OAT Organic Chemistry Reactions 2 — Questions and Answers
Question 1: Which reagent converts an alkene to a vicinal diol via a syn addition mechanism?
- OsO4 followed by NaHSO3 (Correct answer)
- mCPBA
- Br2/H2O
- H2SO4/H2O
Correct answer: OsO4 followed by NaHSO3
OsO4 performs syn dihydroxylation, adding two OH groups to the same face of the alkene.
Question 2: What is the major product when toluene reacts with Cl2 in the presence of FeCl3?
- Benzyl chloride
- Ortho- and para-chlorotoluene (Correct answer)
- Meta-chlorotoluene
- Chlorocyclohexane
Correct answer: Ortho- and para-chlorotoluene
The methyl group is an ortho/para director, so electrophilic aromatic substitution gives predominantly ortho and para products.
Question 3: Which of the following conditions promotes an E1 elimination reaction preferentially?
- Strong base, low temperature
- Weak base, polar protic solvent, high temperature (Correct answer)
- Strong base, polar aprotic solvent
- NaOH in DMSO
Correct answer: Weak base, polar protic solvent, high temperature
E1 is favored by weak bases, polar protic solvents, and elevated temperatures that stabilize carbocation intermediates.
Question 4: What product forms when an ester is treated with excess Grignard reagent followed by aqueous workup?
- Carboxylic acid
- Primary alcohol
- Tertiary alcohol (Correct answer)
- Ketone
Correct answer: Tertiary alcohol
Excess Grignard reacts twice with the ester—first to give a ketone intermediate, then again—yielding a tertiary alcohol.
Question 5: In a Diels-Alder reaction, which diene conformation is required for the reaction to proceed?
- S-trans
- S-cis (Correct answer)
- Anti
- Gauche
Correct answer: S-cis
The diene must adopt the s-cis conformation so both ends can simultaneously bond to the dienophile.
Question 6: Which reagent sequence converts a primary alkyl halide into a primary amine via the Gabriel synthesis?
- Phthalimide/K2CO3, then N2H4 (Correct answer)
- NH3, then LiAlH4
- NaN3, then H2/Pd
- HNO3, then Fe/HCl
Correct answer: Phthalimide/K2CO3, then N2H4
Gabriel synthesis alkylates potassium phthalimide, and hydrazinolysis cleaves the imide to yield the primary amine.
Question 7: What is the stereochemical outcome of an SN2 reaction at a chiral center?
- Retention of configuration
- Inversion of configuration (Correct answer)
- Racemization
- Elimination only
Correct answer: Inversion of configuration
The backside attack mechanism of SN2 results in inversion of configuration (Walden inversion).
OAT Organic Chemistry Reactions 2
Which reagent converts an alkene to a vicinal diol via a syn addition mechanism?