Download document

Luminol: Structure,
Synthesis, chemical
reaction, and its function.
By: Hau Huynh
Abstract
• Chemiluminescence is the emission of
light during a chemical reaction. Luminol
is used to reveal a light-producing
chemical reaction between chemicals and
hemoglobin, an oxygen-carrying protein in
the blood. The focus of this presentation
will be on the synthesis of luminol, the
chemical reaction, and how investigators
use luminol to solve the crimes.
Outline
•
•
•
A. What is chemiluminescene?
B. The structure of Luminol.
C. Spectroscopic features
•
•
•
•
•
•
IR, C NMR, H NMR
D. Synthesis of Luminol
E. The chemical reaction
F. Applications
G. Conclusion
H. Reference
What is chemiluminescence?
• Chemiluminescence is the emission of light during a
chemical reaction.
• A molecule that is chemiluminescent is oxidized in a
chemical reaction to an excited state product and emits
light upon deexcitation.
• Chemiluminescence is distinct from fluorescence and
phosphorescence in that a chemical is used to excite a
molecule and an external source of photons is not
needed.
• Luminol is chemiluminescent molecule which was
discovered by the German scientist H.O. Albrecht in
1928. It has been used in many chemical applications
because of its chemiluminescent properties.
Structure of luminol
• Name: 5-amino-2,3dihydro-1,4phthalazine-dione .
• Formula : C8H7N3O2
• Melting point: 319 320oC
IR
C=0
http://www.aist.go.jp/RIODB/SDBS/cgi-bin/direct_frame_top.cgi?lang=eng
C NMR
C3
C2
C6
C7
C4
C5
C1
C8
H NMR
Hd
Hb
Ha
Hc
The synthesis of Luminol
hydrazine
3-nitrophthalic
acid
The synthesis of Luminol
• 3-nitrophthalic acid (1) combines with aqueous
hydrazine in a triethylene glycol solution and
under heat, which substitutes the carboxylic acid
-OH groups with -NH groups.
• This releases two water molecules and creates 3nitrophthalhydrazide (2). 3-nitrophthalhydrazide
combines with aqueous sodium hydrosulfite,
which substitutes amino groups for the nitro
groups on the benzene ring.
The chemical reaction of Luminol
3-aminophthalate
The chemical reaction of Luminol
• 3-aminophthalhydrazide (4) combines with a basic solution, which
removes the hydrogen protons from the nitro groups to release two
water molecules.
• The resulting molecule (5) undergoes keto-enol tautomerization to
move the negative formal charges onto the carbonyl oxygens.
• A metal ion catalyst (such as copper (II), iron (III) or cobalt (II))
decomposes the hydrogen peroxide (or other oxidizing molecule)
solution to make peroxide molecules available.
• A peroxide molecule is cyclically added to the enolate form (6) of the
intermediate molecule. Nitrogen gas is released and 3aminophthalate is formed in its triplet state (7). The electrons
undergo intersystem crossing and then decay to their ground state,
which emits a photon of light (8)
Applications
A basic luminol solution combined with
hydrogen peroxide and a thickening
agent can be sprayed on surfaces with
suspected blood traces. The solution
will glow if catalyzed by the presence of
a metal ion, such as iron in blood
hemoglobin.
•
Disadvantage
– Luminol can be catalyzed by
substances such as bleach,
copper, potassium permanganate
(found in many dyes), saliva, brain
tissue, bone marrow, rust, and
vegetable enzymes.
– Secondly, luminol can destroy
some genetic markers in cell DNA.
– Thirdly, it can smear bloody
impressions and make prints and
splatters more difficult to analyze.
Applications
Biology and Chemistry
Research
–
–
In biology research, Luminol can detect
proteins and DNA in very small
concentrations.
In chemistry research, concentration of
a metal ion can be detected and
reaction rate analysis of oxidizers can
be tracked by the intensity of the glow
of luminol.
Commercial
an emergency light source for
vehicles, businesses, schools,
and the military.
Glowsticks are occasionally made
using luminol, which are sold at
many events
Conclusion
• Luminol is a chemiluminescent
compound, which means that a
release of light is a result of a
chemical reaction.
• When luminol is placed in a
basic solution, the luminol is
oxidized.
• Luminol is used in biology and
biochemistry for a multitude of
testing
• This hemoglobin reacts with
the luminol as the catalyst.
Reference
• http://www.sas.upenn.edu/~hickeyj/lumrxn.html
• http://cas.bellarmine.edu/chem117a/lab/luminol.ht
m
• http://people.howstuffworks.com/luminol4.htm
• Journal of Physical Chemistry B July 26, 2001
v105 i29 p6993-6999
• The American Journal of Physiology April 2000
v278 i4 pC646
• Journal of the American Chemical Society Sept 4,
2002 v124 i35 p10250(2)