Nuclear magnetic resonance

What is the relative area of the six peaks in a sexet in an ¹H NMR spectrum?

1:5:10:10:5:1

Which of the following gives the furthest downfield shift from TMS in its proton NMR spectrum?

CH₃F

Which of the following is not true regarding ¹H NMR spectroscopy?

a "downfield" peak appears at a lower value of δ

Which of the following protons gives an NMR signal with the highest chemical shift value (farthest downfield)?

F—CH₂CH₂CH₂CH₂CH₂—Br

1

2

3

4

5

1

Which of the following is true for pair of enantiotopic protons?

1.	They will appear at the same chemical shift in an achiral (i.e., nonchiral environment)
2.	They will appear at the same chemical shifts in a chiral environment

Only 1

The protons marked H_a and H_b in the molecule below are ________.

enantiotopic

Which of the following functional groups has the most deshielded proton and would be predicted to show an NMR signal that is the farthest downfield?

Aldehyde-it

The protons marked H_a and H_b in the molecule below are ________.

chemically equivalent or homotopic

Identify which one of the following isomers of C₆H₁₄ has the C-13 NMR below.

CH₃CH₂C(CH₃)₃

A triplet and quartet pattern in ¹H NMR often indicates the presence of a(n)

ethyl group

Which of the following compounds gives a ¹H NMR spectrum consisting of only two triplets and a singlet?

CH₃OCH₂CH₂CH₂CH₂OCH₃

How many nuclear spin states are allowed for the ¹H nucleus?

2

Which feature in the ¹H NMR spectrum provides information about the electronic environment of the protons in a compound?

chemical shift

How many distinct triplets would you expect in the ¹H NMR of the compound below?

2

Which one of the following isomeric C₈H₁₈ compounds has five peaks in its ¹³C NMR spectrum?

4-methylheptane

Which of the following electromagnetic wave types is used in nuclear magnetic resonance spectroscopy?

Radio

If two signals differ by 3 ppm, how do they differ in Hertz in a 60 MHz spectrometer?

180 hz

What is the approximate chemical shift of an alkynyl carbon in ¹³C NMR spectroscopy?

70 ppm

What splitting pattern is observed in the proton NMR spectrum for the indicated hydrogens?

CH₃OCH₂CH₂OCH₃

Triplet

Which of the following compounds gives the highest chemical shift value (farthest downfield) in the NMR spectrum?

V

Deduce the identity of the compound from the data provided.

C5H8O4:

IR (cm-1): 2800-3300 (broad), 2950, 1740

¹³C NMR (δ, splitting): 17.3 (q), 44.3 (s), 210.5 (s)

HO₂CC(CH₃)₂CO₂H

How many signals would you expect to see in the ¹H NMR spectrum of the following compound?

3

Predict the integration for each proton in the ¹H NMR spectrum.

a = 3H; b = 2H; c = 2H; d = 2H; e = 3H

What is the approximate chemical shift of an alkynyl carbon in ¹³C NMR spectroscopy?

70

Which of the following combinations of peaks appears in the ¹H NMR spectrum of 1,4-dimethyoxyethane, CH₃OCH₂CH₂CH₂CH₂OCH₃?

a singlet and two triplets

Which of the following is true for pair of diastereotopic protons?

1.	They will appear at the same chemical shift in an achiral (i.e., nonchiral environment)
2.	They will appear at the same chemical shifts in a chiral environment

How many signals would you expect to see in the ¹H NMR spectrum of the following compound?
CH₃CH₂CH₂CH₃How many signals would you expect to see in the ¹H NMR spectrum of the following compound?
CH₃CH₂CH₂CH₃

2

Which of the following protons gives an NMR signal with the highest chemical shift value (farthest downfield)?

F—CH₂CH₂CH₂CH₂CH₂—Br

1

2

3

4

5

1

Which carbon signal is furthest down field in a proton spin decoupled ¹³C NMR spectrum?

A

Which of the structures shown below is consistent with the C-13 NMR (off resonance splitting for each peak is shown as a table within the figure) and H-NMR spectra? (formula = C₉H₁₁OBr)

How many signals would you expect to see in the ¹H NMR spectrum of the following compound?

