2,4-Dinitrophenylhydrazine

2,4-Dinitrophenylhydrazine (2,4-DNPH or DNPH) is the organic compound C₆H₃(NO₂)₂NHNH₂. DNPH is a red to orange solid. It is a substituted hydrazine. The solid is relatively sensitive to shock and friction. For this reason DNPH is usually handled as a wet powder. DNPH is a precursor to the drug Sivifene.

2,4-Dinitrophenylhydrazine

Names
Preferred IUPAC name (2,4-Dinitrophenyl)hydrazine
Other names 2,4-DNPH 2,4-DNP DNPH Brady's reagent Borche's reagent
Identifiers
CAS Number	119-26-6 Y
3D model (JSmol)	Interactive image
ChEBI	CHEBI:66932 Y
ChEMBL	ChEMBL352799 Y
ChemSpider	3001507 Y
ECHA InfoCard	100.003.918
EC Number	204-309-3
KEGG	C11283 Y
PubChem CID	3772977
UNII	1N39KD7QPJ
CompTox Dashboard (EPA)	DTXSID2059485
InChI InChI=1S/C6H6N4O4/c7-8-5-2-1-4(9(11)12)3-6(5)10(13)14/h1-3,8H,7H2 Y Key: HORQAOAYAYGIBM-UHFFFAOYSA-N Y InChI=1/C6H6N4O4/c7-8-5-2-1-4(9(11)12)3-6(5)10(13)14/h1-3,8H,7H2 Key: HORQAOAYAYGIBM-UHFFFAOYAM
SMILES c1cc(c(cc1[N+](=O)[O-])[N+](=O)[O-])NN
Properties
Chemical formula	C6H6N4O4
Molar mass	198.14 g/mol
Appearance	Red or orange powder
Melting point	198 to 202 °C (388 to 396 °F; 471 to 475 K) dec.
Solubility in water	Slight
Hazards
Occupational safety and health (OHS/OSH):
Main hazards	Flammable, possibly carcinogenic
GHS labelling:
Pictograms
Signal word	Warning
Hazard statements	H228, H302, H319
Precautionary statements	P210, P240, P241, P264, P270, P280, P301+P312, P305+P351+P338, P330, P337+P313, P370+P378, P501
Safety data sheet (SDS)	MSDS
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). N verify (what is YN ?) Infobox references

Synthesis

It can be prepared by the reaction of hydrazine sulfate with 2,4-dinitrochlorobenzene:^[1]

DNP test

DNPH is a reagent in instructional analytical chemistry laboratories. Brady's reagent or Borche's reagent, is prepared by dissolving DNPH in a solution containing methanol and some concentrated sulfuric acid. This solution is used to detect ketones and aldehydes. A positive test is signalled by the formation of a yellow, orange or red precipitate of the dinitrophenylhydrazone. Aromatic carbonyls give red precipitates whereas aliphatic carbonyls give more yellow color.^[2] The reaction between DNPH and a generic ketone to form a hydrazone is shown below:

RR'C=O   +   C₆H₃(NO₂)₂NHNH₂   →   C₆H₃(NO₂)₂NHN=CRR'   +   H₂O

This reaction is, overall, a condensation reaction as two molecules joining together with loss of water. Mechanistically, it is an example of addition-elimination reaction: nucleophilic addition of the -NH₂ group to the C=O carbonyl group, followed by the elimination of a H₂O molecule:^[3]

X-ray structure of DNP-derived hydrazone of benzophenone. Selected parameters: C=N, 128 pm; N-N, 1.38 pm, N-N-C(Ar), 119^[4]

When 3-heptanone is added to a solution of 2,4-DNPH and heated, an orange-red precipitate forms.

DNP-derived hydrazones have characteristic melting points, facilitating identification of the carbonyl. In particular, the use of DNPH was developed by Brady and Elsmie.^[5] Modern spectroscopic and spectrometric techniques have superseded these techniques.

DNPH does not react with other carbonyl-containing functional groups such as carboxylic acids, amides, and esters, for which there is resonance-associated stability as a lone-pair of electrons interacts with the p orbital of the carbonyl carbon resulting in increased delocalization in the molecule. This stability would be lost by addition of a reagent to the carbonyl group. Hence, these compounds are more resistant to addition reactions. Also, with carboxylic acids, there is the effect of the compound acting as a base, leaving the resulting carboxylate negatively charged and hence no longer vulnerable to nucleophilic attack.

Safety

Dry DNPH is friction and shock sensitive. For this reason, it’s supplied damp or ‘wetted’ when a school purchases it from a chemical supplier.^[6] If DNPH is stored improperly and left to dry out, it can become explosive. It is an artificial uncoupler of the electron transport chain (ETC).^[7]

See also

• Tollens' reagent
• Fehling's reagent
• Schiff test