Nuclear Magnetic Resonance Spectroscopy With Answers

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Chapter 16
Nuclear Magnetic Resonance Spectroscopy
Review of Concepts
Fill in the blanks below. To verify that your answers are correct, look in your textbook at
the end of Chapter 16. Each of the sentences below appears verbatim in the section
entitled Review of Concepts and Vocabulary.
• A spinning proton generates a magnetic _____________, which must align either
with or against an imposed external magnetic field.
• All protons do not absorb the same frequency because of ___________________,
a weak magnetic effect due to the motion of surrounding electrons that either
shield or deshield the proton.
• ________________ solvents are generally used for acquiring NMR spectra.
1
• In a
H NMR spectrum, each signal has three important characteristics: location,
area and shape.
• When two protons are interchangeable by rotational symmetry, the protons are
said to be ___________.
• When two protons are interchangeable by rotational symmetry, the protons are
said to be ___________.
• The left side of an NMR spectrum is described as _____field, and the right side is
described as _____field.
• In the absence of inductive effects, a methyl group (CH
) will produce a signal
3
near _____ppm, a methylene group (CH
) will produce a signal near _____, and
2
a __________ group (CH) will produce a signal near _____. The presence of
nearby groups increases these values somewhat predictably.
• The _______________, or area under each signal, indicates the number of protons
giving rise to the signal.
• _______________represents the number of peaks in a signal. A __________has
one peak, a __________has two, a __________has three, a __________has four,
and a __________has five.
• Multiplicity is the result of spin-spin splitting, also called __________, which
follows the n+1 rule.
• When signal splitting occurs, the distance between the individual peaks of a signal
is called the coupling constant, or _____ value, and is measured in Hz.
• Complex splitting occurs when a proton has two different kinds of neighbors,
often producing a __________.
13
C is an __________of carbon, representing _____% of all carbon atoms.
13
1
• All
C-
H splitting is suppressed with a technique called broadband
13
______________, causing all of the
C signals to collapse to ___________.

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