Base-degraded solution, products

Several products were also detected in base-degraded D-fructose solution acetoin (3-hydroxy-2-butanone 62), l-hydroxy-2-butanone, and 4-hydroxy-2-butanone. Three benzoquinones were found in the product mixture after sucrose had been heated at 110° in 5% NaOH these were 2-methylbenzoquinone, 2,3,5-trimethylbenzoquinone, and 2,5-dimethyl-benzoquinone (2,5-dimethyl-2,5-cyclohexadiene-l,4-dione 61). Compound 62 is of considerable interest, as 62 and butanedione (biacetyl 60) are involved in the formation of 61 and 2,5-dimethyl-l,4-benzenediol (63) by a reduction-oxidation pathway. This mechanism, shown in Scheme 10, will be discussed in a following section, as it has been proposed from results obtained from cellulose. 

It appears that both JL, and 3 are produced as intermediates during the decomposition of an Amadori compound. There is little evidence, based on end product isolation that the 4-deoxyosone (2) is produced to any extent in these reactions. An early isolation of 1, by Anet (6), was accomplished by decomposing an Amadori compound ("difructose glycine") in aqueous solution. Subsequent studies have shown that Amadori compounds are easily converted to HMF in dilute acid solution as well. Furthermore, Kato s (8) published preparation of 3-deoxyosone, in which glucose is reacted with N-butyl amine almost certainly involves the intermediate formation of an Amadori compound and its decomposition in situ. Thus, it can be reasonably concluded that 3-deoxyosones are produced from Amadori compounds during their degradation. 

As the solution pH increases, the rate of degradation is sharply reduced. For instance, no degradation-phase products were observed in a 10 m base at room temperature [473]. However, this does not mean that degradation does not affect the near-surface layers of HTSC oxide. The chemistry of the HTSC surface in concentrated alkaline solutions is practically unknown. But it has been observed that in an alkaline melt which contained water, YBCO rapidly decomposed to the individual oxides at 500 °C while in a dry base it remained sufficiently stable [477],... 

Impurities of major significance in alkali silicates are iron, alumina, calcium and magnesium, chloride, sulfate, carbonate and titania. They may originate as impurities in raw materials, be added from the manufacturing equipment, or be absorbed from the atmosphere. The degradation of product quality may be manifested as undesirable color, turbidity in solution, corrosiveness, loss of alkalinity or altered reactivity of products made from the silicate (e.g., iron or sulfate may poison a silica-based catalyst manufactured from a silicate solution). 

In order to learn about the effect of substituents close to the ester bond of surface-active esters on the kinetics of the hydrolysis, a series of well-defined PEG esters of fatty acids were synthesized and their hydrolysis rates were investigated both below and above the critical micelle concentration (CMC) [1]. The ester surfactants studied are shown in Fig. 1. They were synthesized in pure form by reacting the acid chloride with a large excess of tetra(ethylene glycol) using pyridine as nonnucleophilic base. The desired product, i.e., the PEG monoester, was removed from the excess tetra(ethylene glycol) by extraction into ethyl acetate from a saturated sodium chloride solution (so-called Weibull extraction). The degradation profile at various pH values was... 

TABLE 3 Acid and Base Degradation Conditions (for Solution Drug Product) ... 

Solution Process. With the exception of fibrous triacetate, practically all cellulose acetate is manufactured by a solution process using sulfuric acid catalyst with acetic anhydride in an acetic acid solvent. An excellent description of this process is given (85). In the process (Fig. 8), cellulose (ca 400 kg) is treated with ca 1200 kg acetic anhydride in 1600 kg acetic acid solvent and 28—40 kg sulfuric acid (7—10% based on cellulose) as catalyst. During the exothermic reaction, the temperature is controlled at 40—45°C to minimize cellulose degradation. After the reaction solution becomes clear and fiber-free and the desired viscosity has been achieved, sufficient aqueous acetic acid (60—70% acid) is added to destroy the excess anhydride and provide 10—15% free water for hydrolysis. At this point, the sulfuric acid catalyst may be partially neutralized with calcium, magnesium, or sodium salts for better control of product molecular weight. 

Advantages The major advantages of the thermoplastic-based disposal systems are by dispiosin of the waste in a dry condition, the overall volume of the waste is greatly reduced most thermoplastic matrix materials are resistant to attack by aqueous solutions microbial degradation is minimal most matrices adhere well to incorporated materials, therefore, the final product has good strength and materials embedded in a thermoplastic matrix can be reclaimed if needed. 

O-isopropylidene derivative (57) must exist in pyridine solution in a conformation which favors anhydro-ring formation rather than elimination. Considerable degradation occurred when the 5-iodo derivative (63) was treated with silver fluoride in pyridine (36). The products, which were isolated in small yield, were identified as thymine and l-[2-(5-methylfuryl)]-thymine (65). This same compound (65) was formed in high yield when the 5 -mesylate 64 was treated with potassium tert-hx Xy -ate in dimethyl sulfoxide (16). The formation of 65 from 63 or 64 clearly involves the rearrangement of an intermediate 2, 4 -diene. In a different approach to the problem of introducing terminal unsaturation into pento-furanoid nucleosides, Robins and co-workers (32,37) have employed mild base catalyzed E2 elimination reactions. Thus, treatment of the 5 -tosylate (59) with potassium tert-butylate in tert-butyl alcohol afforded a high yield of the 4 -ene (60) (37). This reaction may proceed via the 2,5 ... 

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