Paper 2 2018

Question 1

Which compound is used as a standard for NMR chemical shift measurements?
1. Si(CH3)4
2. CDCl3
3. D2O
4. CCl4

Answer 1

Si(CH3)4

Question 2

Which compound does not react with nucleophiles?
1. CH3CH2CHO
2. CH3CHCH2
3. CH3CH2COCH3
4. CH3CH2CH2Cl

Answer 2

CH3CHCH2

Question 3

Which molecule is not planar?
1. C2H4
2. C2H6
3. H2CO
4. HCN

Answer 3

C2H6

Question 4

What is the number of peaks in the H NMR spectrum of HOOCCH2CHOHCH2COOH?

Answer 4

4

Question 5

Ethanol can be prepared by different reactions. Which reaction has the lowest atom economy?
1. C6H12O6 –> 2C2H5OH + 2CO2
2. C2H4 + H2O –> C2H5OH
3. C2H5Br + H2O –> C2H5OH + HBr
4. CH3COOC2H5 + H2O –> C2H5OH + CH3COOH

Answer 5

C2H5Br + H2O –> C2H5OH + HBr

Question 6

The breakdown of ozone is catalysed by NO radicals. Which equation is a propagation step in the mechanism for this process?
1. NO + O2 –> N + O3
2. NO + O2 –> NO2 + O
3. N + O3 –> NO + O2
4. NO2 + O –> NO + O2

Answer 6

NO2 + O –> NO + O2

Question 7

Benzene reacts with an organic reagent in the presence of a halogen carrier to form phenyl-ethanoate. What organic reagent is required?

Answer 7

CH3COCl

Question 8

How many straight-chain structural isomers of C7H15Cl contain a chiral carbon atom?

Answer 8

2

Question 9

Which statement(s) support(s) the delocalised model for the structure of benzene?
1. All carbon-carbon bonds have the same length.
2. The enthalpy change of hydrogenation of benzene is less exothermic than expected.
3. Bromine reacts with benzene less readily than with cyclohexene.

Answer 9

1, 2 and 3

Question 10

A solid organic compound can be purified by recrystallisation. Which statement(s) about recrystallisation is/are true?
1. The organic compound is more soluble in hot solvent.
2. The hot solution is cooled before the purified organic compound is collected.
3. The melting point of the purified organic compound is lower than the impure compound.

Answer 10

Only 1 and 2

Question 11

What is the structural formula of 3-methyl-butan-2-ol?

Answer 11

(CH3)2CHCHOHCH3

Question 12

3-methyl-butan-2-ol is heated with an acid catalyst. Suggest the names of two alkenes formed.

Answer 12

• 3-methyl-butene
• 2-methyl-but-2-ene

Question 13

3-methyl-butan-2-ol is heated with sodium chloride and sulfuric acid. Construct a balanced equation for this reaction.

Answer 13

3-methyl-butan-2-ol + NaCl + H2SO4 –> 3-methyl-2chlor-butane + NaHSO4 + H20

Question 14

3-methyl-butan-1,2,3-triol is oxidised to form a single organic product. Suggest the name of this product.

Answer 14

• 3-methyl-butan-2-ol _ 3[O] –> 3-methyl-3-hydroxyl-butanal-oic-acid + 2H2O
• 3-methyl-3-hydroxyl-butanal-oic-acid

Question 15

HOOCCH=CHCOOH is reacted with excess CH3OH/H2SO4. What is the organic product formed?

Answer 15

H3COOCCH=CHCOOCH3

Question 16

HOOCCH=CHCOOH is reacted with excess H3PO4/steam. What is the organic product formed?

Answer 16

HOOCCH2CH(OH)(COOH)

Question 17

Phenol undergoes nitration more readily than benzene. A student carries out the nitration of phenol with dilute nitric acid to produce 2-nitrophenol and 4-nitrophenol. A small amount of 3-nitrophenol is also produced. The student thought that 13C NMR spectroscopy could be used to distinguish between these three nitrophenols. Explain whether the student is correct.

