Isoascorbic acid

Concern for personnel exposure to hydrazine has led to several innovations in packaging to minimize direct contact with hydrazine, eg, Olin s E-Z dmm systems. Carbohydrazide was introduced into this market for the same reason it is a soHd derivative of hydrazine, considered safer to handle because of its low vapor pressure. It hydrolyzes to release free hydrazine at elevated temperatures in the boiler. It is, however, fairly expensive and contributes to dissolved soHds (carbonates) in the water (193). In field tests, catalyzed hydrazine outperformed both hydrazine and carbohydrazide when the feedwater oxygen and iron levels were critical (194). A pubUshed comparison is available (195) of these and other proposed oxygen scavengers, eg, diethyUiydroxylarnine, ydroquinone, methyethylketoxime, and isoascorbic acid. 

Isay reaction, 2, 79-80 3, 259 Ismelin 7, 656 Isoalloxazine oxidation states, 1, 252 Isoaminopterin synthesis, 3, 327 Isoarsindolines, 1, 543-544 Isoarsinoline, tetrahydro-synthesis, 1, 552-553 stability, 1, 552 Isoascorbic acid structure, 4, 552 ( )-IsoavenacioIide synthesis, 1, 416 Isoazapenem synthesis, 1, 465 Isobacteriochlorin synthesis, 4, 419 Isobacteriochlorin, dimethyl-biosynthesis, 1, 105 Isobacteriochlorin, methyl-biosynthesis, 1, 105 Isobacteriochlorin, trimethyl-biosynthesis, 1, 105 Isobarbituric acid Mannich reaction, 3, 71 synthesis, 3, 133... 

NOTE Where MU requirements exceed 5 to 10% ofLTHW system volume per month, or 5% of the steam output ofLP steam boilers, a separate oxygen scavenger is required. This usually is tannin, diethylhydroxylamine (DEHA), or erythorbic acid (isoascorbic acid). 

Isoascorbic acid, l-ascorbic acid [C6Hg06 or 0C4H 0(0H)2-CHOH(CH)2OH] has a MW of 176.1, It is available as white to yellow granular crystals, It is soluble in water to the extent of 43%. 

Because of thermal decomposition, the use of tannin above 20 bar (290 psig) or isoascorbic acid above 60 bar (870 psig) is not recommended. 

Iodine starch inclusion compounds 46 Iodine vapor reagent 46, 64, 78 2-Iodoestrone 66 Ipecacuanha alkaloids 46, 263 Ipecacuanhae radix extract 263 Iron cadons 144, 217, 311 Iron(IIl) chloride reagent 170,216,314 Iron(III) thiocyanate reagent 170 Isoascorbic acid 376 Isoleucine 246,247... 

Bilyk, A. and Howard, M., Reversibility of thermal degradation of betacyanines under the influence of isoascorbic acid, J. Agric. Food Chem., 30, 906, 1982. 

Figure 6-10. Ascorbic acid, arabinose, isoascorbic acid.

Stablizers. Stabilizers are ingredients added to a formula to decrease the rate of decomposition of the active ingredients. Antioxidants are the principal stabilizers added to some ophthalmic solutions, primarily those containing epinephrine and other oxidizable drugs. Sodium bisulfite or metabisulfite are used in concentration up to 0.3% in epinephrine hydrochloride and bitartrate solutions. Epinephrine borate solutions have a pH range of 5.5 7.5 and offer a more difficult challenge to formulators who seek to prevent oxidation. Several patented antioxidant systems have been developed specifically for this compound. These consist of ascorbic acid and acetylcysteine, and sodium bisulfite and 8-hydroxyquinoline. Isoascorbic acid is also an effective antioxidant for this drug. Sodium thiosulfate is used with sodium sulfacetamide solutions. 

Fischer and Armstrong17 suggested the application of the benzaldehyde method for the decomposition of D-xylose phenylosazone, and a slight modification of this method180 was later employed in obtaining D-xylosone for the synthesis of D-isoascorbic acid,12-181-182 and L-xylosone182 for the... 

Weidenhagen46 obtained L-xylosone in 60% yield on oxidizing L-xylose by his modification of the copper acetate method.46 This method was employed by Salomon, Bums and King63 in the preparation of C14-labeled ascorbic acid and by Hamilton and Smith69 in the preparation of isoascorbic acid. 

D-isoascorbic acid D-mannitol D-mannose D-quinic acid D-ribolactone D-ribose D-saccharic acid D-sorbitol L-sorbose D-xylose (—)-a-Pinene (+)-a-Pinene (—)-/ -Pinene (i )-(+)-pulegone... 

Figure 3.31 Analytical isotachophoresis. Ascorbic acid (vitamin C) is naturally present in many foods and is often added to others. Occasionally the cheaper isomer, is oascorbic acid, which has no vitamin action, is used and is distinguishable from the natural isomer by many analytical methods, (a) shows the analysis of a sample of commercial fruit juice while (b) shows the same fruit juice to which a known amount (4 nmol) of isoascorbic acid has been added. (Reproduced by permission of LKB, Stockholm, Sweden.)...

Atorvastatin, an antihypercholesterolemic agent, is a synthetic drug that was initially produced in kilogram quantities using an 11-step chemical route. The iy -l,3-diol-con-taining side chain was produced from the chiral starting material, isoascorbic acid (Scheme 1.25). ... 

Difluorocysteine, like 3,3-difluoroserine, is unstable. However, a protected derivative has been described. Conversely, 3,3-difluoro-L-homocysteine and 3, 3-difluoro-L-methionine are much more stable. They are prepared from difluoro-homoserine. This latter is prepared through a multistep synthesis starting from isoascorbic acid (Figure 5.24). ... 

To this end, several routes passing through the known (S)-methyl-4-bromo-3-hydroxybutyrate 26, an intermediate used m prior syntheses of HMGRIs, were developed. This key intermediate was derived most efficiently from isoascorbic acid as shown in Scheme 5. Protection of 26 as the f-butyl-dimethylsilylether, followed by conversion to the nitnle provided an advanced intermediate (27) that could be taken in several directions. 

C6Hs06 D-Isoascorbic acid D-arabino-ascorbic acid4... 

Fruits and vegetables are the most common food sources for vitamin C (15-18). In food, vitamin C exists as two vitamers L-ascorbic acid (AA) and its oxidation product, dehydro-L-ascor-bic acid (DHAA) (Fig. 1) (15,17-19). Total Vitamin C is the sum of the AA and the DHAA contents. A stereoisomer, isoascorbic acid (IAA) is often added to food as an antioxidant. Both LAA and its oxidation product, dehydroisoascorbic acid (DHIAA), can interfere in Total Vitamin C determinations. 

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