U4 Organic materials, structure & properties

Question 1

B.p M.p trends with number of carbon atoms in Alkanes&Alkenes

Answer 1

More carbon atoms, larger size of moelcule, stronger IMF bonds, higher temp needed to overcome bonds.

Straight chain higher b.p than branched.

Question 2

What is volatility? Discuss volatility in terms of the functional groups

Answer 2

Volatility refers to the ease of a substance becoming a gas. Low volatility = High energy needed to become gas. Breaking of Intermolecular forces of the molecules results in gaseous form. Stronger IMF, More energy needed to break, lower the volatility.

Question 3

Solubility trends of organic in water.

Answer 3

More carbons, the more hydrophobic non-polar parts, the more insoluble it becomes. Alcohol/Carboxylic etc have polar bonds, so more easily soluble.

Question 4

What is a polymer?

Answer 4

Many monomers bonded together through polymerisation. -> Condensation / Addition

Question 5

Brief describe Primary vs Secondary vs Tertiary vs Quarternary

Answer 5

Primary: Different order sequence of monomers. e.g ABUHD vs ODJBL
Secondary: The shape of these polymer. a-helix / b-pleated sheets. Due to IMF interactions.
Tertiary: Refers to the overall 3-D shape of polymer. Depends on types of bonding etc
Quarternary: Shape of two ore more polymers bonded together.

Question 6

Biodegradability in polymers

Answer 6

The breakdown of organic matter. Natural polymers easier to degrade. Enzymes break down substances like protein etc.

Question 7

Density in polymers

Answer 7

The mass per unit of volume. Increase in branching / side chain = Decrease in ability to compact = Decrease in density

Question 8

What are enzymes, and describe the characteristics of biological catalysts.

Answer 8

Enzymes are biological catalysts, usually large proteins, used to increase reaction rates. They have high catalytic power and display high specificity for the substrates (don’t interact with other substances)
Usually end with -ase

Question 9

What are amino acids

Answer 9

Organic substances that contain both an amine and carboxylic acid function groups.

Question 10

What are proteins? Explain polypeptides and peptides.

Answer 10

Proteins are one or more polypeptides. Polypeptides are a specific type of polyamide where there is chain of many bonded peptides. Peptides are polymers of amino acid monomers bonded together through condensation polymerisation.

Question 11

What are the amide bonds (peptide bonds) in a polypeptide.

Answer 11

The bond between the carbon of the carboxylic tail of one peptide to the nitrogen amine tail of another peptide.

Question 12

Explain the secondary structure of proteins. (a-helix b-sheets)

Answer 12

A-helix, forms a spiral like structure due to the hydrogen bonding between the oxygen in the carbonyl group (C=O) to the hydrogen (H-N) in the amine group of another peptide.
B-sheets forms folded paper like structure also due to the hydrogen bonding.

Question 13

What are carbohydrates?

Answer 13

Natural polymers that are made of mono/di/polysaccharides.

Question 14

What are monosaccharides?

Answer 14

Sugars that cannot be further decomposed. Have the empirical formula CH2O. Contain either aldose (aldehyde group) or ketose (ketone group) and several -OH.

Question 15

What are the differences between a-glucose and b-glucose?

Answer 15

In a-glucose, the right-most OH group facing down. (In data booklet) In b-glucose this OH group facing up.

Question 16

Explain the structural properties of starch.

Answer 16

Made of amylose and amylopectin, which are both entirely made of a-glucose monomers. Amylose is straight chain 1-4 glycosidic linkage, whereas amylopectin is branched 1-4/1-6.

Question 17

Explain structural properties of cellulose.

Answer 17

Polymer of b-glucose. Forms a strong crystalline cross-linked structure.

Question 18

What are lipids and their types.

Answer 18

Lipids are polymers and large ester molecules like triglycerides. If liquid at room temp, then it is an oil. If solid at room temp, then it is a fat.

Question 19

What is glycerol?

Answer 19

Propan-1,2,3-triol. 3 Carbons, 3 -OH ends.

Question 20

What is a fatty acid? Distinguish between poly/mono/un/saturated.

Answer 20

A very long carbon chain with a carboxylic end. Can have 1 C=C double bond (monounsaturated), many double bonds (polyunsaturated) or no double (saturated).

Question 21

How are triglycerides formed? Include reversal reaction

Answer 21

Glycerol + 3 fatty acids -> triglyceride + h2o.
In condensation reaction.
Hydrolysis reaction can be used to split.

Question 22

How are soaps produced? Explain their structure + why they are useful

Answer 22

Triglceride reacts with NaOH/KOH -> Glycerol + Sodium salts of fatty acids.
Has a carboxylate ion head O- Na+, which is polar and bonds with the polar water, whereas the long carbon chain is hydrophobic but bonds with the dirt and grease.

Question 23

Can soaps be used in hard water?

Answer 23

Hard water is water with calcium or magnesium ions however the carboxylic tail of the soap molecules forms an insoluble precipitate when reacting with the ions. Detergents do not contain a carboxylate tail but does have a hydrophilic tail.

Question 24

What is polyethene and how is it created?

Answer 24

Polyethene is when multiple ethene molecules link together through addition polymerisation to form long chains. They can either be LDPE or HDPE.

Question 25

What is LDPE, it’s structure and it’s properties?

Answer 25

It is low-density polyethene and has significant branching due to alkyl groups replacing some hydrogens. High branching = More space = Lower IMF = Low B.p m.p, Low density, Higher flexibility.

Question 26

What is HDPE, structure and properties?

Answer 26

High-density polyethene. Unbranched chains which allows the molecules to be closely fit = high density = stronger dispersion forces = higher b.p m.p = less flexibility.

Question 27

What is polypropene/polypropylene?

Answer 27

When multiple propene compound undergo addition polymerisation, resulting ina. side methyl chain CH3.

Question 28

What is isotactic, syntactic and atactic? And their properties

Answer 28

Atactic is when the side methyl chain is randomly placed, syntactic is when the chain is above and below the chain repeatedly. Isotactic is when the side chain is all either above or below the main chain.

Isotactic has strong dispersion forces (chains lie close together and high m.p and is strong material.
Syntactic, stronger than tactic but weaker than isotactic.
Atactic chains do not lie together, weak dispersion, lower m.p, soft, rubbery flexible

Question 29

what is PTFE

Answer 29

Long carbon chain with only flurine instead of carbons. very strong and used for non-stick. polar between carbon and fluorine