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Higher Chemistry > Unit 2 > Flashcards

Unit 2 Flashcards

1
Q

What is the functional group present in an ester

A

-COO

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2
Q

Characteristic smell of an ester

A

Sweet and Fruity

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3
Q

How are esters formed

A

Condensation reaction between a carboxylic acid and an alcohol is the presence of a catalyst (concentrated sulfuric acid). H2O is removed

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4
Q

How are esters used

A

Flavouring
Fragrances
non-polar industrial solvents

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5
Q

How can an ester be hydrolysed.

A

With an alkali catalyst (Sodium Hydroxide for example)

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6
Q

Why are fats and oils necessary in our diet

A

They supply the body with energy and are a more concentrated source of this than carbohydrates. They are essential for the transport and storage of fat soluble vitamins in the body

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7
Q

Structure of fats and oils

A

They are esters made when an alcohol (glycerol) (propane-1,2,3-triol) condenses with three carboxylic acid molecules known as fatty acids.

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8
Q

Difference in mp of fats and oils.

A

Oil - Lower as highly unsaturated. The presence of double bonds causes the molecule to become distorted. Preventing the pile molecules from packing closely. This poorer packing makes the VDWs weaker between oil molecules. Less heat is required to separate the oil molecules

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9
Q

Functions of Proteins

A

Major structural materials of animal tissue.
Maintenance and regulation of life processes.
Enzymes are proteins.

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10
Q

Building blocks of proteins

A

Amino Acids

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11
Q

What two functional groups are present in an amino acids

A

Carboxyl (COOH) and Amino group (NH2)

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12
Q

What are essential amino acids

A

Thé body cannot make all the amino acids required for body proteins and is dependent on dietary proteins for the supply of certain essential amino acids.

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13
Q

What reaction occurs when amino acids form peptide links and a protein is formed?

A

Condensation

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14
Q

What is the formula of an amide link

A

O=C-N-H

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15
Q

How is the diverse range of proteins needed to fulfil diff roles in the body produced from just 20 amino acids

A

Proteins specific to the body’s needs are built up by many condensation reactions. The sequence by which the amino acids are joined together differs in different protein molecules. The sequence of amino acids are controlled from the information in the nucleus of the cell.

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16
Q

What reaction takes place when protein is converted into amino acids

A

Hydrolysis

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17
Q

How are the amino acids present in a sample of hydrolysed protein analysed and identified

A

First hydrolyse the protein using acid or alkali and then use chromatography. The application of known amino acids to the chromatogram alongside the hydrolysed protein allows identification of the amino acids present

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18
Q

What does the side chain -H produce on an amino acid

A

Glycine (Aspartic acid)

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19
Q

What does the side chain -CH3 produce on an amino acid

A

Alanine (Methionine)

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20
Q

What does the side chain -CH CH3 CH3 produce on an amino acid

A

Valine (Phenylalanine)

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21
Q

How can proteins be classified

A

Fibrous - Long and thin, the major structural materials of animal tissues.
Globular - have the spiral chains folded into compact units. They have a significant proportion of polar groups on the outside of the globule, this allows H bonding with water and makes the globular protein soluble. They are involved in the maintenance and regulation of life processes and include enzymes.

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22
Q

Proteins are chemicals containing the element…

A

Nitrogen

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23
Q

Why are volatile molecules important to flavour

A

The majority of what we describe as flavour comes from odour identified by nasal cells. That required the flavour molecules to be wafted up from the mouth. The flavours of foods are due to the presence of volatile organic molecules.

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24
Q

Do volatile substances have high or Low BPs?

