Contamination, by methanol

This control is analyzed to ensure there is no contamination by methanol or acetic acid. If methanol or acetic acid is detected in the HPLC trace from this tube, the experiment should be repeated. 

In the fractionation scheme shown in Figure 1, fraction A could be contaminated by pentane, benzene, or ethanol fractions B and C are most likely to be contaminated by benzene and fractions D and E are most likely to be contaminated by methanol. The NMR spectrum of fraction A showed ethanol contamination amounting to 7% of the sample, but apparently no pentane was present, as none was picked up in the hexane elutriation while preparing subfraction Al. No methanol was detected in the NMR spectra of fractions D and E. All fractions showed monoaromatic hydrogen, which could result from monoaromatic structures in the original coal, from combined phenol, or from contamination by benzene used in the fractionation scheme. Thus apart from the small amount of ethanol in fraction A, the main constituent of the added material was phenol and/or benzene. Fortunately, because of the structural similarities of these two, the final answer obtained for the coal structure will not be very sensitive to assumptions made about the relative quantities of these two present. 

Process 2 - Inputs. A mixture of THF/ ethylacetate contaminated by methanol, ethanol, water, and methylacetate had to be recovered. The average concentrations of the raw material are summarized in Table 2. 

Analyze the NMR spectrum by comparing it to the NMR spectrum of vegetable oil with some of the signals labeled that is shown below. Look for evidence in the NMR spectrum for contamination by methanol, free fatty acids, or the original vegetable oil. Indicate any impurities found based on the NMR spectrum. 

Preliminary estimates for full-scale treatment costs of uranium-contaminated soils were developed based on laboratory-scale studies. The process design uses polyethylene glycol (PEG) (15% solution) and sodium carbonate (10% salt solution) for the aqueous biphasic extractiou system. Uranium is recovered from the salt-rich phase by methanol precipitation. Methanol is then recovered by distillation. 

TCDD is formed during the industrial preparation of 2,U,5 trichlo-rophenol from 1,2,, 5-tetrachlorobenzene. This reaction takes place at about 180° and, when the solvent is methanol, the pre-sure rises to about 7 KPa. The formation of TCDD is an unwanted side reaction, and a 2,U,5 T sample, possibly prepared by this method, was found to be contaminated by 6 0 yg/g of TCDD (30). 

Minh, T.B., Watanabe, M., Tanabe, S., Miyazaki, N., Jefferson, T.A., Prudente, M.S., Subramanian, A., Karuppiah, S., 2000a. Widespread contamination by tris (4-chloro-phenyl) methan and tris (4-chlorophenyl) methanol in cetaceans from the North Pacific and Asian coastal waters. Environ. Pollut. 110, 459-468. 

Examples of anti-Stokes data contaminated by an SFG artifact are shown in Fig. 11a and c, where the higher energy C-H stretching transition of neat methanol is pumped at u>ir = 3020 cm-1. The artifact will be centered at col + anti-Stokes emission from methanol vibrational transitions at 3020 cm-1 (actually the higher energy tail of the C-H stretch transition at 2940 cm-1). The spectral and temporal properties of the artifact can be independently characterized by purposely generating SFG in a thin ( 50 pm) slab of KTP placed at the location of the sample. However, the amplitude of the SFG artifact in the spectrum is unknown. 

When 3,4-di-O-acetyl-D-xylal (5), prepared by a modification of the procedure of Helferich and coworkers, was allowed to react with a mixture of carbon monoxide and hydrogen at a pressure of about 4000 Ib./in. and at a temperature of about 130° for about 90 minutes, in the presence of preformed dicobalt octacarbonyl in benzene as the catalyst, a mixture of two inseparable, partially acetylated hexitols was obtained in over 90% yield. Deacetylation of the latter with sodium methoxide in methanol yielded, in almost equimolar proportions, the chromatographically separable hexitols, l,5-anhydro-4-deoxy-L- yio-hexitol (6) and l,5-anhydro-4-deoxy-D-arahino-hexitol (7). Whenever the mixture of products was contaminated by the precursor aldehydo compounds, a prior reduction of these with sodium borohydride greatly facilitated the isolation of (6) and (7) in pure form. 

Sodium borohydride in methanol/dichloromethane (1 1) at-78 °C reduced ketones in the presence of conjugated enones with excellent selectivity. Competition experiments were complemented by reductions of diones to illustrate the synthetic value of the method. The Wieland-Miescher ketone was reduced to the 1-p-alcohol contaminated by less than 3% diol in quantitative yield. The same reagent in acetic acid was shown to be effective at reducing aromatic ketones with ortho hydroxy or ortho amino substituents rapidly.Other aromatic ketones were relatively inert under the same conditions. Presumably the success of this procedure relies on activation and intramolecular delivery of the acetoxyborohy-dride by the ortho substituent. 

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