Question 1

Which of the following statements best describes the information provided by the total number of signals in a $$^1H $$NMR spectrum?

Accepted Answer

It reveals how many different types of hydrogens (non-equivalent protons) are present in the molecule.

Question 2

In $$^1H $$NMR, what is the effect of an electronegative atom (such as O, Cl, or Br) near a proton?

Accepted Answer

It deshields the proton, causing its signal to move downfield (higher ppm).

Question 3

Refer to the molecule below. How many unique $$^1H $$NMR signals would you expect for the following structure?

![tert-butyl ethyl ketone](https://i.imgur.com/4QwQwQw.png)

(CH$$_3$$)$$_3$$CCH$$_2$$COCH$$_3$$

Accepted Answer

4

Question 4

Which splitting pattern would you expect for the methylene ($$-CH$_2-) $$protons in ethyl acetate (CH$$_3$$COOCH$$_2CH$_3$$)?

Accepted Answer

Quartet

Question 5

A $$^1H $$NMR spectrum shows three signals with an integration ratio of 3:2:2. Which of the following molecules is most likely to produce this spectrum?

Accepted Answer

CH$$_3CH$_2$$OCH$$_2CH$_3$$

Question 6

Which of the following protons would appear most downfield (highest ppm) in a $$^1H $$NMR spectrum?

Accepted Answer

Aldehyde proton ($$-$$CHO)

Question 7

A molecule with the formula C$$_4H$_{10}O $$shows the following $$^1H $$NMR data: 0.9 ppm (6H, doublet), 1.8 ppm (1H, nonet), 2.4 ppm (1H, singlet), 3.3 ppm (2H, doublet). Which structure fits this data?

Accepted Answer

2-Butanol

Question 8

Which of the following statements about spin-spin splitting (multiplicity) in $$^1H $$NMR is correct?

Accepted Answer

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

Question 9

Which of the following compounds will give only one peak in both its $$^1H $$and $$^{13}C $$NMR spectra?

Accepted Answer

Cyclohexane

Question 10

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

Accepted Answer

Aldehyde

Question 11

Which of the following best describes the relationship between the two protons circled in the first image (cyclopentene derivative)?

Accepted Answer

Enantiotopic

Question 12

Given the following $$^{13}C $$NMR chemical shift ranges, which carbon environment would appear between 160–210 ppm?

Accepted Answer

Carbonyl

Question 13

A molecule shows a $$^1H $$NMR spectrum with a singlet, a triplet, and a pentet. Which of the following is the most likely structure?

Accepted Answer

CH$$_3$$OCH$$_2CH$_2CH$_2$$OCH$$_3$$

Question 14

Which splitting pattern is expected for the methyl group in an ethyl group ($$-CH$_2CH$_3) in$$ $$^1H $$NMR?

Accepted Answer

Triplet

Question 15

Which of the following is the correct order of chemical shifts (from most deshielded to most shielded) for the protons in the following groups: aldehyde, aromatic, alkene, alkane?

Accepted Answer

Aldehyde \u003e Aromatic \u003e Alkene \u003e Alkane

Question 16

A $$^1H $$NMR spectrum shows a quartet at 4.1 ppm integrating to 2H and a triplet at 1.2 ppm integrating to 3H. Which compound is most likely responsible for this spectrum?

Accepted Answer

Ethyl bromide

Question 17

Which of the following best describes the integration in $$^1H $$NMR spectroscopy?

Accepted Answer

It measures the area under each signal, corresponding to the relative number of protons for each signal.

Question 18

Which of the following coupling constants ($$J$$ values) would you expect for a trans-alkene proton pair?

Accepted Answer

$$13-18 Hz$$

Question 19

A molecule with the formula C$$_3H$_8O$_2$$ shows two singlets in its $$^1H $$NMR spectrum at 3.36 ppm (6H) and 4.57 ppm (2H). Which structure fits this data?

Accepted Answer

CH$$_3$$OCH$$_2$$OCH$$_3$$

Chapter 13: NMR Spectroscopy – Principles and Applications

Guida di studio - Domande di pratica

Study guide - Flashcard