Flashcards on Nuclear Magnetic Resonance Spectroscopy (NMR)

NMR Spectroscopy Explained: Your Guide to Proton and Carbon-13

SummaryKnowledge testFlashcardsPodcastMindmap
1 / 68

What is the equation to calculate chemical shift (in ppm) on the δ scale for 1H NMR?

chemical shift (ppm) = (observed chemical shift in Hz downfield from TMS) ÷ (operating frequency of the NMR spectrometer in MHz).

Tap to flip · Swipe to navigate

NMR Spectroscopy

68 cards

Card 1

Question: What is the equation to calculate chemical shift (in ppm) on the δ scale for 1H NMR?

Answer: chemical shift (ppm) = (observed chemical shift in Hz downfield from TMS) ÷ (operating frequency of the NMR spectrometer in MHz).

Card 2

Question: Why are chemical shifts reported in ppm rather than Hz?

Answer: Reporting as a fraction of the operating frequency (ppm) makes the units independent of the spectrometer frequency.

Card 3

Question: What four features of a 1H NMR spectrum provide structural information about a compound?

Answer: a) Number of signals, b) Position of signals, c) Intensity of signals, d) Spin–spin splitting of signals.

Card 4

Question: What determines the number of signals in a 1H NMR spectrum?

Answer: The number of different types of protons (non-equivalent protons). Equivalent protons give the same NMR signal.

Card 5

Question: How should you determine proton equivalency in cycloalkanes and alkenes?

Answer: Always draw all bonds to hydrogen to identify equivalent protons; for rings/double bonds, two protons are equivalent only if they are cis (or trans) t

Card 6

Question: In 1,1-dichloroethylene, how many types of H and how many NMR signals are observed?

Answer: There is 1 type of H and 1 NMR signal.

Card 7

Question: In 1-bromo-1-chloroethylene, how many types of H and how many NMR signals are observed?

Answer: There are 2 types of H and 2 NMR signals.

Card 8

Question: In chloroethylene (vinyl chloride), how many types of H and how many NMR signals are observed?

Answer: There are 3 types of H and 3 NMR signals.

Card 9

Question: What is the rule for equivalency of two hydrogens on a ring or double bond?

Answer: They are equivalent only if they are cis (or trans) to the same substituent groups.

Card 10

Question: How many NMR signals do all hydrogens give in cyclopropane?

Answer: All H's are equivalent in cyclopropane, so 1 NMR signal.