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Organic Chemistry > Carboxylic Acids > Flashcards

Carboxylic Acids Flashcards

(98 cards)

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1
Q

What is the functional group of a carboxylic acid?

A

-COOH

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2
Q

How are carboxylic acids formed?

A

Oxidising primary alcohols under reflux

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3
Q

Which carboxylic acids are more soluble?

Why?

A

Those with a lower Mr

The -COOH forms hydrogen bonds with water

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4
Q

Why are carboxylic acids only weak acids?

A

They only slightly dissociate in water

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5
Q

How is a carboxylate ion formed?

A

The carbonyl group attracts e- away from the -OH group which leads to the -OH bond being weakened so a proton is easily lost

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6
Q

Why are alcohols not acidic?

A

The -OH bond does not easily break

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7
Q

How does adding a halogen to a carboxylic acid affect the pH?

Eg chloroethanoic acid

A

Chlorine atom is more electronegative so withdraws e- density away from the carbonyl carbon. This causes the O-H bond to become more polar and weaken.
More H+ is therefore released, decreasing the pH

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8
Q

What is more acidic: ethanoic acid or chloroethanoic acid

Why?

A

chloroethanoic acid

Cl pulls e- towards itself

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9
Q

How are acyl chlorides formed?

A

The -OH group of the carboxylic acid is replaced by a chlorine atom

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10
Q

Why is the carbon atom in acyl chlorides readily attacked by nucleophiles?

A

Cl and O are more electronegative than C so the C atom is delta positive

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11
Q

How are acyl chlorides named?

A

It is derived from their corresponding carboxylic acid

Eg ethanoic acid forms ethanoyl Chloride

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12
Q

When there is an -OH in the middle of a carbon chain, how can you refer to it in the name?

A

With ‘hydroxy’

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13
Q

How to form acid anhydrides from carboxylic acids?

A

-OH group is replaced by -OCOR

When two molecules of carboxylic acids join with the elimination of water

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14
Q

How do you name an acid anhydride?

A

The suffix -anhydride replaces the -acid suffix at the end of the carboxylic acid name

If the two C chains are different, write them in alphabetical order

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15
Q

What is a good leaving group?

A

A stable species removed during a chemical reaction

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16
Q

What is the leaving group of acyl chlorides?

What is the by product?

A

Cl-

HCl

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17
Q

What is the leaving group of an acid anhydride?

What is the by product?

A

-OCOR

The corresponding carboxylic acid

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18
Q

Name the mechanism and reaction name for acylation

A

Nucleophilic addition elimination

Reduction

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19
Q

Describe nucleophilic addition elimination

A

Nucleophile attacks the delta positive carbon of the carbonyl group forcing the e- to move from the carbonyl bond to the O making an oxyanion

Carbonyl bond remade causing elimination of the leaving group

Nucleophile loses a H+

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20
Q

How are carboxylic acids formed? (3)

A

1) primary alcohols or aldehydes oxidised by acidified potassium dichromate
2) acyl chlorides react with water (nucleophilic addition elimination)
3) acid anhydrides react with water

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21
Q

Test for carboxylic acids

What is formed?

A

Add Sodium carbonate and CO2 is evolved and fizzing is seen

Ionic salts - these are soluble in water

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22
Q

Name of reaction to form an Ester

What are the reactants?

What is the byproduct?

A

Esterification

Carboxylic acid + alcohol with concentrated H2SO4 (or another strong acid) as a catalyst

Water

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23
Q

What is the isomerism linking esters and carboxylic acids?

A

They are functional group isomers

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24
Q

How do you name an Ester?

A

The alkyl chain of the alcohol is the prefix

The second part of the name is derived from the carboxylic acid - -oic is replaced with -oate

