?
Reversible.
What does hydrolysis of an ester produce?
The parent alcohol and carboxylic acid.
What does heating under reflux involve?
Heating the mixture in a flask with a condenser attached.
What happens in Acid Hydrolysis?
When esters are heated under reflux with an acid catalyst the hydrolysis reaction is reversible.
What happens in Alkaline Hydrolysis?
When esters are heated under reflux with an alkali the hydrolysis reaction goes to completion.
What two stages are in an alkaline hydrolysis reaction?
Stage 1 - reversible (alcohol and acid are produced)
Stage 2 - non-reversible: The alkali reacts with the carboxylic acid formed in a neutralised reaction.
What can be observed at the production of an ester?
Distinct layers and a distinct fruity smell.
What is the structure of a fat or oil?
Glycerol - trihydric alcohol.
It has 3 hydroxyl groups per molecule.
What is the systematic name for Glycerol?
propane-1,2,3-triol.
What is the ratio of Triglyceride to Fatty Acids?
1:3
How is a triglyceride molecule produced?
Glycerol can undergo condensation reactions with 3 fatty acid molecules.
Describe a Fat
Fatty acid chains which make up the fats are mostly SATURATED. This gives rise to molecules with carbon chains which can PACK CLOSELY with other fat molecule, allowing MANY LONDON DISPERSION FORCES to be set up, resulting in a SOLID at room temperature, and HIGHER MELTING POINTS.
Describe an Oil
The fatty acids that make up oil molecules have one or more carbon to carbon double bond in their chain i.e. the fatty acids are UNSATURATED. The carbon to carbon double bonds in the oil molecules DISTORTS the long fatty acid chains and the molecules CANNOT PACK CLOSELY with other molecules, giving rise to WEAKER/FEWER LONDON DISPERSION FORCES. Thus LESS ENERGY is required to separate the molecules, resulting in LOWER MELTING POINTS and LIQUIDS at room temperature.
How to test fats and oils for unsaturation?
Shaking a fat or oil with bromine water.
Bromine solution decolourises slowly with lard (fat) but rapidly with sunflower oil (oil) showing that the degree of unsaturation of the oil is greater.
What is hydrogenation?
The addition of hydrogen across a carbon to carbon double bond. This is called Hardening.
What catalyst is used in hydrogenation?
Nickel catalyst
What are fats and oils used for in our diets?
Source of energy
Animal fats contain important fat soluble vitamins such as vitamin D and E.
What makes fats and oils good solvents for non-polar solvents?
The non-polar nature of fats and oils means they are good solvents for non-polar vitamins such as vitamin A, D, E and K.
What produces soap?
Saponification (alkaline hydrolysis of fats and oils).
What is the most common type of soap?
Sodium stearate.
Describe the soap molecule.
Non-polar, uncharged covalent, hydrophobic tail.
Polar, negatively charged ionic, hydrophilic head.
Explain the cleansing action of soap
- The covalent, non-polar, hydrophobic tails will dissolve in grease, oil and other non-polar solvents, which the ionic, hydrophillic heads will dissolve in water and aqueous solutions.
- The negative ionic heads covering the surface of a grease layer.
- With agitation, the grease is broken up into small ball-like structures called micelles.
- These micelles repel each other and the grease is dispersed through the water.
- The grease has been emulsified by the soap and rinsing with clean warer washes these grease and oil droplets away.
Are detergents natural or synthetic?
Synthetic
What is hard water?
Water containing dissolved calcium and magnesium ions.
In hard water areas, what is better to use?
Soapless detergents.
Describe the detergent structure?
Detergents have a soap-like structure in that they have a hydrocarbon tail and a (sulfonate ion) ionic head, but these molecules will not form a precipitate with the Ca2+ and Mg2+ ions present in hard water, and do not form a scum as they remain in solution.
Are soaps or detergents more water soluble?
Detergents are much more water soluble than soaps.
(The sulfonate ion attracts the water molecules more strongly than the carboxylate ion of a soap)
What is an emulsion?
An emulsion contains small droplets of one immiscible liquid dispersed in another.
What does an emulsifier do?
An emulsifier makes an emulsion more stable by holding the oil droplets in water for longer.
Examples of emulsifiers in food?
-Mayonaise is a mixture of oil and vinegar.
-Lecithin, a natural emulsifier in egg yolk, acts as an emulsifier helping the oil and vinegar stay mixed.
How are synthetic emulsifiers for food made?
By reacting edible oils with glycerol.
How are emulsifiers made from edible oils?
How are proteins formed?
By joining together many amino acids which form a peptide which then fold into a protein molecule.
What two functional groups do amino acids have?
Amino group (-NH2) and a Carboxyl group (-COOH).
What structure is an amide link?
H-N~C=O
How do amino acid molecules from proteins?
Proteins are formed in a condensation reaction when amino acid molecules join together and a water molecule is removed.
What is an essential amino acid?
The body cannot make all the amino acids required to build different proteins. It relies on protein intake from our diet.
How are proteins broken down?
Protein molecules can be broken down by hydrolysis by water molecules.
What happens in digestion of proteins?
enzymes in our bodies break the proteins we eat down into amino acids by hydrolysis. These amino acids are transported around the body by blood.
How are proteins built up?
Condensation reactions build the amino acids up to produce proteins required by the body.
What are the two shapes of proteins?
Fibrous and Globular.
What are Fibrous proteins?
- Found in animal hair, nails and muscle.
- Have long spiral chains folded to form long, thin shapes.
- They are strong and are generally insoluble in water.
- E.G. collagen.
What are Globular proteins?
- Involved in the regulation of life processes.
- Have spiral chains folded into spherical shapes and are generally soluble in water.
-E.G. haemoglobin, insulin and enzymes.
What happens when cooking proteins?
When the proteins are heated, the molecules become agitated and move around, causing the intermolecular bonds (hydrogen) between the protein chains or within a folded protein chain to be broken. This causes the protein to denature, which changed the texture of foods.
Enzymes
All enzymes are proteins, they are specific which means one enzyme has one job.
What is the effect of temperature on enzyme activity?
Heating increases the kinetic energy of the atoms in a molecule and causes the hydrogen bonds to break, changing the shape of the active site.
What is the effect of pH on enzyme activity?
pH disrupts the hydrogen bonding in proteins, causing the active site of the enzyme to change shape. Extremes of pH produce lots of OH- or H+ ions which can interfere with the polar bonds that give rise to the H bonding.
What is optimum temperature or pH?
When the rate of reaction or enzyme activity is greatest.
Volatility
Generally, molecules with a GFM lower than 300 are likely to be volatile.
General rule of molecule containing only C and H atoms.
It will be non-polar and therefore oil/fat soluble.
General rule of a molecule containing C, H, O and/or N.
If a molecule also contains O and/or N atoms it is more likely to be polar and therefore water soluble.
What does the non-polarity of long hydrocarbon chains do?
Can cancel the effect of a single polar group and make the molecule behave as non-polar.
What functional group does the aldehyde and ketone have?
Carbonyl group, C=O.
Aldehydes
- Have their carbonyl functional group at the beginning of the carbon chain.
- Names all end in -al
- Have general formula CnH2nO.
Ketones
- Carbonyl group is never at the end of the carbon chain.
