Question 1

Which of the following statements best explains why phenol is more acidic than a secondary alcohol?

Accepted Answer

Phenol's conjugate base is stabilized by resonance with the aromatic ring.

Question 2

In mass spectrometry, a compound containing chlorine will show a prominent M+2 peak. What is the reason for this?

Accepted Answer

Chlorine has two major isotopes, $$^{35}\mathrm{Cl}$$ and $$^{37}\mathrm{Cl}$$, with significant natural abundance.

Question 3

Which of the following best describes the n+1 rule in $$^1\mathrm{H}$$ NMR spectroscopy?

Accepted Answer

A proton with n equivalent neighboring protons will be split into n+1 peaks.

Question 4

A compound with a conjugated diene undergoes addition of HX. Which product is kinetically favored?

Accepted Answer

The 1,2-addition product is kinetically favored.

Question 5

Which functional group would show a strong, broad absorption around $$3300\ \mathrm{cm}^{-1} in an IR $$spectrum?

Accepted Answer

Alcohol (O-H stretch)

Question 6

Which of the following molecules is aromatic according to Huckel's rule?

Accepted Answer

Cyclopentadienyl anion ($$\mathrm{C}_5\mathrm{H}_5^-) $$with 6 $$\pi$$ electrons

Question 7

In the Diels-Alder reaction, which of the following factors makes a dienophile 'better'?

Accepted Answer

The presence of electron-withdrawing groups on the dienophile.

Question 8

Which of the following statements about halogens as substituents on benzene is correct?

Accepted Answer

Halogens are deactivating but ortho/para-directing groups.

Question 9

A molecule absorbs UV light at a longer wavelength as the number of conjugated $$\pi$$ electrons increases. What is the primary reason for this?

Accepted Answer

Increasing conjugation lowers the energy gap between HOMO and LUMO.

Question 10

Which of the following is a typical fragmentation mechanism observed in mass spectrometry for carbonyl compounds with a gamma carbon?

Accepted Answer

McLafferty rearrangement

Question 11

Which of the following groups is an activating, ortho/para-directing group in electrophilic aromatic substitution?

Accepted Answer

Methoxy ($$-$$OCH_3$$)

Question 12

In $$^1\mathrm{H}$$ NMR, which factor causes a proton to be more deshielded?

Accepted Answer

Being near an electronegative atom such as oxygen or nitrogen.

Question 13

Which of the following is true about the heats of hydrogenation for aromatic compounds?

Accepted Answer

Aromatic compounds have less exothermic heats of hydrogenation compared to non-aromatic compounds with the same number of double bonds.

Question 14

Which of the following conditions favors nucleophilic aromatic substitution?

Accepted Answer

Presence of strong electron-withdrawing groups and a strong base as nucleophile.

Question 15

Which of the following statements about the Sandmeyer reaction is correct?

Accepted Answer

It uses diazonium salts and copper(I) salts to rapidly substitute aromatic amines.

Question 16

Which of the following best describes the polygon method for arranging energies of cyclic $$\pi-$$system molecular orbitals?

Accepted Answer

The vertices of a regular polygon inscribed in a circle represent the energy levels of the molecular orbitals.

Question 17

Which of the following is true about the Diels-Alder reaction stereochemistry?

Accepted Answer

The stereochemistry of the dienophile is retained in the product.

Question 18

Which of the following is a plausible reason why the benzyne intermediate leads to a 50/50 mix of isomers in nucleophilic aromatic substitution?

Accepted Answer

Nucleophilic addition can occur at either carbon of the triple bond, leading to two possible products.

Question 19

Which of the following statements about the IR absorption intensity is correct?

Accepted Answer

Intensity is determined by the change in dipole moment during the vibration.

Spectroscopy, Conjugation, and Aromatic Chemistry: Exam 1 Study Guide

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