Organic Chemistry

Question 1

How do you make a polysaccharide?

Answer 1

• Through condensation polymerization reactions.
• A polysaccharide can be separated into its monomers using hydrolysis. Condensation and hydrolysis is an equilibrium reaction.

Question 2

What are the chain and cyclic structures for glucose?

Answer 2

See page.

Question 3

What are the chain cyclic structures for fructose?

Answer 3

See page.

Question 4

What bond do sugars connect with in polymerization?

Answer 4

A single ‘o’ bond. They lose a hydroxyl group from one side, and a hydrogen from the other. The other ‘o’ from the hydroxyl group is used to connect the sugars to form a polysaccharide.

Question 5

Molecular formula for glucose and fructose.

Answer 5

C6H12O6

Question 6

Solubility of carbohydrates.

Answer 6

Monosaccharides - soluble in water.
- They are smaller so have less dispersion forces which are weaker and therefore they are easily separate in water.
- They contain many polar hydroxyl groups which can form hydrogen bonds with water.

Disaccharides:
- Same as monosaccharide.

Polysaccharides:
- Typically too large of a molecule. They contain too many dispersion forces which increase their strength and hold the molecule together firmly, reducing water’s ability to break it up.
- Even though it contains many polar hydroxyl groups this is still the case.

Question 7

How do you make a triglyceride. Use the reaction equation.

Answer 7

Glycerol + fatty acid (carboxylic acid) —> ester.

Glycerol:
Three carbon going down, with three alcohol groups (propan-1,2,3,-triol).

Carboxylic acid:
3 COOH group’s and a variable R group.

Triglyceride:
Three C-O=O-R

Question 8

Triglyceride solubility in water.

Answer 8

• Insoluble in water because they have stronger dispersion forces along the long non-polar hydrocarbon chain.

Question 9

Would you expect a saturated or unsaturated molecule to be a fat? Explain why.

Answer 9

• Saturated.
• Saturated molecules are saturated with hydrogen ions and therefore do not have any double or triple bonds along the carbon chain.
• This reduces the amounts of kinks in the chain and makes it packed more closely together.
• This increases the amount of dispersion forces, meaning there is a higher melting point because more energy is required to break these bonds.
• This results in a solid fat at room temperature.

Question 10

Describe the process of hydrogenation and its reaction conditions.

Answer 10

• The breaking of an alkene into a single carbon chain through addition polymerization.
• Hydrogen gas is used to saturate the molecule.
• Reaction conditions: high pressure, presence of a nickel catalyst and high temperatures.

Question 11

When does saponification occur in ester hydrolysis?

Answer 11

• Soap forms in basic conditions because the ester separates into the alcohol (glycerol) and a carboxylate ion.
• This carboxylate ions consists of a long non-polar hydrocarbon chain and a hydrophilic head which is soap.

Question 12

How do micelles work to remove oil from a pan?

Answer 12

• A long non-polar hydrocarbon chain absorbs to the non-polar oil from the pan because like dissolves like, whilst the polar hydrophilic head remains in the water.
• Upon agitation, a micelle forms to encapsulate the oil droplet within the non-polar hydrophobic interior.
• The polar, hydrophilic heads are charged and can form ion-dipole bonds with water but they also repel each other, causing separation of the oil molecules and suspension in water within water-soluble micelles until they are washed away.

Question 13

Why can amino acids form zwitterions and under what conditions does this occur in?

Answer 13

• Amino acids have an acidic and basic group, to which the acidic group can donate a proton to the basic group under neutral conditions (pH 7).
• The acidic group is the carboxylic acid and the basic group is the amine group.

Question 14

Zwitterions at different conditions (pH 1, pH 7, and pH12)

Answer 14

• At pH 1, the conditions are acidic so the amine group is maximized. The amine group forms NH3+, and the carboxylic acid remains acidic (forms a cation).
• At pH 7, it forms its zwitterion, so the amine group is positive and the carboxylic acid group is negatively charged.
• At pH 12, it forms an anion, so the OH group is maximized. The carboxylic acid turns into a carboxylate ion whilst the amine group remains the same.

Question 15

Describe the intermolecular bonding in secondary protein structures.

Answer 15

• Hydrogen bonding between the hydrogen atoms from the amine group and the oxygen atoms from the carbonyl group.
• They form alpha or beta sheets.
• Alpha form when there are hydrogen bonds between the hydrogen and oxygen, forming a spiral shape.
• Beta sheets are when two adjacent rejoins of the peptide chain are connected through hydrogen bonds.

Question 16

What are tertiary structures dependent on in proteins?

Answer 16

• The bonding between amino acid side chains within the same polypeptide chain.
• These bonds are typically:
• Covalent (disulfide bridges)
• Ionic
• Hydrogen bonds
• Dipole-dipole bonds
• Dispersion forces

Question 17

What happens to an amino acid at different pH’s?

