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A2 Chemistry > Carbonyl groups > Flashcards

Carbonyl groups Flashcards

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1
Q

What is the carboxyl group?

A

COOH

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2
Q

What is the carboxyl group made up of?

A

carbonyl group and hydroxyl group

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3
Q

Why are carboxylic acids weak acids?

A

bc they dissociate partially

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4
Q

Why are short chain carboxylic acids soluble in water?

A

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

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5
Q

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

A

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

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6
Q

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

A

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

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7
Q

what is the metal salt of a carboxylic acid called?

A

carboxylate

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8
Q

how does an aqueous carboxylic acid dissociate in water?

A

RCOOH RCOO- + H+

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9
Q

how does a carboxylic acid react with water?

A

RCOOH + H2O —> RCOO- + H3O+

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10
Q

how does a carboxylic acid react with carbonates?

A

RCOOH + Na2CO3 —-> RCOONa + CO2 + H2O

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11
Q

carboxylic acid + carbonate –> ?

A

CO2 + H2O + RCOONa

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12
Q

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

A

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

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13
Q

how do you test for a carboxylic acid?

A

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

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14
Q

acid + metal —> ?

A

salt + hydrogen

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15
Q

what do you observe when an acid and metal react?

A

effervescence and colourless solution

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16
Q

acid + base —> ?

A

salt + water

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17
Q

what do you observe when an acid and base react?

A

heat and colourless solution

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18
Q

carboxylic acid + ammonia —>

A

ammonium carboxylate

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19
Q

what kind of reaction forms esters?

A

condensation reaction

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20
Q

what is produced when carboxylic acids and alcohols react?

A

ester and water are formed

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21
Q

name the four uses of esters

A

plasticisers, solvents, perfumes, food flavourings

22
Q

by what processes are esters broken down?

A

hydrolysis

23
Q

what does the acid hydrolysis of esters produce?

A

an equilibrium with carboxylic acids and alcohols

24
Q

what are the conditions for acid hydrolysis?

A

heat under reflux with dilute hydrochloric acid

25
Q

explain how alkaline hydrolysis of esters works

A

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

26
Q

what is a triglyceride?

A

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

27
Q

what is the chemical formula for glycerol?

A

propane-1,2,3-triol

28
Q

what is saponification?

A

the alkaline hydrolysis of esters

29
Q

what are soaps?

A

the salts produced by the saponification of triglycerides

30
Q

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

A

glycerol can be used in cosmetics and pharmaceuticals

31
Q

what is trans-esterification?

A

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

32
Q

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

A

to remove any unreacted acid and remove unreacted acid catalyst

33
Q

when preparing an ester, why is calcium chloride added?

A

to remove any unreacted alcohol

34
Q

by what process is biodiesel made?

A

transesterification

35
Q

how is biodiesel made?

A

reacting triglycerides with methanol to form biodiesel and glycerol

36
Q

what is biodiesel

A

methyl esters

37
Q

acyl chloride + alcohol

A

ester + hydrogen chlorise

38
Q

acid anyhydride + alcohol

A

ester and carboxylic acid

39
Q

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

A

no toxic HCl fumes made
cheaper
easier to control

40
Q

acyl chloride + water

A

carboxylic acid + hydrogen chlorise

41
Q

acid anhydride + water

A

carboxylic acid 1 + carboxylic acid 2

42
Q

acyl chloride + ammonia

A

amide + ammonium chloride

43
Q

acid anhydride + ammonia

A

amide + ammonium carboxylate

44
Q

acid chloride + 2amine

A

N-substituted amide

alkyl ammonium chloride

45
Q

acid anyhdride + 2amine

A

N substituted amide

salt

46
Q

explain how to prepare and purify an ester

A

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

47
Q

explain the recrystallisation process

A

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)

48
Q

why is the minimum volume of hot solvent used?

A

to ensure crystals form on cooling

so the solution is saturated

49
Q

why is gravity filtration done with HOT solvent

A

so it doesnt crystallise during filtration

50
Q

why do you do gravity filtration?

A

to remove insoluble impurities

51
Q

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

A

lower temp = lower solubility so it removes soluble impurities

52
Q

why do you compress the substance in the buchner funnel?

A

increased air flow through the substances

A2 Chemistry (17 decks)

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