Acetyl determination

Acetyl values from fully acetylated xylan preparations indicate a D. P. of about 100 or greater. The theoretical acetyl value for a fully acetylated xylan molecule of infinite size is 39.8%. As the molecule decreases in length, its acetyl content increases because of the increasing proportion of triacetyl-bearing end units. Assuming an accuracy of 0.1% for the acetyl determination, a noticeable deviation from theory would be apparent in acetylated xylan of less than D. P. 100. 

Ester Value after Acetylation Determine as directed under Total Alcohols, Appendix VI, using about 2 g of the dried acetylated oil, accurately weighed. Reflux for a period of 2 h. Calculate the Ester Value after Acetylation by the formula... 

Ester Value Determine as directed under Ester Value, Appendix VI, using about 5 g of sample, accurately weighed. Ester Value after Acetylation Determine as directed under Ester Value, Appendix VI, except acetylate a 10-mL sample as directed under Total Alcohols, Appendix VI, and use about 1.5 g of the dried, acetylated oil, accurately weighed. Solubility in Alcohol Determine as directed under Solubility in Alcohol, Appendix VI. The oil does not usually dissolve clearly in 95% alcohol. 

Fig. 7. Top mass spectra of FHV y-peptide after acetylation. The degree and site of acetylations, determined by tandem mass spectrometry, can be used to characterize surface accessible regions of the peptide. Bottom a viral capsid protein ion generated by ESI undergoes hydrogen-deuterium exchange. The multiple populations of ions generated can help distinguish between multiple conformers present for a capsid protein...

Following a single oral dose of 1 g given to 12 slow acetylators and 11 rapid acetylators (determined with reference to dapsone), the following mean peak plasma concentrations ( ig/ml, time in hours) were reported ... 

Wernimont reported an example of a nested design, which is an example of fractional replication. It was desired to evaluate an interlaboratory study of a method of acetyl determination. Results obtained by two analysts in each of eight laboratories were compared by having each analyst perform two tests on each of 3 days. The design was... 

The use of lead tetraacetate for adding acetoxy groups to a double bond, as here used for preparing the pentaacetate (76), has been widely applied in synthetic organic chemistry, but there have been only a few applications to carbohydrates (see Perlin s review in this Series, for other examples). The conversion of (76) to the dicarbonyl derivative (77) (in 65% yield and in the crystalline state) was made by autohydrolysis in water at room temperature for 3 hr. The structure was deduced from elemental analysis, acetyl analysis, and the absence of methoxyl groups, and from its mode of synthesis. The acetyl determination could be made by direct titration with... 

Substance 0 was obtained from the flowers of C. autumnale by chromatographic separation of the mother liquors from the crystallization of colchicine (303). The material, m.p. 254 256°, [a]o —144° (chloroform), contains four methoxyl groups and one acetyl function. A carbon-hydrogen determination was not reported, but on the basis of the methoxyl and acetyl determination, a molecular formula, CgjHjjNOe, was proposed. The tropolone ring appears to be absent. 

SPECTROSCOPY FOR STRUCTURAL CHARACTERIZATION AND THE DEGREE OF N-ACETYLATION DETERMINATION... 

Figure 1.18 Dicobalt hexacarbonyl derivatives of fructopyranose 41,42, and 43. The degree of acetylation determines the lipophilicity and correlates with their cytotoxicity in MCF-7 breast cancer cells [128].

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