With dihydrogen phosphat

MacrocycHc receptors 31a and 31b were found to bind both dihydrogen phosphate and chloride in exclusively 1 1 host/guest stoichiometries. Binding constants were calculated for 31a and 31b with dihydrogen phosphate and chloride and revealed that dihydrogenphosphate was bound more strongly (2.5 X 10 M for 31a and 4.0 x 10 M for 31b) than chloride (500 for 31a and <50 M for 31b). 

In the case of receptor 40 with dihydrogen phosphate in DMSO-slow exchange on the NMR timescale. This is shown in Figure 25. The addition of up to 1 equivalent of anion led to the downfield shift of the amide NH resonance this was followed by the appearance of new peaks in the NMR spectrum as further aliquots of anion were added. These new peaks appeared significantly downfield compared to the resonance associated with the assumed 1 1 complex. 

Description of Method. The water-soluble vitamins Bi (thiamine hydrochloride), B2 (riboflavin), B3 (niacinamide), and Be (pyridoxine hydrochloride) may be determined by CZE using a pH 9 sodium tetraborate/sodlum dIhydrogen phosphate buffer or by MEKC using the same buffer with the addition of sodium dodecyl-sulfate. Detection Is by UV absorption at 200 nm. An Internal standard of o-ethoxybenzamide Is used to standardize the method. 

Procedure. A vitamin B complex tablet Is crushed and placed In a beaker with 20.00 mL of a 50% v/v methanol solution that Is 20 mM In sodium tetraborate and contains 100.0 ppm of o-ethoxybenzamIde. After mixing for 2 min to ensure that the B vitamins are dissolved, a 5.00-mL portion Is passed through a 0.45- xm filter to remove Insoluble binders. An approximately 4-nL sample Is loaded Into a 50- xm Internal diameter capillary column. For CZE the capillary column contains a 20 mM pH 9 sodium tetraborate/sodlum dIhydrogen phosphate buffer. For MEKC the buffer Is also 150 mM In sodium dodecylsulfate. A 40-kV/m electric field Is used to effect both the CZE and MEKC separations. 

Starch sodium phosphate monoesters [11120-02-8] are prepared by heating mixtures of 10% moisture starch and sodium monohydrogen and dihydrogen phosphates or sodium tripolyphosphate. Starch phosphate monoesters are used primarily in foods, such as pudding starches and with oH-in-water emulsions. 

Dissolve 680 mg potassium dihydrogen phosphate in 50 ml water and add 4.6 ml 0.1 M caustic soda then dilute 1+9 with water. 

FIGURE 7.14 A Fractogel EMD BioSEC Superformance column (600-16) was loaded with 500 /il of BSA, ovalbumin, and cytochrome c (5/5/3 mg/ml) at I ml/min. The test covered 100 individual runs with the standard proteins as samples. The buffer system used was 20 m/VI sodium dihydrogen phosphate, 300 m/VI NaCI, pH 7.2. After each individual run the column was rinsed with I /VI NaOH (60 min with I /VI NaOH at 2 ml/min). No significant change in retention times and resolution was observed after 100 cycles. 

Then 0.75 cc of freshly distilled ethyl formate is added. The air in the system is replaced with nitrogen and 150 mg of sodium hydride (as a 57% dispersion in mineral oil) is added. The mixture is stirred under nitrogen at room temperature for three hours. Then 15 cc of a saturated aqueous solution of sodium dihydrogen phosphate is added and the product is extracted into ether. 

The ether extracts are extracted with 2 N sodium hydroxide and the sodium hydroxide extracts are acidified with sodium dihydrogen phosphate and extracted again into ether. 

Deoxy-D-jcylo hexose 6-(dihydrogen phosphate) (21) has also been synthesized (2) the reaction sequence makes use of 3-deoxy l 2,5 6-di-O-isopropylidene D-galactofuranose (16), a compound that can be easily prepared from D-glucose (2, 60). The mono-isopropylidene derivative (17) formed by partial hydrolysis of the di-ketal is converted into the 6-tosylate (18) by reaction with one molar equivalent of p-toluenesulfonyl chloride. From this the epoxide (19) is formed by reaction with sodium methoxide. Treatment of the anhydro sugar with an aqueous solution of disodium hydrogen phosphate (26) leads to the 6-phosphate (20)... 

Methyl-5-oxo-l-phenyl-4,5-dihydropyrazol-4-ylidene)-2,3-dihydro-l//-azepine (3), formed in 62% yield by the condensation of 2-amino- or 2-butoxy-37/-azepine with 3-methyl-l-phenylpyrazol-5(4//)-one, with Meerwein s reagent yields the tetrafluoroborate salt 4 which, on treatment with sodium dihydrogen phosphate, liberates the free base 5.64... 

The rate of the reaction in various buffer solutions, covering the pH range 4-8, was determined, and in hydrogen phosphate-dihydrogen phosphate buffers the rate at constant pH decreased as the concentration of dihydrogen phosphate increased. Similarly, with acetic acid-acetate and phosphoric acid-dihydrogen phosphate buffers the rate was inversely dependent upon the concentration of the molecular acid in addition, with the latter buffer, the kinetic plots showed an unexplained departure from linearity after 50 % reaction. 

---