Brainscape's Knowledge GenomeTM


Top Flashcards (Certified)
All Flashcards

A Level - Chemistry > 17: Chirality and Carbonyls > Flashcards

17: Chirality and Carbonyls Flashcards

(70 cards)

Start Studying
1
Q

Define optical isomers

A

Isomers of which one is the non-superimposable mirror image of the other

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

What is chirality caused by?

A

A carbon with 4 different groups attached to it

Called a chiral centre

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

What are optical isomers known as?

A

Enantiomers

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

Why are chiral molecules known as optical isomers?

A

The isomer can rotate the plane of polarisation of plane-polarised monochromatic light

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

Define a racemic mixture

A

A solution containing equal amounts of 2 isomers

Does not rotate plane of plane-polarised monochromatic light

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

Compare and contrast enantiomers

A

Identical physical and chemical properties

React differently with plane-polarised light

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

What is the structure of an aldehyde functional group?

A

Carbon bonded to a H, double bond O, and a R group

Found on the end of a chain

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

What is the structure of a ketone functional group?

A

Carbon with a double O bond, and two R groups

Found in the middle of a carbon chain

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

What is significant about a carbon oxygen double bond?

A

Oxygen is more electronegative, causes a polar bond

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

Why can aldehydes and ketones not hydrogen bond with each other?

A

No hydrogen atoms bonded to the oxygen atoms

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

Are ketones and aldehydes soluble in water?

A

Small aldehydes and ketones are soluble in water

Solubility decreases as carbon chain increases

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

Why are only small carbonyls soluble in water?

A

They can hydrogen bond with water molecules
Hydrocarbon tails are hydrophobic
Solubility breaks hydrogen bonding in water, and if they are not replaced by strong inter molecular bonds then it will be insoluble
Hydrocarbon chains only have id-id so the longer, the less soluble

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

What is the main form of reactions carbonyls undergo and why?

A

Nucleophillic addition
Condensation
Due to 𝛿+ carbon atom attracting nucleophiles

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

What is the test for a carbonyl group?

A

Adding 2,4-DNP
Forms yellow crystals (2,4-dinitrophenylhydrazone crystals)
Condensation reaction

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

What are the 3 oxidation tests for aldehydes (not ketones)?

A

Tollens reagent - ammonial silver nitrate
Fehlings solution - copper 2+ ions
Acidified dichromate - H+/Cr2O7 2-

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

Why are oxidation tests used to test for aldehydes not ketones?

A

Aldehydes can be further oxides ex to carboxylic acids

Ketones cannot be futher oxidised

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

How is tollens reagent formed?

A

Ag+ + 2NH3 -> Ag[NH3]2 +

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

What are the half equations for the tollens reagent in presence of an aldehyde?

A

R-CHO + H2O -> R-COOH + 2e + 2H+
Ag+ + e -> Ag

Combined:
R-CHO + H2O + 2Ag+ -> R-COOH + 2Ag + 2H+

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

What is observed in the Tollens reagent test in the presence of an aldehyde?

A

A silver mirror will form on the inside of the test tube

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

What is in fehlings solution?

A

Solution of Cu2+ ions

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

What is reduced in the Fehlings test?

A

Cu2+ -> Cu+

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

What are the half equations for the Fehlings test?

A

R-CHO + H2O -> R-COOH + 2e + 2H+
2Cu2+ + H2O + 2e -> Cu2O + 2H+

Combined:
R-CHO + 2H2O + 2Cu -> R-COOH + Cu2O+ 4H+

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

What is the colour change if acidified potassium dichromate is in solution with an aldehyde?

A

Orange to green

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

What is the change in oxidation state when potassium dichromate is oxidised?

