Question 1

A compound with a molecular ion peak (M+) at $$m/z = 86$$ and a significant M+2 peak with an intensity approximately one-third that of the M+ peak is analyzed by mass spectrometry. Which element is most likely present in the compound?

Accepted Answer

Chlorine

Question 2

An IR spectrum shows a broad, strong absorption centered around $$3300\ 	ext{cm}^{-1}$$ and a sharp absorption at $$1710\ 	ext{cm}^{-1}. $$Which functional groups are most likely present in the compound?

Accepted Answer

Alcohol and ketone

Question 3

A $$^1H $$NMR spectrum of an unknown compound shows a triplet at $$\delta = 1.0$$ ppm (integration: 3H) and a quartet at $$\delta = 2.4$$ ppm (integration: 2H). Which structure best fits this data?

Accepted Answer

Ethyl group adjacent to a carbonyl (e.g., ethyl ketone)

Question 4

Which of the following statements best explains why the absorption maximum ($$\lambda_{	ext{max}}) in UV-$$Vis spectroscopy increases (shifts to longer wavelength) as the conjugation in a molecule increases?

Accepted Answer

The energy gap between the HOMO and LUMO decreases with increased conjugation.

Question 5

A compound is treated with $$\ce{OsO4}$$ followed by $$\ce{NaHSO3} in $$water. What is the major product of this reaction if the starting material is 2-butene?

Accepted Answer

2,3-Butanediol (syn addition of two OH groups)

Question 6

Which of the following best describes the regioselectivity and stereoselectivity of hydroboration-oxidation of alkenes?

Accepted Answer

Anti-Markovnikov and syn addition

Question 7

A student proposes the following mechanism for the acid-catalyzed ring opening of an epoxide: Protonation of the epoxide oxygen, followed by nucleophilic attack at the less substituted carbon. Which statement is correct?

Accepted Answer

The nucleophile should attack the more substituted carbon due to better carbocation stabilization.

Question 8

Which of the following is the correct IUPAC name for a benzene ring with a methyl group at position 1 and a nitro group at position 3?

Accepted Answer

m-Nitrotoluene

Question 9

Which of the following statements about the Diels-Alder reaction is correct?

Accepted Answer

It is a concerted cycloaddition between a diene and a dienophile.

Question 10

A compound with the formula $$\ce{C3H8O} is $$oxidized with PCC (pyridinium chlorochromate) and gives a product with a strong IR absorption at $$1715\ 	ext{cm}^{-1}. $$Which is the most likely starting material?

Accepted Answer

2-Propanol

Question 11

Which of the following best describes the product of the reaction of 1-bromopropan-2-ol with base?

Accepted Answer

An epoxide (oxirane ring) via intramolecular Williamson ether synthesis

Question 12

Which of the following statements about the hydration of alkenes is correct?

Accepted Answer

Oxymercuration-demercuration gives Markovnikov alcohols without carbocation rearrangement.

Question 13

A $$^1H $$NMR spectrum shows a singlet at $$\delta = 9.8$$ ppm. Which functional group is most likely present?

Accepted Answer

Aldehyde

Question 14

Which of the following is the correct order of increasing chemical shift (downfield, higher ppm) for the following protons: methyl ($$\ce{CH3}$$), aromatic ($$\ce{C6H5}$$), aldehyde ($$\ce{CHO}$$)?

Accepted Answer

$$\ce{CH3} \u003c \ce{C6H5} \u003c \ce{CHO}$$

Question 15

Which of the following best describes the equilibrium between a carbonyl compound and its hydrate?

Accepted Answer

Aldehydes generally form hydrates more readily than ketones due to less steric hindrance and greater electrophilicity.

Question 16

Which of the following is a correct statement about the acid-catalyzed hydration of an alkene?

Accepted Answer

It proceeds via a carbocation intermediate, which can rearrange.

Question 17

A student is asked to synthesize 1,2-epoxypropane (propylene oxide) from propene. Which sequence of reagents would be most efficient?

Accepted Answer

Peroxyacid (e.g., $$\ce{mCPBA}) in $$one step

Question 18

Which of the following is the correct application of the n+1 rule in $$^1H $$NMR spectroscopy?

Accepted Answer

A proton with $$n$$ equivalent neighboring protons will appear as a multiplet with $$n+1$$ peaks.

Question 19

Which of the following is a plausible error in a proposed mechanism for the Diels-Alder reaction?

Accepted Answer

Drawing a carbocation intermediate in the mechanism.

Question 20

A compound absorbs UV light at $$\lambda_{	ext{max}} = 220\ 	ext{nm}. If $$the energy of a photon is given by $$E = \dfrac{hc}{\lambda}$$, what is the energy (in kJ/mol) of a photon at this wavelength? ($$h = 6.626 	imes 10$$^{-34}$$\ 	ext{J}\cdot	ext{s}$$, $$c = 3.00 	imes 10^8$\ 	ext{m/s}$$, $$N_A = 6.022 	imes 10$$^{23}$$\ 	ext{mol}^{-1})$$

Accepted Answer

$$545\ 	ext{kJ/mol}$$

Spectroscopy, Structure Elucidation, and Functional Group Transformations in Organic Chemistry

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