Yellow-orange color development

A colorimetric assay of griseofulvin, based on the yellow-orange color (Xmax=420 nm) which develops when griseofulvin is heated with isonicotinic acid hydrazide in alkaline medium has been described by Unterman (35) and the mechanism investigated by Unterman and Duca (36). 

The submitter obtained a colorless solution of boron triflate, but the checkers observed development of a yellow-orange color upon addition of triflic add. Regardless of the color, the triflate solution could be used without a decrease in yields. 

A yellow-orange color is developed upon the condensation ofp-dimethylaminoaniline with A -3-ketosteroids under the action of perchloric acid in methanol [76]. The condensation reaction is performed at room temperature. 

The reaction of A -3-ketosteroids with 2,6-di-tertbutyI-p-cresol is specific, and different analytes yield various colors. In alkaline media and in the presence of an oxidant (e.g., hydrogen peroxide), A" -3,1 1-diketo steroids (such as cortisone and prednisone, at levels of 5-25 pg) develop yellow-orange colors with this reagent. 

In regard to this latter point, Cubbon and Margerison noted (31) that adding n-butyllithium to toluene led to the formation of solutions which "developed a yellow-orange color.") If the spectrum of benzyllithium in toluene in the presence of anisole resembles that in benzene where the X max is reported (32,33) to be 292 nm, the decay in absorbance with time noted (13) at 330 nm may be attributable to transmetallation involving toluene rather them the foregoing aromatic ethers. 

Solutions should not be used if a yellow color has developed. Storage of furosemide (l.Omg/mL in 0.9% sodium chloride packaged in a glass infusion bottle) solution at room temperature while exposed to ambient illumination for 70 days resulted in about an 80% loss of the active substance and the formation of a yellow-orange precipitate (81). The UV irradiation of furosemide solutions under different testing conditions is reported to cause photooxidation, photohydrolysis, and dechlorination of the active substance, resulting in the formation of various degradation products (82). 

Maples are characterized by the shape of their leaves, which in most species are broadly palmate with a three- or five-lobed outline, and are arranged in an opposite fashion on their branches. Maples have seasonally deciduous foliage, which is shed in the autumn. The leaves of many species of maples develop beautiful yellow, orange, or red colors in the autumn, prior to shedding for the winter. Maple flowers appear early in the springtime, and consist of non-showy, rather inconspicuous inflorescences. The flowers of some species produce nectar and are insect-pollinated, while other species shed their pollen into the air and are wind-pollinated. Maples have distinctive, winged seeds known as samaras, which are arrar ed in opposite pairs. 

The main consequences of these reactions involving phenols in red wines are changes in color intensity, a tendency to develop a yellow-orange hue (generally accompanied by loss of color) and various modifications in the tannins, responsible for their gradual softening. 

The above transformations result in a reduced anthocyanin content, contrasting with the increase in color. The new condensed pigments formed are more intensely colored than anthocyanins. Other anthocyanin and tannin breakdown reactions may lead to a loss of color, generally accompanied by a tendency towards yellow-orange hues. This is characteristic of the normal development of bottle-aged red wines. The breakdown of anthocyanins involves a loss of molecular structure in the red coloring matter, possibly accompanied by the appearance of a yellowish hue. 

To a solution of A vinylcarbazole in ethyl acetate is added 0.1-1% aqueous solution of perchloric acid. A yellow-orange color develops immediately and the polymer spontaneously precipitates to give a polymer of MW 600-2000 (cryo-scopically in QH ). 

---