4

Give the structure of a compound that has a formula of C₆H₁₂O and has a triplet (3H, 1.1 ppm), doublet (6H, 1.2 ppm), quartet (2H, 2.4 ppm), and septet (1H, 2.7 ppm) in the ¹H NMR spectrum.

How many signals appear in proton-decoupled ¹³C NMR spectrum of 2,5-dimethylhexane?

3

Which C₉H₁₀O compound gives the following ¹H NMR spectrum?

2

Deduce the identity of the compound from the data provided.

C7H12:

IR (cm-1): 3300, 2950, 2220; 13C NMR: 5 signals

4,4-dimethyl-1-pentyne

Which of the following isomeric dibromopropanes has only a single peak in its proton NMR spectrum?

2,2-dibromopropane

How many signals appear in the proton-decoupled ¹³C NMR spectrum of 1,4-dibromobenzene?

2

If a molecule contains 4 elements of unsaturation and signals in the ¹H NMR spectrum between δ 7.0 and 8.0 ppm, what structural group is likely to be present?

an aromatic ring

Which of the following is not true regarding ¹H NMR spectroscopy?

a "downfield" peak appears at a lower value of δ

Which of the protons in the following molecule appear at the highest δ-value in the ¹H NMR spectrum?

4 near acid group

Which feature in the ¹H NMR spectrum provides information about the relative number of each type of proton in a compound?

integral

Which C₄H₉Br compound gives a doublet at approximately 3.3 ppm in the ¹H NMR spectrum?

3

How many signals would you expect to see in the ¹H NMR spectrum of the following compound?

3

How many peaks appear in the proton spin decoupled ¹³ C NMR spectrum of the compound below?

5

¹H nuclei located near electronegative atoms tend to be ________ relative to ¹H nuclei which are not.

deshielded

What is the appearance of the signal corresponding to the CH₂ protons in the ¹H NMR spectrum of ethyl methyl ether, CH₃CH₂OCH₃?

a quartet

What is the multiplicity of the indicated carbon in an off-resonance decoupled C-13 NMR spectrum? (In off-resonance decoupled spectra, direct ¹³C-¹H coupling is observed.)

doublet

An unknown compound, C₉H₁₂, gave the following NMR spectrum:

Triplet at 1.21 ppm (3H) Singlet at 2.30 ppm (3H) Quartet at 2.60 ppm (2H) Singlet at 7.04 ppm (4H)

What is the structure of the compound?

The chemical shift of the protons of acetone, CH₃COCH₃, is 2.1 ppm when the spectrum is obtained at 250 MHz. What is the chemical shift of these protons when the spectrum is acquired at 500 MHz?

2.1 ppm

Which one of the following isomers of C₈H₁₈ has only two peaks in its ¹³C NMR?

D

An unknown compound, C₉H₁₂, gave the following NMR spectrum:

Triplet at 1.21 ppm (3H) Singlet at 2.30 ppm (3H) Quartet at 2.60 ppm (2H) Singlet at 7.04 ppm (4H)

What is the structure of the compound?

2

Using a 60 MHz spectrometer, the protons in dichloromethane appear at 5.30 ppm. When the same sample is placed in a 100 MHz instrument, where does the signal appear?

5.30

Which of the following is true for pair of homotropic protons?

1.	They will appear at the same chemical shift in an achiral (i.e., nonchiral) environment
2.	They will appear at the same chemical shifts in a chiral environment

Not only 1

A nucleus with an ________ atomic number or an ________ mass number has a nuclear spin that can be observed by the NMR spectrometer.

Odd odd

Which of the carbon atoms in the molecule appears furthest downfield in the ¹³C NMR spectrum?

4

How many signals would you expect to see in the ¹H NMR spectrum of the following compound?

3

The chemical shift of the protons of acetone, CH₃COCH₃, is 2.1 ppm when the spectrum is obtained at 250 MHz. What is the chemical shift of these protons when the spectrum is acquired at 500 MHz?

2.1

What are the approximate intensities of the four lines in the quartet from the proton NMR of diethyl ether, (CH₃CH₂)₂O? (Assume distortion of the quartet is minimal.)

1:3:3:1