PCAT Organic Chemistry 2

Question 1

Which reagent converts a primary alcohol to an aldehyde without over-oxidizing to a carboxylic acid?

Accepted Answer

PCC (pyridinium chlorochromate)

Answer

PCC oxidizes primary alcohols to aldehydes and stops there because it is a mild oxidant used in non-aqueous conditions.

Question 2

What is the major product when 2-butene undergoes acid-catalyzed hydration?

Accepted Answer

2-butanol

Answer

Markovnikov addition of water across the double bond of 2-butene places the OH on the more substituted carbon, giving 2-butanol.

Question 3

Which spectroscopic feature is most diagnostic for a carbonyl group (C=O) in IR spectroscopy?

Accepted Answer

Strong absorption near 1700 cm⁻¹

Answer

The C=O stretch appears as a strong, sharp absorption near 1700 cm⁻¹ (exact position varies with functional group).

Question 4

In an E2 elimination reaction, the hydrogen and leaving group must be in what geometric relationship?

Accepted Answer

Anti-periplanar

Answer

E2 requires a concerted, single-step mechanism where H and the leaving group must be anti-periplanar (180°) to allow orbital overlap.

Question 5

Which of the following compounds is aromatic?

Accepted Answer

Pyridine

Answer

Pyridine is aromatic because it is planar, fully conjugated, and has 6 π electrons (4n+2, n=1) satisfying Hückel's rule.

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