Solubility solid phases

There are numerous experimental complications in the measurement of solubility. Solid phases, formed incipiently, are often metastable with respect to a... 

The concentration of some ions in soil solution is controlled mainly by the presence of poorly soluble solid phase components. Good examples of this are iron and aluminium, both of which are highly insoluble at the pH of most soils, and which are controlled by the solubility of the... 

A solution that is in equilibrium with the soluble solid phase is said to be saturated in respect of the solid. It is possible however to have a concentration in solution that is greater than that referred to as saturated. The term supersaturation is applied to this enhanced solubility of the solid. In the laboratory considerable... 

Precipitation generally refers to a relatively rapid formation of a sparingly soluble solid phase from a liquid solution phase. Precipitation is rather poorly understood when compared with crystallization of more soluble materials. It generally involves the simultaneous and rapid occurrence of nucleation, crystal growth, and other processes, such as Ostwald ripening and agglomeration. All these processes are difficult to separate and independently investigate both mechanistically and experimentally. 

Then N-Boc-O-benzylserine is coupled to the free amino group with DCC. This concludes one cycle (N° -deprotection, neutralization, coupling) in solid-phase synthesis. All three steps can be driven to very high total yields (< 99.5%) since excesses of Boc-amino acids and DCC (about fourfold) in CHjClj can be used and since side-reactions which lead to soluble products do not lower the yield of condensation product. One side-reaction in DCC-promoted condensations leads to N-acylated ureas. These products will remain in solution and not reaa with the polymer-bound amine. At the end of the reaction time, the polymer is filtered off and washed. The times consumed for 99% completion of condensation vary from 5 min for small amino acids to several hours for a bulky amino acid, e.g. Boc-Ile, with other bulky amino acids on a resin. A new cycle can begin without any workup problems (R.B. Merrifield, 1969 B.W. Erickson, 1976 M. Bodanszky, 1976). 

Tills table shows tlie amoiuit of aiiliydroiis substance tliat is soluble in 100 g of water at tlie temperature in degrees Celsius as indicated when tlie name is followed by t, tlie value is expressed in grams of substance in 100 cm of saturated solution. Solid phase gives tlie hydrated form in equilibrium witli tlie saturated solution. 

As shown in Fig. 18-57, the mutual solubility of two salts can be plotted on the X and Y axes with temperatures as isotherm hues. In the example shown, all the solution compositions corresponding to 100°C with solid-phase sodium chloride present are shown on the Tine DE, All the solution compositions at equihbrium with solid-phase KCl at 100°C are shown by the line EE If both sohd-phase KCl and NaCl are present, the solution composition at equilibrium can only be represented by point E, which is the invariant point (at constant pressure). Connecting all the invariant points results in the mixed-salt hne. The locus of this line is an important consideration in making phase separations. 

Crystal Formation There are obviously two steps involved in the preparation of ciystal matter from a solution. The ciystals must first Form and then grow. The formation of a new sohd phase either on an inert particle in the solution or in the solution itself is called nucle-ation. The increase in size of this nucleus with a layer-by-layer addition of solute is called growth. Both nucleation and ciystal growth have supersaturation as a common driving force. Unless a solution is supersaturated, ciystals can neither form nor grow. Supersaturation refers to the quantity of solute present in solution compared with the quantity which would be present if the solution were kept for a veiy long period of time with solid phase in contac t with the solution. The latter value is the equilibrium solubility at the temperature and pressure under consideration. The supersaturation coefficient can be expressed... 

Oxytocin [50-56-6] M 1007.2, m dec on heating, [a] -26.2"(c 0.53, N AcOH). A cyclic nonapeptide which was purified by countercurrent distribution between solvent and buffer. It is soluble in H2O, rt-BuOH and isoBuOH. [Bodanszky and du Vigneaud J Am Chem Soc 81 2504 1959 Cash et al. J Med Pharm Chem 5 413 1962 Sakakibara et al. Bull Chem Soc Jpn 38 120 1965 solid phase synthesis Bayer and... 

A third method, or phenomenon, capable of generating a pseudo reaction order is exemplified by a first-order solution reaction of a substance in the presence of its solid phase. Then if the dissolution rate of the solid is greater than the reaction rate of the dissolved solute, the solute concentration is maintained constant by the solubility equilibrium and the first-order reaction becomes a pseudo-zero-order reaction. 

Flocculation and sedimentation arc two processes used to separate waste streams that contain both a liquid and a solid phase. Both are well-developed, highly competitive processes, which arc oflcii used in the complete treatment of waste streams. They may also be used instead of, or in addition to, filtration. Some applications include the removal of suspended solid particles and soluble heavy metals from aqueous streams. Many industries use both processes in the rcmowal of pollutants from their wastewaters. These processes work best when the waste stream contains a low concentration of the contaminating solids. Although they are applicable to a wide variety of aqueous waste streams, these processes arc not generally used to treat nonaqueous or semisolid waste streams such as sludges and slurries. 

The test divides the drilling fluid into three phases the liquid phase, the suspended particulate phase, and the solid phase. These phases are designed to represent the anticipated conditions that organisms would be exposed to when drilling mud is discharged into the ocean. Certain drilling fluid components are water column, others are fine particulates which would stay suspended, and still water soluble and will dissolve in the other material would settle rapidly to the bottom. 

