Hydrolysis controlled

Environmental Considerations. Environmental problems in Ziegler chemistry alcohol processes are not severe. A small quantity of aluminum alkyl wastes is usually produced and represents the most significant disposal problem. It can be handled by controlled hydrolysis and separate disposal of the aqueous and organic streams. Organic by-products produced in chain growth and hydrolysis can be cleanly burned. Wastewater streams must be monitored for dissolved carbon, such as short-chain alcohols, and treated conventionally when necessary. 

Bromine ttifluoride is commercially available at a minimum purity of 98% (108). Free Br2 is maintained at less than 2%. Other minor impurities are HF and BrF. Free Br2 content estimates are based on color, with material containing less than 0.5% Br2 having a straw color, and ca 2% Br2 an amber-red color. Fluoride content can be obtained by controlled hydrolysis of a sample and standard analysis for fluorine content. Bromine ttifluoride is too high boiling and reactive for gas chromatographic analysis. It is shipped as a Hquid in steel cylinders in quantities of 91 kg or less. The cylinders are fitted with either a valve or plug to faciUtate insertion of a dip tube. Bromine ttifluoride is classified as an oxidizer and poison by DOT. 

In the second procedure, calcium nitrate was replaced by calcium alkoxide (60). Calcium and sificon alkoxides have very different rates of hydrolysis. To avoid the production of inhomogeneities, a slow and controlled hydrolysis of a mixture of sificon, calcium, and phosphorous alkoxide was performed. The resulting materials were highly homogenous, and monolithic pieces could be produced. The bioactivity of the gel-derived materials is equivalent or greater than melt-derived glasses. 

A second practical route to AT-unsubstituted amides is by the controlled hydrolysis of nitriles, which can often be made (in the 5-position) by primary synthesis or (elsewhere) by displacement of an ammonio grouping. Thus 4,6-dimethylpyrimidine-2-carbonitrile (798 R = CN) in warm aqueous ammonia gives the amide (798 R = CONH2) in good yield... 

Veratramine, C27H3g02N, occurs naturally in V. viride and V. grandi-florum and is also formed by the hydrolysis of veratrosine. It has m.p. 209-210-5°, fa] — 68° (MeOH), and yields a dihydro-derivative, m.p. 198-200°, and a triacetyl-derivative, m.p. 204-6°, which on controlled hydrolysis leaves a. V-acetyl derivative, m.p. 177-180°. Aceording to Saito, veratramine on treatment with methyl iodide in methyl alcohol in presence of sodium carbonate, yields A-methylveratramine methiodide, m.p. 268° (dec.), from whieh the methoehloride, m.p. 277°, ean be prepared. 

Recent work by Syhora, Edwards and Cross " has confirmed the p-orientation of the substituent introduced at C-6 in 5, 19-cyclo steroid (69) in the kinetically controlled hydrolysis of A -19-methanesulfonoxy steroids. 

The selective separation range of P-6/S-200 was determined with Blue Dextran (Vexdi exclusion limit) and fructose (V,o total permeation limit). Molecular weight (degree of polymerization) calibration (Fig. 16.22) was established with dextran standards and low dp pullulans (dp 3, 6, 9, 12, 15, 18) formed by the controlled hydrolysis of high dp pullulan. 

Si(OEt)4 is an important industrial chemical that is made on the kilotonne scale by the action of EtOH on SiCU. It has mp -77°, bp 168.5°, and djo 0.9346gcm . Almost all uses depend on its controlled hydrolysis to produce silica in an adhesive or film-producing form. It is also a source of... 

SbOF and SbOCl can be obtained as polymeric solids by controlled hydrolysis of SbX3. Several other oxide chlorides can be obtained by varying the conditions, e.g. ... 

Early attempts to prepare 5-amino- and 5-acylaminobenzofuroxans by hypochlorite oxidation of the corresponding o-nitroanilines met with failure. Pyrolysis of the appropriate azide, however, gives 5-dimetliylamino- and 5-acetamidobenzofuroxan, whereas urethans of type (33) are produced by Curtius degradation of the 5-carboxylic acid. Controlled hydrolysis of the acetamido compound and the... 

A variant on this theme contains mixed acyl groups. In the absence of a specific reference it may be speculated that the synthesis starts with the diacetyl derivative (15). Controlled hydrolysis would probably give the monoacetate (16) since the ester para to the ketone should be activated by that carbonyl function. Acylation with anisoyl chloride followed by reduction would then afford nisobuterol (18). 