Answer 17

• At pH 7 ionic bonds form between NH3+ and COO-, to form the amide/peptide bond, connecting the polypeptide chain.
• In acidic conditions, the ionic bond is broken because NH3+ and COOH, therefore the amide bond cannot be formed, resulting in a cation. This will form different secondary interactions and intermolecular bonds, thus denaturing the protein because the shape is not the same. Shape determines function, so if the shape is not correct, the protein will not function in the correct manner.
• In basic conditions, the ionic bond is broken because NH2 and COO-. This forms an anion. As discussed above, it changes the intermolecular bonds, which disrupt the secondary, tertiary and quaternary structures, resulting in a differently shaped protein. Structure is function therefore if the shape is not good, the protein will not function effectively/correctly.

Question 18

How does temperature denature an enzyme?

Answer 18

• An increase in temperature increases the kinetic energy and therefore increases particle movement. This disrupts the intermolecular bonding, shifting it to be in different places. This ultimately changes the secondary, tertiary and quaternary structure of the enzyme. Shape is function, so if the enzyme is not shaped correctly, it will not be able to catalyze reactions efficiently.

Question 19

How are polymers formed?

Answer 19

• Polymerization;
• Two types include condensation polymerization and addition polymerization.

Question 20

What are the functional groups required for the monomers of a condensation polymerization reaction?

Answer 20

Can either be formed through an ester bond or an amide bond.

Therefore function groups required are:
COOH and OH
NH2 and COOH

Question 21

What are the functional groups required for monomers of an additional polymerization reaction?

Answer 21

• Linked through alkanes (a single carbon backbone).
• Therefore, the functional group are alkenes (C=C).

Question 22

What are the similarities and differences between polyesters and polyamides?

Answer 22

Similarity:
- Both formed through condensation polymerization reactions.

Differences:
- Polyesters are formed through ester bonds
- Polyamides are formed through amide bonds.

Question 23

Differences between natural vs synthetic polymers?

Answer 23

Natural:
- Made by plants and animals such as hair, silk, DNA, or starch.

Synthetic:
- Are man-made and are therefore customizable to have specific properties (plastics, fibers, paints, lubricants).

Question 24

What are the customizable features of a synthetic polymer that can alter is use?

Answer 24

• Chain length
• Cross-linkages
• Branching side-chains
• Polarity of side chains
• Additives such as dyes and UV adsorbers.

Question 25

Advantages and disadvantages of synthetic polymers.

Answer 25

Advantages:
- Polymers replacing glass are cheaper and less dense (lighter).
- Polymers replacing car parts are cheaper, less dense and do not corrode as much.
- Polymers replacing wool and textiles are cheaper and more durable.

Disadvantages:
- Polymers are susceptible to UV damage.
- Polymers are heat sensitive (especially thermoplastics).
- Polymers are non-biodegradable.

Question 26

What are biodegradable polymers and how are they biodegradable?

Answer 26

• Due to the presence of strong covalent bonds between carbons, addition polymers are typically non-biodegradable.
• Biodegradable polymers can be broken down in the environment by bacteria through hydrolysis, therefore typically condensation polymers (synthetically made) and natural polymers are biodegradable.

Question 27

How do you make photodegradable polymers?

Answer 27

• When synthesizing, include many carbonyl groups because they can be broken down by UV, therefore ensuring that they will degrade overtime by sunlight.

Question 28

What are the advantages and disadvantages of biodegradable polymers?

Answer 28

Advantages:
- Reduces the amount of waste in landfill.
- When decomposed, it can be used a a fertilizer for plant crops.

Disadvantages:
- Currently, there are a limited amount of synthetic polymers that are degradable.
- Oxygen and water are required for decomposition and this will not be accessible if they are deep in landfill.
- Greenhouse gasses are released during decomposition.

Question 29

Advantages and disadvantages of biomass derived polymers.

Answer 29

Advantages:
- They are derived from a renewable feedstock.
- Plants and crops are a relatively abundant feedstock.
- Plants and crops are easily extracted and processed.
- By-products or waster products from farming crops can be a source of biomass.

Disadvantages:
- This is a new area of research, so currently not that many are being produced.
- The production of synthetically produced biodegradable polymers may compete with land for food production.

Question 30

What are the advantages and disadvantages of petrol derived polymers?

Answer 30

Advantages:
- Fossil fuels are an abundant feedstock.
- Petroleum is easily extracted and processed.
- There are existing processes for producing polymers based from petroleum.
- There are a wide variety of polymers produced from petroleum.

Disadvantages:
- Petroleum is a non-renewable feedstock.
- The reserves of petroleum are being used at a much faster rate than they can be replenished - non-renewable.

Question 31

Why is esterification done under reflux conditions.

Answer 31

• Esterification is a very slow reaction at room temperature therefore heat is required to increase the rate of reaction.
• Due to temperature increase, volatile substances evaporate off therefore a condenser is required to condense the vapor back to liquid and go back into the reaction mixture.