Dibromine extraction

For the preparation of o-btuiriuphenol the amount of phenol is doubled, the amounts of phenol and of t-butylamine are halved, and the work-up is as follows The brominated reaction mixture is extracted with a 425 ml. and a 200 ml. portion of 10% aqueous sodium hydroxide. The total extract is acidified in a 2-1. separatory funnel and the oil which separates is transferred to another 2-1. separatory funnel. The remaining aqueous solution is then washed with two 500-ml. portions of hexane and the washings added to the oil in the separatory funnel. The resulting mixture of oil and hexane is then washed thoroughly with four 500-ml. portions of de-ionized water which removes the unreacted phenol (a step of importance since in the preparation of o-bromophenol a large excess of phenol is necessary to reduce the extent of dibromination). 

Fig. 2 Ion chromatograms of a third extract derived from a Rhine water sample. Mono- and dibrominated (methxyphenyl)propionic acids appeared as methylated derivatives. The elution pattern is compared with those of authentical reference compounds derived from chemical syntheses. It has to be noted, that the relative concentrations are not reflected by the peak areas or peak heights due to different relative proportions of the ion fragments 172 and 352 m/z within the individual mass spectra (see Fig. 3 and 4).

Additionally, the bound fraction of numerous further anthropogenic contaminants were investigated by quantitation of the extractable and nonextractable matter. The selection of the contaminants (including chlorinated and brominated naphthalenes, 2,4,6-tribromoaniline, mono-and dibrominated phenols, phthalates, tri-n-butylphosphate, 2,4,4-trimethylpentane-l,3-dioldi-Ao-butyrate, bisphenol A, butylated nitrophenols, 4-nitrobenzoic acid, galaxolide and tonalide) was based on the results of extended GC-MS-screening analyses applied to the extracts of the sediment samples as well to the extracts derived from selective chemical degradation procedures. 

In 1971, it was suggested (44) that the level of a-epoxide in human serum may be related to the severity of atherosclerosis. This hypothesis was based on the measurement of very high concentrations (250-3,250 yg/100 ml serum) of a-epoxide in Type II hypercholesterolemia patients, whereas controls contained less than 5 yg/100 ml serum. Imai et al. (40) demonstrated angiotoxic effects from contaminants of USP-grade cholesterol. By the use of methanolic extraction, USP-grade cholesterol was purified and the oxidation products concentrated. Both newly purchased and 5 year old cholesterol were extracted. Purified cholesterol was obtained by the dibromination procedure according to Fieser (45). 

---