Q: Which of the following pairs contains the stronger nucleophile in aqueous solution?

$\mathrm{HO^-}$$\text{ vs. }$$\mathrm{H_2O}$: $\mathrm{HO^-}$

Q: Which rule must be observed so that Fischer projections stand for certain three-dimensional structures?

Horizontal lines represent bonds projecting out of the plane toward the viewer.

Question 1

Which of the following best describes the first mechanistic step in the aldol reaction between two molecules of butanal in alkaline solution?

Accepted Answer

Deprotonation of the alpha hydrogen by hydroxide to form an enolate ion.

Question 2

Which of the following is the correct IUPAC name for the compound with the structure $\mathrm{CH_3CH_2COCH_2CH_3}$?

Accepted Answer

2-pentanone

Question 3

When assigning R/S configuration to a chiral center, which step comes first?

Accepted Answer

Assign priorities to the four substituents based on atomic number.

Question 4

Which reagent would you use to oxidize the aldehyde group of 3-hydroxy-2-methylpropanal to a carboxylic acid?

Accepted Answer

Potassium permanganate ($\mathrm{KMnO_4}$)

Question 5

Which of the following pairs contains the stronger nucleophile in aqueous solution?

Accepted Answer

$\mathrm{HO^-}$$	ext{ vs. }$$\mathrm{H_2O}$: $\mathrm{HO^-}$

Question 6

A solution of (S)-2-chlorobutane is reacted with NaOH, and the produced alcohol is optically active. Which mechanism is most likely responsible for this result?

Accepted Answer

An $\mathrm{S_N2}$ mechanism, because it inverts the configuration at the chiral center.

Question 7

Arrange the following compounds in order of decreasing boiling point: 1-butanol, ethyl acetate, isopropyl acetate, 2-methyl-1-propanol, propanoic acid.

Accepted Answer

Propanoic acid > 1-butanol > 2-methyl-1-propanol > ethyl acetate > isopropyl acetate

Question 8

Which of the following compounds is expected to be the most acidic?

Accepted Answer

Benzenesulfonic acid

Question 9

Which statement about geometric isomers of alkenes is correct?

Accepted Answer

They are configurational isomers because they cannot be interconverted without breaking a bond.

Question 10

Which of the following correctly describes the difference between the $\sigma$-bond and the $\pi$-bond in a double bond?

Accepted Answer

The $\sigma$-bond is formed by head-on overlap of orbitals, while the $\pi$-bond is formed by side-on overlap.

Question 11

What is the product of the hydrolysis of N-methylacetamide in aqueous acid?

Accepted Answer

Acetic acid and methylamine

Question 12

What is another name for the amide bond between two amino acids?

Accepted Answer

Peptide bond

Question 13

Which atom in the side chain of arginine is the most basic?

Accepted Answer

The nitrogen atom in the guanidino group ($\mathrm{=NH}$)

Question 14

Which pH range is necessary to have 90% of arginine fully protonated, given its p$K_a$ values of 2.0, 9.0, and 12.1?

Accepted Answer

pH < 2.0

Question 15

Which rule must be observed so that Fischer projections stand for certain three-dimensional structures?

Accepted Answer

Horizontal lines represent bonds projecting out of the plane toward the viewer.

Question 16

Why does the $\beta$-anomer of D-galactopyranose predominate in equilibrium, but only with 68%?

Accepted Answer

The $\beta$-anomer is more stable due to the equatorial position of the anomeric hydroxyl group, but steric and electronic factors limit its predominance.

Question 17

Which statement about enantiomers is correct?

Accepted Answer

Enantiomers are stereoisomers and mirror images of each other.

Question 18

Which statement about aromatic structures is correct?

Accepted Answer

Aromatic structures must be cyclic and composed of carbon atoms.

Question 19

Which statement about resonance is correct?

Accepted Answer

Resonance means the delocalization of $\pi$-electrons.

Question 20

Which statement about protein structure is correct?

Accepted Answer

Disulfide bridges result from the oxidation of thiol groups.

Organic Chemistry Exam Study Guide: Mechanisms, Structures, and Concepts

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