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AQA A Level Chemistry > Carboxylic Acids + Derivatives > Flashcards

Carboxylic Acids + Derivatives Flashcards

1
Q

What is a carboxylic acid and it’s functional group ?

A

-COOH (C=O and C-OH)

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2
Q

How do you name carboxylic acids ?

A

Carbon chain length -oic acid.

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3
Q

Are carboxylic acids soluble in water ?

A

•Yes, acid group forms hydrogen bonds with water
•Carbon chain length affects solubility

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4
Q

What intermolecular forces are there in carboxylic acids ?

A

Hydrogen bonds and van ver waals

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5
Q

What are esters (functional group), what are they formed from ?

A

•They are formed from carboxylic acids and alcohols
•RCOOR (C=O C-O-C)

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6
Q

Write an equation for the reaction of ethanoic acid and propan-1-ol

A

CH3COOH + CH3CH2CH2OH -> CH3COOCH2CH2CH3 + H2O

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7
Q

How do you name esters ?

A

•Start with the group that replaced the H, then acid suffix
•Eg, propanol + ethanoic acid = propylethanoate

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8
Q

What characteristic physical properties do esters have ?

A

Volatile, fruity smells

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9
Q

What are the uses of esters ?

A

Flavourings, perfumes (long chain)
Solvents, plasticisers (short chain)

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10
Q

What are some common natural esters ?

A

Fats and oils

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11
Q

How are carboxylic acids polarised ?

A

C d+
Both O d-

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12
Q

Write an equilibrium formed by ethanoic acid in solution ?

A

CH3COOH -> CH3COO- + H+

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13
Q

What happens to the negative charge in an ethanoate ion in terms of electrons ?

A

Electrons become delocalised and are shared across the whole group

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14
Q

How would you distinguish carboxylic acids from other OH containing compounds ?

A

Add NaHCO3, acids will produce sodium salt, water and CO2

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15
Q

Write an equation for the reaction of ethanoic acid and sodium hydroxide

A

CH3COOH + NaOH -> CH3COONa + H2O

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16
Q

Write an equation for the reaction of ethanoic acid and NaCO3

A

2CH3COOH + Na2CO3 -> 2CH3COONa + H2O + CO2

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17
Q

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

A

Concentrated strong acid eg H2SO4

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18
Q

What catalyst is needed for the hydrolysis of esters ?

A

Dilute strong acid eg H2SO4

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19
Q

What is an alternative method of hydrolysis of esters ?

A

Base hydrolysis

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20
Q

What are the advantages of base hydrolysis of esters ?

A

Reaction goes to completion due to neutralisation by base - more product in the mixture catalysed by hydrolysis

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21
Q

Which alcohols forms the esters that make up animal and vegetable oils ?

A

Glycerol / propan-1,2,3-triol

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22
Q

What is the difference between oil and fat ?

A

Oils are liquid at room temperature fats are solids
Fats are usually saturated

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23
Q

What are the products of producing fats and oils ?

A

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

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24
Q

What are the uses of Propan-1,2,3-triol and sodium salts ?

