#1: A LEVEL CHEMISTRY OCR A PAPER 2 EXAM Qs
Questions And Answers 2025/2026
Q1 a] >>> This question is about unsaturated hydrocarbons.
Compound A and compound B are isomers. [refer to the PMT QP for the
structures of the compounds]
Compound A has a lower melting point than compound B.
Suggest why [2 marks] - CORRECT ANSWER-- Compound A has more branching
than compound B
- This means that compound A has fewer points of contact between molecules
- This means fewer and weaker induced dipole - dipole interactions between
molecules of compound A
Q2 a] >>> Compound C, CH3CH2CH=CHCH2CH2OH, exists as cis and trans
stereoisomers. Name compound C. - CORRECT ANSWER-Hex-3-en-1-ol
[6 x C for longest chain]
[1x OH on C1]
[1x C = C on C3]
Q2 b] >>> Define the term stereoisomers. - CORRECT ANSWER-Compounds with
the same structural and molecular formula but different arrangements of atoms in
space
, Q3 a] >>> Compound D, shown below, reacts with hydrogen bromide by
electrophilic addition. A mixture of two organic compounds, E and F, is formed.
[refer to the PMT QP for the equation]
Suggest how an HBr molecule can act as an electrophile [1 mark] - CORRECT
ANSWER-The H atom in the HBr molecule accepts a pair of electrons [from the H -
Br bond when it breaks by heterolytic fission]
Q3 b] >>> Draw the structures of the two organic compounds E and F - CORRECT
ANSWER-1. D = 2-methylpent-2-ene
2. E must be 2-methyl-2-bromopentane
3. F must be 2-methyl-3-bromopentane
Q3 c] >>> Outline the mechanism of the reaction between compound D and
hydrogen bromide to form either compound E or compound F.
Include curly arrows and relevant dipoles. - CORRECT ANSWER-
Q3 d] >>> Which of E or F is the major organic product ? Explain your answer. -
CORRECT ANSWER-Major organic product: E
Explanation:
- the bromine attaches to the carbon with the most carbons attached to it
- the tertiary carbocation intermediate is more stable [than the secondary
carbocation intermediate in the formation of F]
Q4 >>> Myrcene, C10H16, is a naturally occurring hydrocarbon containing more
than one carbon-carbon double bond
Questions And Answers 2025/2026
Q1 a] >>> This question is about unsaturated hydrocarbons.
Compound A and compound B are isomers. [refer to the PMT QP for the
structures of the compounds]
Compound A has a lower melting point than compound B.
Suggest why [2 marks] - CORRECT ANSWER-- Compound A has more branching
than compound B
- This means that compound A has fewer points of contact between molecules
- This means fewer and weaker induced dipole - dipole interactions between
molecules of compound A
Q2 a] >>> Compound C, CH3CH2CH=CHCH2CH2OH, exists as cis and trans
stereoisomers. Name compound C. - CORRECT ANSWER-Hex-3-en-1-ol
[6 x C for longest chain]
[1x OH on C1]
[1x C = C on C3]
Q2 b] >>> Define the term stereoisomers. - CORRECT ANSWER-Compounds with
the same structural and molecular formula but different arrangements of atoms in
space
, Q3 a] >>> Compound D, shown below, reacts with hydrogen bromide by
electrophilic addition. A mixture of two organic compounds, E and F, is formed.
[refer to the PMT QP for the equation]
Suggest how an HBr molecule can act as an electrophile [1 mark] - CORRECT
ANSWER-The H atom in the HBr molecule accepts a pair of electrons [from the H -
Br bond when it breaks by heterolytic fission]
Q3 b] >>> Draw the structures of the two organic compounds E and F - CORRECT
ANSWER-1. D = 2-methylpent-2-ene
2. E must be 2-methyl-2-bromopentane
3. F must be 2-methyl-3-bromopentane
Q3 c] >>> Outline the mechanism of the reaction between compound D and
hydrogen bromide to form either compound E or compound F.
Include curly arrows and relevant dipoles. - CORRECT ANSWER-
Q3 d] >>> Which of E or F is the major organic product ? Explain your answer. -
CORRECT ANSWER-Major organic product: E
Explanation:
- the bromine attaches to the carbon with the most carbons attached to it
- the tertiary carbocation intermediate is more stable [than the secondary
carbocation intermediate in the formation of F]
Q4 >>> Myrcene, C10H16, is a naturally occurring hydrocarbon containing more
than one carbon-carbon double bond
