Sensitivity to water

Phenyl isothiocyanate is not sensitive to water the reaction may be carried out with an aqueous solution of an amine. 

The phenylhydantoic acid is prepared similarly, using phenyl isocyanate. The latter is more sensitive to water than a-naphthyl isocyanate and therefore does not keep so well. 

Adhesives. Poly(vinyl alcohol) is used as a component in a wide variety of general-purpose adhesives to bond ceUulosic materials, such as paper and paperboard, wood textiles, some metal foils, and porous ceramic surfaces, to each other. It is also an effective binder for pigments and other finely divided powders. Both fully and partially hydrolyzed grades are used. Sensitivity to water increases with decreasing degree of hydrolysis and the addition of plasticizer. Poly(vinyl alcohol) in many appHcations is employed as an additive to other polymer systems to improve the cohesive strength, film flexibiUty, moisture resistance, and other properties. It is incorporated into a wide variety of adhesives through its use as a protective coUoid in emulsion p olymerization. 

A water-reducible coating or resin is one that is diluted with water before use. Water-reducible alkyds give comparable drying performance to solvent-bome alkyds. However, they are not widely used because film properties tend to be poorer than those of solvent-bome alkyds, especially in air-dry systems (26). This is pardy because of alcoholysis of the alkyd by primary alcohols such as 1-butanol [71-36-3] C H qO, a common solvent in water-reducible alkyds (27,28) secondary alcohols such as 2-butanol [78-92-2] C qH O, minimize this problem (27). In any case, the slow loss of amine or ammonia leads to short-term high sensitivity to water. Even in the fully dry films, the presence of unreacted carboxyHc acid groups leads to films having comparatively poor water resistance limiting their usehilness. 

Most of the above can be made into plastic films - primarily used for wrapping. Film properties vary widely from permeable for food to impermeable to preserve dryness. Paper, treated or untreated, has been used for many years as a covering film, but has low strength when wet and is difficult to make transparent. In the 1920s, the transparency of cellophane revolutionized wrap. It is regenerated cellulose, like viscose rayon, except it is extruded in sheet instead of fiber, unfortunately it is sensitive to water and humidity. 

Boronic esters are easily prepared from a diol and the boronic acid with removal of water, either chemically or azeotropically. (See Chapter 2 on the protection of diols.) Sterically hindered boronic esters, such as those of pinacol, can be prepared in the presence of water. Boronic esters of simple unhindered diols are quite sensitive to water and hydrolyze readily. On the other hand, very hindered esters, such as the pinacol and pinanediol derivatives, are exceedingly difficult to hydrolyze and often require rather harsh conditions to achieve cleavage. 

The disadvantage of this method is that the dichloridites and monochloridites are sensitive to water and thus could not be used readily in automated oligonucleotide synthesis. This problem was overcome by Beaucage and Caruthers, who developed the phosphoramidite approach. In this method, derivatives of the form R 0P(NR2)2 react with one equivalent of an alcohol (catalyzed by species such as l//-tetrazole) to form diesters, R OP(OR")NR2, which usually are stable, easily handled solids. These phosphoroamidites are easily converted to phosphite triesters by reaction with a second alcohol (catalyzed by l//-tetrazole). Here, again, oxidation of the phosphite triester with aqueous iodine affords the phosphate triester. Over the years, numerous protective groups and amines have been examined for use in this approach. Much of the work has been reviewed. ... 

Precipitated K—salt crystals are carefully filtrated and washed so as to separate them from the mother solution. Drying of filtrated K-salt is also a very delicate and important process that must be performed under conditions that avoid hydrolysis of the material. Potassium heptafluorotantalate is sensitive to water, basic compounds and alcohols, especially at elevated temperatures. The main product of K-salt hydrolysis is Marignac s salt. For a long time it was believed that the composition of Marignac s salt is K/Ta Fg. However, X-ray crystal structure analysis and precise chemical analysis of the... 

