Chapter 13 NMR Spectroscopy
NMR - correct answer-nuclear magnetic resonance
NMR is most powerful tool for organic structure determination - correct answer-used for wide
variety, uses radio waves
What does NMR tell you - correct answer-# of chemically unique H's (# of signals)
Types of H's present (eg. aromatic, vinyl, aldehyde) (Chemical shift)
Number of each chem. unique H's (integration
H's proximity (spin-spin splitting
A nucleus with a ____ or a _____ has a nuclear spin that can be observed - correct
answer-odd atomic number
or
odd mass number
Protons are surrounded by electrons that shield them from external field - correct
answer-circulating electrons create an induced magnetic field that opposes the external
(nucleus is shielded)
When electrons are drawn away, proton is - correct answer-deshielded
# of NMR signals - correct answer-show how many different kinds of PROTONS are present
location of NMR signals - correct answer-show how shielded or deshielded is the proton
intensity of NMR signals - correct answer-show # of protons of that type
splitting of NMR signals - correct answer-show # of protons on adjacent atoms
more shielded methyl protons appear towards the right of the spectrum (higher field, upfield)
- correct answer-less shielded hydroxyl proton appears toward the left (lower field,
downfield)
TMS, tetramethylsilane - correct answer-added to sample as internal standard
protons are highly shielded
organic protons absorb downfield of TMS signal
Chemical shift - correct answer-the difference in ppm b/t the resonance frq. of the proton
being observed and TMS
NMR - correct answer-nuclear magnetic resonance
NMR is most powerful tool for organic structure determination - correct answer-used for wide
variety, uses radio waves
What does NMR tell you - correct answer-# of chemically unique H's (# of signals)
Types of H's present (eg. aromatic, vinyl, aldehyde) (Chemical shift)
Number of each chem. unique H's (integration
H's proximity (spin-spin splitting
A nucleus with a ____ or a _____ has a nuclear spin that can be observed - correct
answer-odd atomic number
or
odd mass number
Protons are surrounded by electrons that shield them from external field - correct
answer-circulating electrons create an induced magnetic field that opposes the external
(nucleus is shielded)
When electrons are drawn away, proton is - correct answer-deshielded
# of NMR signals - correct answer-show how many different kinds of PROTONS are present
location of NMR signals - correct answer-show how shielded or deshielded is the proton
intensity of NMR signals - correct answer-show # of protons of that type
splitting of NMR signals - correct answer-show # of protons on adjacent atoms
more shielded methyl protons appear towards the right of the spectrum (higher field, upfield)
- correct answer-less shielded hydroxyl proton appears toward the left (lower field,
downfield)
TMS, tetramethylsilane - correct answer-added to sample as internal standard
protons are highly shielded
organic protons absorb downfield of TMS signal
Chemical shift - correct answer-the difference in ppm b/t the resonance frq. of the proton
being observed and TMS
