Chapter 9
Nuclear Magnetic Resonance
and Mass Spectroscopy:
Tools for Structure Determination
This
preview
has intentionally blurred sections.
Sign up to view the full version.
Spectroscopic Methods
Matter interacts with radiation energy across a very wide
spectral range from the ultraviolet-visible to
the
radiofrequency, but the modes of interaction differ greatly.
M
h
!
uv-visible
M
*
electronic transition
M
h
!
rf in presence
of a magnetic field
M
*
nuclear spin transition
The information obtained by nuclear magnetic resonance (nmr)
spectroscopy provides the most detailed structural description of
organic compounds of any methodology.
Nuclear Magnetic Spectroscopy
The nuclear particles (
neutrons
and
protons
) have the property
of spin and a spin quantum number of 1/2.
These particles
contribute to the net spin quantum number for the nucleus (
I
).
If
I = 0,
the nucleus has a net nuclear spin angular momentum
and an associated nuclear magnetic moment (magnetic dipole
moment).
spinning charge with non-zero
nuclear spin quantum number
generates
magnetic dipole moment
In the presence of an
external magnetic field
, this nuclear
magnetic moment can have more than one orientation relative to
the external magnetic field.
Each orientation has a
different
energy
, and is a different
nuclear spin state
.
The number of nuclear spin states (
N
) is given by
N
= 2
I
+ 1
where
I
is
the nuclear spin quantum number.
This
preview
has intentionally blurred sections.
Sign up to view the full version.
Some Empirical Rules for Values of
I
(1) Nuclei with
even mass numbers and even atomic numbers
This is the end of the preview.
Sign up
to
access the rest of the document.
- Summer '07
- Jung
- Organic chemistry, Proton, Magnetism, Magnetic Field, Fundamental physics concepts, Nuclear magnetic resonance
-
Click to edit the document details
