Glycine solutions, table

An additional example for ion pair extraction of QTA (ipratropium) was described by Tang et al. mixing equine urine with alkaline saturated borax buffer prior to extraction with EE allowing to remove more lipophilic compounds. Subsequently, the EE layer was discarded and an alkaline potassium iodide-glycine solution was added to the aqueous phase. Afterwards, the ipratropium-ion pair complex was extracted twice with dichloromethane yielding in a recovery of 82 % [24] (Table 3). 

When comparing the experimental vibrational frequencies of the aqueous glycine solution and the aqueous solution of the system glycine-KI-l2 as discussed in [21], it was noted that the coordination of the carboxyl group with molecular iodine results in the reduction of the valence vibration frequency of the carboxyl group (from 1332 to 1322 cm ). As can be seen from Table 10.3, no shift to the short-wave region in the lib complex is observed. The band at 1322 cm is wider than the bands at 1580 and 1497 cm , therefore the vibrational frequencies of the... 

A poorly water-soluble active substance such as theophylline becomes soluble by the addition of glycine and sodium hydroxide. In this way a theophylline rectal solution (Table 11.14) can be formulated with theophylline as sodium glycinate. 

In the two sets of results plotted in Fig. 34 no maximum is observed in either case within the range of temperature covered by the experiments nevertheless, in both cases the values appear to be tending toward a maximum lying just outside the experimental range, namely, at — 5.4°C for chloracetic acid, and at 53.9 for glycine. In 1934, Harned and Embree, surveying all the data (in Table 9) that had been obtained up to that time in aqueous solution, found a remarkable uniformity in... 

A Chart of Occupied and Vacant Proton Levels. With two exceptions, each of the values of J given in Tables 9, 10, and 11 refers to the process where a proton is raised to the vacant proton level of an HsO molecule from a lower occupied proton level of a species of molecule or molecular ion in each case the value of J gives the amount by which this initially occupied level lies below the vacant level of H20. Obviously, using these values, it is at once possible to map out a chart of the proton levels of these various particles in aqueous solution, as has been done in Fig. 36. The two exceptions in Table 9 are the values derived from the KB of glycine and alanine. In these cases, as shown in (125), a proton is transferred to a vacant level from the ordinary occupied proton level in a water molecule the value of J gives the amount by which the vacant level lies above this occupied proton level of H20. 

TABLE 18.3. Partial Molar Volumes in Aqueous Solutions of Glycine... 

Table 18.5 lists the relative partial molar enthalpies of glycine and its aqueous solutions at 25°C. [Reprinted with permission from Ref. 9. Copyright 1940 American Chemical Society.]... 

TABLE 20.2. Thermodynamic Data for Glycine and its Aqueous Solutions... 

Schiff s base formation occurs by condensation of the free amine base with aldehyde A in EtOAc/MeOff. The free amine base solution of glycine methyl ester in methanol is generated from the corresponding hydrochloride and triethylamine. Table 4 shows the reaction concentration profiles at 20-25°C. The Schiffs base formation is second order with respect to both the aldehyde and glycine ester. The equilibrium constant (ratio k(forward)/ k(reverse)) is calculated to be 67. 

Stability constant determinations are few 1170 they are summarized in Table 100. Complexa-tion by acidic amino acids is obviously of relevance to the tanning of leather the stability constants for L-glutamic and aspartic acid1171 complexes are much greater than those for glycine or L-alanine.1172,1173,1174 This is probably because the acidic amino acids form tridentate complexes. In contrast, cysteine1173 appears to form glycine-like complexes in moderately acidic solution however, in the solid state L-cysteine is known to be tridentate vide infra). 

Preparation of Model Compound Test Solutions. Individual stock solutions containing 500 mg/L were prepared by dissolving quinaldic acid, glycine, and glucose in OFW 5-chlorouracil in 2 N NH4OH phenanthrene, 1-chlorododecane, 2,4 -dichlorobiphenyl, and 2,2, 5,5 -tetrachlorobiphenyl in hexane and the remaining compounds in methanol. Humic acid stock solution was prepared in 0.02 N NaOH. The composition of the test solutions is reported in Table I. Test solutions (500 mL) were prepared by adding salts and the required volumes of stock solutions in OFW. Phenanthrene, 1-chlorododecane,... 

Table 9.4. In the regions of overlapping solutes, glycine, and lysine have low relative weight responses. In addition, methionine, ornithine, histidine, arginine, tryptophan, and cysteine have significantly low responses.

One type of oligoamide that can readily be prepared on supports without the need for any partially protected monomers (which are often tedious and expensive to synthesize) are N-substituted oligoglycines (Figure 16.21). These compounds are prepared by a sequence of acylation of a support-bound amine with bromoacetic acid, displacement of the bromide with a primary aliphatic or aromatic amine, and repeated acylation with bromoacetic acid. Because primary amines are cheap and available in large number, this approach enables the cost-efficient production of large, diverse compound libraries. Alternatively, protected N-substituted glycines can also be prepared in solution and then assembled on insoluble supports (Entry 5, Table 16.2). 

Not mentioned in Table 2 (and often not in the original papers ) is the optical form (chirality) of the amino acids used. All the amino acids, except for glycine (R = H), contain an asymmetric carbon atom (the C atom). In the majority of cases the optical form used, whether l, d or racemic dl, makes little difference to the stability constants, but there are some notable exceptions (vide infra). Examination of the data in Table 2 reveals (i) that the order of stability constants for the divalent transition metal ions follows the Irving-Williams series (ii) that for the divalent transition metal ions, with excess amino acid present at neutral pH, the predominant spedes is the neutral chelated M(aa)2 complex (iii) that the species formed reflect the stereochemical preferences of the metal ions, e.g. for Cu 1 a 2 1 complex readily forms but not a 3 1 ligand metal complex (see Volume 5, Chapter 53). Confirmation of the species proposed from analysis of potentiometric data and information on the mode of bonding in solution has involved the use of an impressive array of spectroscopic techniques, e.g. UV/visible, IR, ESR, NMR, CD and MCD (magnetic circular dichroism). 

The effect of ionic form on the reaction of the hydrated electron with amino acids has been examined. The cationic form could not be examined since appreciable amounts of H + would have to be present, and with currently available techniques the electron would disappear too rapidly. But by making the solutions alkaline it has been possible to study the anionic form. For glycine (Table I), and several other amino acids and peptides (7), it has been shown that the amino acids are less reactive in the anionic form, agreeing with the conclusion drawn by Garrison. The results for glycine however cannot be interpreted on the basis of the known pK together with assumed rate constants for zwitterion and anion. Other factors are evidently present, and further work is required. 

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