Derivatives Of Carboxylic Acids

Question 1

Definition of a monoester

Answer 1

An Ester which contains only one Ester group

Question 2

Definition of tranesterification

Answer 2

A reaction where the alkyl group of an Ester is exchanged with the alkyl group of an alcohol

Question 3

Definition of biodiesel

Answer 3

A fuel, similar to diesel, which is made from vegetable sources

Question 4

What is the functional group of an Ester

Answer 4

R-COO-R

See notes

Question 5

What is the functional group of acyl chlorides

Answer 5

See notes

Question 6

How to name esters

Answer 6

Parent alcohol at start and parent acid at end

Eg ethanol and propanoic acid forms ethyl propanoate

Question 7

How to draw esters

Answer 7

Acid then alcohol

Question 8

Physical properties of esters

Answer 8

1. Colourless
2. Neutral
3. Pleasant fruity smell

Question 9

Describe the solubility of esters

Answer 9

⭕️ Small = fairly soluble ➡️ falls as chain increases
⭕️ can’t H bond with themselves
⭕️ H bond with water

Question 10

What are the bonds in esters

Answer 10

Mostly VDW

Some permanent dipole dipole C=O

Question 11

Describe the boiling points of esters compared to carboxylic acids

Answer 11

Lower than carboxylic acids ➡️ can’t H bond with themselves

Question 12

Write the equation for the formation of esters via carboxylic acids and state conditions

Answer 12

See notes
Conc sulfuric acid
Reflux

Question 13

Why is conc sulfuric acid needed in the preparation of esters via carboxylic acid

Answer 13

Removes water

Question 14

Why is the formation of esters via carboxylic acids not the best

Answer 14

Less than 100% yield

Question 15

Write the general equation for the formation of esters via acyl chlorides

Answer 15

See notes

Question 16

Why is the formation of an Ester via acyl chlorides good

Answer 16

1. Fast and no reflux
2. Irreversible
3. No catalyst needed
4. Higher yield

Question 17

Describe acid catalysed hydrolysis of esters

Answer 17

Heat under reflux with excess water and dilute HCl

Question 18

State the products formed from acid catalysed hydrolysis of esters

Answer 18

Carboxylic acid

Alcohol

Question 19

Why is acid catalysed hydrolysis of esters a poor method

Answer 19

1. Reversible

2. Some Ester left unhydrolysed

Question 20

Describe base catalysed hydrolysis of an Ester

Answer 20

1. Reflux Ester with NaOH (aq)
2. Sodium salt of acid produced
3. Acid liberated from salt via addition of strong acid

Question 21

Why is base catalysed hydrolysis better than acid based hydrolysis

Answer 21

Irreversible

Question 22

How are acyl chlorides formed

Answer 22

When carboxylic acid reacts with PCl5

Question 23

Write the general equation for the formation of acyl chlorides

Answer 23

See notes

Question 24

What are the products when acyl chlorides react with alcohol

Answer 24

Ester and HCl

Question 25

What are the products when acyl chlorides react with water

Answer 25

Hydrolysis | Produces carboxylic acid and HCl

Question 26

Describe the structure of fats and oils

Answer 26

⭕️ triesters of glycerol and fatty acids | ⭕️ formed via condensation reactions

Question 27

What does a glycerol and three fatty acids produce

Answer 27

A triglyceride and 3 waters | See notes

Question 28

Describe saturated fatty acids

Answer 28

⭕️ NO C=C ⭕️ fit compactly - strong vdw ⭕️ higher mp than unsaturated ⭕️ usually solid

Question 29

Describe unsaturated fatty acids

Answer 29

⭕️ one or more C=C ⭕️ cannot align compactly - tend to coil - due to C=C ⭕️ weak vdw low mp ⭕️ usually liquid

Question 30

What is the name for a fatty acid with one C=C

Answer 30

Monosaturated

Question 31

What is the name of a fatty acid with 2 or more C=C

Answer 31

Polysaturated

Question 32

Describe hydrogenation of oils and fats

Answer 32

⭕️ oils become fats - increase in vdw ⭕️ finely divided nickel catalyst ⭕️ 180 degrees ⭕️ H2 gas bubbled through

Question 33

Draw the structural equation of hydrogenation of oils and fats

Answer 33

See notes

Question 34

Name of hydrolysis of fats

Answer 34

Alkaline hydrolysis | Saponification

Question 35

Name the products of hydrolysis of fats

Answer 35

Glycerol Sodium salt of fatty acid (soap) See notes for structural equation

Question 36

Write the general equation for transesterification and state what happens

Answer 36

Swap alkyl group in an Ester for another ⭕️ alcohol + Ester ➡️ different alcohol + different Ester See notes for structural equation

Question 37

Describe the two different forms of transesterification in fats

Answer 37

1. Intramolecular - within same fat molecule | 2. Intermolecular - between two fat molecules

Question 38

What is transesterification useful for

Answer 38

Produces biofuel and margarine

Question 39

What is biodiesel made from

Answer 39

Triglycerides in vegetable oils

Question 40

How is biodiesel made

Answer 40

Triglyceride heated with methanol | Presence of base (catalyst)

Question 41

What are the products of biodiesel reaction

Answer 41

Biodiesel | glycerol (used in other industries)

Question 42

Conditions for the formation of biodiesel

Answer 42

400K Alkali Glycerol Catalyst

Question 43

Describe the method of preparing a carboxylic acid from an alcohol

Answer 43

See notes