Transcript Spectra

Mass Spectroscopy
• Mass spectroscopy is a powerful tool
in organic chemistry that can be used
to provide information about the
molecular formula and structural sub
units
• When it is combined with techniques
of infrared and NMR it can be very
useful in identifying unknown
compounds
The Design of a Mass
Spectrometer
•
The Design of a Mass
Spectrometer
•
The Mass Spectrometer
• The mass spectrometer
contains a vacuum
chamber into which a
small amount of a
compound is vaporized.
The molecules are then
bombarded by high
energy electrons which
cause the molecule to
fragment into molecular
ions
The Mass Spectrometer
• The accelerated
fragments are passed
though a magnetic field
that causes them to be
deflected. The amount
to which a particle
isdeflected depends on
its molecular mass
Mass Spectra
A typical molecule may fragment in
several different places. The ion formed
from the loss of the electron is called the
parent ion. The parent ion may fragment
into smaller pieces. Each fragment is
deflected to a different extent . Hence
each peak appears in the Mass Spectrum
Peaks in the Mass Spectrum
Butane could in
four different
ways, each of
which forms a
signal in the mass
spectrum
Multiplicity of Peaks
Carbon has isotopes 13C and 14C as well as
12C. Likewise there are isotopes of hydrogen
including 1H, 2H and 3H. Hence a fragment
with the formula CH3 has a a predominate
mass of 15 but has smaller peaks
representing the heavier isotopes of carbon
and hydrogen
Mass Spectra for Butane
Mass Spectrum for Acetone
Mass Spectrum Ethanoic Acid
Mass Specturm for Toluene
Web Site References
http://www.chemguide.co.uk/analysis/masspec/mplus.html