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Chemistry A Level 2023 > Carboxylic Acids and Derivatives > Flashcards

Carboxylic Acids and Derivatives Flashcards

1
Q

what is a carboxylic acid functional group

A

-COOH (C=O and C-OH)

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2
Q

how do you name carboxylic acids

A

-oic acid

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3
Q

are carboxylic acids soluble in water? why? what influences?

A

yes
acid group can form hydrogen bonds with water molecules

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4
Q

what are intermolecular forces in carboxylic acids

A

hydrogen bonds in solid states - very strong

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5
Q

what are esters

A

formed from carboxylic acids and alcohols

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6
Q

ester general formula

A

RCOOR’ (C=O, C-O-C)

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7
Q

how do you name esters

A

start with group that replaced the hydrogen, then the acid
e.g. propyl (from alcohol) ethanoate (from carboxylic acid)

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8
Q

what characteristic physical properties do esters have

A

volatile, pleasant fruity smells e.g. apple, pear drops

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9
Q

what are some uses of esters

A

long chain: flavourings and perfumes
short chain: solvents
also plasticisers

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10
Q

what are some common natural esters

A

fats and oils

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11
Q

equation for equilibrium by ethanoic acid

A

CH3COOH <—> CH3COO- + H+

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12
Q

what happens to the negative charge on the ethanoate ion in terms of electrons

A

electrons delocalise so the negative charge is shared across the whole of the carboxylate group

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13
Q

how could you distinguish carboxylic acids from other -OH containing compounds

A

add NaHCO3, acids will produce sodium salt, water and carbon dioxide

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14
Q

write an equation for the reaction of ethanoic acid with NaOH

A

CH3COOH + NaOH –> H2O + CH3COO-Na+

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15
Q

write an equation for the reaction of ethanoic acid with Na2CO3

A

2CH3COOH + Na2CO3 –> 2CH3COO-Na+ + H2O + CO2

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16
Q

what catalyst is needed for the formation of esters from alcohols and carboxylic acids

A

concentrated strong acid e.g. H2SO4

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17
Q

what catalyst is needed for the hydrolysis of esters

A

dilute strong acid e.g. H2SO4

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18
Q

what is an alternative method of hydrolysis

A

base hydrolysis

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19
Q

what are the advantages of base hydrolysis

A

reaction goes to completion due to neutralisation by base - more product in the mixture than acid catalysed hydrolysis

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20
Q

which alcohol forms esters that make up animal and vegetable oils

A

glycerol / propane-1,2,3-triol

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21
Q

what is the difference between oil and fat

A

oils are liquid at room temperature, fats are solid
fats are usually saturated, oils are not

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22
Q

what are the products of hydrolysing fats and oils

A

propane-1,2,3-triol and sodium salts of the acids that make up the ester (hydrolysed with NaOH)

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23
Q

what are the uses of propane-1,2,3-triol and sodium salts

A

soaps and cleaning products

24
Q

what does the long hydrocarbon chain of carboxylate ion do

A

mixes with grease

25
Q

what does the COO- group do

A

mixes with water

26
Q

how does the carboxylate ion with a long carbon chain make a good cleaning agent

A

means that grease can be removed from water

27
Q

what is the systematic name of glycerol

A

propane-1,2,3-triol

28
Q

what are some common used of glycerol

A
  • used in the pharmaceutical and cosmetic preparation
  • solvent in many medicine
  • solvent in food industry
  • plasticising various materials like sheets and gaskets, cellophane and paper
29
Q

how do you make biodiesel

A

NaOH catalyst, 60 degrees celsius
lipids (fats/oils - esters) + 3CH3OH –> 3methylesters + glycerol

30
Q

what does transesterification mean

A

converting one type of ester to another

31
Q

what kind of crops is biodiesel made from

A

rapeseed oil or soybean oil

32
Q

how is the reaction mixture of biodiesel purified and separated

A

selling tank or centrifuge, remove remainder with water
add acid to neutralise excess alkali catalyst
solid soap is formed - easy to remove

33
Q

how is the reaction mixture of biodiesel purified and separated

A

selling tank or centrifuge, remove remainder with water
add acid to neutralise excess alkali catalyst
solid soap is formed - easy to remove

34
Q

what is the problem with producing biodiesel

A

crops that could be used to make food are being used to make fuel - are resources being best used

35
Q

what are carboxylic acid derivatives

A

molecules that have the acyl group as part of their structure, formed from carboxylic acids

36
Q

name 2 acid derivatives and give their functional groups

A

acyl chlorides: ROCOCl
acid anhydrides: RCOOCR / (RCO)2O

37
Q

which factors determine how readily the acylation of a nucleophile by an acid derivative occurs

A
  • magnitude of the delta + charge on the carbonyl carbon, which depends on the electronegativity of the atom/group being substituted
  • how easily the atom/group being substituted is lost
  • how good the nucleophile is (how readily will it donate electrons)
38
Q

what effect do the Cl and O atoms in acyl chlorides/acid anhydrides have on the partial charge of the carbonyl carbon

A

increase the partial + charge by attracting electrons
this means that they react more readily with nucleophiles

39
Q

are acyl chlorides or acid anhydrides more reactive

A

acyl chlorides

40
Q

what is the name of the mechanism by which acyl chlorides and acid anhydrides acylate nucleophiles

A

addition-elimination

41
Q

if the nucleophile is ammonia for acylation of acyl chlorides or acid anhydrides, what is the product of reaction

A

an amide

42
Q

if the nucleophile is a primary amine, what are the products of the acylation of acyl chlorides or acid anhydrides

A

N-substituted amide

43
Q

if the nucleophile is an alcohol, what are the products of acylation of acyl chlorides or acid anhydrides

A

an ester

44
Q

if the nucleophile is water, what are the products of the acylation of acyl chlorides or acid anhydrides

A

carboxylic acid (hydrolyses ester linkage)

45
Q

what is the name of the acylation of acyl chlorides/acid anhydrides with water as a nucleophile

A

hydrolysis

46
Q

what is a commercially important acylation reaction

A

manufacture of aspirin

47
Q

what are the advantages of using ethanoic anhydride as an acylating agent over ethanoyl chloride

A

it is cheaper, less corrosive and does nor react as readily with water

it is safer, as ethanoic acid is produced, rather than HCl which is corrosive

48
Q

what would you observe in a melting point determination if the sample was not pure

A

sample melts over a range
sample’s melting point is below accepted value due to impurities disrupting structure

49
Q

why might the melting point appear different to the true value

A

temperature of material in the machine might be different to the temperature shown on the thermometer - apparatus error

50
Q

when removing flue gases, what are the issues

A

disposal of large amounts of CaSO3 and CO2 is produced

51
Q

what condition are needed to form methyl esters from an acid anhydride or acyl chloride

A

react w methanol and heat gently under reflux

52
Q

when purifying by recrystallisation, why is the minimum volume of hot solvent used

A

so that a saturated solution is created, so that as many crystals will fall out of solution as possible when it is cooled

53
Q

why is the solution filtered hot when purifying by recrystallisation

A

to remove insoluble impurities and ensure that the crystals do not form in the filter paper

54
Q

why is the solution cooled in an ice bath when purifying by recrystallisation

A

remove soluble impurities

55
Q

how would you separate the crystals from the reaction mixture when purifying by recrystallisation

A

filter under reduced pressure using a Buchner funnel

56
Q

why might percentage yield be below 100% for recrystallisation

A
  • product is lost during filtration, drying and weighing - spills, not all transferred from one apparatus to another
  • product is left dissolved in solution - some does not crystallise, sample still wet

Chemistry A Level 2023 (8 decks)

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