Alcohols, acetylation detection

Bemoyl chloride may replace acetyl chloride as a class reagent it possesses the advantage that it is only very slowly decomposed by cold water and consequently may be employed for detecting alcohols even in aqueous solution. The reaction is usually carried out in aqueous solution containing sufficient caustic alkali to decompose any excess of benzoyl chloride into the water-soluble alkali benzoate (Schotten - Baumann reaction compare Section IV,52). The benzoyl esters formed are insoluble in water ... 

Some examples of the behavior of unsaturated ketonucleosides under alkaline conditions have also been reported. The enol acetate 61a is more stable than the parent ketonucleoside 36a. In 0.1 M methanolic sodium hydroxide, free theophylline was detected only after 4 h, by which time, loss of the acetyl group was complete a reaction time of more than 18 h was needed for complete cleavage of the glycosylic bond.51 In alcoholic solution, the unsaturated 4 -ketonucleoside 66 was very sensitive to nucleophilic attack, and decomposed rapidly, with elimination of the nitrogenous base.31 Thus, treatment with sodium borohydride at — 70° led to complete decomposition within 10 min but, when sodium borohydride was added to a solution of 66 in 1,2-dichloroethane containing acetic acid, fast reduction occurred, and no degradation was observed.31... 

Alcohols with Aldehydes and Ketones,—When an essential oil contains, besides the alcoholic compounds, also aldehydes and ketones, the determination of the alcohols by acetylation is no longer accurate, since aldehydes and ketones react with acetic anhydride. In such cases the aldehydes may be eliminated by means of their insoluble compounds with alkaline bisulphite or other reagent see paragraph 10 Detection of... 

Chitosan is insoluble in water, concentrated acids, alkalis, alcohol, and acetone, but dissolves readily in dilute acids. Water-soluble salts of chitosan include the nitrate and the perchlorate. As described on p. 377, formation of chitosan sulfate and the color reaction of chitosan with iodine have been widely used as qualitative tests for the detection of chitin. Nitration of chitosan with a mixture of acetic and nitric acids or with absolute nitric acid enabled both the free ester and its nitrate salt to be isolated. The perchlorate salt of this ester was also prepared, but it was unstable. Chitosan can be W-acetylated to give products similar to chitin except for their greatly reduced chain-length W-formyl-, iV-propionyl-, JV-butyryl-, and iV-benzoyl-chitosan were also prepared. ... 

The substrate, 4-(6-methoxy-2-benzoxazolyl)acetophenone, the R and S enantiomers of the product, 4-(6-methoxy-2-benzoxazolyl)phenethyl alcohol, and the internal standard, 3-acetyl-7-(dimethylamino)coumarin, were separated by chromatography on a cellulose-based chiral column (Chiracel OD from Daicel). The mobile phase was a 93 7 mixture (v/v) of n-hexane and 2-propanol, which was used at ambient temperature and a flow rate of 1.2 mL/ min. Detection of the enantiomeric alcohols and the internal standard was by fluorescence, with excitation and emission wavelengths of 315 and 375 nm, respectively. 

Prolonged heating of Bi(02CMe)3 with amines or alcohols around 150°C affords the respective acetylated derivatives in moderate yields [73JOC764]. Bi(02CMe)3 can be used successfully for the Prevost type reaction of olefins [89CC407]. The reaction is highly stereospecific no trans isomer is detectable under wet conditions, while no cis isomer is formed under dry conditions. 

Derivatization is also useful to detect volatile metabolites. Liu et al. [282] described a specific, rapid, and sensitive in situ derivatization solid-phase microextraction (SPME) method for determination of volatile trichloroethylene (TCE) metabolites, trichloroacetic acid (TCA), dichloroacetic acid (DCA), and trichloroethanol (TCOH), in rat blood. The metabolites were derivatized to their ethyl esters with acidic ethanol, extracted by SPME and then analyzed by gas chromatography/negative chemical ionization mass spectrometry (GC-NCI-MS). After validation, the method was successfully applied to investigate the toxicokinetic behavior of TCE metabolites following an oral dose of TCE. Some of the common derivatization reagents include acetyl chloride and TV-methyl-iV- ft-b u (y Idi methyl si I y I) tro (1 uoroacctam i nc (MTBSTFA) for phenols and aliphatic alcohols and amines, dansyl chloride and diazomethane for phenols, dansyl chloride for amines, acidic ethanol and diazomethane for carboxylic acids, and hydrazine for aldehydes. 

Esters, Ethers, and Related Derivatives of Alcohols.— Although acetylation with acetic anhydride-pyridine is one of most familiar reactions, the detailed mechanism does not seem to have been elucidated.Spectroscopic detection of the acetylpyridinium ion resulting from the equilibrium ... 

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