3.3.9 Carboxylic acids and derivatives (A2)

Question 1

what is the functional group of carboxylic acids?

Answer 1

R-COOH

Question 2

what is the pH of carboxylic acids?

Answer 2

weak acids - pH 3-6

Question 3

what is the name of a carboxylic acid which includes a benzene ring?

Answer 3

benzanoic acid

Question 4

can carboxylic acids form H bonds with water? what does this mean?

Answer 4

yes
carboxylic acids with up to and including 4 carbons are completely soluble in water

Question 5

when can carboxylic acids form H bonds with eachother?

Answer 5

in the solid state

Question 6

what do the H bonds account for in terms of properties?

Answer 6

much higher boiling point than their counterpart alkanes

Question 7

what is mechanism is likely to happen in carboxylic acids? why?

Answer 7

nucleophilic addition
delta positive carbon is very susceptible to nucleophilic attack and addition reactions are likely to happen as there is an area of unsaturation

Question 8

what happens to carboxylic acids in solution?

Answer 8

partially ionised
forms carboxylate ion and a proton (H+)

Question 9

what is the chemical reactivity of carboxylic acids?

Answer 9

despite being weak acids, any carboxylic acid will still react with sodium hydrogencarbonate (NaHCO3)

Question 10

what happens in the reaction between sodium hydrogen carbonate (NaHCO3) and a carboxylic acid?

Answer 10

releases carbon dioxide
we would see bubbling

Question 11

what can we use to distinguish between carboxylic acids and alcohols?

Answer 11

sodium hydrogencarbonate
carboxylic acid bubbles
alcohol gives no reaction

Question 12

what do we use the test with sodium hydrogencarbonate to do?

Answer 12

distinguish between carboxylic acids and alcohols
carboxylic acids bubble - release of CO2
and alcohols give no reaction

Question 13

what are carboxylic acids in a reaction?

Answer 13

proton donors

Question 14

what are the salts produced by the reactions of carboxylic acids called generally?

Answer 14

carboxylate salts

Question 15

what would a reaction of a ethanoic acid produce as a salt?

Answer 15

ethanoate salts

Question 16

what salt would be produced from a reaction involving methanoic acid?

Answer 16

methanoate salts

Question 17

what does the reaction of ethanoic acid and sodium hydroxide produce?

Answer 17

sodium ethanoate and water

Question 18

what does a reaction between propanoic acid and aqueous sodium carbonate produce?

Answer 18

sodium propanoate
water
carbon dioxide

Question 19

do carboxylic acids ionise partially or completely in water?

Answer 19

partially ionise in solution

Question 20

what is the charge on a carboxylate ion called?

Answer 20

delocalised electron charge

Question 21

what is the functional group of an ester?

Answer 21

RC=OO-R’

Question 22

what are esters used for?

Answer 22

cleaning products, perfumes, flavourings

Question 23

how do we form an ester?

Answer 23

carboxylic acid + alcohol

Question 24

what is the equation for forming an ester?

Answer 24

carboxylic acid + alcohol –> ester + water

Question 25

how would we get a higher yield of ester from the carboxylic acid + alcohol reaction?

Answer 25

increase volume of carboxylic acid / alcohol remove water is it is formed

Question 26

how can we get the carboxylic acid and alcohol back from the ester?

Answer 26

hydrolysis

Question 27

what does an addition elimination reaction of an ester form?

Answer 27

carboxylic acid alcohol

Question 28

what conditions does an addition elimination reaction involving an ester?

Answer 28

room temperature acid catalyst

Question 29

what do we obtain after addition elimination of esters? how do we obtain the desired product?

Answer 29

mixture of carboxylic acid, water, ester and alcohol fractional distillation

Question 30

other than an acid catalyst for addition elimination, what else can be used to hydrolyse an ester?

Answer 30

bases

Question 31

when we use a base to hydrolyse an ester, what are the products?

Answer 31

alcohol and salt of the carboxylic acid (carboxylate salt)

Question 32

what happens when we use a base to hydrolyse an ester?

Answer 32

products are carboxylate salt and alcohol because this is removing the carboxylic acid from the mixture, an equilibrium is NOT REACHED so reaction goes to EQUILIBRIUM

Question 33

what type of mechanism is the hydrolysis of esters?

Answer 33

addition elimination

Question 34

what is the use of esters as plasticisers?

Answer 34

added to plastics to make them more flexible

Question 35

why are esters used as plasticisers?

Answer 35

ester (small molecule) can get in between the long chain molecules of plastic and allow them to slide over each other

Question 36

what is the reaction for making fats and oils a reaction between? what does it form?

