OAT Organic Chemistry Reactions 3

Question 1

Which reaction converts an aldehyde to a cyanohydrin?

Accepted Answer

Addition of HCN

Answer

HCN adds to the carbonyl of an aldehyde via nucleophilic addition to produce a cyanohydrin (α-hydroxy nitrile).

Question 2

Which of the following is the best description of Markovnikov's rule for HBr addition to propene?

Accepted Answer

Br adds to the more substituted carbon

Answer

Markovnikov's rule states the halide (nucleophile) adds to the more substituted carbon, forming the more stable carbocation intermediate.

Question 3

What reagent is used in ozonolysis to work up the ozonide and obtain aldehydes rather than carboxylic acids?

Accepted Answer

Zn/H2O (reductive workup)

Answer

Reductive workup with Zn and H2O (or Me2S) cleaves the ozonide to give aldehydes, preventing further oxidation.

Question 4

In the aldol condensation, what type of intermediate is formed in the first step under basic conditions?

Accepted Answer

Enolate ion

Answer

Base removes an α-hydrogen to form an enolate, which then acts as the nucleophile attacking the carbonyl of another molecule.

Question 5

Which reaction mechanism is involved in the saponification of an ester?

Accepted Answer

Nucleophilic acyl substitution with OH⁻

Answer

Saponification proceeds via nucleophilic acyl substitution where hydroxide attacks the carbonyl carbon, forming a tetrahedral intermediate that expels the alkoxide.

OAT - Optometry Admission Test Practice Test

OAT - Optometry Admission Test Practice Test

OAT Organic Chemistry Reactions 3