DPPH
DPPH is a common abbreviation for the organic chemical
compound 2,2-diphenyl-1-picrylhydrazyl. It is a dark-colored
crystalline powder composed of stable free-radical molecules. DPPH
has two major applications, both in laboratory research: one is a
monitor of chemical reactions involving radicals, most notably it is a
common antioxidant assay,[1] and another is a standard of the
position and intensity of electron paramagnetic resonance signals.
DPPH
Properties and applications
DPPH has several crystalline forms which differ by the lattice
symmetry and melting point (m.p.). The commercial powder is a
mixture of phases which melts at ~130 °C. DPPH-I (m.p. 106 °C) is
orthorhombic, DPPH-II (m.p. 137 °C) is amorphous and DPPH-III
(m.p. 128–129 °C) is triclinic.[2]
DPPH is a well-known radical and a trap ("scavenger") for other
radicals. Therefore, rate reduction of a chemical reaction upon
addition of DPPH is used as an indicator of the radical nature of that
reaction. Because of a strong absorption band centered at about
520 nm, the DPPH radical has a deep violet color in solution, and it
becomes colorless or pale yellow when neutralized. This property
allows visual monitoring of the reaction, and the number of initial
radicals can be counted from the change in the optical absorption at
520 nm or in the EPR signal of the DPPH.[3]
Names
IUPAC name
di(phenyl)-(2,4,6trinitrophenyl)iminoazanium
Other names
2,2-diphenyl-1-picrylhydrazyl
1,1-diphenyl-2-picrylhydrazyl
radical
2,2-diphenyl-1-(2,4,6trinitrophenyl)hydrazyl
Diphenylpicrylhydrazyl
Identifiers
CAS Number
1898-66-4 (http://ww
w.commonchemistry.
org/ChemicalDetail.a
spx?ref=1898-66-4)
3D model
(JSmol)
Interactive image (ht
tps://chemapps.stola
f.edu/jmol/jmol.php?
model=c1ccc%28cc
1%29N%28c2ccccc
2%29%5BN%5Dc3
c%28cc%28cc3%5B
N%2B%5D%28%3D
O%29%5BO-%5D%
29%5BN%2B%5D%
28%3DO%29%5BO%5D%29%5BN%2
B%5D%28%3DO%2
9%5BO-%5D)
Abbreviations DPPH
ChemSpider
2016757 (http://ww
w.chemspider.com/C
hemical-Structure.20
16757.html)
ECHA
InfoCard
100.015.993 (https://
echa.europa.eu/sub
stance-information/-/
substanceinfo/100.0
15.993)
PubChem
CID
74358 (https://pubch
em.ncbi.nlm.nih.gov/
compound/74358)
CompTox
Dashboard
(EPA)
DTXSID8061896 (htt
ps://comptox.epa.go
v/dashboard/DTXSI
D8061896)
InChI
InChI=1S/C18H12N5O6/c24-21(25)15-11-16
(22(26)27)18(17(12-15)23(28)29)19-20(13
-7-3-1-4-8-13)14-9-5-2-6-10-14/h1-12H
Key: HHEAADYXPMHMCT-UHFFFAOYSA-N
InChI=1/C18H13N5O6/c24-21(25)15-11-16(2
2(26)27)18(17(12-15)23(28)29)19-20(13-7
-3-1-4-8-13)14-9-5-2-6-10-14/h1-12,19H
Key: WCBPJVKVIMMEQC-UHFFFAOYAG
InChI=1/C18H12N5O6/c24-21(25)15-11-16(2
2(26)27)18(17(12-15)23(28)29)19-20(13-7
-3-1-4-8-13)14-9-5-2-6-10-14/h1-12H
Key: HHEAADYXPMHMCT-UHFFFAOYAG
SMILES
c1ccc(cc1)N(c2ccccc2)[N]c3c(cc(cc3[N+](=O)
[O-])[N+](=O)[O-])[N+](=O)[O-]
Properties
Chemical
formula
C18H12N5O6
Molar mass
394.32 g/mol
Appearance
Black to green
powder, purple in
solution
Density
1.4 g/cm3
Melting point
135 °C (275 °F;
408 K)
(decomposes)
Solubility in
water
insoluble
Solubility in
methanol
10 mg/mL
Hazards
Safety data
sheet
NFPA 704
(fire diamond)
MSDS (http://datash
eets.scbt.com/sc-20
2591.pdf)
0
1
0
Except where otherwise noted, data
are given for materials in their
standard state (at 25 °C [77 °F],
100 kPa).
verify (what is
?)
