Moisture sensitive

DuPont currentiy practices a butadiene-to-adiponittile route based on direct addition of HCN to butadiene (6—9). It was first commercialized in 1971. AH reactions are catalyzed by soluble, air and moisture sensitive, ttiarylphosphite-nickel(0) complexes. 

Molybdenum hexafluoride [7783-77-9] MoF, is a volatile liquid at room temperature. It is very moisture sensitive, hydrolysing immediately upon contact with water to produce HF and molybdenum oxyfluorides. MoF should therefore be handled in a closed system or in a vacuum line located in a chemical hood. The crystals possess a body-centered cubic stmcture that changes to orthorhombic below —96° C (1,2). The known physical properties are Hsted in Table 1. 

Refrigera.tion in Transportation. Styling is unimportant. The volume of insulation and a low thermal conductivity are of primary concern. Volume is not large, so appHcation methods are not of prime importance. Low moisture sensitivity and permanence are necessary. The mechanical properties of the insulant are quite important owing to the continued abuse the vehicle undergoes. Cost is of less concern here than in other appHcations. 

Dinuclear stmctures are known for molybdenum(III) in a series of air and moisture sensitive compound containing multiple Mo—Mo bonds. Examples include Mo2(N(CH2)2)g (Fig- 5b) and Mo2(CH2Si(CH2)3)g in which there is a strong Mo—Mo bond, presumably of triple-bond character (28). 

The MSDS (46) for thiophosgene describes it as highly toxic, corrosive lachrymator and moisture sensitive compound. It may be fatal if inhaled, swallowed, or absorbed through the skin. When using this material one should wear the appropriate NIOSH/OSHA-approved respirator, chemical-resistant gloves, safety goggles, and other protective clothing. It should be used only in a chemical fume hood. 

In choosing a SAM system for surface engineering, there are several options. Silane monolayers on hydroxylated surfaces are an option where transparent or nonconductive systems are needed. However, trichlorosilane compounds are moisture-sensitive and polymeri2e in solution. The resulting polymers contaminate the monolayer surface, which occasionally has to be cleaned mechanically. CarboxyUc acids adsorb on metal oxide, eg, AI2O2, AgO through acid—base interactions. These are not specific therefore, it would be impossible to adsorb a carboxyUc acid selectively in the presence of, for example, a terminal phosphonic acid group. In many studies SAMs of thiolates on Au(lll) are the system of choice. 

Chelated titanates are made simply by mixing the chelating agent with TYZOR TPT or another alkoxide. The Hberated alcohol is usually left in the product to maintain the products fluidity. It may, however, be removed by distillation if desirable. Organic titanates are normally shipped in 208-L dmms, totes, cylinders, or tank tmcks. Most titanates are moisture-sensitive and must be handled with care, preferably under dry nitrogen. 

The addition of an alkanolamine, such as diethanolamine, to TYZOR TBT, as well as the use of a less moisture-sensitive alkanolamine titanate complex such as TYZOR TE, has been reported to prolong catalyst life and minimi2e ha2e formation in the polymer (475—476). Several excellent papers are available that discuss the kinetics and mechanism of titanate-cataly2ed esterification and polycondensation reactions (477—484). 

Gas-Barrier Properties. The oxygen-barrier properties of PVA at low humidity ate the best of any synthetic resin. However, barrier performance deteriorates above 60% th (Fig. 9). No additives or chemical modifiers are known that can effectively reduce moisture sensitivity. The gas-barrier performance is affected by the degree of hydrolysis and rapidly diminishes as the hydrolysis is decreased below 98%. 

An important reason for the ongoing interest in these copolymers is that vinyl acetate reduces hydrophilidty so that appHcations that require less moisture-sensitive films such as those employed to set hair are less prone to plasticize and become tacky under high humidity conditions (139) (Fig. 5). 

Copolymers of acrylonitrile [107-13-1] are used in extmsion and molding appHcations. Commercially important comonomers for barrier appHcations include styrene and methyl acrylate. As the comonomer content is increased, the permeabiUties increase as shown in Figure 3. These copolymers are not moisture-sensitive. Table 7 contains descriptions of three high nitrile barrier polymers. Barex and Cycopac resins are mbber-modified to improve the mechanical properties. 

Polyethylene. Low pressure polymerization of ethylene produced in the Phillips process utilizes a catalyst comprised of 0.5—1.0 wt % chromium (VI) on siUca or siUca-alumina with pore diameter in the range 5—20 nanometers. In a typical catalyst preparation, the support in powder form is impregnated with an aqueous solution of a chromium salt and dried, after which it is heated at 500—600°C in fluid-bed-type operation driven with dry air. The activated catalyst is moisture sensitive and usually is stored under dry nitrogen (85). 

Moisture sensitivity and vapor-permeabiUty rate of cellulose acetate increase with decreasing acetyl (increasing hydroxyl) content. Thermoplastic characteristics are gready improved as the acetyl content is increased from ca 20% (DS(acetyl) = 1) to ca 39% (DS(acetyl) = 2.4) (9). 

The hquid vehicle in a slurry should have a low vapor pressure for Hquid extraction and drying be compatible with the soHds and casting mold be inexpensive and be capable of dissolving and dispersing deflocculants and other additives. Distilled or deionized water is generally used as the Hquid vehicle, however, organic Hquids must be used for such moisture sensitive oxide powders as CaO and MgO, and for oxidation sensitive nonoxide powders, eg, AIN. 

These hahdes generally display a coordination number of six, have a distorted octahedral geometry, are moisture sensitive, and are easily oxidized when exposed to humid air. 

Both the siHcone base and the catalyst compositions are moisture sensitive and subject to deterioration when exposed to the atmosphere. 

Acetoxypropionyl chloride [36394-75-9] M 150.6, h 51-53"/llmm, 64 1.19, 1.423, [a]V-33", (c 4, CHCI3), [a]s4s -38" (c 4, CHCI3). It is moisture sensitive and is hydrolysed to the corresponding acid. Check the IR spectrum. If the OH band above 3000cm is too large and broad then the mixture should be refluxed with pure acetyl chloride for Ih, evapd and distd under reduced pressure. 

Carbazole-9-carbonyl chloride [73500-82-0J M 300.0, m 100-103 , 103.5-104.5 . Recrystd from C6H6. If it is not very pure (presence of OH or NH bands in the IR) dissolve in pyridine, shake with phosgene in toluene, evaporate and recrystallise the residue. Carry out this experiment in a good fume cupboard as COCI2 is very TOXIC, and store the product in the dark. It is moisture sensitive. The amide has m 246.5-247 , and the dimethylaminoethylamide hydrochloride has m 197-198 . [Weston et al. J Am Chem Soc IS 4006 1953.]... 

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