Nitroanilines VOLUME

Heat a mixture of 15 g. of p-nitroacetanilide and 75 ml. of 70 per cent, sulphuric acid (1) under a reflux water condenser for 20-30 minutes or until a test sample remains clear upon dilution with 2-3 times its volume of water. The p-nitroaniline is now present in the hquid as the sulphate. Pour the clear hot solution into 500 ml. of cold water and precipitate the p-nitroanihne by adding excess of 10 per cent, sodium hydroxide solution or of concentrated ammonia solution. When cold (cool the mixture in ice water, if necessary), filter the yellow crystalline precipitate at the pump, wash it well with water, and drain thoroughly. Recrystallise it from a mixture of equal volumes of rectified (or methylated) spirit and water or from hot water. Filter, wash and dry. The yield of p-nitroanihne, m.p, 148°, is 11 g. 

Dissolve 10 g. of p-nitroaniline (Section IV,51) in a mixture of 21 ml. of concentrated hydrochloric acid and an equal volume of water, and cool rapidly to 0° in order to obtain the hydrochloride of the base in a fine state of division. Diazotise in the usual way (see Section IV,68) by the gradual addition of a solution of 6 0 g. of sodium nitrite in 12 ml. of water. Continue the stirring for a few minutes, filter the solution rapidly, and add it from a separatory funnel to an ice-cold solution of 41 g. of sodium sulphite (90 per cent. NajS03,7H20) in 100 ml. of water containing... 

A series of 2- and 4-nitroaniline derivatives and analogues when heated with cone, sulfuric acid to above 200°C undergo, after an induction period, a vigorous reaction. This is accompanied by gas evolution which produces up to a 150-fold increase in volume of a solid foam, and is rapid enough to be potentially hazardous if confined. 

Subsequently, catalysts were fabricated using nanotechnology routes to yield more prachcal materials. Both carbon and TiC supports were modified wifh nitroaniline precursors and transition metals (not disclosed). The best of fhese maferials showed remarkably high activify. At 0.7 V, a current density of 0.1 Acm was achieved on H2/O2 (80°C) in MEAs. Af very low current densities, a similar Tafel slope to Pt was observed and achieved a volume current density of 19 Acm af 0.8 V—twice as high as previously reported. Additionally, a TiC-supported version has shown 1,000 h durability (0.15 Acm 2,0.6 V, H2/air, 75°C). 

Example.—1-01 gms. nitrobenzene are sulphonated as described above, then cooled and the volume carefully diluted to 1 litre. 20 c.cs. are withdrawn and reduced with 50 c.cs. TiCl3 solution (as for p-nitroaniline). 

Selected data published by Patsias and Papadopoulou-Mourkidou [114] illustrate sorption s dependence on sample volume (Figure 2.36). Their research pursues development of an automated online SPE-HPLC methodology for analysis of substituted anilines and phenols. Recovery (%) was measured for numerous compounds on various polymeric sorbents, but the only data presented here are those in which a styrene-divinylbenzene polymeric sorbent was used for analysis of aniline, phenol, 4-nitroaniline, and 4-nitrophenol. Aqueous sample volumes of 5, 10, 25, 50, 75, 100, 125, and 150 mL were acidified to pH 3 before SPE. 

Recovery for 4-nitroaniline and 4-nitrophenol begins to decrease when the analytes break through from the sorbent between the sample volumes of 10 and 25 mL. Breakthrough volumes for phenol and aniline are less... 

Despite these shortcomings it will become clear that in the one-dimensional NLO-phores treated in this section, which display a wide range of seemingly disparate chemical structures, the crude model works surprisingly well. Thus, as a consequence of the validity of the two-state model, their second-order polarizabilities in principle reduce to p-nitroaniline . The reader may even gain the impression that the efforts to improve on the hyperpolarizabilities of even the simplest and most easily accessible -n systems (like p-nitroaniline) have been futile. It is true that an efficiency-transparency trade-off exists At a given wavelength of absorption (related to A ) a maximum value for the second-order molecular polarizability per volume element exists which is not tremendously different from that of very basic unoptimized rr systems. However, for applications like the electro-optical effect, a bathochromic shift of the UV-visible absorption is tolerable so that to strive for maximum hyperpolarizabilities is a viable quest. Furthermore, molecular structures with the same intrinsic second-order polarizabilities may differ substantially in their chemical stabilities and their abilities to be incorporated into ordered bulk structures. 

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