Sodium acetate, acetylation catalyst

Attempts with D-galactose, o-mannose or N-troc-D-glucosamine and sodium acetate as catalyst gave also excellent yields of the corresponding acetyl derivates within 11 min. Loupy et al. [7] performed peracetylation of 3 with a slight excess of acetic anhydride and catalytic amounts of zinc dichloride either with classical heating or under microwave activation, but they obtained rather similar yields irrespective of the conditions used. 

For complete acetylation of polyhydric compounds, such as glucose (p. 141) and mannitol (p. I42), even undiluted acetic anhydride is insufficient, and a catalyst must also be employed. In such cases, the addition of zinc chloride or anhydrous sodium acetate to the acetic anhydride usually induces complete acetylation. ... 

Mannitol, CH,0H(CH0Hi4CH40H, is a hexahydric alcohol obtained by the reduction of mannose. Since ring formation does not occur in mannitol, the hexacetyl derivative can exist in only one form, and therefore either zinc chloride or sodium acetate can be used as a catalyst for the acetylation. 

Acetates. Complete acetylation of all the hydroxyl groups is desirable in order to avoid mixtures. In some cases, the completely acetylated sugars may be obtained in the a- and p-forms depending upon the catalyst, e.g., zinc chloride or sodium acetate, that is employed in the acetylation. The experimental details for acetylation may be easily adapted from those already given for a- and p-glucose penta-acetates (Section 111,137). 

Polymer is separated from the polymerisation slurry and slurried with acetic anhydride and sodium acetate catalyst. Acetylation of polymer end groups is carried out in a series of stirred tank reactors at temperatures up to 140°C. End-capped polymer is separated by filtration and washed at least twice, once with acetone and then with water. Polymer is made ready for extmsion compounding and other finishing steps by drying in a steam-tube drier. 

The nitroalcohols are esterified by the usual acylating agents in the presence of acidic catalysts. With the nitroglycols of the sugar series, acetic anhydride containing a trace of sulfuric acid gives rapid and complete acetylation. Basic acetylation catalysts, such as pyridine or sodium acetate, are not satisfactory, presumably due to interaction with the nitro group. 

Place 1 g of salicylic acid in each of four 13 x 100-mm test tubes and add to eachtube2 mL of acetic anhydride. To the first tube addO.2 gof anhydrous sodium acetate, note the time, stir with a thermometer, and record the time required for a 4°C rise in temperature. Replace the thermometer and continue to stir occasionally while starting the next acetylation. Obtain a clean thermometer, put it in the second tube, add 5 drops of pyridine, observe as before, and compare with the first results. To the third and fourth tubes add 5 drops of boron trifluoride etherate and 5 drops of concentrated sulfuric acid, respectively. What is the order of activity of the four catalysts as judged by the rates of the reactions ... 

Sodium acetate, a mild acetylation catalyst, has been extensively used in the acetylation of carbohydrate material. When used in conjunction with acetic anhydride or with acetic anhydride and acetic acid at reflux temperatures, it is capable of producing only a slow acetylation of untreated starch granules. After four days of refluxing with acetic anhydride and sodium acetate, com starch has been acetylated to 43.5% acetyl content, but the acetylation is non-uniform since the product can be fractionated into parts having different acetyl contents. The slow acetylation of ordinary starch in these cases is probably due to the compact structure of the starch granules, and a much more rapid and complete acetylation would be expected to occur with a starch pretreated as described in Section II. 

The reaction is acid or base catalyzed. Many catalysts have been tried, including potassium acetate and sodium acetate (27), dimeth-ylformamide (DMF) (28-30), urea ammonium sulfate (29), magnesium perchlorate (31-33), trifluoroacetic acid (32), boron trifluoride (30), sodium acetate (31), potassium hydrogen phosphate (34), and y-rays (35). The best acetylation condition, however, is uncatalyzed acetic anhydride in xylene at 100-130 C (36). 

Recently, imidazole has been successfully applied as a catalyst for the acetylation of carbohydrates in acetonitrile [199]. A variety of other catalysts in combination with excess of acetic anhydride and solvent includes sodium acetate [200], sulfuric acid [201], perchloric acid [202], and a number of Lewis acid catalysts such as, iodine [203], Sc(OTf)3 [204], Cu(OTf)2 [205], C0CI2 [206], BiOCl-SOCl2 [207], LiC104 [208], FeCls [209], BiCls [210], and a series of heterogeneous catalysts such as, montmorillonite K-10 [211], zeolites [212], nafion-H [213], HC104-Si02 [214], or molecular sieves [215]. Recently, a ZnCl2-sodium acetate combina-... 

Common starch esters include the acetates. High d.s. starch acetates have been formed by using acetic anhydride with either sodium acetate or pyridine catalysts at 90-100 °C [158,159,160]. The major use of starch acetates have been in the study of the stmctures of amylose and amylopectin after acid hydrolysis. Acetylation of granular starch in aqueous suspension by acetic anhydride at pH 10-11 is used to produce low d.s. starch acetates that are primarily used for the stabilization of their viscosity and for their water-soluble clarity. The acetylation decreases the hydrophilic character and increases the hydrophobic character of starch. The major uses of starch acetates is in the paper industry for surface sizing to give improved print quality, uniform porosity, surface strength, and resistance to various solvents [161]. 

Hydroquinone diacetate has been prepared by the treatment of hydroquinone with acetic anhydride, both in the presence and in the absence of strong acid catalysts, by the treatment of the sodium salt of hydroquinone with acetic anhydride, and by the reaction of hydroquinone with acetic anhydride in the presence of sodium acetate. - It has also been prepared from hydroquinone and acetyl chloride the acetylation with acetyl chloride is reported to be improved by the addition of metallic magnesium. ... 

Acetylation. A comparative student experiment with salicylic acid and acetic anhydride demonstrates that common acetylation catalysts fall into the following order of relative effectiveness coned. H2SO4 > boron trifluoride etherate > pyridine > sodium acetate. Although it is a relatively weak catalyst, sodium acetate is completely nondestructive and can be employed in much larger than truly catalytic amounts. An example is the acetylation of furylcarbinol. A mixture of the reactants and solvent benzene was heated on the steam bath with stirring to prevent caking... 

Acetylation Acetic anhydride. N-Acetoxyphthalimide. 2- and 3-Acetoxypyridine. Acetyl chloride. N-Acetylimidazole. Boron trifluoride. Catalysts (see Acetic anhydride). Ketene. Magnesium. Methyl oxocarbonium hexafluoroantimonate. Perchloric acid. Phenyl acetate. Pyridine. Sodium acetate. Tetraelhylammonium acetate. p-Toluenesulfonic acid. Tri-n-hexylethyl ammonium hydroxide. 2,4,6-Triisopropylbenzenesulfonyl chloride. Trityl-sodium. Zinc chloride. 

Acetylation of the highly substituted 6-hydroxyindoxazene 52 (R1 = H, R2 = N02, R3 = H) in acetic anhydride with sulfuric acid as catalyst proceeds normally to give the acetate (52 R1 = H, R2 = N02, R3 = Ac), whereas with acetic anhydride and sodium acetate ring cleavage to the cyanodiacetate (53 R1 = H, R2 = N02) is the favored process.13... 

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