Extreme water sensitivity

Expedient removal of the volatiles after the epoxidation with dimethyldioxirane is crucial to achieve reproducible yields because the epoxide is extremely water sensitive. 

One of the best examples of the utility of enzymatic synthesis in catalyzing reactions that cannot be accomplished by any other route is the synthesis of substituted oxazolidine diesters. The oxazolidine ring is extremely water sensitive, the oxazolidine rapidly reverting back to the alkanolamine and aldehyde in the presence of water. Bis-oxazolidines have been used as hardeners for polymer coatings but the diester based on the hydroxyethyl oxazolidine and adipic acid cannot be synthesized directly with chemical catalysis because of the rapid rate of reaction of the oxazolidine ring with either the water from the esterification or the alcohol from transesterification. ... 

A rather difficult experimental problem is the liberation and isolation of the extremely water-sensitive ethynylamines HOCNRj. 

The ynediamines are extremely water-sensitive and anhydrous conditions must be maintained throughout the experiments. 

NA-Dimethylhydrazone 68, furnished from keto-acid 33 upon treatment with WV-dimethylhydrazine, was found to be extremely water sensitive. Attempts to form the hydrazone were thwarted by low yields under a number of conditions in which solvents were present. Azeotropic removal of water, with or without molecular sieves, was also unsatisfactory. Eventually, it was found most convenient to simply dissolve the keto-acid in neat dimethylhydrazine without desiccant. After heating for a number of hours, followed by cooling and removal of excess dimethylhydrazine, formation of the desired hydrazone was apparent by NMR due to loss of the methyl ketone resonance at 5 2.14. This initially formed hydrazone existed as a dimethylhydrazonium carboxylate, but it was found that reversion to free carboxylic acid 68 occurred in vacuo, as evidenced by the proton NMR run in dry CDClj. 

Because XejFn AuF " is extremely water sensitive, the utmost precautions were taken to exclude water from all apparatus and materials. 

All compounds were characterized by their respective x-ray powder patterns and Raman spectra, and the xenon compounds were analyzed quantitatively for Xe using a Dumas nitrometer previously saturated with xenon. Since all of these compounds are extremely water sensitive, the utmost precautions were taken to exclude moisture from all apparatus and materials. Absorber capsules were loaded in a Vacuum Atmospheres Corp. Drilab (Ng atm), and were checked after Mossbauer measurements to ensure the sustained quality of the samples. 

As a reaction medium for transition rnetal-catalyzed polymerizations, water will, most likely, not be the first choice. The extreme water sensitivity of Ziegler or Phillips catalysts is well known. However, carrying out polymerization reactions in aqueous systems offers unique advantages. Thus, traditional free-radical emulsion and suspension polymerization are carried out on a large scale industrially. A brief review of these established reactions demonstrates some specific properties of polymerizations in aqueous systems. 

A comparison of the position of the 3 relaxation peaks for various counterions was not performed due to the extreme water sensitivity of the 8 peak. A slight presence of moisture can drastically affect the results. In the lowest temperature y region, it was found that the Y peak position is unaffected by variations in counterion size and degree of neutralization as demonstrated in a later section. However, magnitude of the tan <5 peak in y region is inversely proportional to the counterion radius, except for the acid for which it is anomalously low. Introduction of water into both the acid and the salts does not appreciably affect the position of the y peak, at least at the low levels of water content investigated. 

Group 3 elements have emerged as being useful Lewis-acidic metal centers for the ROP of cyclic esters. While these elements are highly reactive for this transformation, one significant challenge remains - the extreme water sensitivity of yttrium and other group 3 metals. [52b]... 

Compound (51) is extremely water sensitive and loses the r-butyl group to give (52) <8lTL424i, 82JOC2275>. 

This procedure gives a synthetically useful example of the Fritsch-Wiechell-Buttenberg rearrangement [95,204]. The intermediate anionic species cannot be intercepted, because it immediately loses potassium chloride with simultaneous migration of a dimethylamino group. Other ynediamines can be prepared in a similar way. The ynediamine is extremely water-sensitive, so that a dry work-up is required. 

Special methods are necessary for the production of polyurethane dispersions because of the thermodynamically unstable nature of these two-phase systems. A simple application of the emulsion polymerization techniques for isocyanate polyaddition reactions is not possible, due to the reactivity of the NCO group with water. The extreme water sensitivity of all polyurethane preparation procedures which calls for the complete absence of water is obviously a major problem to be overcome in their preparation. It is surprising, given the basic hydrolytic degradability of polyurethane elastomers, to find that polyurethane latex has good long-term stability when it is a two-phase system. This is in contrast to the situation that applies when it is present in a one-phase system. 

Coupling Processes. The coupling can be carried out as in Equation 1 by preparing a sulfonylisocyanate by treating the sulfonamide with phosgene in the presence of butyl isocyanate (BuNCO) in xylene at reflux. Frequently 1,4-diazabicyclooctane (DABCO) aids in catalyzing this reaction. The sulfonyl isocyanate which is usually an oil can be added to a solution or sus nsion of the aminoheterocycle in a solvent such as methylene chloride or acetonitrile. The desired sulfonylurea usually precipitates as a white crystalline solid. Dry conditions are essential to avoid hydrolysis of the extremely water sensitive isocyanate. 

Caution. Sodium metal is air and (extremely) water sensitive and should be handled under an inert atmosphere or only briefly in dry air. Ammonia has a sharp, penetrating odor and can be fatal if inhaled in excess. 

Ifote 2. All operations of the isolation procedure must be carried out without any delay. The distillation apparatus must be perfectly dry, since allenic amines are extremely water-sensitive. 

Rice Hull (127) 1.0 4 15 20 10 Z6020 (1) Panel is extremely water-sensitive and disintegrated rapidly. 

The overflush should normally be 2%-8% ammonium chloride solution. An overflush of 5% NH Cl is recommended. Weak HCl or acetic acid (3%-5%), filtered diesel, and even lease crude can be used as overflush fluids. If acetic acid alone is used, 5% NH Cl should be added to improve clay stability. The use of ammonium chloride/acetic acid mixtures has gained popularity, especially in the Gulf of Mexico. In gas wells and sometimes in extremely water-sensitive formations, nitrogen is an effective overflush. If oil-soluble particulates have been used to divert acid, an aromatic solvent stage preceding the ammonium chloride overflush may be needed. 

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