2,4-Dinitrophenylhydrazine 1919588 215621683 2008-05-29T00:05:38Z Naidevinci 7045825 /* See also */ {{Chembox new | ImageFileL1 = 2,4-Dinitrophenylhydrazine.png | ImageSizeL1 = 110px | ImageFileR1 = 24dnp3d.png | ImageSizeR1 = 110px | IUPACName = (2,4-dinitrophenyl)hydrazine | OtherNames = 2,4-DNPH; 2,4-DNP; Brady's reagent | Section1 = {{Chembox Identifiers | CASNo = 119-26-6 | PubChem = | SMILES = NNc1ccc(cc1[N+]([O-])=O)[N+]([O-])=O }} | Section2 = {{Chembox Properties | Formula = C<sub>6</sub>H<sub>6</sub>N<sub>4</sub>O<sub>4</sub> | MolarMass = 198.14 | Appearance = Red or orange powder | Density = | MeltingPt = 198 - 202 °C dec. | BoilingPt = | Solubility = Slight }} | Section7 = {{Chembox Hazards | MainHazards = Flammable, possible carcinogen | FlashPt = | Autoignition = }} }} '''2,4-Dinitrophenylhydrazine''' ('''DNPH''', '''Brady's reagent''') is the [[chemical compound]] C<sub>6</sub>H<sub>3</sub>(NO<sub>2</sub>)<sub>2</sub>NHNH<sub>2</sub>. Dinitrophenylhydrazine is relatively sensitive to [[Shock (mechanics)|shock]] and [[friction]]; it is a shock explosive so care must be taken with its use. It is a red to orange solid, usually supplied wet to reduce its explosive hazard. It is a substituted [[hydrazine]], and is often used to qualitatively test for [[carbonyl group]]s associated with aldehydes and ketones. The hydrazone [[Derivative (chemistry)|derivatives]] can also be used as evidence toward the identity of the original compound. ==Synthesis== 2,4-Dinitrophenylhydrazine is commercially available usually as a wet powder. It can be prepared by the reaction of [[hydrazine]] with 2,4-dinitrochlorobenzene.<ref>{{OrgSynth | author = Allen, C. F. H. | prep = cv2p0228 | title = 2,4-Dinitrophenylhydrazine | collvol = 2 | collvolpages = 228 | year = 1943}}</ref> ==Brady's test== 2,4-Dinitrophenylhydrazine can be used to qualitatively [[chemical test|detect]] the carbonyl functionality of a [[ketone]] or [[aldehyde]] functional group. A positive test is signaled by a yellow or red [[precipitate]] (known as a [[dinitrophenylhydrazone]]): :RR'C=O + C<sub>6</sub>H<sub>3</sub>(NO<sub>2</sub>)<sub>2</sub>NHNH<sub>2</sub> → C<sub>6</sub>H<sub>3</sub>(NO<sub>2</sub>)<sub>2</sub>NHNCRR' + H<sub>2</sub>O This reaction can be described as a condensation reaction, with two molecules joining together with loss of water. It is also called addition-elimination reaction: nucleophilic addition of the -NH<sub>2</sub> group to the C=O carbonyl group, followed by the removal of a H<sub>2</sub>O molecule. :The mechanism for the reaction between 2,4-dinitrophenylhydrazine and an aldehyde or ketone is shown:<ref>Adapted from ''Chemistry in Context'', 4th Edition, 2000, Graham Hill and John Holman</ref> :[[Image:Brady's-reagent-mechanism.png|480px|Reaction mechanism]] Crystals of different hydrazones have characteristic melting and boiling points, hence 2,4-dinitrophenylhydrazine can be used to distinguish between various compounds containing carbonyl groups. The method was particularly important because melting point determinations require only low-cost instrumentation. This application in analytical chemistry was developed by Brady and Elsmie.<ref>{{cite journal | author = Brady, O. L.; Elsmie, G. V. | title = The use of 2:4-dinitrophenylhydrazine as a reagent for aldehydes and ketones | journal = [[Analyst (journal)|Analyst]] | volume = 51 | pages = 77–78 | year = 1926 | doi = 10.1039/AN9265100077}}</ref> [[Image:24-dinitrophenylhydrazonederiv.jpg|thumb|right|2,4-DNP reacting with 2-heptanone]] Dinitrophenylhydrazine does not react with other carbonyl-containing functional groups such as [[carboxylic acids]], [[amides]], and [[esters]]. For [[carboxylic acids]], [[amides]] and [[esters]], there is resonance associated stability as a lone-pair of electrons interacts with the p-orbital of the carbonyl carbon resulting in increased delocalisation 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. ==See also== * [[Tollens' reagent]] * [[Fehling's reagent]] ==References== <references/> ==External links== *[http://www.jtbaker.com/msds/englishhtml/d7464.htm MSDS for 2,4-Dinitrophenylhydrazine] {{DEFAULTSORT:Dinitrophenylhydrazine, 2,4-}} [[Category:Aromatic compounds]] [[Category:Reagents for organic chemistry]] [[Category:Hydrazines]] [[de:2,4-Dinitrophenylhydrazin]] [[es:2,4-dinitrofenilhidracina]] [[fr:2,4-dinitrophénylhydrazine]] [[it:2,4-dinitrofenilidrazina]] [[pl:2,4-dinitrofenylohydrazyna]] [[zh:2,4-二硝基苯肼]]