2,4-Dinitrophenol, spectrum

Such reductions may result in loss or diminution of the harmful effects as microorganisms convert the broad-spectrum poison 2,4-dinitrophenol to 2-amino-4-and 4-amino-2-nitrophenol, the fungicide pentachloronitrobenzene to penta-chloroaniline, and the insecticide Parathion to aminoparathion. 

To test the first hypothesis, solutions of 3,5-dinitroanisole and hydroxide ions were flashed and the absorption spectra at different time intervals after excitation were compared. The absorption ( max 400-410 nm) that remains after all time-dependent absorptions have decayed can be shown to be due to 3,5-dinitrophenolate anion, the photosubstitution product of 3,5-dinitroanisole with hydroxide ion. When the absorption band of the 550-570 nm species is subtracted from the spectrum of the solution immediately after the flash, there remains an absorption at 400-410 nm, which can also be ascribed to 3,5-dinitrophenolate anion. The quantity of this photoproduct does not increase during the decay of the 550-570 nm species. Therefore the 550-570 nm species cannot be intermediate in the aromatic photosubstitution reaction of 3,5-dinitroanisole with hydroxide ion to yield 3,5-dinitrophenolate. Repetition of the experiment with a variety of nucleophiles on this and other aromatic compounds yielded invariably the same result nucleophilic aromatic photosubstitution is, in all cases studied, completed within the flash duration (about 20jLts) of our classical flash apparatus. 

Analytical Methods. Of the substances investigated, only parathion does not exhibit a characteristic absorption spectrum suitable for direct measurement of concentration within the ranges used in these experiments. Spectrophotometric data for the other pesticides and related dinitrophenols are listed in Table II. 

Finally, ortho effects involving the radical cations of various nitro-substituted alkylphe-nols are mentioned here. In these cases, two sequential ortho effects have been observed. For example, the El mass spectra of 2-ethyl-4,6-dinitrophenol and its 2-cyclohexyl analogue exhibit pronounced peaks for the formation of [M — H20] + and [M — H2O — OH]+ ions and the spectrum of 2-isopropyl-4,6-dinitrophenol even indicates that the secondary fragmentation step is faster than the primary one, because an ion abundance ratio [M — H2O - OH]+/[M - H20] + = 25 was found . 

Other nitrogenous herbicides are derived from phenols and show the same UV spectrum shape as nitrophenol, such as dinoterb (terbutyl dinitrophenol, Fig. 57), for instance. 

A portion of the organic by-products was dissolved in carbon tetrachloride or chloroform (spectroscopic grade) for infra-red cuialysis. The absorption peaks corresponded to nitrophenols, nitrocresols, dinitrophenols, dinitrocresols, traces of trinitro conpounds euid nitro-hydroxy carboxylic acids. The presence of individual compounds wais confirmed by comparison with the absorption spectrum of the pure compounds euid by thin-layer chromotography. Quantitative cuialyses of the concentrations of several components of the by-products were made. If a component did not have an absorption bcuid free from interference by euiother constituent of the mixture, queuititative cUialysis could still be achieved by mectsurement of the extinction coefficients of the interfering components at severcLL different frequencies, together with the absorbance of the mixture at these frequencies. Characteristic absorption bands used are shown in Tetble I. 

Although fluazinam has a broad spectrum of fungicidal activity it is less potent on rusts and powdery mildews [72, 156] (in contrast to the dinitrophenols, which are generally most effective against powdery mildews) and has not been commercialized for use on cereal crops. It has, however, found wide application in other crops since its first launch in New Zealand in 1988. 

---