CPC CPC Organic Chemistry & Synthesis 1 â Questions and Answers
Question 1: Which reaction mechanism involves the simultaneous breaking and forming of bonds in a single concerted step?
- SN1
- SN2 (Correct answer)
- E1
- E1cb
Correct answer: SN2
SN2 (bimolecular nucleophilic substitution) proceeds via a concerted mechanism with simultaneous bond breaking and formation in one transition state.
Question 2: In a Diels-Alder reaction, the diene must be in which conformation for the reaction to proceed?
- s-trans
- s-cis (Correct answer)
- anti-periplanar
- gauche
Correct answer: s-cis
The diene must adopt the s-cis conformation so that both double bonds can overlap simultaneously with the dienophile's Ï system.
Question 3: Which reagent is most commonly used to reduce an aldehyde to a primary alcohol?
- NaBH4
- LiAlH4
- H2/Pt
- NaBH4 or LiAlH4 (Correct answer)
Correct answer: NaBH4 or LiAlH4
Both NaBH4 and LiAlH4 can reduce aldehydes to primary alcohols, with NaBH4 being milder and LiAlH4 being more powerful.
Question 4: What is the product of ozonolysis of a terminal alkene followed by reductive workup (Me2S)?
- Carboxylic acid and formaldehyde
- Ketone and water
- Aldehyde and formaldehyde (Correct answer)
- Diol
Correct answer: Aldehyde and formaldehyde
Reductive workup of a terminal alkene ozonolysis yields an aldehyde from the internal carbon and formaldehyde from the terminal CH2.
Question 5: Which of the following best describes a Grignard reagent acting as a nucleophile?
- Electrophile attacking a carbonyl
- Carbon-metal bond donating electrons to an electrophile (Correct answer)
- Proton donor to a base
- Radical species reacting with oxygen
Correct answer: Carbon-metal bond donating electrons to an electrophile
Grignard reagents (RMgX) act as nucleophiles because the polarized CâMg bond makes the carbon electron-rich, allowing it to donate electrons to electrophiles.
Question 6: Which protecting group is selectively removed under acidic conditions to reveal an alcohol?
- TBS (tert-butyldimethylsilyl)
- THP (tetrahydropyranyl) (Correct answer)
- Bn (benzyl)
- Cbz
Correct answer: THP (tetrahydropyranyl)
THP ethers are acid-labile and are selectively cleaved by dilute acid to reveal the free alcohol.
CPC CPC Organic Chemistry & Synthesis 1
Which reaction mechanism involves the simultaneous breaking and forming of bonds in a single concerted step?