Photo AI
The aldehyde CH₃CH₂CH₂CHO reacts with KCN followed by dilute acid to form a racemic mixture of the two stereoisomers of CH₃CH₂CH(OH)CH(CN)N - AQA - A-Level Chemistry - Question 4 - 2017 - Paper 2
Question 4
The aldehyde CH₃CH₂CH₂CHO reacts with KCN followed by dilute acid to form a racemic mixture of the two stereoisomers of CH₃CH₂CH(OH)CH(CN)N. 0 4.1 Give the IUPAC na... show full transcript
Worked Solution & Example Answer:The aldehyde CH₃CH₂CH₂CHO reacts with KCN followed by dilute acid to form a racemic mixture of the two stereoisomers of CH₃CH₂CH(OH)CH(CN)N - AQA - A-Level Chemistry - Question 4 - 2017 - Paper 2
Step 1
Step 2
Describe how you would distinguish between separate samples of the two stereoisomers of CH₃CH₂CH(OH)CH(CN)N.
Answer
You can distinguish between the two stereoisomers using plane polarized light. One stereoisomer will rotate the plane of polarized light to the right (dextrorotatory) and the other will rotate it to the left (levorotatory). This difference in rotation can be observed using a polarimeter.
Step 3
Explain why the reaction produces a racemic mixture.
Answer
The reaction produces a racemic mixture because the aldehyde reacts with KCN at a carbonyl group that is not planar, allowing the attack of the cyanide ion from either side of the carbonyl carbon. This results in the formation of equal amounts of both stereoisomers, hence a racemic mixture.
Step 4
An isomer of CH₃CH₂CH₂CHO reacts with KCN followed by dilute acid to form a compound that does not show stereoisomerism.
Answer
The structure of the compound formed would be C₄H₉CN with a molecular formula of C₄H₉OH, which does not have a chiral center. Since there is no carbon atom attached to four different groups, it does not exhibit stereoisomerism.
Structure:
C₄H₉OH
Justification: This compound does not contain a chiral center, as it is symmetrical and does not have any carbon atom bonded to four different substituents.