W-Nitroaniline

The w-nitroaniline used in these experiments was a commercial specimen of 98.4 per cent purity. A less pure specimen did not give a greatly decreased yield. 

The w-nitroaniline may also be added to the mixture prepared by adding the ice to the diluted acid, but this procedure is not quite so satisfactory. 

FIGURE 3 Release of -nitroaniline and the degradation of PCPA versus time. Disks (1.4 cm in diameter and 1 mm thick) of poly-(carboxyphenoxyacetic acid) (PCPA) were prepared containing 5% (w/w) -nitroaniline by compression molding, and degraded in 0.1 M pH 7.4 phosphate buffer at 37°C. The cumulative release of p-nitroaniline and degradation of PCPA were measured by absorbance at 380 and 235 nm, respectively. 

In a 500-cc. round-bottom flask are placed 200 cc. of water, 100 cc. of concentrated sulfuric acid, and 50 g. of powdered w-nitroaniline. The hot mixture is shaken until solution is complete, and the hot m-nitroaniline sulfate solution is then poured into a 5-I. flask containing 1000 cc. of water and 800-1000 g. of cracked ice. During this procedure there must be good agitation, so that the m-nitroaniline sulfate forms a finely divided precipitate. Generally, the amount of ice used is sufficient to lower the temperature of the mixture to o°, but if not, more ice is added till o° is reached. 

In diazotizing w-nitroaniline sulfate, it is necessary to add the sodium nitrite as rapidly as possible in order to prevent any of the diazonium salt from coupling with undia/.otized m-nitroaniline and forming a yellow precipitate of diazoamino compound. The presence of the excess of sulfuric acid, which does not interfere with the formation of the t-nitrophenol, tends to avoid this same difficulty. 

A solution of 26 g. of sodium nitrite in 200 cc. of water is then rapidly added (Note i) to the cold w-nitroaniline sulfate suspension continual shaking or mechanical stirring should be used until the w-nitroaniline sulfate dissolves completely. This requires about five minutes, during which period the solution gradually darkens. A small flocculent precipitate forms at the same time and should be filtered off. 

The above procedure is a modification of the method of Groll 1 a more laborious method of purification has been described. w-Nitrodimethylaniline can also be prepared by methylation of w-nitroaniline using methyl sulfate.3... 

From w-nitroaniline by the Sandmeyer reaction. Kohman, J. Phys. Chem. 29, 1052 (19.25). 

Porphyrins are often employed in sensors on account of their ability to act as cation hosts and, with a suitable metal ion coordinated, as redox catalysts. Electropolymerised poly(metalloporphyrin)s have been used as potentiometric anion-selective electrodes [131] and as amperometric electrocatalytic sensors for many species including phenols [132], nitrous oxide [133] and oxygen [134]. Panasyuk et al. [135] have electropolymerised [nickel-(protoporphyrin IX)dimethylester] (Fig. 18.10) on glassy carbon in the presence of nitrobenzene in an attempt to prepare a nitrobenzene-selective amperometric sensor. Following extraction of the nitrobenzene the electrode was exposed to different species and cyclic voltammetric measurements made. A response was observed at the reduction potential of nitrobenzene (the polyporphyrin film acts only to accumulate the analyte and not in a catalytic fashion). Selectivity for nitrobenzene compared with w-nitroaniline and o-nitroto-luene was enhanced compared with an untreated electrode, while a glassy carbon-... 

Muraour and Ertaud [52] exposed lead azide, mercury fulminate, di azo-w-nitroaniline perchlorate, lead trinitroresorcinate, and tetracene to total thermal neutron fluxes up to lO n/cm . The y component was not given. No explosions occurred. The only effect noticed was a slight color change from white to light brown in tetracene. The lead azide was exposed to a total thermal neutron dose of3 X lO " n/cm". 

A. l-(m-Nitrophenyl)-3,3-dimethyltriazene. To a 3-1. threenecked flask containing 276 g. (2 moles) of technical grade m-nitroaniline (Note 1) are added 250 ml. of concentrated hydrochloric acid and 500 ml. of hot water. The contents of the flask are heated to about 85° to dissolve the w-nitroaniline then 550 ml. of concentrated hydrochloric acid is added, and the solution is cooled rapidly. A stirrer, a thermometer, and a longstemmed dropping funnel are attached to the flask, and its contents are then cooled to —3 to —5° by means of a salt-ice bath. A solution of 144 g. (2.09 moles) of sodium nitrite in 350 ml. of water is added dropwise under the surface of the acid solution... 

A mixture of nitric acid (d 1.42 200 ml) and concentrated sulfuric acid (200 ml) is dropped slowly into a stirred solution (prepared with cooling) of A,A-dimethylaniline (363 g) in concentrated sulfuric acid (1270 ml) at 5°. The mixture is stirred for a further 1 h at 5-10°, then poured into ice-water (61) and treated with concentrated aqueous ammonia until precipitation of the p-nitro compound is complete, this being recognized by a change in the color of the precipitate from yellow (p-nitro compound) to orange (/w-nitro compound). The p-nitro compound is filtered off and further ammonia is added to the filtrate until the pH is 3 this precipitates the A,A-dimethyl-/w-nitroaniline, which is obtained pure (m.p. 59-60°) in 56 to 63% yield (280-316 g) by recrystallization from ethanol (400 ml). 

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