Unit 2 Organic chemistry

Question 1

What are the aspects of life that esters can be used in?

Answer 1

Esters can be found in nature in
- Fruits
- Vegetables
- Flowers
Esters also can be man-made and used for
- artificial flavoring
- solvents for paints
- varnishes
- ingredients in perfumes

Question 2

What chemical reaction is used to produce esters?

Answer 2

condensation reactions are used to produce an ester (condensation of a carboxylic acid, reacting with an alcohol)

Question 3

What is meant by a condensation reaction?

Answer 3

A condensation reaction is a reaction in which two molecules or functional groups combine to form a larger molecule and loose a water molecule

Question 4

What can we call the type of condensation reaction involving the production of an ester?

Answer 4

Esterification

Question 5

Why can we not simply place a carboxylic acid and an alcohol in a mixture and produce an ester?

Answer 5

As esterification requires a concentrated sulfuric acid catalyst. This catalyst both increases the rate of the reaction and absorbs water molecules to favour the forwards reaction in this reversible system

Question 6

What type of reaction is caused by an ester reacting with water?

Answer 6

Hydrolysis

Question 7

What is meant by a Hydrolysis reaction?

Answer 7

A chemical reaction in which a water molecule breaks down a large molecule into smaller molecules

Question 8

What are some of the problems of producing esters using the standard setup apparatus?

Answer 8

The reactants of the condensation reaction include alcohol which is extremely flammable this means that we cannot use a bunsen burner to supply energy for the reaction as this involves the use of a naked flame. Instead we must use a water bath to provide the energy required for the reaction to take place.
The alcohol involved in the reaction will evaporate because of the temperatures required to supply energy for the reaction. This means that we have to place a wet paper towel at the top of the test tube causing any evaporated alcohol to condense and this prevents the contents of the test tube from being lost.

Question 9

What can we do to separate a mixture that contains at least two different liquids?

Answer 9

We can separate the different liquids using distillation, The mixture should be heated and the liquids will evaporate when their boiling point is met. The evaporated liquids can then be seperated in order of their boiling points and water can be removed

Question 10

What makes up an ester?

Answer 10

An ester has two parts a carboxylic acid part and an alcohol part

Question 11

What does the first part of an ester’s name come from?

Answer 11

The first part of an ester’s name comes from the name of the alcohol used in its production this ends in the prefix “yl”

Question 12

What does the second part of an ester’s name come from?

Answer 12

The second part of an ester’s name comes from the name of the carboxylic acid that is used to produce it and ends in the prefix “oate”

Question 13

What is the functional group present in all esters?

Answer 13

The carboxylate group is present in all ester molecules. Hence the functional group is called the ester link (-COO-)

Question 14

What happens during an esterification reaction?

Answer 14

The (OH) from the carboxylic acid reacts with the hydrogen from the alcohol part and causes the formation of the carboxylate group between the alcohol and the carboxylic acid thus forming the larger ester molecule

Question 15

What is the main trick that we use when determining the name of a carboxylic acid from it’s short structural formula?

Answer 15

The carbon that has no hydrogens attached to it will always represent the end of the Carboxylic acid part of the ester as this is the same carbon that would contain the carboxyl group of the carboxylic acid should the ester react with water in a hydrolysis reaction

Question 16

What type of molecule are fats and oils?

Answer 16

fats and oils are both esters

Question 17

What are some of the key differences between fats and oils?

Answer 17

Fats tend to be solids and they are saturated meaning that they do not contain double (C=C) bonds through their structure. Whereas oils tend to be liquids and are unsaturated as they contain at least one (C=C) double bond

Question 18

What primary use do we have for fats and oils

Answer 18

Fats and oils act as a concentrated source of energy

Question 19

What are the sources from which we can derive fats and oils

Answer 19

The three main sources include
- Animal
- vegetable
- Marine

Question 20

What alcohol is used to produce fats and oils?

Answer 20

The alcohol used in the production of fats or oils is propan - 1,2,3- triol, otherwise called glycerol

Question 21

Comment on the features of a molecule of glycerol?

Answer 21

Glycerol is described as a trihydric alcohol as it has three hydroxyl functional groups

Question 22

What do we call the acid part of a fat or an oil molecule?

Answer 22

The carboxylic acids that join to the glycerol are given the name of fatty acids. They are usually 4-24 carbons long

Question 23

What is an alternative name for fats or oils?

Answer 23

Fats or oils may also be referred to as triglycerides as they consist of three fatty acids and a glycerol molecule and have three ester links thanks to the three carboxylate functional groups that form as a result of the condensation reaction that takes place to produce them

Question 24

What are the three categories of saturation of triglycerides?

Answer 24

• Saturated
• Monounsaturated (only contains a single (C=C) double bond)
• Polyunsaturated (contains multiple (C=C) double bonds through the structure of the molecule

Question 25

What is the predominant type of intermolecular force holding together the fats and oils?

Answer 25

London dispersion forces are the primary intermolecular force due to the large hydrocarbon character of the molecules

Question 26

What is the reason for the difference in melting and boiling points of the oils and fats?

Answer 26

- Fat molecules are unsaturated meaning that they are tightly packed and have the most possible london dispersion forces in their structure. Whereas oils are unsaturated, this causes the fatty acids to kink, and this kinking causes the molecule to be less tightly packed resulting in fewer london dispersion forces forming and a lower melting and boiling point than the tightly packed fats

Question 27

How do we produce a soap?

Answer 27

By the alkaline hydrolysis of a fat or an oil

Question 28

What type of reaction produces the soap molecules?

Answer 28

A neutralisation between the fatty acid and the alkali causes the production of a salt and water which is soap.

Question 29

What is a soap?

Answer 29

A soap is a sodium salt produced by the alkaline hydrolysis of a fat or an oil

Question 30

What is an emulsion?

Answer 30

An emulsion is where a liquid is dispersed within another liquid

Question 31

What is the purpose of a soap?

Answer 31

To act as an emulsifier/ emulsifying agent

Question 32

What is an emulsifier?

Answer 32

An emulsifier is a substance that stabilises emulsions stopping them from separating out