A Level Chemistry Ocr > Module 6 Chapter 26 > Flashcards

Module 6 Chapter 26 Flashcards

(73 cards)

Study These Flashcards
1
Q

What is the carbonyl functional group

A

A group with a carbon double bonded to an oxygen

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What is a feature of the carbon oxygen double bonded

A

Due to electronegativity of O it is a polar bond

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What are the two simplest examples of carbonyls and what are their relative functional groups

A

Aldehydes - DRAW IT

Ketones - DRAW IT

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What are features of aldehydes

A

Where the carbonyl is bonded to at least one hydrogen

Suffix al

Carbon is the carbonyl group

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What are features of ketones

A

Carbonyl bonded to two carbons

Suffix ‘one’

Carbon 1 is the closest to the carbonyl

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

How are carbonyl compounds formed

A

As a result of the oxidation of alcohols
—> where acidified dichromate ions are used as the oxidising agent

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What are the oxidation reactions that primary alcohols undergo

A

Partial oxidation (distillation) forms aldehydes (CHO)

Complete oxidation (reflux) forms carboxylic acids (COOH)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What are the oxidation reactions that secondary alcohols undergo

A

OH is attached to carbon with 2 carbon chains and 1 H atom

Complete oxidation (reflux) forms ketone

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

What can aldehydes be oxidised to and what are the reagents and colour changes

A

They will be oxidised by acidified potassium dichromate
—> forming carboxylic acids

The orange Cr2O7 2- ions are reduced forming green Cr3+

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What are features of the oxidation reactions that ketones can undergo

A

As ketones are difficult to oxidise, so will not undergo the same oxidation reactions therefore there is no colour change.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Therefore how can you identify the difference between an aldehyde or ketone

A

As when heated under reflux with acidified potassium dichromate, it will remain orange if it is a ketone and will turn green if it is an aldehyde.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What causes the reactivity of aldehydes and ketones

A

The nature of the C=O bond
As the C=O bond has both pi bonding and sigma bonding
It is polar

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

What occurs due to the polarity of the C=O bond

A

Aldehydes and ketones can take part nucleophilic attack where a nucleophile attacks a partially positive C resulting in addition across C=O

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What can aldehydes and ketones be reduced to and what is required

A

Their respective alcohols with a reducing agent

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What is the reagent when ketones and aldehydes are reduced

A

Warm sodium tetrahydroborate (III) solution (NaBH4)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

What is the reaction when ethanal is reduced to ethanol

A

CH3CHO + 2[H] —> CH3CH2OH

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

What are and ketones aldehydes reduced to

A

Aldehyde —> Primary alcohol
Ketones —> Secondary alchol

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

What is required for the nucleophilic addition of aldehydes and ketones

A

NaBH4 which releases a hydride ion (H-) that act as nucleophiles and attack the electron deficient carbon atom in the C=O bond

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

What does the H- ion do in nucleophilic addition

A

Donating a pair of electrons making a dative bond
At the same time the pi bond of the carbonyl breaks

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

Draw the mechanism for the nucleophilic addition of propanal with NaBH4

A

DRAW IT

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

What happens after the intermediate anion forms in nucleophilic addition

A

The intermediate anion that forms donates a pair of electrons to a hydrogen on a water molecule, creating a bond, whilst at the same time the O-H bonds breaks.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