Answer 17

• 2-nitrophenol AND 3-nitrophenol have six peaks/environments/types of carbon
• 4-nitrophenol has four peaks/environments/types of carbon
• 4-nitrophenol can be distinguished but 2-nitrophenol and 3-nitrophenol cannot be distinguished

Question 18

Explain why phenol is nitrated more readily than benzene.

Answer 18

• In phenol a (lone) pair of electrons on O is partially delocalised/donated into the pi-system / ring
• Electron density increases/is higher than benzene
• Making phenol more susceptible to electrophilic attack

Question 19

This question is about the hydrolysis of haloalkanes. The rate of hydrolysis of a haloalkane depends on the halogen present. State and explain how the halogen in the haloalkane affects the rate of hydrolysis.

Answer 19

• The weaker the bond the faster the reaction
• Weaker bonds have lower bond enthalpy
• C–F bond is hydrolysed slowest and C–I bond is hydrolysed fastest
• C–I bond is the weakest and C-F bond is the strongest

Question 20

Suggest a suitable chemical test to confirm the presence of an unsaturated carbon chain.

Answer 20

• Br2
• Declourises

Question 21

Describe a chemical test to confirm the presence of an aldehyde functional group.

Answer 21

• Tollens’s reagent
• Silver mirror forms

Question 22

Describe a chemical test to confirm the presence of a carbonyl group. How could the products of the test be used to distinguish the compound?

Answer 22

• Add 2,4-dinitrophenylhydrazine, orange crystal ppt will form
• Take melting point of crystals
• Compare to known values/database

Question 23

Aldehyde to nitrile.

Answer 23

NaCN/H+

Question 24

Aldehyde + NaBH4.

Answer 24

Alcohol

Question 25

Nitrile + H+.

Answer 25

Carboxylic acid

Question 26

Nitrile + H2/Ni

Answer 26

Amine

Question 27

Methylcinnamaldehyde reacts with iodine monochloride, ICI, by electrophilic addition. The reaction produces a mixture containing two different organic products. The electronegativity values of chlorine and iodine are given in the table below: CI = 3.0 I = 2.5 Explain which of the two possible organic products is more likely to be formed.

Answer 27

- C6H5CH(I)C(CHO)(Cl)CH3 = Major - C6H5CH(Cl)C(CHO)(l)CH3 = Minor - Major is more product has the more stable carbonation - I is more electropositive and will act as the electrophile in the reaction, reacting first

Question 28

4-hydroxylbenzoic acid + Na2CO3.

Answer 28

C6H4(OH)(COO-NA+)

Question 29

4-hydroxylbenzoic acid + NaOH.

Answer 29

C6H4(O-Na+)(COO-NA+)

Question 30

4-hydroxylbenzoic acid + Br2.

Answer 30

C6H3(OH)(Br)(COOH)

Question 31

Reagents that turn 4-hydroxylbenzoic acid to acyl chloride.

Answer 31

SOCl2

Question 32

Write an equation for the incomplete combustion of heptane.

Answer 32

C7H16 + 3.5O2 --> 7CO + 8H2O

Question 33

Boiling point: Hexane = 69 Pentan-1-ol = 138 Heptane = 98 Explain the difference in the boiling points.

Answer 33

- Heptane has a longer chain so has more points of contact than hexane = more surface interaction between molecules = stronger/more induced dipole(–dipole) interactions - Pentan-1-ol has hydrogen bonds that are stronger than the induced dipole–dipole interactions of heptane and hexane - More energy required to break forces More energy is required to break induced dipole(–dipole) interactions in heptane than hexane and more energy is required to break hydrogen bonds

Question 34

Fuel additives are often used to improve the combustion of a fuel. Compound N is a fuel additive containing carbon, hydrogen and oxygen only. Complete combustion of 1.71g of compound N produces 2.97 g of CO2 and 1.62g of H2O. The relative molecular mass of compound N is 76.0. Calculate the molecular formula of N and suggest a possible structure for the compound.

Answer 34

- n(CO2) = 2.97/44 = 0.0675 (mol) - n(H2O) = 1.62/18 = 0.0900 (mol) - Ratio of C : H = 3 : 8 - Molecular formula: C3H8O2