Determination acetyl bromide method

Determination of Lignin in Wood and Pulp by the Acetyl Bromide Method... 

The lignin contents of P radiata and E regnans woods and pulps determined by the standard Klason method and by the conventional and modified acetyl bromide methods are listed in Table 2 2 4 The lignin contents determined using the modified procedure generally agree better with those obtained by the Klason method than do results obtained using the conventional acetyl bromide method... 

Marton J (1967) Determination of lignin in small pulp and paper samples using the acetyl bromide method Tappi 50 335 - 337... 

Yield (%) based on lignin content determined by the acetyl bromide method. 

The absorbance at either 205 or 280 nm is the basis of several techniques for the quantitative determination of lignin. The extinction coefficient depends on species and solvent, and varies from 10 to about 26 L g cm. Summaries of extinction coefficients are available in reviews by Dence [18], Lin [2], and Fengel and Wegener [19]. Lin [2] has provided guidelines for measurement of lignin absorption spectra, while Dence [18] provides instructions for determination of acid-soluble lignin and lignin solubilized by the acetyl bromide method. 

The acetyl bromide procedure was developed by Johnson et al. (1961) to determine lignin content in small samples from woody species. This method uses acetyl bromide (4.10) to acetylate unbound hydroxyl groups in the lignin (4.11), while the hydroxyl group on the a-carbon is substituted with a bromine group. The substituted lignin derivative (4.12) is soluble under acidic conditions, and its concentration can be measured with a spectrophotometer at 280 nm. 

Fukushima, R. S., and Hatfield, R. D., 2001, Extraction and isolation of lignin for utilization as a standard to determine lignin concentration using the acetyl bromide spectrophotometric method, J. Agric. Food Chem. 49 3133-3139. 

It is probable that the test of Wolski88 for sulphoxides depends on the first reaction. He used acetyl chloride or bromide the product from the former gave a red colour with nitrite ion, absorption maximum at 545 nm, and the latter gave a yellowish-orange colour directly. The method was used also by Besyadetskaya and colleagues89 to determine dimethyl sulphoxide in ointments. 

Another approach consists of an in-situ acetylation and extraction of NPEOs and further analysis of the acetyl derivatives. The method has been applied to analyse effluent water and sewage sludges [102,103], sediments [104] and river waters [105]. Silylated derivatives [106] using BSA or BSTFA have also been used to determine NPEO (n < 6) in seawater [107] and wastewater [107,108], sediments [109] and sludges from wool scour effluents [110]. Halogenated derivatives of alkylphenols (AP) can also be formed as a result of chlorination practices in water treatment or wastewater if bromide is present. Brominated OPs and NPs (BrAPEOs) have been identified by GC-MS in sewage [111] and tap water [89], respectively. 

Earlier work of this school was concerned to establish heats of formation of halogen-containing organic compounds by measuring heats of hydrolysis. Heats of hydrolysis of acetyl fluoride, chloride, bromide, and iodide402 of the chloro-substituted acetyl chlorides oi of the benzoyl halides and of chloral and bromal 3 have also been made. Comparison with heats of formation derived from heats of combustion is not normally possible, but there is a large discrepancy between the two methods for benzoyl chloride, where an early combustion measurement is available, in the sense that the determined heat of combustion appears to be about 14 kcal low. 

Acronychia haplophylla Eng. (A. tetrandra F. Muell.) (Rutaceae) Acrophylline, C17H17O3N (mp 120°) (I) and acrophyllidine, C17H19O4N (mp 177°) (II). The structures were determined largely by spectroscopic methods but the hexahydro derivative of I was shown to have structure III by a synthesis. For this purpose A-acetyl-m-anisidine was alkylated with isoamyl bromide in the presence of sodium hydride in DMF. Hydrolysis gave A-isoamyl-m-anisidine which on heating to reflux temperature with diethyl malonate in diphenyl ether gave III (mp 174°) (3a). 

Mixed vapors of acrolein and ethyl alcohol were passed over the catalyst in a heated stainless steel tube at atmospheric pressure. Products were condensed and fractionated in a 20-plate bubble tray column. Fractions taken were acetaldehyde, 20-36°, and acrolein-ethyl alcohol, 36-78.4°. At this point water was added to the distillation kettle and an ethyl alcohol-aUyl alcohol-water fraction, 78-95°, was taken overhead. Fractions were analyzed for aldehydes by the hydroxylamine hydrochloride method, for im-saturation by reaction with bromine in aqueous potassium bromide, for alcohol by the nitrite ester method, and for water with Fischer reagent. Propyl alcohol in the water-free allyl alcohol recovered from the azeotrope was calculated by difference from the total alcohol determined by reaction with acetyl chloride and the unsaturated alcohol determined by reaction with aqueous bromine solution. Fresh catalyst was used for each experiment. 

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