Acetyl hydrolysis

The solution process consists of four steps preparation of cellulose for acetylation, acetylation, hydrolysis, and recovery of cellulose acetate polymer and solvents. A schematic of the total acetate process is shown in Figure 9. 

Processes for Triacetate. There are both batch and continuous process for triacetate. Many of the considerations and support faciUties for producing acetate apply to triacetate however, no acetyl hydrolysis is required. In the batch triacetate sulfuric acid process, however, a sulfate hydrolysis step (or desulfonation) is necessary. This is carried out by slow addition of a dilute aqueous acetic acid solution containing sodium or magnesium acetate (44,45) or triethanolamine (46) to neutrali2e the Hberated sulfuric acid. The cellulose triacetate product has a combined acetic acid content of 61.5%. 

Recent Developments. A considerable amount of cellulose acetate is manufactured by the batch process, as described previously. In order to reduce production costs, efforts have been made to develop a continuous process that includes continuous activation, acetylation, hydrolysis, and precipitation. In this process, the reaction mixture, ie, cellulose, anhydride, catalyst, and solvent, pass continuously through a number of successive reaction zones, each of which is agitated (92,93). In a similar process, the reaction mass is passed through tubular zones in which the mixture is forced through screens of successively small openings to homogenize the mixture effectively (94). Other similar methods for continuous acetylation of cellulose have been described (95,96). 

Figure 111-4 (a) Hemiacetal and acetal formation and acetyl hydrolysis. (b) Internal hemiacetal formation with the OH on carbon 5 of hexoses yields two six-membered rings. 

Carbamates such as carbachol are also able to serve i substrates for AChE. forming a catbamylated enzyme iffiii mediate (E-C). The rate of carbamylation (k ) is slo enlL the rate of acetylation. Hydrolysis (kv. decatbamylaliec of the carbaniyl-cnzyme intermediate is 10 times sloar than that of its acetyl counterpart. The slower hyMi rate limits the optimal functional capacity of AChE allw ing carbamate substrates to be semircversible inhibiton i AChE. 

A CD-PEI derivative containing macrocyclic metal centers have been prepared by random functionalization (34), Here, the secondary and the tertiary amino groups were blocked by acetylation. Hydrolysis of a nitrophenyl carboxylate ester... 

A 4,5- to 4,7-dione isomerization under different conditions has been observed. For example, the carbazoledione 11 is oxidized in dilute alkali into the p-quinone 12 (63JOC1169). Isomerization is possible also via reductive acetylation, hydrolysis, and subsequent oxidation with ferric chloride (79FES1062) or air, as in the case of conversion of 13 to 14 (65JOC4381). A mixture of the 4,5- (15) and 4,7-dione (16) was obtained in low yield after oxidation of 2,6-dimethyl-l-ethyl-4-hydroxyindole with Fremy s salt. The... 

The hydrolysis and methanolysis of the branched-chain sugar derivative (253) gave the products shown in Scheme 95 on acetylation hydrolysis of (253) with an... 

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