2,4-Dinitrophenylhydrazine (2,4-DNPH or DNPH) is the
organic compound
In chemistry, organic compounds are generally any chemical compounds that contain carbon- hydrogen or carbon-carbon bonds. Due to carbon's ability to catenate (form chains with other carbon atoms), millions of organic compounds are known. Th ...
C
6H
3(NO
2)
2NHNH
2. DNPH is a red to orange solid. It is a substituted
hydrazine
Hydrazine is an inorganic compound with the chemical formula . It is a simple pnictogen hydride, and is a colourless flammable liquid with an ammonia-like odour. Hydrazine is highly toxic unless handled in solution as, for example, hydrazin ...
. The solid is relatively sensitive to
shock and
friction
Friction is the force resisting the relative motion of solid surfaces, fluid layers, and material elements sliding (motion), sliding against each other. There are several types of friction:
*Dry friction is a force that opposes the relative la ...
. For this reason DNPH is usually handled as a wet powder. DNPH is a precursor to the drug
Sivifene
Sivifene (INN, USAN; developmental code name A-007) is a small-molecule antineoplastic agent and immunomodulator that was under development in the 2000s by Tigris Pharmaceuticals (now Kirax Corporation) as a topical treatment for cutaneous cancer ...
.
Synthesis
It can be prepared by the reaction of
hydrazine sulfate with
2,4-dinitrochlorobenzene
2,4-Dinitrochlorobenzene (DNCB) is an organic compound with the chemical formula (O2N)2C6H3Cl. It is a yellow solid that is soluble in organic solvents. It is an important intermediate for the industrial production of other compounds.
DNCB is p ...
:
:
DNP test
DNPH is a reagent in instructional laboratories on
qualitative organic analysis. 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 ketone
In organic chemistry, a ketone is a functional group with the structure R–C(=O)–R', where R and R' can be a variety of carbon-containing substituents. Ketones contain a carbonyl group –C(=O)– (which contains a carbon-oxygen double bon ...
s and
aldehyde
In organic chemistry, an aldehyde () is an organic compound containing a functional group with the structure . The functional group itself (without the "R" side chain) can be referred to as an aldehyde but can also be classified as a formyl group ...
s. A positive test is signalled by the formation of a yellow, orange or red
precipitate
In an aqueous solution, precipitation is the process of transforming a dissolved substance into an insoluble solid from a super-saturated solution. The solid formed is called the precipitate. In case of an inorganic chemical reaction leading ...
of the dinitrophenylhydrazone. Aromatic carbonyls give red precipitates whereas
aliphatic
In organic chemistry, hydrocarbons ( compounds composed solely of carbon and hydrogen) are divided into two classes: aromatic compounds and aliphatic compounds (; G. ''aleiphar'', fat, oil). Aliphatic compounds can be saturated, like hexane, ...
carbonyls give more yellow color. The reaction between DNPH and a generic ketone to form a
hydrazone
Hydrazones are a class of organic compounds with the structure . They are related to ketones and aldehydes by the replacement of the oxygen =O with the = functional group. They are formed usually by the action of hydrazine on ketones or aldehydes. ...
is shown below:
:RR'C=O + C
6H
3(NO
2)
2NHNH
2 → C
6H
3(NO
2)
2NHN=CRR' + H
2O
This reaction is, overall, a
condensation reaction
In organic chemistry, a condensation reaction is a type of chemical reaction in which two molecules are combined to form a single molecule, usually with the loss of a small molecule such as water. If water is lost, the reaction is also known as a ...
as two molecules joining together with loss of water. Mechanistically, it is an example of
addition-elimination reaction: nucleophilic addition of the -NH
2 group to the C=O carbonyl group, followed by the elimination of a H
2O molecule:
:
DNP-derived hydrazones have characteristic melting points, facilitating identification of the carbonyl. In particular, the use of DNPH was developed by Brady and Elsmie. Modern spectroscopic and spectrometric techniques have superseded these techniques.
DNPH does not react with other carbonyl-containing functional groups such as
carboxylic acids
In organic chemistry, a carboxylic acid is an organic acid that contains a carboxyl group () attached to an R-group. The general formula of a carboxylic acid is or , with R referring to the alkyl, alkenyl, aryl, or other group. Carboxyl ...
,
amide
In organic chemistry, an amide, also known as an organic amide or a carboxamide, is a compound with the general formula , where R, R', and R″ represent organic groups or hydrogen atoms. The amide group is called a peptide bond when it is ...
s, and
esters
In chemistry, an ester is a compound derived from an oxoacid (organic or inorganic) in which at least one hydroxyl group () is replaced by an alkoxy group (), as in the substitution reaction of a carboxylic acid and an alcohol. Glycerides are ...
, 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. If DNPH is stored improperly and left to dry out, it can become explosive.
It is artificial uncoupler of electron transport chain (ETC).
See also
*
Tollens' reagent
Tollens' reagent (chemical formula Ag(NH3)2OH) is a chemical reagent used to distinguish between aldehydes and ketones along with some alpha-hydroxy ketones which can tautomerize into aldehydes. The reagent consists of a solution of silver nitr ...
*
Fehling's reagent
*
Schiff test
References
{{DEFAULTSORT:Dinitrophenylhydrazine, 2, 4-
Nitrobenzenes
Reagents for organic chemistry
Hydrazines