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{{chembox |
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| verifiedrevid = 396323266 |
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| verifiedrevid = 441743867 |
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| Name = |
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| ImageFile = DPPH.svg |
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| ImageFile = DPPH.svg |
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| ImageSize = |
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| ImageSize = 220 |
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| ImageAlt = Skeletal formula of DPPH |
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| IUPACName = di(phenyl)-(2,4,6-trinitrophenyl)iminoazanium |
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| ImageFile1 = Dpph sample.jpg |
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| OtherNames = 2,2-diphenyl-1-picrylhydrazyl <br/>1,1-diphenyl-2-picrylhydrazyl radical <br/> 2,2-diphenyl-1-(2,4,6-trinitrophenyl)hydrazyl<br>Diphenylpicrylhydrazyl |
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| ImageSize1 = 220 |
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| ImageAlt1 = sample |
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{{Chembox Identifiers |
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| PIN = 2,2-Diphenyl-1-(2,4,6-trinitrophenyl)hydrazin-1-yl |
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| OtherNames = 2,2-Diphenyl-1-picrylhydrazyl<br/>1,1-Diphenyl-2-picrylhydrazyl radical<br/>2,2-Diphenyl-1-(2,4,6-trinitrophenyl)hydrazyl<br/>Diphenylpicrylhydrazyl |
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| Section1 = {{Chembox Identifiers |
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| Abbreviations = DPPH |
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| Abbreviations = DPPH |
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| ChemSpiderID_Ref = {{chemspidercite|correct|chemspider}} |
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| ChemSpiderID_Ref = {{chemspidercite|correct|chemspider}} |
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| CASNo_Ref = {{cascite|correct|CAS}} |
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| CASNo_Ref = {{cascite|correct|CAS}} |
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| CASNo = 1898-66-4 |
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| CASNo = 1898-66-4 |
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| UNII_Ref = {{fdacite|Correct|FDA}} |
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| UNII = DFD3H4VGDH |
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| EINECS = |
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| EINECS = |
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| PubChem = 74358 |
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| PubChem = 74358 |
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| SMILES = c1ccc(cc1)N(c2ccccc2)c3c(cc(cc3(=O))(=O))(=O) |
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| SMILES = c1ccc(cc1)N(c2ccccc2)c3c(cc(cc3(=O))(=O))(=O) |
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| InChI = 1/C18H13N5O6/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/h1-12,19H |
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| InChI = 1/C18H13N5O6/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/h1-12,19H |
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}}| Section2 = {{Chembox Properties |
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| Section2 = {{Chembox Properties |
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| Formula = C<sub>18</sub>H<sub>12</sub>N<sub>5</sub>O<sub>6</sub> |
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| Formula = C<sub>18</sub>H<sub>12</sub>N<sub>5</sub>O<sub>6</sub> |
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| MolarMass = 394.32 g/mol |
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| MolarMass = 394.32 g/mol |
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| Density = 1.4 g/cm<sup>3</sup> |
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| Density = 1.4 g/cm<sup>3</sup> |
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| MeltingPtC = 135 |
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| MeltingPtC = 135 |
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| Melting_notes =decomposes |
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| MeltingPt_notes = (decomposes) |
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| Solubility = insoluble |
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| Solubility = insoluble |
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| Solubility1 = 10 mg/mL |
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| Solvent1 = methanol |
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| Solvent = ], ] |
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| Solvent = ], ] |
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| pKb =}} | Section7 = {{Chembox Hazards |
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| Section7 = {{Chembox Hazards |
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| NFPA-H = 0 |
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| NFPA-H = 0 |
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| NFPA-F = 1 |
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| NFPA-F = 1 |
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| NFPA-R = 0 |
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| NFPA-R = 0 |
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| PEL =}} |
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'''DPPH''' is a common abbreviation for an organic ] 2,2-diphenyl-1-picrylhydrazyl. It is a dark-colored crystalline powder composed of stable ] molecules. DPPH has two major applications, both in laboratory research: one is a monitor of chemical reactions involving radicals and another is a standard of the position and intensity of ] signals. |
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'''DPPH''' is a common abbreviation for the organic ] '''2,2-diphenyl-1-picrylhydrazyl'''. It is a dark-colored crystalline powder composed of stable ] 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 ] assay,<ref>{{cite journal|title=DPPH antioxidant assay revisited |first1=Om P. |last1=Sharma |first2=Tej K. |last2=Bhat |journal=Journal of Food Chemistry |volume=113 |issue=4 |date=15 April 2009 |pages=1202–1205 |doi=10.1016/j.foodchem.2008.08.008}}</ref> and another is a standard of the position and intensity of ] signals. |
