QUESTION 1 All of the following are true concerning NMR spectroscopy EXCEPT: Pro

Question

QUESTION 1

All of the following are true concerning NMR spectroscopy EXCEPT:

Protons are distinguished when they absorb magnetic energy at different field strengths.

Downfield is to the left on an NMR spectrum.

Functional groups are distinguished when they absorb magnetic energy at different field strengths.

Delocalized electrons generate magnetic fields that can either shield or deshield nearby protons.

1 points   

QUESTION 2

Which of the following chemical shifts would correspond to an aldehyde proton signal in a 1H NMR spectrum?

9.5 ppm

7.0 ppm

11.0 ppm

1.0 ppm

1 points   

QUESTION 3

List the following protons in order of decreasing chemical shift (largest shift first).

a; b; c

b; c; a

c; b; a

a; c; b

1 points   

QUESTION 4

What would be the splitting pattern (singlet, doublet, etc.) observed for each of the following indicated protons?

a = singlet; b = quartet; c = triplet

a = singlet; b = triplet; c = quartet

a = singlet; b = doublet; c = doublet

a = singlet; b = multiplet; c = multiplet

1 points   

QUESTION 5

A NMR spectrum shows a singlet at 7.3 ppm, a triplet at 4.3, a triplet at 2.9, and a singlet at 2.0. The relative areas are 5, 2, 2, and 3 respectively. Which of the following compounds is compatible with this spectrum?

a

b

c

d

1 points   

QUESTION 6

How many types of nonequivalent protons does the following compound contain? (Example: CH3CH2Cl has two types, CH3 and CH2.)

(CH3)2CHCl

Three types; 2 CH3 and 1 CH

Two types CH3 and CH

One type; all protons are the equivalent.

There are seven nonequivalent protons in this compound.

1 points   

QUESTION 7

What is the purpose of TMS?

It is the reference standard used in NMR.

It determines how many nonequivalent protons are in the compound.

It always appears at 1.5 ppm.

It has no purpose.

1 points   

QUESTION 8

What are the effects of attached electronegative atoms on adjacent protons?

The protons are shielded and appear upfield closer to TMS.

The protons are shielded and appear downfield away from TMS.

The protons are deshielded and appear upfield closer to TMS.

The protons are deshielded and appear downfield away from TMS.












Use the following instructions for questions 9 and 10. Listed here are 1H NMR absorption peaks for several compounds. Propose a structure that is consistent with each set of data. In some cases characteristic IR absorptions are given as well. Relative areas are given in parenthesis.

1 points   

QUESTION 9

C4H8O 1H NMR
Triplet at 1.05 ppm (3H)
Singlet at 2.13 ppm (3H)
Quartet at 2.47 ppm (2H)


IR Spectrum: There is a strong peak near 1700 cm-1.

a

b

c

d

1 points   

QUESTION 10

C4H9Cl 1H NMR
Doublet at 1.04 ppm (6H)
Multiplet at 1.95 ppm (1H)
Doublet at 3.35 ppm (2H)

a

b

c

a.

Protons are distinguished when they absorb magnetic energy at different field strengths.

b.

Downfield is to the left on an NMR spectrum.

c.

Functional groups are distinguished when they absorb magnetic energy at different field strengths.

d.

Delocalized electrons generate magnetic fields that can either shield or deshield nearby protons.

Explanation / Answer

QUESTION 1 c. is not true ( the magnetic energy is absorbed by protons/nuclei, not by functional

groups.)

QUESTION 2: a. 9.5 ppm (commonly 9...10 ppm)

QUESTION 3 missing image. Look to the electronegativity of the neighbor atoms to evaluate how

much the protons are deshielded and then the signal shift.

QUESTION 4 missing image. Look to the neighbor C, the multiplicity rule is n+1.

QUESTION 5 This generic formula satisfies the combination of equivalent protons (5H,2H,2H,3H)

and the multiplicity of the signal.

C6H5

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