Question 1

How many signals appear in the broadband-decoupled ¹³C NMR spectrum of 1,3-dibromobenzene?

Accepted Answer

The answer of How many signals appear in the broadband-decoupled...

Question 2

Answer the following question(s) for the compound whose S1U1P11S1S1P0H NMR spectra is shown below.
CS1U1B14S1U1B0HS1U1B18S1U1B0O  (Spectrum obtained from: SDBSWeb: http://www.aist.go.jp/RIODB/SDBS/)
-Refer to instructions. Propose a structure for this compound.

Accepted Answer

The answer of Answer the following question(s) for the compound...

Question 3

Answer the following question(s) for the compound whose S1U1P11S1S1P0H NMR spectra is shown below.
CS1U1B14S1U1B0HS1U1B18S1U1B0O  (Spectrum obtained from: SDBSWeb: http://www.aist.go.jp/RIODB/SDBS/)
-Refer to instructions. Describe each signal in terms of its integration, splitting and chemical shift.

Accepted Answer

The answer of Answer the following question(s) for the compound...

Question 4

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

Accepted Answer

The chemical shift in an NMR spectrum provides information about the electronic environment of the protons in a compound. This is because the chemical shift is influenced by the magnetic environment around the proton, which in turn is influenced by the electronic distribution around the proton.

Question 5

The following questions pertain to the display of NMR spectra. Match a term to each description below.
-The exact place on the spectrum at which a nucleus absorbs is called its _____.

Accepted Answer

The exact place on the spectrum at which a nucleus absorbs is referred to as its chemical shift, which is a measure of the environment around the nucleus affecting its magnetic field.

Question 6

If the proton attached to C2 in 1,1,2-tribromopropane is coupled with the protons on C1 (J = 3.5 Hz) and C3 (J = 6.8), draw the tree diagram of the C2 proton and predict the splitting pattern.

Accepted Answer

The answer of If the proton attached to C2 in...

Question 7

How many positive and negative peaks appear in the DEPT-135 and in the DEPT-90 spectrum of 2-methylpentane?

Accepted Answer

In the DEPT-135 spectrum, the methyl and methylene carbons give positive peaks, while the methine carbon gives a negative peak. In the DEPT-90 spectrum, only the methyl carbon gives a positive peak.

Question 8

Which of the following compounds gives a ¹H NMR spectrum consisting of only two singlets?

Accepted Answer

The NMR spectrum of compound C consists of two singlets, which suggests that the molecule has two distinct environments for the protons. The other compounds have either more than two environments or protons that are chemically equivalent and therefore give the same signal in the NMR spectrum.

Question 9

Which of the following combinations of peaks appears in the ¹H NMR spectrum of diethyl ether, CH₃CH₂OCH₂CH₃?

Accepted Answer

Diethyl ether (CH3CH2OCH2CH3) has two types of hydrogen environments: the CH3 groups (6 hydrogens) and the CH2 groups (4 hydrogens) adjacent to the oxygen. The CH3 groups are split by the adjacent CH2 groups into a triplet, and the CH2 groups are split by the CH3 groups into a quartet.

Question 10

Which of the following combinations of peaks appears in the ¹H NMR spectrum of 2-methylpropane?

Accepted Answer

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Question 11

How many sets of equivalent protons are there in hexane, 2-methylhexane, and 3-methylhexane, respectively?

Accepted Answer

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Question 12

How many signals appear in the broadband-decoupled ¹³C NMR spectrum of 1,2-dibromobenzene?

Accepted Answer

1,2-dibromobenzene has a plane of symmetry through the 1,2-positions. This symmetry results in three unique carbon environments in the molecule, leading to three signals in the broadband-decoupled ¹³C NMR spectrum.

Question 13

The following questions pertain to the display of NMR spectra. Match a term to each description below.
-When looking at an NMR spectrum the right-hand part of the chart is the _____.

Accepted Answer

The right-hand part of an NMR spectrum is referred to as the high-field or upfield side, which corresponds to lower chemical shift values.

Question 14

The following questions pertain to the display of NMR spectra. Match a term to each description below.
-The NMR spectrum are calibrated using an arbitrary scale that is divided into _____ units.

Accepted Answer

The NMR spectrum is calibrated using an arbitrary scale divided into delta (δ) units, which represent the chemical shift. This scale is dimensionless and standardized across different spectrometer frequencies.

Question 15

How many positive and negative peaks appear in the DEPT-135 spectrum of 2,4-dimethylpentane?

Accepted Answer

The DEPT-135 spectrum of 2,4-dimethylpentane will show two positive peaks for the methyl carbons and one negative peak for the methine carbon.

Question 16

Which of the following compounds gives a ¹H NMR spectrum consisting of only a singlet and two signals in the ¹³C NMR?

Accepted Answer

2,2-dibromopropane has a symmetrical structure with all hydrogen atoms equivalent, resulting in a single singlet in the ¹H NMR. It also has two types of carbon environments, leading to two signals in the ¹³C NMR.

Question 17

Which feature in the ¹H NMR spectrum provides information about the number of neighboring protons of each proton in the compound?