Note. Anhydrous reaction conditions are generally essential since the silylated derivatives are sensitive to water in varying degrees. 

Electron Capture Detector In the electron capture detector (ECD), a beta emitter such as tritium or 63Ni is used to ionize the carrier gas. Electrons from the ionization migrate to the anode and produce a steady current. If the GC effluent contains a compound that can capture electrons, the current is reduced because the resulting negative ions move more slowly than electrons. Thus, the signal measured is the loss of electrical current. The ECD is very sensitive to materials that readily capture electrons. These materials frequently have unsaturation and electronegative substituents. Because the ECD is sensitive to water, the carrier gas must be dry. 

LAS is moderately sensitive to water hardness such that at certain concentration levels governed by the solubility product (Ksp) and the CMC, Ca(LAS)2 will precipitate out of solution [26]. The precipitation boundary diagram provides a useful method to study the interaction of LAS with calcium ions. From this diagram, approximate values of the CMC and Ksp for LAS and Ca2+ can be approximated [27]. 

Table 7 gives the apparent CMC and Ksp values for C12 LAS [28]. As carbon chain length increases, the Ksp decreases, which is an indication that the LAS becomes more sensitive to water hardness [27]. It has been reported that the internal phenyl isomers of C,2 LAS are more sensitive to precipitation with Ca2+ than the 2-phenyl isomer [29]. This is presumably due more to the lower CMC of the 2-phenyl LAS isomer than to any increase in the Ksp. 

It has been reported that LAS/AOS combinations exhibit favorable synergy in detergency performance and a reduced sensitivity to water hardness [49]. 

The well-known traditional detergent basic material soap often causes problems because of its sensitivity to water hardness, i.e., poor lime dispersibility we encounter stability problems, reduced detergent power, and inferior foaming properties in hard water. 

In addition to their poor solubility in water, alkyl phosphate esters and dialkyl phosphate esters are further characterized by sensitivity to water hardness [37]. A review of the preparation, properties, and uses of surface-active anionic phosphate esters prepared by the reactions of alcohols or ethoxylates with tetra-phosphoric acid or P4O10 is given in Ref. 3. The surfactant properties of alkyl phosphates have been investigated [18,186-188]. The critical micelle concentration (CMC) of the monoalkyl ester salts is only moderate see Table 6 ... 

Relative sensitivity to water deficit of the expansive growth of different plant parts... 

The major disadvantage of the alkylation process is that acid is consumed in considerable quantities (up to 100 kg of acid per ton of product). Hence, solid acids have been explored extensively as alternatives. In particular, solid super acids such sulfated zirconia SO/ IZr02) show excellent activities for alkylation, but only for a short time, because the catalyst suffers from coke deposition due to oligomerization of alkenes. These catalysts are also extremely sensitive to water. 

This sensitivity to water has practical implications. A cement liquid is stable in an atmosphere of 70 % relative humidity. It will gain water in more humid atmospheres and lose it to drier ones, and this will adversely affect cement properties (Paffenbarger, Schoonover Souder, 1938 Worner Docking, 1958 Wilson et al., 1970a). 

A valine-derived oxazaborolidine derivative has been found to be subject to activation by Lewis acids, with SnCl4 being particularly effective.98 This catalyst combination also has reduced sensitivity to water and other Lewis bases. 

The pyrimido[2,T ][l>3]oxazines 301 are sensitive to water and suffer reversible ring opening to the lactams 302. The equilibrium favors the ring-opened product (Equation 31) <20050BC1964>. 

A 13 liter, semispherical sampling vessel with a flow rate of 0.5 /min was used. The electrode (38 mm diameter) in front of the ZnS(Ag) scintillator was placed in the center of the bottom and was set at -3,000 V relative to the vessel wall. Since the ERM is sensitive to water vapor (Porstendorfer et al, 1980 Dalu et al., 1983), the air sample was passed through a dehumidefier to maintain the relative humidity in the chamber less than 2.9 %. 

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