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25
What are the 3 ways to form an Ester?
Esterification Acyl Chlorides reacting with alcohols Acid anhydrides react with alcohols
26
What is the name for the formation of esters from acyl chlorides?
Nucleophilic addition elimination
27
What is esterification?
Mixing a carboxylic acid and an alcohol in the presence of a concentrated H2SO4 catalyst to form an Ester and water
28
What is a base added after the formation of an Ester from acyl chlorides?
To neutralise HCl
29
Why are acyl chlorides preferred to carboxylic acids in the formation of esters?
No acid catalyst required Purer product Yield of Ester is higher as acyl chloride reaction is not reversible
30
What is the mechanism to form an Ester from alcohols and acid anhydrides? What is formed?
Nucleophilic addition elimination An Ester and a carboxylic acid
31
What is the most preferable way to form esters? Why?
From acid anhydrides Acid anhydrides are cheaper They react less exothermically so it is less dangerous Acid anhydrides are less vulnerable to hydrolysis No corrosive HCl is formed
32
What is a major use of ethanoic anhydride? Why is this used over ethanoyl Chloride ?
In aspirin Ethanoic anhydride is cheaper, less corrosive, less vulnerable to hydrolysis, and less dangerous to use
33
What is the method for the re-crystallisation of crude product?
Dissolve sample in a minimum amount of hot solvent Filter hot Cool filtrate in a beaker placed in an ice bath Filter sample using a Büchner funnel Wash thoroughly to remove any SOLUBLE product Alllow product to dry
34
Why do you dissolve the sample in a minimum amount of hot solvent when filtering under pressure/ during recrystallisation?
To Create a saturated solution and increase the yield
35
Why do you filter hot during recrystallising?
To prevent recrystallisation whilst filtering and to remove insoluble impurities
36
Why do you cool the filtrate during recrystallisation?
To increase amount of crystals formed
37
What is the method to test the melting point of the final product of recrystallisation of a crude product?
Use melting point apparatus provided to heat sample gently Heat slowly close to melting point of aspirin If aspirin is pure the sample should melt over 1-2 degrees and should have a melting point close to data book value Impurities will cause melting point to be lower and have a larger range
38
Describe apparatus for filtering under pressure
Wide funnel, with horizontal filter paper, going into sealed Büchner funnel Arm going off to the side leading to a vacuum pump
39
What is hydrolysis?
Breaking up a molecule with H2O or another small molecule
40
What is hydration?
Addition of water
41
What is dehydration?
Elimination of water
42
What is hydrogenation?
Addition of hydrogen
43
What is the reverse of esterification? Describe
The hydrolysis of an Ester Ester is hydrolysed back to their carboxylic acid and alcohol groups using water and dilute sulphuric acid catalyst
44
The hydrolysis of an Ester is a reversible reaction. How do you make the hydrolysis as complete as possible?
Add an excess of water
45
What occurs when an Ester is heated with an alkali? What are the 2 mains steps to finally form a carboxylic acid?
It is hydrolysed to an alcohol and a carboxylate salt ``` Add NaOH to form carboxylate salt Add acid (dilute H2SO4) to form a carboxylic acid ```
46
Why can’t you draw a line between | CH3COO- and Na+?
It is an ionic bond (not covalent) so you have to write them next to each other with their charges showing
47
What is a triglyceride? Where do they occur?
A triester of long chain carboxylic acids (fatty acids) and propane-1,2,3-triol In fats and oils
48
How can triesters be hydrolysed?
Using HOT NaOH to form glycerol and the sodium salts of long chain carboxylic acids
49
What can sodium carboxylate salts be used for?
Soap
50
Why is glycerol useful and for what?
Is has 2 -OH bonds so forms hydrogen bonds very easily in water Cosmetics, food, wine, glues (to prevent materials drying too fast)
51
How to remember that sodium carboxylate salts make soap?
Sibilance: “Sodium SaltS = SoapS”
52
What is a biofuel?
A fuel produced from renewable biological sources
53
What does an Ester + CH3OH (methanol) —>?
Methylester + alcohol
54
Define biodiesel
Liquid fuel consisting of a mixture of methyl esters of long-chain carboxylic acids from vegetable oils
55
What is a possible solution to our reliance on crude oil?
Biodiesel- a renewable fuel formed from crops eg rape seed Rape seed oil is a triglyceride Ester
56
How do you make biodiesel from rape seed oil?
React it with methanol (and a strong acid or alkali as a catalyst) to form a mixture of methyl esters
57
Give the key features of bioethanol
Raw materials: sugar cane Made via fermentation Used as a mixture with petrol for cars Increasingly available in the UK
58
