Carbonyl compounds: Carboxylic acids and esters

Question 1

What is the functional group of carboxylic acid?

Answer 1

-COOH (carboxyl functional group)

Question 2

Does the carboxylic acid take priority when compounds are named?

Answer 2

Yes, as they go at the end so they take priority when compounds involving carboxylic acids are named

Question 3

Are carboxylic weak or strong acids? And what is the equilibrium position when it reacts with water

Answer 3

They are weak acids and so only partially dissociate into H+ ions, so the equilibrium lies well to the left

Question 4

Carboxylic acid + water

Answer 4

Carboxylate ion (RCO2-) + water

Question 5

carboxylic acids + carbonates CO3(2-
e.g. CH 3 COOH + Na 2 CO 3

Answer 5

carbon dioxide + water + salt (e.g.)

CH 3 COOH + Na 2 CO 3 → 2 CH 3 COONa + CO 2 + H 2 O

Question 6

what functional group do esters belong to?

Answer 6

-COO

Question 7

How are esters most often formed?

Answer 7

Carboxylic acid + alcohol in the presence of a strong acid catalyst such as concentrated sulfuric acid in a process known as esterification

Question 8

How do you name an ester?

Answer 8

1. First stems from the alcohol e.g. propyl
2. Second bit is from the ethanoic acid, where the oic acid is replaced with oate e.g. ethanoate
3. Add the 2 together e.g. propyl ethanoate
   If the chain is branched then, number from the C carbon in C-O-C bond, e.g. propyl 2-methyl ethanoate

Question 9

What type of liquid are esters and hence what dissolves in them?

Answer 9

They are polar liquids and polar organic compounds dissolve in them

Question 10

Why are esters useful as glues and paints?

Answer 10

They have low boiling points and so evaporate from mixes easily

Question 11

How are esters used as plasticisers and what happens to them over time?

Answer 11

They are added to plastics during polymerisation to make them more flexible, the plasticisers can escape over time and then it becomes brittle and stiff

Question 12

What forms as esters are hydrolysed by water?

Answer 12

They form alcohol

Question 13

Why are acids or bases added when esters and water react?

Answer 13

To sped up the process

Question 14

What occurs and forms in the acid hydrolysis of the ester: ethyl ethanoate?

Answer 14

1. Reflux the ester with a dilute acid, e.g. sulfuric or hydrochloric acid to reach equilibrium
2. forming an ethanol (alcohol) and ethanoic acid (acid)

Question 15

What occurs and forms in the base hydrolysis of the ester: ethyl ethanoate?

Answer 15

1. Reflux the ester with an alkali such as sodium hydroxide to reach equilibrium
2. Ethanol (alcohol) and ethanoate (carboxylate ion) are both formed

Question 16

what are fatty acids?

Answer 16

They are long chains of carboxylic acids, which can be saturated or unsaturated

Question 17

glycerol + fatty acids

Answer 17

Form esters which are fats and oils

Question 18

Why are animal fats solid at room temperature?

Answer 18

They are mostly saturated, so pack tightly with stronger van der waals between them, so they require higher temperatures to melt and are therefore solid at room temperature

Question 19

Why are plant oils liquid at room temperature?

Answer 19

They are unsaturated which means the double bonds cause them to bend, so they don’t pack tightly, hence weaker van der waals and are easier to melt

Question 20

what is the by product of ester, animal fat and vegetable oil hydrolysis when its heated with sodium hydroxide?

Answer 20

They form glycerol, soap and fatty acids

Question 21

How is biodiesel formed?

Answer 21

veg oils, e.g. rapeseed oil is heated in the presence of a potassium hydroxide catalyst , you get a mixture of methyl esters of fatty acids- biodiesel

Question 22

CH 3 COOH + NaH CO 3

Answer 22

CH 3 COOH + Na H CO 3 –> CO2 + H2O + CH3COONa