2- Amino-5-nitrophenol, reaction with

Bodanszky and Birkhimer found that in certain cases an N-protected amino acid reacts with p-nitrophenol in the presence of 2 equivalents of ethoxyacetylene at 50° for 1 hr. and at room temperature for 24 hrs. to give the p-nitrophenyl ester. However, the reaction often stops at the ethoxyvinyl ester stage or at the anhydride stage. 

MoL wt. 232,05, m.p. 145°. Prepared by bromomethylation of p-nitrophenol. The reagent has high selectivity for reaction with the tryptophane residues of proteins. The only other amino acid that reacts is cysteine, and this reacts more slowly. ... 

PROBLEM 27.18 p-Nitrophenyl esters are made from Z-protected amino acids by reaction with p-nitrophenol in the presence of W,W -dicyclohexylcarbodMmide. Suggest a reasonable mechanism for this reaction. 

These derivatives are stable to extended storage, and yet the p-nitrophenolate anion is a sufficiently good leaving group that reaction with free amino groups occurs readily. 2,4,5-Trichlorophenyl esters are occasionally employed in the same fashion. ... 

The p-nitrophenol fonned as a byproduct in this reaction is easily removed by extraction with dilute aqueous base. Unlike free amino acids and peptides, protected peptides are not zwitterionic and are more soluble in organic solvents than in water. 

Workers in the dinitrophenol plant should be protected in the usual way (i.e. gloves, respirators, chMige of clothes, bath, etc.). Selection of workers hMidling dinitrophenol is also recommended since it has been shown that a great mMiy people are resistant to its toxic effects, Selection is based on 15 days medical observation of each new worker in the dinitrophenol plant, in particular in the analysis of the mine every other day. A test for the presence of Mninonitrophenols is particularly importance. Usually Denien s reaction [33] is used. According to Lazarev [31], the reaction comprises acidification of the mine with 10% sulphuric acid and diazotization with sodium nitrite, followed by shaking up the prepMed solution with an ammoniacal solution of p- naphthol. If a red colour appeMS it indicates the presence of 4-amino-2-nitrophenol in the mine, while a violet shade is evidence for the presence of 2-Mnino-4-nitrophenol. 

Nitrate and nitrite photochemistry might also play a role in atmospheric hydrometeors. Nitrite photolysis has been shown to account for the majority of hydroxyl photoformation in irradiated fog water from a polluted site [ 14]. In addition, the generation of mutagenic and carcinogenic compounds from amino acids and amines dissolved in fog water [147] is a process that can be linked with nitrite photochemistry [20,141]. Furthermore, the formation of atmospheric nitrophenols partially takes place in aqueous solution. Reactions in the aqueous phase can account for about 30% of the atmospheric sources of mononitrophenols and for the vast majority of the dinitrophenol ones [ 148], and irradiation of nitrate and nitrite can possibly play a role in the process (see Sect. 3.2). Mono- and dinitrophenols are toxic compounds, and their occurrence in rainwater is thought to be a contributory factor in forest decline [149-151]. 

In the reaction of chloronitrobenzene and nitraniline with alkali the halogen atom or the amino group is only mobile in the 0 andp isomers and is replaceable by OH (also by CN, CNS etc.) much more readily than in chlorobenzene or aniline. This is a reaction of the nucleophilic OH- ion. 0-Nitrophenol and some -nitrophenol, but no meta, can indeed be produced from nitrobenzene with alkali also, though with difficulty. 

Historically, the first practicable reagent for the synthesis of N -Boc amino acids, tert-butyl 4-nitrophenyl carbonate (52), was developed by Anderson and McGregorb (Scheme 25). Due to the low reactivity of this mixed carbonate, drastic reaction conditions are required and yields remain unsatisfactory because of the difficult and laborious separation of the byproduct 4-nitrophenol. Alternative mixed carbonates have been proposed such as tert-butyl 2,4,5-trichlorophenyl carbonate (53),b32] lert-butyl pentachlorophenyl carbonate (54),b33] tert-butyl 2-pyridyl carbonate (55)0-tert-hvXy 5-4,6-dimethylpyrimidin-2-yl thiocarbonate (56).b3 1 With the latter two reagents the byproducts, pyridin-2-ol and 4,6-dimethylpyrimidine-2-thiol, respectively, are acid soluble and, thus, readily removed. 

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