A

Soaps and cleaning products

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25
What does the long hydrocarbon chain of the carboxylate ion do ?
Mixes with grease (conditioner)
26
What does the COO- group do ?
Mixes with water
27
Why does a carboxylate ion with a long hydrocarbon chain make a good cleaning agent ?
Carboxylate ion mixes with the grease which can then be removed from water
28
What is the IUPAC name of glycerol ?
Propane-1,2,3-triol
29
What are some common uses of glycerol ?
•Used in pharmaceutical and cosmetic preparations, eg stops cream drying •A solvent in many medicines eg toothpaste •A solvent in the food industry eg food colourings •Plasticisers
30
How do you make biodiesel (general equation and conditions)
•NaOH catalyst, 60C •Lipid + 3CH3OH -> 3 methyl esters + glycerol
31
What is transesterification?
Converting one type of ester to another
32
What kind of seed is biodiesel made from ?
Rapeseed oil or soybean oil
33
How is the reaction mixture of biodiesel purified and separated?
•Setting tank or centrifuge •Remove remainder with water •Add acid to neutralise excess alkali catalyst •Soap is formed, easy to remove.
34
What is an issue with producing biodiesel ?
Crops that could be used for food are used for fuel
35
What are carboxylic acid derivatives ?
Molecules that have an acyl group as a part of their structure, formed from carboxylic acids
36
Name two carboxylic acid derivatives and give their functional groups
Acyl chlorides RCOCl Acid anhydrides RCOOCR / (RCO)2O
37
Draw the mechanism for the acylation of a nucleophile by an acid derivative
•C d+ O d- (C=O) •Arrow from lone pair of Nu- to d+ of C, further arrow from C=O to O •This gives O negative charge, arrow from lone pair of O to bond, further arrow from C-X to X.
38
What factors effect how readily the acylation of a nucleophile by an acid derivative occurs ?
*Magnitude of the d+ charge on the carbonyl group (electronegativity of group being substituted) *How easily the group being substituted is lost *How readily the nucleophile will donate electrons.
39
What effect do the Cl and O atoms in acyl chlorides/acid anhydrides have on the partial charge of the carbonyl atom ?
They increase the d+ charge by attracting electrons, this means that they react more readily with nucleophiles
40
Which are more reactive: Acyl chlorides or acid anhydrides ?
Acyl chlorides
41
What is the name of the mechanism by which acyl chlorides and acid anhydrides acylate nucleophiles?
Nucleophilic addition-elimination
42
If the nucleophile is ammonia for the acylation of acyl chlorides or acid anhydrides, what are the products of the reaction ?
An amide
43
Write an equation for the reaction of ethanoyl chloride and ammonia
CH3COCl + 2NH3 -> CH3CONH2 + NH4Cl
44
Draw / describe the mechanism for the reaction of ethanoyl chloride and ammonia
*d+ on C, d- on O and Cl of ethanoyl *Arrow from lone pair of N (NH3) to d+ C *This produces intermediate whereby the C=O becomes C-O and NH3 joins C, there is now N+ and O- *Arrow from lone pair of O- to C-O, arrow from C-Cl to Cl and arrow from N+-H to N+.
45
If the nucleophile is a primary amide, what are the products of the acylation of acyl chlorides or acid anhydrides ?
N-Substituted amide
46
Write an equation for the reaction of ethanoyl chloride and methylamine
CH3COCl + CH3NH2 -> CH3CONHCH3 + CH3NH3Cl
47
Draw / describe the reaction of ethanoyl chloride and methylamine
*d+ on C, d- on O and Cl of ethanoyl *Arrow from lone pair of N (CH3NH2) to d+ C *This produces intermediate whereby the C=O becomes C-O and CH3NH2 joins C, there is now N+ and O- *Arrow from lone pair of O- to C-O, arrow from C-Cl to Cl and arrow from N+-H to N+.
48
If the nucleophile is an alcohol, what are the products of the acylation of acyl chlorides or acid anhydrides ?
An ester
49
Write an equation for the reaction of ethanoyl chloride and ethanol
CH3COCl + CH3CH2OH -> CH3COOCH2 + HCl
50
Draw / describe the mechanism for the reaction of ethanoyl chloride and ethanol
*d+ on C, d- on O and Cl of ethanoyl chloride *Arrow from lone pair of O (ethanol) to d+ C *This produces intermediate whereby the C=O becomes C-O and ethanol joins C via the OH group, there is now O+ and O- *Arrow from lone pair of O- to C-O, arrow from C-Cl to Cl and arrow from O+-H to O+.
51
If the nucleophile is water, what are the products of the acylation of acyl chlorides or acid anhydrides ?
Carboxylic acids (hydrolyses ester linkage)
52
What is the name of the reaction of the acylation of acyl chlorides/acid anhydrides with water as a nucleophile?
It is a hydrolysis reaction
53
Write an equation for the reaction of ethanoyl chloride and water
CH3COCl + H2O -> CH3COOH + HCl
54
Draw / describe the mechanism for the reaction of ethanoyl chloride and water
*d+ on C, d- on O and Cl of ethanoyl chloride *Arrow from lone pair of O (H2O) to d+ C *This produces intermediate whereby the C=O becomes C-O and water joins C via the O , there is now O+ and O- *Arrow from lone pair of O- to C-O, arrow from C-Cl to Cl and arrow from O+-H to O+.
55
What is a commercially important acylation reaction ?
The manufacture of aspirin
56
What are the advantages if using ethanoic anhydride as a acylating agent over ethanoyl chloride ?
*It is cheaper, less corrosive and does not react readily with water *It is safer as ethanoic acid is produced rather than HCl which is corrosive.
57
What would you observe in a melting point determination if the sample was not pure ?
*The sample would melt over a large temperature range (more than 3 C) *Samples melting point may be below the theory value due to impurities disrupting structure.
58
Why might the melting point of a substance appear different from its true value ?
The temperature of the material in the apparatus may be different to the temperature reading displayed - apparatus error
59
When removing flue gasses, what are the issues ?
Disposal of large amounts of CaSO3, and CO is produced
60
What conditions are needed to form methyl esters from an acid anhydride or acyl chloride
React with methanol and heat gently under reflux
61
When purifying via recrystallisation, why is the minimum volume of hot solvent required used ?
So that a saturated solution is created, this means that as many crystals will fall out of the solution as possible when it is cooled
62
Why is the solution filtered hot when purifying by recrystallisation ?
To remove insoluble impurities and ensure that crystals do not form in the filter paper
63
Why is the solution cooled in an ice bath when purifying by recrystallisation ?
To ensure that as many crystals as possible fall out of solution - yield is higher
64
Why are the crystals washed with cold water when purifying by recrystallisation ?
To remove soluble impurities
65
How would you separate the crystals from the reaction mixture when purifying by recrystallisation ?
Filter under reduced pressure using a Buchner funnel
66
Why may the %yield of purifying by recrystallisation be below 100% ?
*Product is lost during filtration, drying and weighing - not all product is transferred from one piece of equipment to another *Product is left dissolved in the solution - some does not crystalise *Some is left on filter paper.

AQA A Level Chemistry (26 decks)

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