Question 1

A compound with the formula $$\mathrm{C_4H_9Cl}$$ gives a $$^1\mathrm{H}$$ NMR spectrum with four signals in the integration ratio 3:3:2:1 (upfield to downfield). Which structure is most consistent with this data?

Accepted Answer

sec-Butyl chloride ($$\mathrm{CH_3CH_2CHClCH_3})$$

Question 2

A compound with the formula $$\mathrm{C_4H_9Br}$$ shows three signals in its $$^1\mathrm{H}$$ NMR spectrum: two doublets and a 9-line multiplet. Which structure fits this data?

Accepted Answer

1-Bromo-2-methylpropane ($$\mathrm{(CH_3$)_2CHCH_2Br})$$

Question 3

A compound with the formula $$\mathrm{C_4H_8Br_2}$$ gives three signals in its $$^1\mathrm{H}$$ NMR spectrum: a singlet, a triplet, and a quartet. Which structure is most consistent with this data?

Accepted Answer

1-Bromo-2-bromopropane ($$\mathrm{CH_3CHBrCH_2Br})$$

Question 4

A compound with the formula $$\mathrm{C_4H_{10}O_2$}$$ gives only two singlets in the $$^1\mathrm{H}$$ NMR spectrum in an integral ratio of 3:2. Which structure is most consistent with this data?

Accepted Answer

Dimethyl ether ($$\mathrm{CH_3OCH_2CH_2OCH_3})$$

Question 5

Given the $$^1\mathrm{H}$$ NMR spectrum in $$image_1$$, which of the following statements best describes the splitting pattern for the signal at approximately 1.0 ppm?

Accepted Answer

It is a triplet, indicating two neighboring hydrogens.

Question 6

A compound with the formula $$\mathrm{C_8H_{10}O}$$ gives a $$^1\mathrm{H}$$ NMR spectrum with integration (upfield to downfield): 3:1:1:5. Which structure is most consistent with this data?

Accepted Answer

p-Methylanisole ($$\mathrm{p-CH_3C_6H_4OCH_3})$$

Question 7

A compound with the formula $$\mathrm{C_8H_9ClO}$$ gives a $$^1\mathrm{H}$$ NMR spectrum with integration (upfield to downfield): 3:2:2:2. Which structure is most consistent with this data?

Accepted Answer

p-Chloroethylbenzene

Question 8

Which of the following best explains why tert-butyl chloride ($$\mathrm{(CH_3$)_3CCl}) $$gives only one signal in its $$^1\mathrm{H}$$ NMR spectrum?

Accepted Answer

All hydrogens are chemically equivalent due to symmetry.

Question 9

A $$^1\mathrm{H}$$ NMR spectrum shows a quartet at 4.0 ppm and a triplet at 1.2 ppm. Which functional group is most likely present?

Accepted Answer

Ethyl group ($$\mathrm{-CH_2CH_3}) $$attached to an electronegative atom

Question 10

Which of the following best describes the effect of a chlorine atom on the chemical shift of nearby hydrogens in $$^1\mathrm{H}$$ NMR?

Accepted Answer

It causes a downfield shift due to electron withdrawal.

Question 11

A $$^1\mathrm{H}$$ NMR spectrum of a compound with formula $$\mathrm{C_4H_9Cl}$$ shows a signal at 3.5 ppm integrating to 1H. What is the most likely environment for this hydrogen?

Accepted Answer

Hydrogen on a carbon adjacent to chlorine

Question 12

Which of the following compounds would give a $$^1\mathrm{H}$$ NMR spectrum with only one singlet?

Accepted Answer

tert-Butyl chloride

Question 13

A $$^1\mathrm{H}$$ NMR spectrum shows a singlet at 2.1 ppm integrating to 3H and a multiplet at 7.2 ppm integrating to 5H. Which compound is most likely?

Accepted Answer

Toluene

Question 14

A $$^1\mathrm{H}$$ NMR spectrum shows a triplet at 1.0 ppm and a quartet at 2.5 ppm. What is the most likely structure for this fragment?

Accepted Answer

$$\mathrm{CH_3CH_2-}$$

Question 15

Which of the following best explains why a methyl group attached to a benzene ring appears downfield (higher ppm) in $$^1\mathrm{H}$$ NMR compared to a methyl group attached to an alkane?

Accepted Answer

Aromatic ring current deshields the methyl protons.

Question 16

A $$^1\mathrm{H}$$ NMR spectrum shows a singlet at 3.8 ppm integrating to 3H and a multiplet at 6.8–7.2 ppm integrating to 4H. Which compound is most likely?

Accepted Answer

Anisole ($$\mathrm{C_6H_5OCH_3})$$

NMR Spectroscopy Practice: Structure Determination and Signal Interpretation

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