Esters, Fats and Oils

Question 1

How are esters formed?

Answer 1

By the condensation reactions between a carboxylic acid and alcohol - called esterification.

Question 2

What acts as a catalyst in the formation of esters?

Answer 2

Concentrated sulfuric acid

Question 3

What are esters used for?

Answer 3

• as flavorings
• in perfumes
• as solvents (like nail polish)

Question 4

Name the products formed from methanoic acid + ethanol.

Answer 4

Ethyl methanoate + water

The first part of the name is derived from the alcohol, ending in -yl, and the second part comes from the acid, ending in -oate.

Question 5

Is the formation of esters reversible?

Answer 5

Yes

Question 6

What else is formed in the formation of esters?

Answer 6

H20

Question 7

How can esters be broken down into their parent acid and alcohol?

Answer 7

By reacting them with water - hydrolysis. This requires the ester to be heated up with an acid to speed up the process.

Question 8

What would ethyl propanoate + water produce when hydrolysed?

Answer 8

Propanoic acid + ethanol

Question 9

Where does an ester always split when hydrolysed?

Answer 9

At the ester link.

Question 10

What are fats and oils in three points?

Answer 10

• Naturally occurring esters which come from animals and plants.
• They are a concentrated source of energy.
• Essential for the storage and transport of fat-soluble vitamins in the body.

Question 11

How are fats and oils formed?

Answer 11

By a condensation reaction between three long-chain carboxylic acids (fatty acids) and glycerol (propane-1,2,3-triol).

Question 12

Hydrolysis of a fat or oil will always give…

Answer 12

One mole of glycerol and three molecules of fatty acids (which can all be the same or different).

Question 13

How is the ester link formed?

Answer 13

The hydroxyl group of the alcohol reacts with the carboxyl group of the acid - eliminating the small molecule of water in the process.

Question 14

What is hydrolysis?

Answer 14

A molecule breaks down into two smaller molecules by reacting with water.

Question 15

Is the hydrocarbon tail of fatty acids always saturated? - Why?

Answer 15

No, it can be saturated or partially unsaturated. This allows the variety of fatty acids.

Question 16

How many hydroxyl groups does glycerol have in each molecule?

Answer 16

Three, and therefore reacts with three fatty acid molecules.

Question 17

What happens when glycerol reacts with fatty acids?

Answer 17

Each fatty acid forms an ester link with the glycerol molecule.

Question 18

What other name do fats and oils go by?

Answer 18

Triglycerides

Question 19

If the fatty acid chains are mostly saturated…

Answer 19

the triglyceride will likely be solid at room temperature and be called a fat. They will have higher melting points.

Question 20

If the fatty acid chain is mostly unsaturated…

Answer 20

the triglyceride will likely be a liquid at room temperature and be called an oil. They will have lower melting points.

Question 21

Why are fats solid at room temperature?

Answer 21

The shape of the molecule allows them to pack closer together with stronger van der Waals forces; needing more energy to separate the molecules.

Question 22

Why are oils liquid at room temperature?

Answer 22

The double bonds on the fatty acid parts cause the hydrocarbon chains of the fatty acids to be more kinked. They cannot pack closely together and the van der Waals forces are weaker; needing less energy to separate them.

Question 23

What is the functional group in an ester?

Answer 23

Ester link, -COO-

Question 24

What is a condensation reaction?

Answer 24

Two molecules are joined together with the elimination of a small molecule.

Question 25

What type of solvent do esters make?

Answer 25

Solvents for non-polar compounds that do not dissolve in water.

Question 26

What is a hydrolysis reaction?

Answer 26

A molecule reacts with water to break down into smaller molecules.

Question 27

How can fats and oils be classified?

Answer 27

As animal, vegetable, or marine.

Question 28

Why are fats and oils important in a diet?

Answer 28

To supply the body with energy in a more concentrated form than carbohydrates.

Question 29

How can fats and oils be tested for saturation?

Answer 29

With bromine solution

Question 30

What is the primary number of carbons in a fatty acid?

Answer 30

C16 or C18

Question 31

What is the range of carbons in fatty acids?

Answer 31

Always even; C4 to C24

Question 32

How would you convert oils to fats?

Answer 32

It involves the partial removal of unsaturation by the addition of hydrogen.