Infobox references
Because DPPH is an efficient radical trap, it is also a strong inhibitor of radical-mediated polymerization.[4]
Inhibition of polymer chain, R, by DPPH.
As a stable and well-characterized solid radical source, DPPH is the traditional and perhaps the most
popular standard of the position (g-marker) and intensity of electron paramagnetic resonance (EPR) signals
– the number of radicals for a freshly prepared sample can be determined by weighing and the EPR splitting
factor for DPPH is calibrated at g = 2.0036. DPPH signal is convenient by that it is normally concentrated in
a single line, whose intensity increases linearly with the square root of microwave power in the wider power
range. The dilute nature of the DPPH radicals (one unpaired spin per 41 atoms) results in a relatively small
linewidth (1.5–4.7 Gauss). The linewidth may however increase if solvent molecules remain in the crystal
and if measurements are performed with a high-frequency EPR setup (~200 GHz), where the slight ganisotropy of DPPH becomes detectable.[5][6]
Whereas DPPH is normally a paramagnetic solid, it transforms into an antiferromagnetic state upon cooling
to very low temperatures of the order 0.3 K. This phenomenon was first reported by Alexander Prokhorov in
1963.[7][8][9][10]
References
1. DPPH antioxidant assay revisited. Om P. Sharma and Tej K. Bhat, Food Chemistry, Volume
113, Issue 4, 15 April 2009, Pages 1202–1205, doi:10.1016/j.foodchem.2008.08.008 (https://d
oi.org/10.1016%2Fj.foodchem.2008.08.008)
2. Kiers, C. T.; De Boer, J. L.; Olthof, R.; Spek, A. L. (1976). "The crystal structure of a 2,2diphenyl-1-picrylhydrazyl (DPPH) modification". Acta Crystallographica Section B. 32 (8):
2297. doi:10.1107/S0567740876007632 (https://doi.org/10.1107%2FS0567740876007632).
3. Mark S. M. Alger (1997). Polymer science dictionary (https://books.google.com/books?id=OSA
aRwBXGuEC&pg=PA152). Springer. p. 152. ISBN 0-412-60870-7.
4. Cowie, J. M. G.; Arrighi, Valeria (2008). Polymers: Chemistry and Physics of Modern Materials
(3rd ed.). Scotland: CRC Press. ISBN 978-0-8493-9813-1.
5. M.J. Davies (2000). Electron Paramagnetic Resonance (https://books.google.com/books?id=y
wjuZo9UackC&pg=PA178). Royal Society of Chemistry. p. 178. ISBN 0-85404-310-1.
6. Charles P. Poole (1996). Electron spin resonance: a comprehensive treatise on experimental
techniques (https://books.google.com/books?id=P-4PIoi7Z7IC&pg=PA443). Courier Dover
Publications. p. 443. ISBN 0-486-69444-5.
7. A. M. Prokhorov and V.B. Fedorov, Soviet Phys. JETP 16 (1963) 1489.
8. Teruaki Fujito (1981). "Magnetic Interaction in Solvent-free DPPH and DPPH–Solvent
Complexes" (http://www.journalarchive.jst.go.jp/english/jnlabstract_en.php?cdjournal=bcsj1926
&cdvol=54&noissue=10&startpage=3110). Bulletin of the Chemical Society of Japan. 54 (10):
3110. doi:10.1246/bcsj.54.3110 (https://doi.org/10.1246%2Fbcsj.54.3110).
9. Stig Lundqvist (1998). "A. M. Prokhorov" (https://books.google.com/books?id=uywFzcv3Tv8C
&pg=PA118). Nobel lectures in physics, 1963-1970. World Scientific. p. 118. ISBN 981-023404-X.
10. Aleksandr M. Prokhorov, The Nobel Prize in Physics 1964 (http://nobelprize.org/nobel_prizes/p
hysics/laureates/1964/prokhorov-bio.html)
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