Summary of Infrared spectroscopy

INFRARED
SPECTROSCOPY


(IR)

Theory
and
Interpreta.on
of
IR

spectra


, ORGANIC
STRUCTURE

DETERMINATION


How
do
we
know:

• How
atoms
are
connected
together?

• Which
bonds
are
single,
double,

or
triple?

• What
funcHonal
groups
exist
in
the
molecule?

• If
we
have
a
specific
stereoisomer?



The
field
of
organic
structure
determinaHon

aLempts
to
answer
these
quesHons.


, INSTRUMENTAL
METHODS
OF

STRUCTURE
DETERMINATION

• Infrared
Spectroscopy
(IR)
–
Triggering
molecular
vibraHons

through
irradiaHon
with
infrared
light.
Provides
mostly
informaHon

about
the
presence
or
absence
of
certain
funcHonal
groups.

• Nuclear
Magne.c
Resonance
(NMR)
–
ExcitaHon
of
the
nucleus
of

atoms
through
radiofrequency
irradiaHon.
Provides
extensive

informaHon
about
molecular
structure
and
atom
connecHvity.

• Mass
spectrometry
(MS)
–
Bombardment
of
the
sample
with

electrons
and
detecHon
of
resulHng
molecular
fragments.
Provides

informaHon
about
molecular
mass
and
atom
connecHvity.

• Ultraviolet
spectroscopy
(UV)
–
PromoHon
of
electrons
to
higher

energy
levels
through
irradiaHon
of
the
molecule
with
ultraviolet

light.
Provides
mostly
informaHon
about
the
presence
of

conjugated
π systems
and
the
presence
of
double
and
triple
bonds.


, SPECTROSCOPY
-­‐
Study
of
spectral

informaFon

Physical

response
DetecHng


Molecule

sHmulus
instrument


Visual
(most
common)

representaHon,
or

Spectrum



Upon
irradiaHon
with
infrared
light,
certain
bonds
respond
by

vibraHng
faster.
This
response
can
be
detected
and
translated

into
a
visual
representaHon
called
a
spectrum.