Simple hydrates

MgCl2. I2H2O. This compound is of special interest as the most highly hydrated simple salt of which we know the structure. It is stable only at low temperatures, as shown by the transition points ... 

The epoxide hydrolases (EHs ECS.3.2.3) hydrate simple epoxides to vicinal diols, and they hydrate arene oxides to trans-dihydrodiols (also see Table 8.1). 

Hydrates simple epoxides and arene oxides to more polar vicinal diols and tra/w-dihydrodiols... 

There are simple and mixed hydrates. Simple hydrates represent hydrates of separate gases. These hydrates are formed from molecules of water and hydrator, which can be one of hydrocarbon gases. Hydrators of mixed hydrates and hydrates of natural gases are the gas mixtures, rather than single gases. The composition of mixed hydrates and their component structure changes depending on temperature and partial pressure of components in gas phase. 

Although they are more stable than hydrates, simple geminal dithiols (Nos 1660 and 1661) can undergo hydrolysis to yield their parent aldehydes and to release hydrogen sulfide (Mayer et al., 1963). The metabolism of the other simple aliphatic dithiol (No. 1709) is predicted to involve the pathways described above for simple thiols. Urinary metabolites could result from methylation, S-oxidation of a sulfur atom to yield a polar sulfonate and the formation of mixed disulfides by combination with a low molecular weight endogenous thiol such as cysteine. 

Abstract The present knowledge of protein science includes information on amino acid sequence and 3D structure in terms of precise models on the atomic level. Recourse to the respective databanks and advanced computer programs allows a series of molecular features to be calculated. Application of analytical surface calculation programs (SIMS, MSRoU) based on atomic coordinates or the coordinates of gravity centers of amino acids allows precise molecular dot surfaces to be calculated, in addition to numerical data for anhydrous molecular surface and anhydrous molecular volume. Usage of in-house hydration programs (HY-DCRYST, HYDMODEL) permits the putative localization of individual water molecules on the protein envelope to be addressed explicitly. To estimate the overall values of protein volume and hydration, simple approximations based on the amino acid composition and characteristic numbers for the constituents can be used. Derivation of secondary... 

Calculation of the conditions of hydrate formation is generally accomplished by software employing the Parrish and Prausnitz (1972) model. It is difficult to predict the conditions by a simple method. 

The enthalpy of solution is quite small for many simple ionic compounds and can be either positive or negative. It is the difference between two large quantities, the sum of the hydration enthalpies and the lattice energy. 

Prediction of solubility for simple ionic compounds is difficult since we need to know not only values of hydration and lattice enthalpies but also entropy changes on solution before any informed prediction can be given. Even then kinetic factors must be considered. 

Bashin A A and K Namboodiri 1987. A Simple Method for the Calculation of Hydration Enthalpies c Polar Molecules with Arbitrary Shapes. Journal of Physical Chemistry 91 6003-6012. 

Derivatives. The precise identification of a compound normally depends upon the preparation of a derivative and the determination of physical constants such as m.p. in the case of a solid. Many simple compounds can, however, be identified with a fair degree of certainty by intelligently-selected qualitative tests alone, e.g., formates, oxalates, succinates, lactates, tartrates, chloral hydrate. 

This enzyme, sometimes also called the Schardinger enzyme, occurs in milk. It is capable of " oxidising" acetaldehyde to acetic acid, and also the purine bases xanthine and hypoxanthine to uric acid. The former reaction is not a simple direct oxidation and is assumed to take place as follows. The enzyme activates the hydrated form of the aldehyde so that it readily parts w ith two hydrogen atoms in the presence of a suitable hydrogen acceptor such as methylene-blue the latter being reduced to the colourless leuco-compound. The oxidation of certain substrates will not take place in the absence of such a hydrogen acceptor. 

Table 17 3 compares the equilibrium constants for hydration of some simple aldehydes and ketones The position of equilibrium depends on what groups are attached to C=0 and how they affect its steric and electronic environment Both effects con tribute but the electronic effect controls A hydr more than the steric effect... 

Potassium Phosphates. The K2O—P20 —H2O system parallels the sodium system in many respects. In addition to the three simple phosphate salts obtained by successive replacement of the protons of phosphoric acid by potassium ions, the system contains a number of crystalline hydrates and double salts (Table 7). Monopotassium phosphate (MKP), known only as the anhydrous salt, is the least soluble of the potassium orthophosphates. Monopotassium phosphate has been studied extensively owing to its piezoelectric and ferroelectric properties (see Ferroelectrics). At ordinary temperatures, KH2PO4 is so far above its Curie point as to give piezoelectric effects in which the emf is proportional to the distorting force. There is virtually no hysteresis. 

High quahty SAMs of alkyltrichlorosilane derivatives are not simple to produce, mainly because of the need to carefully control the amount of water in solution (126,143,144). Whereas incomplete monolayers are formed in the absence of water (127,128), excess water results in facile polymerization in solution and polysiloxane deposition of the surface (133). Extraction of surface moisture, followed by OTS hydrolysis and subsequent surface adsorption, may be the mechanism of SAM formation (145). A moisture quantity of 0.15 mg/100 mL solvent has been suggested as the optimum condition for the formation of closely packed monolayers. X-ray photoelectron spectroscopy (xps) studies confirm the complete surface reaction of the —SiCl groups, upon the formation of a complete SAM (146). Infrared spectroscopy has been used to provide direct evidence for the hiU hydrolysis of methylchlorosilanes to methylsdanoles at the soHd/gas interface, by surface water on a hydrated siUca (147). 

Antimony pentafluoride is a strong Lewis acid and a good oxidizing and fluorinating agent. Its behavior as a Lewis acid leads to the formation of numerous simple and complex adducts. It reacts vigorously with water to form a clear solution from which antimony pentafluoride dihydrate [65277-49-8], SbF 2H2O, may be isolated. This is probably not a tme hydrate, but may well be better formulated as [H O] [SbF OH]. 

Sodium metaborate hydrates are more alkaline than borax and greater care is required in handling. The metaborate material is harm fill to the eyes and can cause skin irritation. Gloves, goggles, and a simple dust mask should be used when handling sodium metaborate powder. 

The simple cerous salts can be prepared by dissolving the oxide, or preferably a more reactive precursor, in the appropriate acid or, when possible, produced by precipitation from solution. Upon crystallization a wide variety of hydrated species can result. These hydrates tend to be hygroscopic. Basic salts, eg, Ce(OH)C02, maybe formed and these can be contaminants in the sohd salts. 

Miscellaneous Compounds. Among simple ionic salts cerium(III) acetate [17829-82-2] as commercially prepared, has lV2 H2O, has a moderate (- 100 g/L) aqueous solubiUty that decreases with increased temperature, and is an attractive precursor to the oxide. Cerous sulfate [13454-94-9] can be made in a wide range of hydrated forms and has solubiUty behavior comparable to that of the acetate. Many double sulfates having alkaU metal and/or ammonium cations, and varying degrees of aqueous solubiUty are known. Cerium(III) phosphate [13454-71 -2] being equivalent to mona2ite, is very stable. 

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