Question 1

Which of the following functional groups can be identified in an IR spectrum by a strong, broad absorption around $3300\ \mathrm{cm}^{-1}$?

Accepted Answer

Alcohol

Question 2

A compound shows a molecular ion peak (M$^+$) at $m/z = 86$ in its mass spectrum. Using the 'Rule of 13', what is the most likely molecular formula for this compound?

Accepted Answer

$\mathrm{C}_6\mathrm{H}_{14}$

Question 3

Which of the following statements about $^{13}\mathrm{C}$ NMR spectroscopy is correct?

Accepted Answer

Chemically equivalent carbons give rise to the same peak.

Question 4

In $^1\mathrm{H}$ NMR, a triplet is observed for a particular hydrogen signal. What does this indicate about the hydrogen's environment?

Accepted Answer

It is adjacent to two equivalent hydrogens.

Question 5

Which of the following Newman projections represents the most stable conformation of ethane?

Accepted Answer

Staggered conformation

Question 6

A molecule has the IUPAC name 2-methylbutane. Which of the following is its correct structure?

Accepted Answer

A four-carbon chain with a methyl group on carbon 2

Question 7

Which factor most significantly increases the boiling point of alkanes?

Accepted Answer

Increasing molecular weight (number of carbons)

Question 8

Which of the following best describes a meso compound?

Accepted Answer

A compound with chiral centers that is optically inactive due to an internal plane of symmetry

Question 9

How many stereoisomers are possible for a molecule with two chiral centers, assuming it is not meso?

Accepted Answer

$2^2 = 4$

Question 10

Which of the following statements about enantiomers is correct?

Accepted Answer

They have identical physical properties except for the direction in which they rotate plane-polarized light.

Question 11

A compound has the following $^1\mathrm{H}$ NMR data: a singlet at $\delta = 2.1$ ppm integrating to 3H and a quartet at $\delta = 4.1$ ppm integrating to 2H. Which structure is most consistent with this data?

Accepted Answer

Ethyl methyl ether ($\mathrm{CH}_3\mathrm{OCH}_2\mathrm{CH}_3$)

Question 12

Which of the following is NOT a criterion for a carbon atom to be a chiral center?

Accepted Answer

It is part of a double bond.

Question 13

Which of the following best explains why cyclohexane adopts a chair conformation?

Accepted Answer

To minimize both angle strain and torsional strain

Question 14

A sample of a chiral compound has a specific rotation of $+20^{\circ}$. If the enantiomeric excess (ee) is 60%, what is the percentage of the major enantiomer in the sample?

Accepted Answer

80%

Question 15

Which of the following is true about the IR absorption of a carbonyl group (C=O)?

Accepted Answer

It appears as a strong peak near $1700\ \mathrm{cm}^{-1}$.

Question 16

Which of the following best describes a racemic mixture?

Accepted Answer

A 1:1 mixture of two enantiomers that is optically inactive

Question 17

Which of the following statements about the chemical shift in $^1\mathrm{H}$ NMR is correct?

Accepted Answer

Hydrogens attached to electronegative atoms appear downfield (higher ppm).

Question 18

Which of the following is the correct IUPAC name for the molecule with the structure $\mathrm{CH}_3\mathrm{CH}_2\mathrm{CH}(\mathrm{CH}_3)\mathrm{CH}_2\mathrm{CH}_3$?

Accepted Answer

3-Methylpentane

Question 19

Which of the following best describes the relationship between two molecules that are non-superimposable mirror images of each other?

Accepted Answer

Enantiomers

Question 20

A compound with the formula $\mathrm{C}_4\mathrm{H}_{10}\mathrm{O}$ shows two singlets in its $^1\mathrm{H}$ NMR spectrum. Which structure is most consistent with this data?

Accepted Answer

tert-Butyl alcohol ($\mathrm{(CH}_3)_3\mathrm{COH}$)

Organic Chemistry Study Guide: Spectroscopy, Structure, and Stereochemistry

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