Polar yellow

Carotenoids were discovered during the nineteenth century. Wachen in 1831 proposed the term carotene for the hydrocarbon pigment crystallized from carrot roots Berzelius called the more polar yellow pigments extracted from autumn leaves xanthophylls and Tswett separated many pigments by column chromatography and called the whole group carotenoids. ... 

Curcumine S. Mikado yellow, golden yellow and orange, direct yellow, stilbene yellow, diamine fast yellow A, A R diamine orange D, dianil direct yellow S, chloramine orange, naphthamine yellow, diphenyl chrysoine, diphenyl citronine, sun yellow, polar yellow, polyphenol yellow, etc. 

Polar yellow 5G is prepared by condensing p-chloro-m-sulfophenylhydrazine with acetoacetic ester, and coupling the resulting pyrazolone with diazotized p-aminophenol in acetic acid solution. The alkali sensitive dye which is formed is treated at 70°C. with p-toluenesulfonyl chloride, in the presence of soda and 1 mole of sodium hydroxide, to esterify the hydroxyl group. This esterification makes the dye insensitive to alkali and, at the same time, fast to milling on wool. 

Fig. 15.7 Effect of acetic acid on exhaustion of Polar Yellow R...

If a solution rotates plane-polarized yellow light (the Nan line) to the right, the solute is designated a (+) isomer if to the left, a (-) isomer. 

The helices are aligned according to approximate positions within the membrane and with respect to the photosynthetic pigments. LA is the first helix of subunit L, ME is the last helix of subunit M, HA is the only transmembrane helix of subunit H. Charged residues are eol-ored red, polar residues are blue, hydrophobic residues are green, and glycine is yellow. (From T.O. Yeates et al., Proc. Natl. Acad. Sci. USA 84 6438-6442, 1987.)... 

FIGURE 6.24 (a) The alpha helix consisting of residues 153-166 (red) in flavodoxin from Anahaena is a surface helix and is amphipathic. (b) The two helices (yellow and blue) in the interior of the citrate synthase dimer (residues 260-270 in each monomer) are mostly hydrophobic, (c) The exposed helix (residues 74-87—red) of calmodulin is entirely accessible to solvent and consists mainly of polar and charged residues. 

In the first step, the fairly acidic proton on CIO of the red biladiene-ac salt 6 is abstracted and, even in solution in polar solvents, the salts are converted into the corresponding yellow bilatriene-u/ic salts 7. With a base such as piperidine, the salts 7 form the green bilatriene-a/>e free base. For further reaction to the porphyrin it is important that the salts 7 are oxidized to the bilatriene enamines 8 which cyclize via the electrophilic carbon of the terminal pyrrole ring by the loss of the leaving group X to 9. Porphin (10) is finally obtained by the loss of... 

When Wiberg and Pracht (1972b) synthesized 3,3-di-(trimethylsilyl)-l-phenyltri-azene by reacting benzenediazonium chloride with sodium di-(trimethylsilyl)amide they found a faintly yellow compound if the reaction was carried out at -78 °C and an orange form at — 20 °C. NMR spectra were consistent with (Z)/( )-stereoiso-merism. Measurement of the isomerization rates at various temperatures in ether and in pentane indicates that the mechanism involves an inversion transition state (13.5) and not a rotation, because the free reaction enthalpies are independent of the polarity of the solvent. 

Besides the calculation of the different sulfonated species, it is also possible to determine them directly by chromatographic methods. Separation of the ester sulfonate and the disodium salt is achieved by thin-layer chromatography on silica gel plates. With a solvent mixture of acetone and tetrahydrofuran (90 10 v/v) the disodium salt stays at the start whereas the ester sulfonate has an R value of 0.2. With the more polar solvent 0.1 N H2S04 + methanol + chloroform the ester sulfonate and the disalt have Rf values of 0.36 and 0.14. For visualization, the plate is sprayed with pinacryptol yellow. In UV light (254 and... 

The products are yellow or red solids when R = Me, Et, Pr, or Bu, they decompose below —10°, but when R = Ph, or, particularly, when R = Me iCH, the products are more stable. They are oxidized immediately in air to the corresponding distannoxanes, readily exchange the trialkyltin group with trialkyltin hydrides, and add across polar-substituted alkynes or azo compounds. 

The addition is therefore stereospecifically syn and, like catalytic hydrogenation, generally takes place from the less-hindered side of a double bond, though not much discrimination in this respect is observed where the difference in hulk effects is small.Diimide reductions are most successful with symmetrical multiple bonds (C=C, C=C, N=N) and are not useful for those inherently polar (C=N, C=N, C=0, etc.). Diimide is not stable enough for isolation at ordinary temperatures, though it has been prepared as a yellow solid at — 196°C. 

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