CPC CPC Organic Chemistry & Synthesis 2 — Questions and Answers
Question 1: The Markovnikov addition of HBr to propene predominantly gives which product?
- 1-bromopropane
- 2-bromopropane (Correct answer)
- 1,2-dibromopropane
- Propanol
Correct answer: 2-bromopropane
Markovnikov's rule states that HBr adds so that the H goes to the carbon with more hydrogens, placing the Br on the more substituted (more stable) carbon.
Question 2: Which functional group transformation is achieved by the Wittig reaction?
- Alcohol to alkene
- Carbonyl (aldehyde/ketone) to alkene (Correct answer)
- Alkene to alcohol
- Alkyne to ketone
Correct answer: Carbonyl (aldehyde/ketone) to alkene
The Wittig reaction converts aldehydes or ketones to alkenes using a phosphonium ylide, replacing the C=O with C=C.
Question 3: In electrophilic aromatic substitution, an electron-donating group on a benzene ring directs incoming electrophiles to which positions?
- meta positions
- ortho and para positions (Correct answer)
- ipso position
- All positions equally
Correct answer: ortho and para positions
Electron-donating groups activate the ring and direct electrophiles to the ortho and para positions by stabilizing the arenium ion intermediates at those positions.
Question 4: Which reaction converts a primary amide to a primary amine with one fewer carbon?
- Hofmann rearrangement (Correct answer)
- Curtius rearrangement
- Baeyer-Villiger oxidation
- Beckmann rearrangement
Correct answer: Hofmann rearrangement
The Hofmann rearrangement uses Br2/NaOH to convert a primary amide (RCONH2) to a primary amine (RNH2), losing one carbon as CO2.
Question 5: What type of isomerism is exhibited by cis- and trans-2-butene?
- Constitutional isomerism
- Enantiomerism
- Geometric (cis/trans) isomerism (Correct answer)
- Conformational isomerism
Correct answer: Geometric (cis/trans) isomerism
Cis- and trans-2-butene are geometric isomers (E/Z isomers) that differ in the spatial arrangement of groups around the restricted C=C double bond.
Question 6: Which oxidation state change occurs when a secondary alcohol is oxidized to a ketone using PCC?
- No change in carbon oxidation state
- Carbon is oxidized (loses H, gains O) (Correct answer)
- Carbon is reduced
- Oxidation state changes only at oxygen
Correct answer: Carbon is oxidized (loses H, gains O)
PCC oxidizes the secondary alcohol by removing the hydroxyl hydrogen, increasing the carbon's oxidation state as it forms the ketone C=O.
CPC CPC Organic Chemistry & Synthesis 2
The Markovnikov addition of HBr to propene predominantly gives which product?