A

Cr6+ -> Cr3+

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
What is the half equation for potassium dichromate reacting with an aldehyde?
Cr2O7 2- + 14H+ + 6e -> 2Cr 3+ + 7H2O R-CHO + H2O -> R-COOH + 2e + 2H+ Combined: 3R-CHO + Cr2O7 2- + 8H+ -> 3R-COOH + 2H2O + 2Cr 3+
26
How does the increase of chain length effect the oxidation of an aldehyde?
Slower they react | The aldehydes have less reducing power
27
Why do ketones not give a positive result in reducing tests?
They cannot be oxidised easily
28
What is the iodoform (triiodomethane) test?
Tests for the methyl carbonyl and methyl OH groups
29
What are the reagents in the iodoform test?
Iodine and sodium hydroxide
30
What is the sign for a positive iodoform test?
CHI3 - Pale yellow precipitate | Antiseptic smell
31
What is the equation for the iodoform test?
R-CHO + 3I2 + 4NaOH -> CHI3 + HCOO-Na+ + 3NaI + 3H2O
32
What is produced when cyanide and hydrogen cyanide is added to a carbonyl?
Carbonyl -> organic compound with a cyandide and alcohol
33
What are the steps in the nucleophillic addition of cyanide to a ketone?
Lone pair on CN- attacks 𝛿+ Carbon One of double bond breaks and both electrons goes to the Oxygen Lone pair on oxygen forms bond with Hydrogen from HCN CN- ion and organic product is left
34
What can the product of the addition of cyanide be converted into?
Anime - LiAlH4 and dry ether | Carboxylic acid - H2O/H+
35
What is LiAlH4 and what does it do?
Lithium aluminium hydride Reduces C=O bond to OH Reduces CN bond to NH2
36
What is the first step in the addition of HCN to a carbonyl?
Attack by CN- of 𝛿+ on C=O
37
What are the similarities and differences of enantiomers?
Same molecular formula Same structural formula Atoms in different position in 3D space
38
Why is SN2 called this?
SN - Nucleophillic substitution | 2 - 2 species involved in the first step
39
What happens to optical isomers in an SN2 reaction?
The molecule will retain its chirality
40
What type of halogenoalkanes undergo SN2?
Primary
41
What type of halogenoalkanes undergo SN1?
Tertiary
42
What is the effect of SN1 reactions on optical isomers?
Racemic mix is formed | Intermediate is trigonal planar so the nucleophile can be added on either side
43
What is the effect of the SN2 mechanism on optical isomers?
No effect on optical isomers | Single enantiomer reactant produces single enantiomer product
44
What is the difference between addition and condensation polymerisation?
Addition - All monomer atoms present in polymer | Condensation - Water lost
45
What are the typical monomers of condensation polymerisation?
Diol + dicarboxylic acids
46
How are carboxylic acids arranged without water?
Dimers - hydrogen bond with another carboxylic acid
47
How is a carboxylic acid produced from a nitrile?
Reflux with dilute acid in aqueous environments
48
What is the general formula for the production of carboxylic acids from nitriles?
R-CN + H2O + H+ -> R-COOH + NH4+
49
How do carboxylic acid reaction with sodium hydroxide?
Acid + Alkali -> Salt + Water | R-COOH + NaOH -> R-COO- Na+ + H2O
50
How do carboxylic acids react with alcohols?
Carboxylic acid + Alcohol -> Ester + Water | Presence of acid catalyst needed - conc sulphuric acid
51
What is the reaction type of the formation of a ester?
Esterification - Adddition elimination
52
What are the conditions for esterification?
Heated with acid catalyst (sulphuric acid) | Slow and reversible reaction
53
How are esters named?
Take name of alcohol and replace "anol" with "yl" | Second word is carboxylic acid, replace "oic" with "anoate"
54
What occurs in the reaction between LiAlH4 and carboxylic acids?
Carboxylic acid + H- -> Alcohol (OH) | Organic solvent - dry ether
55
How does LiAlH4 work?
H- ion acts as a nucleophile | Will reduce water so organic solvent must be used
56
How are esters made into alcohols and carboxylic acids?
Hydrolysed
57
How are acyl chlorides formed?
R-COOH + PCl5 -> R-OCl + POCl3 + HCl | Releases steamy fumes of HCl
58
How can the presence of HCl fumes be confirmed?
Will produce white smoke in presence of ammonia | Forms ammonium chloride
59
What is the functional group of acyl chlorides?
R-O-Cl
60
How do acyl chlorides typically react?
Nucelophilic substitution
61
What is produced when acyl chlorides react with water?
Carboxlyic acid + HCl
62
What is the defining property of acyl chlorides?
High reactivity Caused by large difference in electronegativity between Cl and C - draws electrons away creating a larger positive charge
63
What is a common alternative to acyl chlorides?
Ethanoic anhydride
64
What is the problem when acyl chlorides being used as a reactant?
Toxic fumes produced | Fume cupboard should be used
65
Which bonds are broken and made in esterification?
Broken: C-O, O-H Made: C-O, O-H
66
How do esters react with NaOH?
R-O-R' + NaOH -> RCOONa + R'-OH
67
What is produced when acyl chlorides react with alcohols (OH)?
Ester + HCl
68
What is produced when acyl chlorides react with amines?
N-substituted amide + HCl
69
What is produced when acyl chlorides react with concentrated ammonia?
Amide + HCl
70
What are the reactions like which involve acyl chlorides?
Vigorous reaction at room temp

A Level - Chemistry (26 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2025 Bold Learning Solutions. Terms and Conditions