Pyridine-Water System

As shown in Fig. 8.5, a pyridine-water mixture has an azeotrope with composition of around 77 mol% H2O and azeotropic temperature of around 95°C. By adding toluene 

---

Figure 9. A comparison of the change with time in antioxidative activity produced by arginine-xylose in a water system and a pyridine-water system. Key O, water system pyridine—water system.

Another solubility phenomenon that may depend partly on H bonding is consolute temperature or critical solution temperature formation in mixtures that have a composition region in which they are im -miscible. The region narrows as the temperature is changed. Above an upper consolute temperature, or below a lower consolute temperature, the components are miscible over the entire composition range. Figure 2-11 shows such loops for 2,4- and 2,5-dimethylpyridine in water, as reported by Andon and Cox (45a). Other pyridine-water systems are... 

The solubility of the benzene/pyridine/water system is such that a treatment of the pyridine/water... 

Figure 8.6 RCM with LLE envelope of pyridine-water system with toluene as the entrainer.

Analysis calculated for C1SH36N2O4S C, 57.41 H, 9.63 N, 7.43 S, 8.51. Found C, 57.60 H, 9.66 N, 7.37 S, 8.25. Thin-layer chromatograms (Note 10) run by the submitters showed a single spot for the product in each of three following solvent systems (solvents, volume ratio of solvents in the same order) chloroform-methanol-acetic acid, 85 10 5, Rf 0.60 1-butanol-acetic acid-water, 4 1 1, Rf 0.58 l-butanol acetic acid-pyridine-water, 15 3 10 12, Rf 0.71. 

The literature reports [a]n +23.2° (c = l, aqueous 5N hydrochloric acid). The product was analyzed by the submitters. Analysis caleulated for C5H11NO2S C, 40.25 H, 7.43 N, 9.39 S, 21.49. Found C, 40.14 H, 7.42 N, 9.50 S, 21.52. The product was homogeneous according to thin-layer chromatograms on precoated silica gel G plates purchased from Analtech, Inc., Newark, Delaware, and developed with the following two solvent systems (solvents, volume ratios of solvents in the same order) 1-butanol-acetic acid-ethyl acetate-water, 1 1 1 1, Rf 0.49 1-butanol-acetic acid-pyridine-water, 15 3 10 12, R/0.51. 

Vitamin Bg and related compoimds (Figure 10.2) were quantitatively separated by preparative TLC on silica gel H. After elution, the pyridoxic acid lactone method was employed for fluorimetric determination of the concentration of the vitamin forms involved [8]. Table 10.2 shows Revalues obtained for various forms of vitamin Bg, using several solvent systems. The solvent selected, ethyl acetate/pyridine/water (2 1 2, v/v), gave excellent separation of pyridoxamine, pyridoxic acid, and pyri-doxine together with pyridoxal. 

Solvent systems used for thin layer chromatography were 1) n-butanol acetic acidiwater (4 1 5 upper phase), 2) acetic acid water (15 85), 3) ethyl acetate pyridine water (12 5 4), and 4) chloroform acetic acid water (50 45 5). Silica gel plates were used for chromatography of flavonoid aglycones and cellulose plates for all other components. Aluminum chloride was used for detection (under long UV light) of flavonoids, aniline phthalate for sugars, ninhydrin for amino acids and iodine for other components. Cellulose thick layer plates were developed with solvents 1 or 2. 

Many papers concerning salt effect on vapor-liquid equilibrium have been published. The systems formed by alcohol-water mixtures saturated with various salts have been the most widely studied, with those based on the ethyl alcohol-water binary being of special interest (1-6,8,10,11). However, other alcohol mixtures have also been studied methanol (10,16,17,20,21,22), 1-propanol (10,12,23,24), 2-propanol (12,23,25,26), butanol (27), phenol (28), and ethylene glycol (29,30). Other binary solvents studied have included acetic acid-water (22), propionic acid-water (31), nitric acid-water (32), acetone-methanol (33), ethanol-benzene (27), pyridine-water (25), and dioxane-water (26). 

The paper-chromatographic properties of the common deoxy and dideoxy sugars have been treated in several reviews,2 28 a book,829 and individual publications. Common solvent-systems are 6 4 3 1-butanol-pyridine-water (Solvent A) 4 1 5 1-butanol-acetic acid-water (Solvent B) and 1-buta-nol-ethanol-water (4 1 5, upper phase, Solvent C or 3 1 1, Solvent D). The four 2-deoxy-D-hexoses and the 2,6-dideoxyhexoses may be separated as their borate complexes. 0 The use of 1-butanol-water on the one hand, and of 2-butanone-borate buffer on the other, usually provides adequate separation and, by use of a combination of solvents, these deoxy sugars may be identified. 80 The use of buffered systems has proved highly advantageous in the separation and identification of the isomeric 6-deoxy-hexoses.8 1 Other systems, such as Solvent A and 2 1 2 ethyl acetate-... 

Figure 8.4. Water and diethylamine have both hydrogen bond donor and acceptor properties through the -OH or = NH groups. They cross-link through hydrogen bonds and can withstand considerable capillary tension. Pyridine has only hydrogen bond acceptor properties and cannot cross-link with itself. Pyridine cannot withstand large capillary forces the energy storage capacity of the pyridine-saturated system is small (Thomas and Krmgstad, 1971).

Straight systems are used for separation of hydrophilic compounds such as amino acids and sugars. The stationary phase is the water in the cellulose ( water-cellulose complex ), and the solvent is an aqueous and organic mixture such as phenol saturated with water, butanol/acetic acid/water (4 1 5 v/v), or ethyl acetate/ pyridine/water (12 5 4 v/v). 

---