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==Properties and applications== |
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== Properties and applications == |
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DPPH has several crystalline forms which differ by the lattice symmetry and ] (m.p.). The commercial powder is a mixture of phases which melts at ~130 °C. DPPH-I (m.p. 106 °C) is ], DPPH-II (m.p. 137 °C) is amorphous and DPPH-III (m.p. 128–129 °C) is ].<ref>{{cite journal|doi=10.1107/S0567740876007632|title=The crystal structure of a 2,2-diphenyl-1-picrylhydrazyl (DPPH) modification|year=1976|last1=Kiers|first1=C. T.|last2=De Boer|first2=J. L.|last3=Olthof|first3=R.|last4=Spek|first4=A. L.|journal=Acta Crystallographica Section B Structural Crystallography and Crystal Chemistry|volume=32|pages=2297}}</ref> |
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DPPH has several crystalline forms which differ by the lattice symmetry and ]. The commercial powder is a mixture of phases which melts at ~130 °C. DPPH-I (m.p. 106 °C) is ], DPPH-II (m.p. 137 °C) is amorphous and DPPH-III (m.p. 128–129 °C) is ].<ref>{{cite journal|doi=10.1107/S0567740876007632|title=The crystal structure of a 2,2-diphenyl-1-picrylhydrazyl (DPPH) modification|year=1976|last1=Kiers|first1=C. T.|last2=De Boer|first2=J. L.|last3=Olthof|first3=R.|last4=Spek|first4=A. L.|journal=Acta Crystallographica Section B|volume=32|pages=2297|issue=8}}</ref> |
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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.<ref>{{cite book|url=http://books.google.com/?id=OSAaRwBXGuEC&pg=PA152|page=152|title=Polymer science dictionary|author=Mark S. M. Alger|publisher=Springer|year=1997|isbn=0412608707}}</ref> |
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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.<ref>{{cite book|url=https://books.google.com/books?id=OSAaRwBXGuEC&pg=PA152|page=152|title=Polymer science dictionary|first=Mark S. M.|last=Alger|publisher=Springer|year=1997|isbn=0-412-60870-7}}</ref> |
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Because DPPH is efficient radical trap, it is also a strong inhibitor of ].<ref name="ca2008">{{cite book|last=Cowie|first=J. M. G.|coauthors=Arrighi, Valeria|title=Polymers: Chemistry and Physics of Modern Materials|publisher=CRC Press|location=Scotland|year=2008|edition=3rd|isbn=0-8493-9813-4}}</ref> |
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Because DPPH is an efficient radical trap, it is also a strong inhibitor of ].<ref name="ca2008">{{cite book|last=Cowie|first=J. M. G.|last2=Arrighi|first2=Valeria|title=Polymers: Chemistry and Physics of Modern Materials|publisher=CRC Press|location=Scotland|year=2008|edition=3rd|isbn=978-0-8493-9813-1}}</ref> |
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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 ] (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 g-anisotropy of DPPH becomes detectable.<ref>{{cite book|url=http://books.google.com/?id=ywjuZo9UackC&pg=PA178|page=178|title=Electron Paramagnetic Resonance|author=M.J. Davies|publisher=Royal Society of Chemistry|year=2000|isbn=0854043101}}</ref><ref>{{cite book|url=http://books.google.com/?id=P-4PIoi7Z7IC&pg=PA443|page=443|title=Electron spin resonance: a comprehensive treatise on experimental techniques|author=Charles P. Poole|publisher=Courier Dover Publications|year=1996|isbn=0486694445}}</ref> |
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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 ] (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 ]). 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 ''g''-anisotropy of DPPH becomes detectable.<ref>{{cite book|url=https://books.google.com/books?id=ywjuZo9UackC&pg=PA178|page=178|title=Electron Paramagnetic Resonance|author=M.J. Davies|publisher=Royal Society of Chemistry|year=2000|isbn=0-85404-310-1}}</ref><ref>{{cite book|url=https://books.google.com/books?id=P-4PIoi7Z7IC&pg=PA443|page=443|title=Electron spin resonance: a comprehensive treatise on experimental techniques|author=Charles P. Poole|publisher=Courier Dover Publications|year=1996|isbn=0-486-69444-5}}</ref> |
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Whereas DPPH is normally a paramagnetic solid, it transforms into an ] state upon cooling to very low temperatures of the order 0.3 K. This phenomenon was first reported by ] in 1963.<ref>A. M. Prokhorov and V.B. Fedorov, Soviet Phys. JETP 16 (1963) 1489.</ref><ref>{{cite journal|url=http://www.journalarchive.jst.go.jp/english/jnlabstract_en.php?cdjournal=bcsj1926&cdvol=54&noissue=10&startpage=3110|page=3110|journal=Bulletin of the Chemical Society of Japan|volume=54|issue=10|year=1981|title= Magnetic Interaction in Solvent-free DPPH and DPPH–Solvent Complexes|author=Teruaki Fujito}}</ref><ref>{{cite book|url=http://books.google.com/?id=uywFzcv3Tv8C&pg=PA118|page=118|title=Nobel lectures in physics, 1963-1970|author=Stig Lundqvist|publisher=World Scientific|year=1998|isbn=981023404X|chapter=A. M. Prokhorov}}</ref><ref></ref> |
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Whereas DPPH is normally a paramagnetic solid, it transforms into an ] state upon cooling to very low temperatures of the order 0.3 K. This phenomenon was first reported by ] in 1963.<ref>A. M. Prokhorov and V.B. Fedorov, Soviet Phys. JETP 16 (1963) 1489.</ref><ref>{{cite journal|page=3110|journal=Bulletin of the Chemical Society of Japan|volume=54|issue=10|year=1981|title=Magnetic Interaction in Solvent-free DPPH and DPPH–Solvent Complexes|first=Teruaki|last=Fujito|doi=10.1246/bcsj.54.3110|doi-access=free}}</ref><ref>{{cite book|chapter-url=https://books.google.com/books?id=uywFzcv3Tv8C&pg=PA118|page=118|title=Nobel Lectures in Physics, 1963–1970|first=Stig|last=Lundqvist|publisher=World Scientific|year=1998|isbn=981-02-3404-X|chapter=A. M. Prokhorov}}</ref><ref></ref> |
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==References== |
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==References== |
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{{reflist|30em}} |
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