Accepted Answer

The splitting of signals in the NMR spectrum (also known as multiplicity) provides information about the number of neighboring protons for each proton in the compound. This allows for the determination of the connectivity and arrangement of atoms in the molecule.

Question 18

The following questions pertain to the display of NMR spectra. Match a term to each description below. -The calibration standard for ¹H and ¹³C NMR is _____.

Accepted Answer

TMS (tetramethylsilane) is the calibration standard for both ¹H and ¹³C NMR. It is assigned a chemical shift of 0 ppm and serves as a reference point for chemical shift measurements. Answer: E The low-field or downfield side of an NMR spectrum corresponds to a higher chemical shift value. This means that the signal is experiencing a stronger magnetic field, which causes it to resonate at a higher frequency. Answer: D Delta (δ) is used to report chemical shifts in NMR spectra. It is defined as the difference in resonance frequency between the observed signal and the TMS reference signal, expressed in parts per million (ppm). Answer: F Chemical shift is a measure of the magnetic environment of an atom in a molecule, and it is reported in units of ppm (parts per million) relative to the TMS reference signal. The chemical shift tells you where the signal appears in an NMR spectrum, relative to the TMS standard. Answer: G Intensity refers to the height or area of an NMR signal. The intensity of a signal is proportional to the number of nuclei contributing to that signal, and it can provide information about the relative abundance of different types of nuclei in a sample. Note: Choices B and C are not applicable to the given descriptions. MHz refers to the frequency of the magnetic field used in NMR spectroscopy, but it is not specifically related to the display of NMR spectra. The terms "high-field" and "upfield" and "low-field" and "downfield" describe the relative positions of NMR signals within a spectrum, but they are not calibration standards or units of measurement.

Question 19

Which structure of molecular formula C₄H₈Cl₂ fits the ¹H NMR and ¹³C NMR spectra shown below? (Spectrum obtained from: SDBSWeb: http://www.aist.go.jp/RIODB/SDBS/)

Accepted Answer

Based on the ¹H NMR spectrum, there is a singlet peak at around 8 ppm, which indicates the presence of a hydrogen atom in a highly deshielded environment, likely due to its proximity to an electronegative atom such as sulfur or oxygen. The only structure containing a hydrogen atom adjacent to a sulfur atom is option B. Similarly, based on the ¹³C NMR spectrum, there are two distinct peaks at around 10 ppm and 160 ppm, which suggest the presence of a carbonyl group. The only structure containing a carbonyl group is option B. Therefore, the best choice is B as it satisfies both NMR spectra.

Question 20

Which feature in the ¹H NMR spectrum provides information about the relative numbers of hydrogen atoms of each type found in a compound?

Accepted Answer

Integration of signals in an NMR spectrum provides information about the relative numbers of hydrogen atoms of each type found in a compound. Integration is the process of measuring the areas under the peaks in an NMR spectrum, which are proportional to the number of hydrogen atoms contributing to each signal.

Quiz 11: Structure Determination: Nuclear Magnetic Resonance Spectroscopy

How many signals appear in the broadband-decoupled ¹³C NMR spectrum of 1,3-dibromobenzene?

Answer the following question(s) for the compound whose ¹H NMR spectra is shown below. C₄H₈O (Spectrum obtained from: SDBSWeb: http://www.aist.go.jp/RIODB/SDBS/) -Refer to instructions. Propose a structure for this compound.

Answer the following question(s) for the compound whose ¹H NMR spectra is shown below. C₄H₈O (Spectrum obtained from: SDBSWeb: http://www.aist.go.jp/RIODB/SDBS/) -Refer to instructions. Describe each signal in terms of its integration, splitting and chemical shift.

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

The following questions pertain to the display of NMR spectra. Match a term to each description below. -The exact place on the spectrum at which a nucleus absorbs is called its _____.

If the proton attached to C2 in 1,1,2-tribromopropane is coupled with the protons on C1 (J = 3.5 Hz) and C3 (J = 6.8), draw the tree diagram of the C2 proton and predict the splitting pattern.

How many positive and negative peaks appear in the DEPT-135 and in the DEPT-90 spectrum of 2-methylpentane?

Which of the following compounds gives a ¹H NMR spectrum consisting of only two singlets?

Which of the following combinations of peaks appears in the ¹H NMR spectrum of diethyl ether, CH₃CH₂OCH₂CH₃?

Which of the following combinations of peaks appears in the ¹H NMR spectrum of 2-methylpropane?

How many sets of equivalent protons are there in hexane, 2-methylhexane, and 3-methylhexane, respectively?

How many signals appear in the broadband-decoupled ¹³C NMR spectrum of 1,2-dibromobenzene?

The following questions pertain to the display of NMR spectra. Match a term to each description below. -When looking at an NMR spectrum the right-hand part of the chart is the _____.

The following questions pertain to the display of NMR spectra. Match a term to each description below. -The NMR spectrum are calibrated using an arbitrary scale that is divided into _____ units.

How many positive and negative peaks appear in the DEPT-135 spectrum of 2,4-dimethylpentane?

Which of the following compounds gives a ¹H NMR spectrum consisting of only a singlet and two signals in the ¹³C NMR?

