Carbonyl groups

Question 1

What is the carboxyl group?

Answer 1

COOH

Question 2

What is the carboxyl group made up of?

Answer 2

carbonyl group and hydroxyl group

Question 3

Why are carboxylic acids weak acids?

Answer 3

bc they dissociate partially

Question 4

Why are short chain carboxylic acids soluble in water?

Answer 4

bc the carbonyl and hydroxyl group form hydrogen bonds with water bc theyre polar

Question 5

Why aren’t long chain carboxylic acids soluble in water?

Answer 5

bc the hydrocarbon chain is non-polar so it cannot form hydrogen bonds with the water

Question 6

why do carboxylic acids have a higher boiling point than alcohols?

Answer 6

bc of the polar carboxyl group, hydrogen bonds form between carboxylic acid molecules to form dimers which are double the size of acid molecules so increased van der Waals forces so higher bp

Question 7

what is the metal salt of a carboxylic acid called?

Answer 7

carboxylate

Question 8

how does an aqueous carboxylic acid dissociate in water?

Answer 8

RCOOH RCOO- + H+

Question 9

how does a carboxylic acid react with water?

Answer 9

RCOOH + H2O —> RCOO- + H3O+

Question 10

how does a carboxylic acid react with carbonates?

Answer 10

RCOOH + Na2CO3 —-> RCOONa + CO2 + H2O

Question 11

carboxylic acid + carbonate –> ?

Answer 11

CO2 + H2O + RCOONa

Question 12

what do you observe when you react a carboxylic acid with carbonate?

Answer 12

effervescence, a gas that turns limewater cloudy and also a colourless liquid remains

Question 13

how do you test for a carboxylic acid?

Answer 13

add a carbonate and watch for effervescence and a gas that turns limewater cloudy

Question 14

acid + metal —> ?

Answer 14

salt + hydrogen

Question 15

what do you observe when an acid and metal react?

Answer 15

effervescence and colourless solution

Question 16

acid + base —> ?

Answer 16

salt + water

Question 17

what do you observe when an acid and base react?

Answer 17

heat and colourless solution

Question 18

carboxylic acid + ammonia —>

Answer 18

ammonium carboxylate

Question 19

what kind of reaction forms esters?

Answer 19

condensation reaction

Question 20

what is produced when carboxylic acids and alcohols react?

Answer 20

ester and water are formed

Question 21

name the four uses of esters

Answer 21

plasticisers, solvents, perfumes, food flavourings

Question 22

by what processes are esters broken down?

Answer 22

hydrolysis

Question 23

what does the acid hydrolysis of esters produce?

Answer 23

an equilibrium with carboxylic acids and alcohols

Question 24

what are the conditions for acid hydrolysis?

Answer 24

heat under reflux with dilute hydrochloric acid

Question 25

explain how alkaline hydrolysis of esters works

Answer 25

ester and alkali react to completely form carboxylate salt and alcohol. carboxylate further reacted with an acid to form carboxylic acid

Question 26

what is a triglyceride?

Answer 26

an ester of propane-1,2,3-triol (glycerol) and fatty acid chains joined together by ester linkages

Question 27

what is the chemical formula for glycerol?

Answer 27

propane-1,2,3-triol

Question 28

what is saponification?

Answer 28

the alkaline hydrolysis of esters

Question 29

what are soaps?

Answer 29

the salts produced by the saponification of triglycerides

Question 30

what is the by-product of saponification of triglycerides and how is it used in industry?

Answer 30

glycerol can be used in cosmetics and pharmaceuticals

Question 31

what is trans-esterification?

Answer 31

when you react an ester with an alcohol to produce a different ester and alcohol

Question 32

when preparing an ester, why is sodium carbonate added to the crude ester?

Answer 32

to remove any unreacted acid and remove unreacted acid catalyst

Question 33

when preparing an ester, why is calcium chloride added?

Answer 33

to remove any unreacted alcohol

Question 34

by what process is biodiesel made?

Answer 34

transesterification

Question 35

how is biodiesel made?

Answer 35

reacting triglycerides with methanol to form biodiesel and glycerol

Question 36

what is biodiesel

Answer 36

methyl esters

Question 37

acyl chloride + alcohol

Answer 37

ester + hydrogen chlorise

Question 38

acid anyhydride + alcohol

Answer 38

ester and carboxylic acid

Question 39

why is acid anhydride preferred over acyl chlorides to make esters?

Answer 39

no toxic HCl fumes made cheaper easier to control

Question 40

acyl chloride + water

Answer 40

carboxylic acid + hydrogen chlorise

Question 41

acid anhydride + water

Answer 41

carboxylic acid 1 + carboxylic acid 2

Question 42

acyl chloride + ammonia

Answer 42

amide + ammonium chloride

Question 43

acid anhydride + ammonia

Answer 43

amide + ammonium carboxylate

Question 44

acid chloride + 2amine

Answer 44

N-substituted amide | alkyl ammonium chloride

Question 45

acid anyhdride + 2amine

Answer 45

N substituted amide | salt

Question 46

explain how to prepare and purify an ester

Answer 46

equimolar volumes of acid and alcohol in pear shaped flask add H2So4 slowly with cooling anti-bumping granules distill and put into a separating funnel add sodium carbonate and invert separate layers and allow lower one to be removed calcium chloride to remove alcohol filter redistil and collect at appropriate fraction

Question 47

explain the recrystallisation process

Answer 47

dissolve impure product in the min volume of hot solvent do gravity filtration of HOT solvent through fluted filter paper in a glass funnel cool and crystallise wash with water suction filtration (press between filter papers for better drying)

Question 48

why is the minimum volume of hot solvent used?

Answer 48

to ensure crystals form on cooling | so the solution is saturated

Question 49

why is gravity filtration done with HOT solvent

Answer 49

so it doesnt crystallise during filtration

Question 50

why do you do gravity filtration?

Answer 50

to remove insoluble impurities

Question 51

why do you allow the solution to cool and form crystals?

Answer 51

lower temp = lower solubility so it removes soluble impurities

Question 52

why do you compress the substance in the buchner funnel?

Answer 52

increased air flow through the substances