Pyridine reagent

Functional Group Analysis. The total hydroxyl content of lignin is determined by acetylation with an acetic anhydride—pyridine reagent followed by saponification of the acetate, and followed by titration of the resulting acetic acid with a standard 0.05 W sodium hydroxide solution. Either the Kuhn-Roth (35) or the modified Bethge-Liadstrom (36) procedure may be used to determine the total hydroxyl content. The aUphatic hydroxyl content is determined by the difference between the total and phenoHc hydroxyl contents. 

The fact that the binder used in the layer can affect the reagent is shown in the monograph on 4-(4-Nitrobenzyl)pyridine reagent. It is not possible to employ this reagent on Nano-SIL C 18-100 UV254 plates (Macherey-Nagel) because the whole surface of the layer is colored bluish-violet. The corresponding water-wettable layers produced by the same manufacturer do not present any difficulties. 

The formation of an epoxyketone (1) is generally favoured when the expected product of oxidation of an allylic alcohol is a cisoid enone. This type of reaction is promoted by acid conditions and may be prevented by using the chromium trioxide-pyridine reagent which gives only the unsaturated ketone (2) corresponding to the starting alcohol. ... 

Occupational air (NIOSH Method 6010) Collection of breathing zone air samples on adsorbent extraction with water treatment with barbituric acid/ pyridine reagent Spectrophotometry (HCN) 1 pg CNb -100% NIOSH 1989b... 

A method involving SPE was developed for the determination of ten A-nitroso amino acids in cured meat products. These compounds were derivatized with diazomethane followed by O-acylation of hydroxyl groups with acetic anhydride-pyridine reagent. The methyl esters and their acylated derivatives were separated by GC on a DB-5 fused silica capillary column and quantified with a TEA-CLD specific for the nitric oxide derived from the thermal denitrosation of nitrosamines recovery exceeded 75% at the 10 ppb level579. 

The cupric acetate-pyridine reagent provides a homogenous and basic reaction medium. The yields are high, and there is seldom precipitation of the cuprous derivative which may slow down the cuprous chloride-oxygen procedure. ... 

J.S. Fritz G.H. Schenk, AnalChem 31, 1808(1959) (Detn of hydroxyl group using acetic anhydride in pyridine reagent catalyzed with perchloric acid for esterification)... 

A. Acylation Methods by a) Acetic anhydride-pyridine reagent (p333) b) Acetyl chloride (p335) and c) Phthalic anhydride (P336)... 

The HF-pyridine reagent is an effective complement to di-methylaminosulfur trifluoride (DAST) reagent6 in the preparation of alkyl fluorides from alcohols. DAST is also useful for the conversion of carbonyl groups to difluoromethylene functions. The... 

Preparation of Tertiary and Secondary-Alkyl Fluorides from Alcohols with Hydrogen Fluoride-Pyridine Reagent... 

HF-pyridine reagent, however, can also be used for the hy-drofluorination of alkenes,7 alkynes,7 cyclopropanes,7 and diazo compounds,8 the halofluonnation of alkenes,9 the preparation of fluoroformates from carbamates,10 the preparation of a-fluorocarboxylic acids from a-amino acids,11 and as a deprotecting reagent in peptide chemistry.12 Examples of the hydrofluonnation of alkenes with HF-pyridine are given in Table II. 

Hydroxyl groups were determined by the acetylation method described by Blom et al. (I). The procedure consisted of treating 1-gram samples with acetic anhydride-pyridine reagent. The acetylated sample was recovered by filtration and thoroughly washed. The amount of hydroxyl function was then determined by hydrolyzing the sample with 0.2N sodium hydroxide and measuring the amount of acetic acid liberated when the hydrolyzate was neutralized with sulfuric acid and steam distilled. 

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