Give the key features of biodiesel
Made from vegetable oil in a reaction with methanol Used in cars, buses etc as a mixture with diesel Can be home made and available at some petrol stations
59
How are amides named?
With the suffix -anamide | Eg propanamide
60
2 ways to form an amide
Acyl chlorides with NH3 | Acid anhydrides with NH3
61
What is the functional group of amides?
R-C=O | NH2
62
Why is an excess of NH3 used in reaction of acyl chlorides with ammonia? Name the mechanism and conditions for this mechanism
To neutralise HCl Nucleophilic addition elimination
63
Mechanism for acid anhydride with NH3
Nucleophilic addition elimination
64
Functional group for N-Substituted Amides
``` R-C=O | N-H | R ```
65
How do you name an N-Substituted Amide?
Using an N-alkyl prefix to indicate alkyl group attached to N only and the suffix “-anamide” to indicate length of C chain attached to carbonyl Eg N-propyl ethanomide
66
How to form N-Substituted Amides using amines
React an acyl chloride or an acid anhydride with an amine Nucleophilic addition elimination
67
What is a biofuel?
A fuel produced from renewable biological sources
68
What does an Ester + CH3OH (methanol) —>?
Methylester + alcohol
69
Define biodiesel
Liquid fuel consisting of a mixture of methyl esters of long-chain carboxylic acids from vegetable oils
70
What is a possible solution to our reliance on crude oil?
Biodiesel- a renewable fuel formed from crops eg rape seed Rape seed oil is a triglyceride Ester
71
How do you make biodiesel from rape seed oil?
React it with methanol (and a strong acid or alkali as a catalyst) to form a mixture of methyl esters
72
Give the key features of bioethanol
Raw materials: sugar cane Made via fermentation Used as a mixture with petrol for cars Increasingly available in the UK
73
Give the key features of biodiesel
Made from vegetable oil in a reaction with methanol Used in cars, buses etc as a mixture with diesel Can be home made and available at some petrol stations
74
How are amides named?
With the suffix -anamide | Eg propanamide
75
2 ways to form an amide
Acyl chlorides with NH3 | Acid anhydrides with NH3
76
What is the functional group of amides?
R-C=O | NH2
77
Why is an excess of NH3 used in reaction of acyl chlorides with ammonia? Name the mechanism and conditions for this mechanism
To neutralise HCl Nucleophilic addition elimination
78
Mechanism for acid anhydride with NH3
Nucleophilic addition elimination
79
Functional group for N-Substituted Amides
``` R-C=O | N-H | R ```
80
How do you name an N-Substituted Amide?
Using an N-alkyl prefix to indicate alkyl group attached to N only and the suffix “-anamide” to indicate length of C chain attached to carbonyl Eg N-propyl ethanomide
81
How to form N-Substituted Amides using amines
React an acyl chloride or an acid anhydride with an amine Nucleophilic addition elimination
82
What is a biofuel?
A fuel produced from renewable biological sources
83
What does an Ester + CH3OH (methanol) —>?
Methylester + alcohol
84
Define biodiesel
Liquid fuel consisting of a mixture of methyl esters of long-chain carboxylic acids from vegetable oils
85
What is a possible solution to our reliance on crude oil?
Biodiesel- a renewable fuel formed from crops eg rape seed Rape seed oil is a triglyceride Ester
86
How do you make biodiesel from rape seed oil?
React it with methanol (and a strong acid or alkali as a catalyst) to form a mixture of methyl esters
87
How do you name an N-Substituted Amide?
Using an N-alkyl prefix to indicate alkyl group attached to N only and the suffix “-anamide” to indicate length of C chain attached to carbonyl Eg N-propyl ethanomide
88
How to form N-Substituted Amides using amines
React an acyl chloride or an acid anhydride with an amine Nucleophilic addition elimination
89
Functional group for N-Substituted Amides
``` R-C=O | N-H | R ```
90
Mechanism for acid anhydride with NH3
Nucleophilic addition elimination
91
Why is an excess of NH3 used in reaction of acyl chlorides with ammonia? Name the mechanism and conditions for this mechanism
To neutralise HCl Nucleophilic addition elimination
92
What is the functional group of amides?
R-C=O | NH2
93
2 ways to form an amide
Acyl chlorides with NH3 | Acid anhydrides with NH3
94
How are amides named?
With the suffix -anamide | Eg propanamide
95
Give the key features of biodiesel
Made from vegetable oil in a reaction with methanol Used in cars, buses etc as a mixture with diesel Can be home made and available at some petrol stations
96
Give the key features of bioethanol
Raw materials: sugar cane Made via fermentation Used as a mixture with petrol for cars Increasingly available in the UK
97
What is the functional group of acid anhydrides?
``` R | C=O | O | C=O | R ```
98
What is the functional group of esters?
``` R | C=O | OR ```

Organic Chemistry (12 decks)

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