What can the anion also donate electrons to apart from water molecules

A

The anion can also donate electrons to a H+ ion from an acid

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

What are the products of the nucleophilic substitution with NaBH4

A

The respective alcohol and a hydroxide ion

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

What can cyanide act as

A

A nucleophile and reduce carbonyl groups so the compound contains:
. A hydroxyl (-OH) group
. A nitrile groups (-C triple bond N)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Draw the reaction between propanone with HCN
DRAW IT
26
Why is HCN used in the nucleophilic substitution
To provide the nucleophile and the hydrogen ion for the hydroxyl group
27
What can be used instead of HCN if the reaction rate is too slow
If the reaction rate is too slow KCN and an acid is often used instead of
28
DRAW THE Mechanism for the nucleophilic addition of HCN to a ketone
DRAW IT
29
What is Brady’s reagent
A solution of 2,4-dinitrophenylhydrazine in a mixture of methanol and H2SO4
30
What does Brady’s reagent do
The amine group (-NH2) of the 2,4-DNP reacts with the carbonyl groups to form a N=C bond A positive result is a yellow/orange precipice (2-4DNP/H), confirming the presence of a carbonyl.
31
DRAW the reaction between Brady’s reagent and an aldehyde
DRAW IT
32
What is Tollen’s reagent used for
It is used to determine whether an aldehyde or ketone is present
33
How is Tollen’s reagent made
1. Adding NaOH to AgNO3 making a brown precipitate of Ag2O(s) 2. Dilute NH3 is added till the Ag2O dissolves forming Ag(NH3)2 (aq)
34
How does Tollen’s reagent differentiate between aldehydes and ketones
It is a weak oxidising agent so can only oxidise aldehydes to form a carboxylic acid and silver metal .Silver mirror is formed
35
How can you use DNP to identify between different isomers of carbonyls
the precipitate is purified by recrystallisation 1. Filtered then dissolved in minimum warm solvent 2. Cooled to cause precipitation then filtered again Melting point apparatus is then used to determine the identity of the 2,4-DNP derivative.
36
What are carboxylic acids
They contain the -COOH functional group and are prepared by the oxidation of primary alcohols under reflux
37
How are carboxylic acids named
They are given the suffix (-oic acid) Carbonyl carbon atom is always carbon -1
38
Why do carboxylic acids act differently to aldehydes and ketones
Due to the O-H group attached to the carbon that the C=O group is attached to
39
What is a feature of carboxylic acids (polarity)
As the C=O groups and OH are both polar, carboxylic acids experience dipole-dipole interactions, as well as being able to form hydrogen bonds so have high boiling points. The ability to form hydrogen bonds allows them to dissolve in water, but their solubility decreases as the chain length increases.
40
When are CA no longer soluble non water
CA with up to 4 carbons are soluble in water, and those beyond are not
41
What occurs to CA in the absence of water
They can form hydrogen bonds with other carboxylic acids to form dimers
42
Draw a diner
43
What is a feature of CA (Acids)
They are able to partially dissociate the hydrogen from the OH bond, so can act as weak acids. HCOOH <-> H+ + HCOO-
44
What occurs when carboxylic acids react with bases
The negative ion carboxylate will accept a cation to form a salt
45
As carboxylic acids are weak acids what does this mean
They are able to react in a similar way. All under REDOX reactions with metals and neutralisation reactions
46
What are carboxylic acid derivates
A compound that can be hydrolysed to form the parent carboxylic acid
47
What is the common sequence of atoms in all carboxylic acid derivates
The acyl group
48
What are examples of CA derivates
Esters, acyl chlorides, acid anhydrides and amides
49
Draw the different CA acid derivates labelling the acyl group and electronegative group
50
What are esters
Compounds that contain the function group COO (an ester linkage)
51
How are esters formed
By reacting an alcohol with carboxylic acid in the presence of a H2SO4 catalyst This is known as esterification
52
Draw the reaction between methanol and methanoic acid
DRAW IT
53
How do you name an ester
The alcohol becomes the prefix and is now named like an acyl chain, and the carboxylic acid gains the -oate suffix
54
What are esters hydrolysed to form
To get back to CA and alcohol acid hydrolysis of an ester is the reverse of esterification Ester is heated under reflux with dilute aqueous acid Ester is broken down by water, with acid acting as a catalyst
55
What is acid hydrolysis the reverse of
Eserification
56
How is ester hydrolysis done in practical
Ester is heated under reflux with dilute aqueous acid Ester is broken down by water, with acid acting as a catalyst
57
How is ester hydrolysis done with NaOH
This can be done by refluxing the ester under: Alkaline conditions (NaOH) to form an alcohol and carboxylate salt.
58
What is features of refluxing esters with NaOH
Aka saponification and this is irreversible
59
What is the reaction between ethyl proponoate and NaOH
DRAW IT
60
Why does the acid formed do
It reacts with eh hydroxide to form a salt.
61
When do carboxylic acids form acyl halides
When they react with sulfur dichloride oxide (thionyl chloride).
62
What is the general reaction between a carboxylic acid and SoCl2
RCOOH + SoCl2 —> RCOCL + SO2 + HCL
63
Because acyl halides and SoCL2 both react with water wash at is a feature of the reaction
The reaction must be carried out under anhydrous conditions. The two gases that evolve are also harmful so this is done in a fume hood.
64
Why do the acyl halides need to be stored
It needs to be stored carefully carefully as they form pungent vapours in air and easily break down.
65
What are the reactions of acyl chlorides
They react with nucleophiles and lose the chlorine ion but keep C=O RCOCl + H-R —> RCOR + HCL Reactions include: Water = carboxylic Alcohols/phenol Ammonia/amide = amide
66
What is a feature of all the reactions of nucleophiles and acyl chlorides
They are not reversible and so the yield is higher than that of conventional reaction pathways
67
Why are a acyl chlorides useful
As they can be used for producing other chemicals such as esters, via elimination reactions.
68
What are acid anhydrides
They are dehydrated carboxylic acids
69
What is the reaction between 2 ethanoic acid
DRAW IT
70
What do acid anhydrides react with to form esters
Alcohols and phenols and gentle heating is required, it is also not a reversible reaction
71
What is the reaction between the simplest acid anhydride and methanol
DRAW IT
72
What is the reaction between acyl chloride + ammonia
DRAW IT
73
What is the reaction acylchloride + CH3NH2
DRAW IT
A Level Chemistry Ocr
flashcards
Decks in class (32)
# Cards
Brainscape helps you reach your goals faster, through stronger study habits.
© 2026 Bold Learning Solutions. Terms and Conditions