A

Low

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25
What does volatile mean
Easily evaporated at normal temps
26
The importance of intermolecular bonding within proteins
Amino acids vary little in length. This means that the peptide links are regular distances apart along the chain thus allowing for hydrogen bonding between peptide links. This hydrogen binding allows chains to form sheets, spirals and other complex shapes
27
Oxidation of a primary alcohol produces…
Aldehydes and then carboxylic acids
28
Secondary alcohols are oxidised to produce….
Ketones
29
Can tertiary alcohols be oxidised?
No
30
What happens during an oxidation reaction
Either oxygen is added OR hydrogen is removed Electrons are removed
31
Oxidation results in (ratio)
An increase to the Oxygen:Hydrogen ratio 1:4 —-> 1:2
32
Explain what can be oxidised
Primary alcohols, Secondsry alcohols and Aldehydes can be oxidised. However, Ketones cannot.
33
Explain the colour changes associated with oxidising agents
When you oxidise with CuO, the black copper (2) oxide is reduced to red-brown copper metal. Benedict’s solution - Blue to Orange Tollens reagent - Silver mirror produced Acidified dichromate - Orange to Green
34
What functional group is present in aldehydes and ketones
Carbonyl - C=O
35
Many aroma molecules are aldehydes - how are these flavours développer in whiskey
Oxygen diffused into the cask forming aldehydes.
36
How does food containing edible oils become rancid
Oxygen molecules interact with the structure of the oil and damage its natural structure in a way that changes its odour, it’s taste and/or it’s safety for consumption.
37
How are foods prevented from turning rancid
Antioxidants are often added to fat-containing food in order to retard the development of rancidity due to oxidation.
38
How can the concentration of something inside something else be measured
Titration
39
How are soaps produced
Hydrolysis of fats and oils using an alkali catalyst. The fatty acids formed are changed into sodium of potassium salts (soap)
40
Cleansing action of soaps
A soap molecule contains a long non-polar hydrocarbon tail (hydrophobic) and an ionic carboxylic head which is hydrophilic. During cleaning, the hydrophobic tails dissolve in droplets of oil and grease while the hydrophilic heads face out into the water causing a ball like structure. This balls holds the grease and oil inside while the negatively charge ionix heads of each ball repel each other, preventing the oil from rejoining and helps disperse it.
41
What is an emulsion
An emulsion is a mixture of two or more immiscible liquids. In an emulsion the small droplets of one liquid are emerged in the other.
42
How do emulsifiers work
Emulsifiers are molecules that have two distinct ends. One is hydrophyllic and a the other is hydrophobic. This means they will coat the surface of oil droplets (in an oil in water emulsion) and effectively insulate them from the water. This keeps them evenly dispersed throughout the emulsion and stops them from clumping together to form their own separate layer.
43
Why do we add emulsifiers to food
An emulsifier keeps the mixture stable and prevents the oil and water separating into two layers.
44
How are emulsifiers made
Reacting fatty acids with glycerol to form molecules with either one or two fatty acid groups linked to the glycerol backbone. NOT THREE - THREE PRODUCES A FAT OR OIL
45
What are essential oils
Essential oils are concentrated extracts of volatile, non water soluble aroma compounds found in plants. They do not as a group have share specific chemical properties or functional groups. Instead they are defined by the fact that they convey characteristic fragrances.
46
Uses of essential oils
Perfumes, Cosmetic products, cleaning products, food flavourings
47
How can essential oils be extracted from plant material
steam Distillation or solvent extraction
48
What is the key component in many essential oils
Terpenes
49
How are terpenes formed
Unsaturated compounds formed from units of isoprene (2-methylbuta-1.3-diene). The isoprene units may be linked tigether « head to tail » to form linear chains or they may be arranged to form rings.
50
What is the molecular formula of terpenes
(C5H8)n Where N is the number of isoprene units linked together
51
The importance of terpenes
They are components in a wide variety of fruit and floral flavours and aromas. Terpenes can be oxidised in plants (now terpenoids) producing some of the components responsible for the aroma of spices.
52
Ultraviolets radiation effect on molecules
UV is a high-energy form of light, present in sunlight. Exposure to UV light can result in molecules gaining sufficient energy for bonds to be broken.
53
Effects of UV light on the human body
Sunburn and Aging
54
How does sunscreen work
Blocks UV light from reaching the skin
55
What is a free radical
Atoms or groups of atoms which have a single unpaired electron. They are highly reactive
56
How are free radicals formed
If a bond splits evenly, each atom getting one of two electrons. This is called homolytic fission. It takes place when UV light breaks bonds.
57
Step one in a free radical reaction
Initiation - UV light generates radicals
58
Step two in a free radical reaction
Propagation - Involves the loss of a radical but also the formation of another radical. The reaction now has to keep going/propagate itself.
59
Step three in a free radical reaction
Termination - Involves radicals coming together to form covalent bonds
60
The effect of free radicals on the body
Free radicals (in particular Oxygen ones) are thought to cause cell damage. Untreated, the damage from free radicals accumulates with age and damage is thought to be the cause of many degenerative diseases.
61
How to free radical scavengers work
Free radical scavengers are molecules that will trap free radicals by reacting with other free radicals to form stable molecules and prevent chain reactions.
62
Examples of free radical scavengers
Melatonin, Vitamin E and beta carotene
63
Why is a cool paper towel required during esterification
To cool down vapour so that it runs back down and can’t escape the reaction.
64
How do you calculate percentage yield
Actual mass ———————— x 100 Theoretical mass
65
Identify the oxidising agent, reducing agent, what has been oxidised and what has been reduced in the following reaction: Cu + I2 —-> Cu2+ + 2I-
Cu - got oxidised I2 - oxidising agent Cu2+ - reducing agent 2I- - got reduced
66
What is atom economy
A measure of how efficient or wasteful a chemical reaction is
67
How do you calculate atom economy
Total mass of desired product ——————————————- x100 Total mass of all reactants
68
how to determine the best solvent for essential oil extraction
something hydrophobic/non water soluble
69
What reaction produces alcohol
Fermentation

Higher Chemistry (4 decks)

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