Answer 36

glycerol (alcohol) + fatty acids (carboxylic acids) forming triglyceride (triester of glycerol)

Question 37

what can we add to triglyceride (ester) to form glycerol (alcohol) and fatty acids (carboxylic acid)?

Answer 37

3 water molecules

Question 38

what happens in the hydrolysis of fats?

Answer 38

boil fats / oils with sodium hydroxide glycerol and 3 sodium carboxylate salts produced

Question 39

what is produced from the hydrolysis of fats?

Answer 39

glycerol (alcohol) and sodium carboxylate salts

Question 40

how is sodium carboxylate salt used?

Answer 40

soap

Question 41

how many molecules of NaOH are added to a triglyceride to hydrolyse it?

Answer 41

3

Question 42

how do the carboxylate ions arrange themselves around an oil droplet in water? why? what is this used for?

Answer 42

arrange themselves with hydrophilic head in the surrounding water and hydrophobic tail in the oil. this leads to separation of the oil and water, used for soaps

Question 43

what is used to produce biodiesel from triglyceride (triester)?

Answer 43

methanol

Question 44

what are the mixture of fatty esters produced by the combination of triglyceride and methanol used for?

Answer 44

biodiesel

Question 45

what is produced by the reaction between triglyceride and methanol?

Answer 45

mixture of fatty esters (biodiesel) glycerol

Question 46

what is the formula of an acyl group?

Answer 46

RC=O

Question 47

what is acylation?

Answer 47

addition of an acyl group to a nucleophile

Question 48

what is the ending when naming acyl chlorides?

Answer 48

(ethan)oyl chloride

Question 49

what is Z called in RC(O)Z?

Answer 49

Z= leaving group

Question 50

what are some examples of leaving groups?

Answer 50

Cl, OR', OCOR'

Question 51

what does the speed of acylation reaction depend on?

Answer 51

depends how delta + the central carbon is depends how stable the Z (leaving group) is depends how strong the nucleophile is

Question 52

what is the relationship between the rate of the acylation reaction and the charge of the central carbon?

Answer 52

the more delta + the central carbon is, the quicker the reaction

Question 53

what is the relationship between the rate of the acylation reaction and the stability of the leaving group?

Answer 53

the more stable the Z (leaving group), the quicker the reaction

Question 54

what is the relationship between the rate of the acylation reaction and the strength of the nucleophile?

Answer 54

the easier the lone pair is donated, the quicker the reaction.

Question 55

what have the fastest acylation reactions?

Answer 55

acyl chlorides

Question 56

why do acyl chlorides have the fastest acylation reactions?

Answer 56

carbon is delta positive leaving group is stable nucleophile is strong (lone pair donated easily)

Question 57

what makes a better nucleophile?

Answer 57

how easily the e- pair is donated (how basic the nucleophile is)

Question 58

what are the drawbacks to using ethanoic (acid) anhydrides?

Answer 58

lower atom economy slower reaction

Question 59

what is the reason we don't use acyl chlorides over acid anhydrides?

Answer 59

toxic by-product of HCl gas

Question 60

what type of molecules are formed when we react a primary amine with an acyl chloride?

Answer 60

amide TOXIC HCl (hydrogen chloride) gas

Question 61

what type of molecules are formed when we react ammonia with an acyl chloride?

Answer 61

amide toxic HCl gas

Question 62

what type of molecules are formed when we react an alcohol with an acyl chloride?

Answer 62

ester toxic HCl gas

Question 63

what type of molecules are formed when we react an acyl chloride with water?

Answer 63

carboxylic acid toxic HCl gas

Question 64

what type of molecules are formed when we react a primary amine with an acid anhydride?

Answer 64

amide carboxylic acid

Question 65

what type of molecules are formed when we react ammonia with an acid anhydride?

Answer 65

amide acid anhydride

Question 66

what type of molecules are formed when we react an alcohol with an acid anhydride?

Answer 66

ester carboxylic acid

Question 67

what type of molecules are formed when we react water with an acid anhydride?

Answer 67

carboxylic acid carboxylic acid

Question 68

what are the positives with reacting acyl chlorides?

Answer 68

reaction is extremely quick high atom economy

Question 69

what are the positives with reacting acid anhydrides?

Answer 69

by-product is NON TOXIC

Question 70

what is the negative when using acyl chlorides in reaction?

Answer 70

TOXIC BY-PRODUCT of hydrogen chloride gas

Question 71

what are the negatives of using acid anhydrides in reaction?

Answer 71

reaction is slower atom economy is lower