Search results
Results from the WOW.Com Content Network
In organic chemistry, nitration is a general class of chemical processes for the introduction of a nitro group (−NO 2) into an organic compound. The term also is applied incorrectly to the different process of forming nitrate esters ( −ONO 2 ) between alcohols and nitric acid (as occurs in the synthesis of nitroglycerin ).
The nitration product produced on the largest scale, by far, is nitrobenzene. Many explosives are produced by nitration including trinitrophenol (picric acid), trinitrotoluene (TNT), and trinitroresorcinol (styphnic acid). [3] Another but more specialized method for making aryl–NO 2 group starts from halogenated phenols, is the Zinke nitration.
Nitrobenzene is prepared by nitration of benzene with a mixture of concentrated sulfuric acid, water, and nitric acid. This mixture is sometimes called "mixed acid." The production of nitrobenzene is one of the most dangerous processes conducted in the chemical industry because of the exothermicity of the reaction (ΔH = −117 kJ/mol). [5] +
Although discussions of directing groups usually focus on electronic effects (e.g. EWG vs EDGs), steric effect can prove influential. Thus, nitration of toluene gives approximately 2:1 ortho vs para-nitrotoluene. In the case of tert-butylbenzene, however, the selectivity is reversed:73% of the product is 4-nitro-tert-butybenzene]]. [4]
1,3-Dinitrobenzene is accessible by nitration of nitrobenzene. The reaction proceeds under acid catalysis using sulfuric acid. The directing effect of the nitro group of nitrobenzene leads to 93% of the product resulting from nitration at the meta-position. The ortho- and para-products occur in only 6% and 1%, respectively. [1]
Synthesis of DNP (right) from phenol and nitric acid via 2-Nitrophenol and 4-Nitrophenol. DNP has the chemical formula HOC 6 H 3 (NO 2) 2. As a solid, it is a yellow, crystalline and has a sweet, musty odor. [1] [2] It sublimates, is volatile with steam, and is soluble in most organic solvents as well as aqueous alkaline solutions. [2]
4-Nitrophenol is a product of the enzymatic cleavage of several synthetic substrates such as 4-nitrophenyl phosphate (used as a substrate for alkaline phosphatase), 4-nitrophenyl acetate (for carbonic anhydrase), 4-nitrophenyl-β-D-glucopyranoside and other sugar derivatives which are used to assay various glycosidase enzymes.
Phenol oxidation with hypervalent iodine reagents leads to the formation of quinone-type products or iodonium ylides, depending on the structure of the phenol. Trapping of either product is possible with a suitable reagent, and this method is often employed in tandem with a second process. [1]