Which feature in the ¹H NMR spectrum provides information about the number of neighboring protons of each proton in the compound?

The following questions pertain to the display of NMR spectra. Match a term to each description below. -The calibration standard for ¹H and ¹³C NMR is _____.

Which structure of molecular formula C₄H₈Cl₂ fits the ¹H NMR and ¹³C NMR spectra shown below? (Spectrum obtained from: SDBSWeb: http://www.aist.go.jp/RIODB/SDBS/)

Which feature in the ¹H NMR spectrum provides information about the relative numbers of hydrogen atoms of each type found in a compound?

Quiz 11: Structure Determination: Nuclear Magnetic Resonance Spectroscopy

How many signals appear in the broadband-decoupled 13C NMR spectrum of 1,3-dibromobenzene?

Answer the following question(s) for the compound whose 1H NMR spectra is shown below. C4H8O (Spectrum obtained from: SDBSWeb: http://www.aist.go.jp/RIODB/SDBS/) -Refer to instructions. Propose a structure for this compound.

Answer the following question(s) for the compound whose 1H NMR spectra is shown below. C4H8O (Spectrum obtained from: SDBSWeb: http://www.aist.go.jp/RIODB/SDBS/) -Refer to instructions. Describe each signal in terms of its integration, splitting and chemical shift.

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

The following questions pertain to the display of NMR spectra. Match a term to each description below. -The exact place on the spectrum at which a nucleus absorbs is called its _____.

If the proton attached to C2 in 1,1,2-tribromopropane is coupled with the protons on C1 (J = 3.5 Hz) and C3 (J = 6.8), draw the tree diagram of the C2 proton and predict the splitting pattern.

How many positive and negative peaks appear in the DEPT-135 and in the DEPT-90 spectrum of 2-methylpentane?

Which of the following compounds gives a 1H NMR spectrum consisting of only two singlets?

Which of the following combinations of peaks appears in the 1H NMR spectrum of diethyl ether, CH3CH2OCH2CH3?

Which of the following combinations of peaks appears in the 1H NMR spectrum of 2-methylpropane?

How many sets of equivalent protons are there in hexane, 2-methylhexane, and 3-methylhexane, respectively?

How many signals appear in the broadband-decoupled 13C NMR spectrum of 1,2-dibromobenzene?

The following questions pertain to the display of NMR spectra. Match a term to each description below. -When looking at an NMR spectrum the right-hand part of the chart is the _____.

The following questions pertain to the display of NMR spectra. Match a term to each description below. -The NMR spectrum are calibrated using an arbitrary scale that is divided into _____ units.

How many positive and negative peaks appear in the DEPT-135 spectrum of 2,4-dimethylpentane?

Which of the following compounds gives a 1H NMR spectrum consisting of only a singlet and two signals in the 13C NMR?

Which feature in the 1H NMR spectrum provides information about the number of neighboring protons of each proton in the compound?

The following questions pertain to the display of NMR spectra. Match a term to each description below. -The calibration standard for 1H and 13C NMR is _____.

Which structure of molecular formula C4H8Cl2 fits the 1H NMR and 13C NMR spectra shown below? (Spectrum obtained from: SDBSWeb: http://www.aist.go.jp/RIODB/SDBS/)

Which feature in the 1H NMR spectrum provides information about the relative numbers of hydrogen atoms of each type found in a compound?

How many signals appear in the broadband-decoupled ¹³C NMR spectrum of 1,3-dibromobenzene?

Answer the following question(s) for the compound whose ¹H NMR spectra is shown below. C₄H₈O (Spectrum obtained from: SDBSWeb: http://www.aist.go.jp/RIODB/SDBS/) -Refer to instructions. Propose a structure for this compound.

Answer the following question(s) for the compound whose ¹H NMR spectra is shown below. C₄H₈O (Spectrum obtained from: SDBSWeb: http://www.aist.go.jp/RIODB/SDBS/) -Refer to instructions. Describe each signal in terms of its integration, splitting and chemical shift.

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

Which of the following compounds gives a ¹H NMR spectrum consisting of only two singlets?

Which of the following combinations of peaks appears in the ¹H NMR spectrum of diethyl ether, CH₃CH₂OCH₂CH₃?

Which of the following combinations of peaks appears in the ¹H NMR spectrum of 2-methylpropane?

How many signals appear in the broadband-decoupled ¹³C NMR spectrum of 1,2-dibromobenzene?

Which of the following compounds gives a ¹H NMR spectrum consisting of only a singlet and two signals in the ¹³C NMR?

Which feature in the ¹H NMR spectrum provides information about the number of neighboring protons of each proton in the compound?

The following questions pertain to the display of NMR spectra. Match a term to each description below. -The calibration standard for ¹H and ¹³C NMR is _____.

Which structure of molecular formula C₄H₈Cl₂ fits the ¹H NMR and ¹³C NMR spectra shown below? (Spectrum obtained from: SDBSWeb: http://www.aist.go.jp/RIODB/SDBS/)

Which feature in the ¹H NMR spectrum provides information about the relative numbers of hydrogen atoms of each type found in a compound?