Sucrose aqueous

Another method to improve the hydrophobic treatment of DLs was presented by Wang, Shi, and Du [106]. They coated the CFP fibers (TGP-Fl-090) with a sucrose aqueous solution for around 6 hours. After that the material was heated at 400°C in order to carbonize the sucrose solution. This process... 

Izquierdo-Gil, M.A., Garcfa-Payo, M.C., and Femandez-Pineda, C. Air gap membrane distillation of sucrose aqueous solutions, J. Membr. Sci., 155, 291, 1999. 

Brazzein, the smallest of sweet proteins, was discovered only in 1994 (Ming and Hellekant, 1994) in Pentadiplandra brazzeana B. This protein, whose sequence contains 54-amino acid residues, is 2000 times sweeter than sucrose when compared to a 2% sucrose aqueous solution. Its taste was described as more similar to sucrose than that of thaumatin (Ming and Hellekant, 1994). As can be seen in Figure 5C, the 3D structure of brazzein, determined by NMR spectroscopy in solution at pH 5.2 (Caldwell et al., 1998), is very simple. It contains one a-helix and three strands of antiparallel )3-sheet. The structure is stabilized by four disulfide bonds, three connecting the helix to the jS-sheet. It does not resemble either that of monellin or that of thaumatin instead, it resembles those of plant y-thionins and defensins and arthropod toxins. According to the SCOP classification (Murzin et al., 1995), brazzein belongs to the Scorpion toxin-like superfamily. 

Figure 1.21 Density of sodium chloride and sucrose aqueous solutions as 20 °C. (Data from Weast 1975.)...

Sucrose (Aqueous) Caustic Solution Benzoyl Chloride Toluene... 

First, a few definitions a system is any region of space, any amount of material for which the boundaries are clearly specified. At least for thennodynamic purposes it must be of macroscopic size and have a topological integrity. It may not be only part of the matter in a given region, e.g. all the sucrose in an aqueous solution. A system could consist of two non-contiguous parts, but such a specification would rarely be usefLil. 

McCain D 0 and Markley J L 1986 Rotational spectral density functions for aqueous sucrose ... 

Of the common disaccharides sucrose does not reduce Fehling s solution. If the cane Sugar is hydrolysed by boiling it with dilute acid and the solution is neutralised with aqueous sodium hydroxide, the reduction of Fehling s solution occurs readily. 

Alkaline Degradation. At high pH, sucrose is relatively stable however, prolonged exposure to strong alkaU and heat converts sucrose to a mixture of organic acids (mainly lactate), ketones, and cycHc condensation products. The mechanism of alkaline degradation is uncertain however, initial formation of glucose and fructose apparendy does not occur (31). In aqueous solutions, sucrose is most stable at —pH 9.0. 

ICUMSA (1) has adopted tables showing the relationship between the concentration of aqueous solutions of pure sucrose, glucose, fmctose, and invert sugar and refractive index at 20.0°C and 589 nm. 

Cane sugar is generally available ia one of two forms crystalline solid or aqueous solution, and occasionally ia an amorphous or microcrystalline glassy form. Microcrystalline is here defined as crystals too small to show stmcture on x-ray diffraction. The melting poiat of sucrose (anhydrous) is usually stated as 186°C, although, because this property depends on the purity of the sucrose crystal, values up to 192°C have been reported. Sucrose crystallines as an anhydrous, monoclinic crystal, belonging to space group P2 (2). 

The specific rotation ia water is [0 ] ° — +66.529° (26 g pure sucrose made to 100 cm with water). This property is the basis for measurement of sucrose concentration ia aqueous solution by polarimetry. 100°Z iadicates 100% sucrose on soHds. 

Table 3. Osmotic Pressure of Aqueous Sucrose Solutions at 25°C ...

Table 4. Dielectric Constant of Aqueous Sucrose Solutions...

Trityl Ethers. Treatment of sucrose with four molar equivalents of chlorotriphenylmethyl chloride (trityl chloride) in pyridine gives, after acetylation and chromatography, 6,1, 6 -tri-O-tritylsucrose [35674-14-7] and 6,6 -di-O-tritylsucrose [35674-15-8] in 50 and 30% yield, respectively (16). Conventional acetylation of 6,1, 6 -tri-O-tritylsucrose, followed by detritylation and concomitant C-4 to C-6 acetyl migration using aqueous acetic acid, yields a pentaacetate, which on chlorination using thionyl chloride in pyridine and deacetylation produces 4,l, 6 -trichloro-4,l, 6 -trideoxygalactosucrose [56038-13-2] (sucralose), alow calorie sweetener (17). 

Leucrose, 6-0-(a-D-glucopyranosyl)-P-D-fmctopyranose [7158-70-5] is synthesized from sucrose usiag a dextranase enzyme from l euconostoc mesenteriodes and a small proportion of fmctose (2%). Pfeifer Langen of Germany have developed a production process for leucrose that iavolves extraction of the enzyme, treatment with 65% aqueous solution of sucrose and fmctose (1 2 wt/wt) at 25°C, separation of the product from fmctose by ion-exchange column chromatography, and crystallization. The product has not yet been launched on the market as of this writing (1996). 

Sodium borate (decahydrate, hydrated borax) [1303-96-4] M 381.2, m 75 (loses 5H2O at 60 ), d 1.73. Crystd from water (3.3mL/g) keeping below 55° to avoid formation of the pentahydrate. Filtered at the pump, washed with water and equilibrated for several days in a desiccator containing an aqueous solution saturated with respect to sucrose and NaCl. Borax can be prepared more quickly (but its water content is somewhat variable) by washing the recrystd material at the pump with water, followed by 95% EtOH, then Et20, and air dried at room temperature for 12-18h on a clock glass. 

The shape of the equilibrium line, or solubility curve, is important in determining the mode of crystallization to be employed in order to crystallize a particular substance. If the curve is steep, i.e. the substance exhibits a strong temperature dependence of solubility (e.g. many salts and organic substances), then a cooling crystallization might be suitable. But if the metastable zone is wide (e.g. sucrose solutions), addition of seed crystal might be necessary. This can be desirable, particularly if a uniformly sized product is required. If on the other hand, the equilibrium line is relatively flat (e.g. for aqueous common salt... 

Equation (7.123)w is often referred to as the law of Van t Hoff, since it was originally proposed by J. H. Van t Hoff. It is interesting to note that equation (7.123) is of the same form as the ideal gas equation, if one takes c as njVx Table 7.3 compares experimental values of II for aqueous sucrose solutions with those calculated using equations (7.120) and (7.123). We see that neither of the equations predicts n with high accuracy. However, the superiority of equation (7.120), especially at higher concentrations, is apparent. 

Table 7.3 Osmotic pressures of aqueous sucrose solutions at T = 293.15 K...

E7.14 Estimate the vapor pressure lowering and the osmotic pressure at 293.15 K for an aqueous solution containing 50.0 g of sucrose (Mi = 0.3423 kg-mol"1) in 1 kg of water. At this temperature, the density of pure water is 0.99729 g em"3 and the vapor pressure is 2.33474 kPa. Compare your results with those given in Table 7.3. 

Calculate the concentrations of each of the following solutions (a) the molality of 13.63 g of sucrose, C 2H22Om, dissolved in 612 mL of water (h) the molality of CsCl in a 10.00% by mass aqueous solution (c) the molality of acetone in an aqueous solution with a mole fraction for acetone of 0.197. 

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