Reactive Brown

Blown and black dyes are generally disazo with exceptions for metallized or polycyclic stmctuies (7). Two disazo dyes are Reactive Brown 11 [70161-17-0] (26) and Reactive Black 5 [17095-24-8] Cl 20505) (27). 

The most important 2 1 metal complex azo dyes are the 2 1 Cr3+ dyes. These may be symmetrical dyes, such as the water-soluble dye Cl Reactive Brown 10 (28), and the solvent-soluble dye Cl Solvent Yellow 21 (29), used in varnishes as a wood stain. They may also be unsymmetrical complexes, such as Cl Acid Violet 121 (30), used for dyeing wool and nylon. 

Fig. 3.131. Structures of (a) Reactive brown 23, (b) Reactive orange 4, and (c) Reactive red 2. Reprinted with permission from K. E. Van Cott et al. [179].

Fig. 3.132. HPLC chromatograms of (a) Reactive brown 23 (420 nm detection), (b) Reactive red 2 (Aldrich, 538 nm), and (c) Reactive orange 4 (490 nm) during hydrolysis. Dyes were dissolved at 10 mg/ml in 50 mM Na2C03 pH 10.5. Samples were removed for HPLC analysis at regular time intervals (t). Reactive brown was diluted to 2 mg/ml and injected Reactive red 2 and Reactive orange...

Methane is undesirable in most synthesis gas applications. The HTW demonstration plant was also designed specifically for reactive brown coal. Therefore, carbon conversion was not a problem, and the gasifier was a bubbling fluidized-bed design. 

Unlike nitrogen monoxide, nitrogen dioxide has properties more typical of an odd electron molecule. It is a coloured (brown), reactive gas which dimerises to the diamagnetic colourless gas dinitrogen tetroxide, N2O4. in which the odd electron is paired. The structure of dinitrogen tetroxide can be represented as a resonance hybrid of ... 

Brown developed the selectivity relationship before the introduction of aromatic reactivities following the Hammett model. The former, less direct approach to linear free-energy relationships was necessary because of lack of data at the time. 

Brown noticed that the reactivities of toluene relative to benzene in aromatic substitutions were proportional to the ratios in which toluene underwent p- and -substitutions. This point is illustrated in table 7.3. 

Fmctose is a highly reactive molecule. When stored in solution at high temperatures, fmctose not only browns rapidly but also polymeri2es to dianhydrides [38837-99-9] [50692-21-2] [50692-22-3] [50692-23-4] [50692-24-5]. Fmctose also reacts rapidly with amines and proteins in the nonen2ymatic or MaiUard browning reaction (5). This is a valued attribute in baked food products where cmst color is important. An appreciation of these properties allows the judicious choice of conditions under which fmctose can be used successfully in food appHcations. 

Cesium forms simple alkyl and aryl compounds that are similar to those of the other alkah metals (6). They are colorless, sohd, amorphous, nonvolatile, and insoluble, except by decomposition, in most solvents except diethylzinc. As a result of exceptional reactivity, cesium aryls should be effective in alkylations wherever other alkaline alkyls or Grignard reagents have failed (see Grignard reactions). Cesium reacts with hydrocarbons in which the activity of a C—H link is increased by attachment to the carbon atom of doubly linked or aromatic radicals. A brown, sohd addition product is formed when cesium reacts with ethylene, and a very reactive dark red powder, triphenylmethylcesium [76-83-5] (C H )2CCs, is formed by the reaction of cesium amalgam and a solution of triphenylmethyl chloride in anhydrous ether. 

Special forms of highly transparent iron oxides are made for use in durable metallized polychromatic finishes. These products are more brown than yellow however, when used in metallized finishes, they impart a golden color. This type of iron oxide tends to be more reactive than the opaque yellows. 

The monochloiotiiazine reactive group is also found in a metallized brown dye [77934-00-0] (72). 

NMR data for 4-methyloxazole have been compared with those of 4-methylthiazole the data clearly show that the ring protons in each are shielded. In a comprehensive study of a range of oxazoles. Brown and Ghosh also reported NMR data but based a discussion of resonance stabilization on pK and UV spectral data (69JCS(B)270). The weak basicity of oxazole (pX a 0.8) relative to 1-methylimidazole (pK 7.44) and thiazole (pK 2.44) demonstrates that delocalization of the oxygen lone pair, which would have a base-strengthening effect on the nitrogen atom, is not extensive. It must be concluded that not only the experimental measurement but also the very definition of aromaticity in the azole series is as yet poorly quantified. Nevertheless, its importance in the interpretation of reactivity is enormous. 

Titanium trichloride [7705-07-9] M 154.3, m >500 , pKj 2.55 (for hydrolysis of Ti to TiOH ). Brown purple powder that is very reactive with H2O and pyrophoric when dry. It should be manipulated in a dry box. It is soluble in CH2CI2 and tetrahydrofuran and is used as a M solution in these solvents in the ratio of 2 1, and stored under N2. It is a powerful reducing agent. [Inorg Synth 6 52 I960, Synthesis 833 7989.]... 

Fig. 11. The variation of the threshold toughness Gy with S when an end-reactive PDMS chain was coupled into a PDMS network (H.R. Brown, W. Hu, J. Koberstein, unpublished work).

The reactivity of NO towards atoms, free radicals, and other paramagnetic species has been much studied, and the chemiluminescent reactions with atomic N and O are important in assaying atomic N (p. 414). NO reacts rapidly with molecular O2 to give brown NO2, and this gas is the normal product of reactions which produce NO if these are carried out in air. The oxidation is unusual in following third-order reaction kinetics and, indeed, is the classic... 

Perhaps the most reactive compound of the group is BiFs- It reacts extremely vigorously with H2O to form O3, OF2 and a voluminous brown precipitate which is probably a hydrated bismuth(V) oxide fluoride. At room temperature BiFs reacts vigorously with iodine or sulfur above 50° it converts paraffin oil to fluorocarbons at 150° it fluorinates UF4 to UF and at 180° it converts Brs to BrFs and BrFs, and CI2 to CIF. 

---