OAT Organic Chemistry Reactions Questions and Answers

Question 1

Which of the following reagents is most suitable for oxidizing a primary alcohol, such as 1-butanol, directly to a carboxylic acid, butanoic acid, in a single step?

Accepted Answer

Potassium permanganate (KMnO₄)

Answer

Strong oxidizing agents are required to convert a primary alcohol directly to a carboxylic acid. Potassium permanganate (KMnO₄) is a powerful oxidizing agent capable of this transformation. PCC and DMP are considered 'weak' oxidants that will oxidize a primary alcohol only to the aldehyde stage. LiAlH₄ is a reducing agent, not an oxidizing agent.

Question 2

In an electrophilic aromatic substitution reaction, which of the following substituents on a benzene ring would direct an incoming electrophile primarily to the meta position?

Accepted Answer

–NO₂ (Nitro)

Answer

The nitro group (–NO₂) is a strong electron-withdrawing group, which deactivates the benzene ring towards electrophilic attack. Deactivating groups direct incoming electrophiles to the meta position. The hydroxyl (–OH), methyl (–CH₃), and amino (–NH₂) groups are all electron-donating, activating groups that direct incoming electrophiles to the ortho and para positions.

Question 3

A student treats acetone (propanone) with methylmagnesium bromide (CH₃MgBr), followed by an acidic workup with H₃O⁺. What is the major organic product of this reaction sequence?

Accepted Answer

tert-Butanol (2-methyl-2-propanol)

Answer

This is a Grignard reaction. The nucleophilic methyl group from the Grignard reagent attacks the electrophilic carbonyl carbon of acetone. This forms a magnesium alkoxide intermediate. The subsequent acidic workup protonates the alkoxide to yield the final product. Since acetone is a ketone, the product will be a tertiary alcohol. The addition of a methyl group to acetone's three carbons results in tert-butanol.

Question 4

The reaction of (2E,4E)-hexa-2,4-diene with maleic anhydride is a classic example of which type of reaction?

Accepted Answer

Diels-Alder Cycloaddition

Answer

The Diels-Alder reaction is a [4+2] cycloaddition that occurs between a conjugated diene (the 4π electron component) and a dienophile (the 2π electron component) to form a six-membered ring. (2E,4E)-hexa-2,4-diene is a conjugated diene, and maleic anhydride is a classic dienophile, making this a Diels-Alder reaction.

Question 5

When 2-bromopropane is treated with sodium ethoxide (NaOEt) in ethanol, two products are formed via competing reaction pathways. Which statement best describes the expected outcome?

Accepted Answer

The SN2 product, 2-ethoxypropane, and the E2 product, propene, will both be formed.

Answer

2-bromopropane is a secondary alkyl halide. Sodium ethoxide is a strong nucleophile and also a strong, non-bulky base. With a secondary substrate and a strong nucleophile/base, both SN2 and E2 reactions will occur competitively. The SN2 pathway yields 2-ethoxypropane, and the E2 pathway yields propene. Neither pathway is typically exclusive under these conditions.

OAT - Optometry Admission Test Practice Test

OAT - Optometry Admission Test Practice Test

OAT Organic Chemistry Reactions Questions and Answers