The basic mechanism of passivation is easy to understand. When the metal atoms of a fresh metal surface are oxidised (under a suitable driving force) two alternative processes occur. They may enter the solution phase as solvated metal ions, passing across the electrical double layer, or they may remain on the surface to form a new solid phase, the passivating film. The former case is active corrosion, with metal ions passing freely into solution via adsorbed intermediates. In many real corrosion cases, the metal ions, despite dissolving, are in fact not very soluble, or are not transported away from the vicinity of the surface very quickly, and may consequently still... 

Sodium reduction development directions, 336 diluted melts, 331-332 of K-Salt, 327-328 principals, 326 Solid-phase interaction mechanism, 34-37 niobium oxyfluorides, 26-31 tantalum oxyfluorides, 32-34 Solubility diagrams (NH4)5Nb3OF18, 22 K2NbF7 in HF solutions, 14 K2TaF7 in HF solutions, 14 RbsNbjOF,, 22-23 Solubility of peroxides, 307 Specific conductivity, 153, 164 Spontaneous polarization, 223 Structural characteristics for X Me=8, 61,... 

The great importance of the solubility product concept lies in its bearing upon precipitation from solution, which is, of course, one of the important operations of quantitative analysis. The solubility product is the ultimate value which is attained by the ionic concentration product when equilibrium has been established between the solid phase of a difficultly soluble salt and the solution. If the experimental conditions are such that the ionic concentration product is different from the solubility product, then the system will attempt to adjust itself in such a manner that the ionic and solubility products are equal in value. Thus if, for a given electrolyte, the product of the concentrations of the ions in solution is arbitrarily made to exceed the solubility product, as for example by the addition of a salt with a common ion, the adjustment of the system to equilibrium results in precipitation of the solid salt, provided supersaturation conditions are excluded. If the ionic concentration product is less than the solubility product or can arbitrarily be made so, as (for example) by complex salt formation or by the formation of weak electrolytes, then a further quantity of solute can pass into solution until the solubility product is attained, or, if this is not possible, until all the solute has dissolved. 

The equation shows that the solubility curve must be continuous all breaks indicate that the solid phase in contact with the saturated solution has altered in character, and we really have to do with two distinct solubility curves meeting at an angle. This occurs, for example, with Glauber s salt at 32° 6, for this is the transition temperature for the reaction... 

Besides the effect of temperature and pressure, the mechanical pressure exerted on the solid phase, and its state of division, influence (although only to a slight extent) its solubility in the liquid. Thus, if a moist precipitate is exposed to pressure in a filter-press, it usually aggregates together, and Hulett (1901) showed that the effect of division (i.e., of surface tension) becomes... 

The equilibrium pressure when (solid + vapor) equilibrium occurs is known as the sublimation pressure, (The sublimation temperature is the temperature at which the vapor pressure of the solid equals the pressure of the atmosphere.) A norma) sublimation temperature is the temperature at which the sublimation pressure equals one atmosphere (0.101325 MPa). Two solid phases can be in equilibrium at a transition temperature (solid + solid) equilibrium, and (liquid + liquid) equilibrium occurs when two liquids are mixed that are not miscible and separate into two phases. Again, "normal" refers to the condition of one atmosphere (0.101325 MPa) pressure. Thus, the normal transition temperature is the transition temperature when the pressure is one atmosphere (0.101325 MPa) and at the normal (liquid + liquid) solubility condition, the composition of the liquid phases are those that are in equilibrium at an external pressure of one atmosphere (0.101325 MPa). 

Since most aaAAs are hydrophobic in nature, peptides rich in aaAAs are generally restricted to study in organic solvents due to their low solubility in aqueous media. There have been very few examples of side-chain functionalized aaAAs that would allow for the synthesis of highly water-soluble peptides rich in aaAA content.3 This is primarily due to difficulty of synthesis, since side-chain functionalized derivatives must be orthogonally protected to allow for incorporation into solid-phase peptide synthesis. The harsh conditions, under which standard methods of aaAA synthesis are performed, make this a difficult task. 

Abstract Current microwave-assisted protocols for reaction on solid-phase and soluble supports are critically reviewed. The compatibility of commercially available polymer supports with the relatively harsh conditions of microwave heating and the possibilities for reaction monitoring are discussed. Instrmnentation available for microwave-assisted solid-phase chemistry is presented. This review also summarizes the recent applications of controlled microwave heating to sohd-phase and SPOT-chemistry, as well as to synthesis on soluble polymers, fluorous phases and functional ionic liquid supports. The presented examples indicate that the combination of microwave dielectric heating with solid- or soluble-polymer supported chemistry techniques provides significant enhancements both at the level of reaction rate and ease of purification compared to conventional procedures. 

Keywords Microwave Heterocyclic Solid-phase Solid-support Soluble-support... 

In addition to the insoluble polymers described above, soluble polymers, such as non-cross-linked PS and PEG have proven useful for synthetic applications. However, since synthesis on soluble supports is more difficult to automate, these polymers are not used as extensively as insoluble beads. Soluble polymers offer most of the advantages of both homogeneous-phase chemistry (lack of diffusion phenomena and easy monitoring) and solid-phase techniques (use of excess reagents and ease of isolation and purification of products). Separation of the functionalized matrix is achieved by either precipitation (solvent or heat), membrane filtration, or size-exclusion chromatography [98,99]. 

PEG polymers are widely used as water soluble supports [99]. Although these polymers suffer from easy loss of PEG oligomers, they are frequently used for the preparation of small organic molecules [100-105] and biopolymers [106,107]. The main benefit of PEG supports is their solubility in water as well as most organic solvents. Also, as opposed to most solid-phase techniques, PEG polymers allow for easy on-bead NMR monitoring. Soluble PEG supports have been used frequently in synthetic microwave chemistry protocols [108-122]. 

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