Carboxylic acids and derivatives

Question 1

Describe the term weak acid

Answer 1

weak acids do not fully dissociate into H+ ions in solution. The equilibria lies far to the left. Carboxylic acids are examples of weak acids

Question 2

how are carboxylic acids produces`

Answer 2

by the oxidation of aldehydes

Question 3

what is formed when carboxylic acids react with alkalis

Answer 3

a salt and water will be formed. the suffix of the salt formed is -oate

Question 4

give the name of the organic product formed when ethanoic acid is reacted with NaOH

Answer 4

sodium ethanoate

Question 5

what is formed when carboxylic acids react with hydrogencarbonates

Answer 5

a salt, water and carbon dioxide

Question 6

what is formed when carboxylic acids react with alcohols

Answer 6

and ester and water. this process is esterification

Question 7

give the organic product formed from the reaction of methanol with ethanoic acid

Answer 7

methyl ethanoate

Question 8

what are the products of the hydrolysis of esters

Answer 8

carboxylic acids and alcohols

Question 9

why is this reaction very slow

Answer 9

because water is a poor nucleophile

Question 10

give the products of acid catalysed hydrolysis of esters

Answer 10

the carboxylic acid and alcohol

Question 11

give the products of base catalysed hydrolysis of ester

Answer 11

the carboxylate salt and alcohol

Question 12

why is the carboxylate salt formed from base catalysed hydrolysis useful?

Answer 12

it is used to make soaps

Question 13

give three uses of esters

Answer 13

• artificial perfumes and flavourings
• as plasticisers. plasticisers weaken the intermolecular forces between polymer chains
• used as solvents. short chain esters are volatile
• as Biodiesel- a mixture of methyl esters. it is made from crops like rapeseed, which is reacted with methanol and an alkali catalyst to form a mixture of methyl esters

Question 14

what is the suffix for acyl chlorides and what is their functional group

Answer 14

• oyl chloride

- functional group is O=C-Cl

Question 15

give the structural formula for propanamide

Answer 15

CH3CH2CHONH2

Question 16

name the two products when an acyl chloride reacts with water

Answer 16

you get HCl and the corresponding carboxylic acid

Question 17

name the mechanism that occurs when a nucleophile reacts with a acyl chloride

Answer 17

addition-elimination reaction.
The acyl chloride is highly susceptible to attack by the nucleophile, due to its highly electron deficient carbonyl group, because of the electron withdrawal from the electronegative chlorine

Question 18

what will be produced when an acyl chloride reacts with NaOH in solution

Answer 18

the carbonyl salt will be produced, instead of the carbpoxylic acid

Question 19

what is formed by reacting an acyl chloride with an alcohol

Answer 19

an ester is formed

Question 20

how could you remove the HCl that is produced

Answer 20

by adding a base like NaOH

Question 21

what is produced by reacting an acyl chloride with a primary amine

Answer 21

an N-substituted amide is produced. If you have excess of the amine, the Cl- ion will be attracted to the N+ on the NH3+, forming an alcyl ammonium salt

Question 22

what is formed by the reaction between an acyl chloride and ammonia?

Answer 22

an amide.

Question 23

why might an excess of the ammonia be used?

Answer 23

to remove the HCl that is formed

Question 24

what are the products formed by reacting an acid anhydride with an alcohol

Answer 24

an ester an a carboxylic acid

Question 25

what is produced when an acid anhydride is reacted with water

Answer 25

two carboxylic acids

Question 26

write a word equation for the formation of Aspirin

Answer 26

2-hydroxy bezoic acid + ethanoic anhydride –> aspirin + ethanoic acid

Question 27

describe how aspirin is purified

Answer 27

• dissolve the impure product in a hot solvent
• use a minimum amount of solvent, to produce a saturated solution
• filter the solution to remove any solid impurities
• cool to recrystallise
• filter under reduced pressure using a buchner funnel
• wash using a cold solvent to remove any impurities on the surface, and dry