Shellac [124,125] is a natural resin used in very old times for varnishes and moulding compounds. The resin secreted by the lac insect, Kerriar paca, is collected by scraping the shellac-encrusted trees found in southern parts of Asia. It consists of a complex mixture of cross-linked polyesters derived from hydroxy acids, principally aleuritic acid (9,10,16-trihydroxyhexadecanoic acid). From a structural point of view, it appears that this material can be used as a crosslinking agent and/or as a monomer for developing dentrite-like polymers. The question is whether it is possible to produce this material from shellac by controlled hydrolysis. 

This highly active epoxidation system, based on the controlled hydrolysis of BTSP with a catalytic amount of water, maximizes the formation of the Re monoperoxide complex at the expense of the more thermodynamically stable bis (peroxide) (Scheme 12.8). BTSP is very stable and can be prepared in molar amounts... 

Upon carefully controlled hydrolysis with hydrochloric acid at room temperature, the corresponding serine methyl esters 4 are obtained in reasonable yields. Higher yields of 4 arc obtained by hydrolyzing with dilute trifluoroacetic acid5. In some cases, the diastereomeric ratio of 4 does not exactly correspond to the d.r. of the adduct 3, which is attributed to different kinetics in the hydrolysis of the diastereomers 4. Subsequent treatment of the methyl ester with excess 5 N hydrochloric acid and methyloxirane as an acid scavenger results in the free amino acid 54,7. 

Another oxyfluoride, PuOF4(c), has recently been reported (35) as a product of controlled hydrolysis of PuFg dissolved in anhydrous HF and precipitation from the solution. Again, no thermodynamic data are available but it appears that the compound is of very limited stability although stable in the solid state at room temperature, it is reported to decompose in the presence of liquid HF according to reaction (8)... 

The slower, more controlled hydrolysis of silicon-methoxy bonds enables the synthesis of a material diat is processable and extremely tough, yet flexible, with the degree of flexibility a direct result of the molar feed ratio of die two monomers since both are incorporated equally in the ADMET copolymerization. Therefore, a series of materials can be made where the properties are adjusted... 

Preparation of Functionally Terminated Siloxane Oligomers via Controlled Hydrolysis of Organo-silanes... 

Controlled Hydrolysis of Organohalosilanes in the Presence of End-Stoppers . Preparation of (Si—H) Terminated Oligomers... 

Note Controlled hydrolysis of quinoxalinecarbonitriles to the corresponding amides (rather than the carboxyhc acids) may be achieved under Radziszewski conditions (H2O2, alkali), sometimes under mildly alkaline conditions, or occasionally in concentrated acid containing only a trace of water. 

Reactions of quinoxalinecarbonitriles that have been discussed already include hydrolysis to quinoxalinecarboxylic acids (Section 7.1.1) and controlled hydrolysis to quinoxalinecarboxamides (Section 7.4.1) the reduction of quinoxalinecarbonitriles to aminomethylquinoxalines and their alcoholysis to quinoxalinecarboximidic... 

In contrast, during the interfacial preparation of poly(iminocar-bonates), the hydrolysis of the dicyanate component regenerates the diphenol component, which is a necessary reactant. Consequently, it is possible to obtain poly(iminocarbonates) simply by the controlled hydrolysis of a dicyanate under phase transfer conditions. 

As already discussed in Section 2.2, crystalline dimethylsilanediol 53 can be prepared by hydrolysis from hexamethylcyclotrisilazane 51, from dimethoxydimethyl-silane [40], and from octamethylcyclotetrasilazane (OMCTS) 52. The most simple preparation of 53 is, however, controlled hydrolysis of dimethyldichlorosilane 48 in the presence of (NH4)2C03 or triethylamine [41]. Likewise, hydrolysis of hexam-ethylcyclotrisiloxane 54 and of octamethylcyclotetrasiloxane 55 eventually gives rise to dimethylsilanediol 53. In all these reactions the intermediacy of the very reactive dimethylsilanone 110 has been assumed, which can be generated by pyrolytic [42, 43] and chemical methods [44—46] and which cyclizes or polymerizes much more rapidly, e.g. in contact with traces of alkali from ordinary laboratory or even Pyrex glassware [40, 47] to 54, 55, and 56 than trimethylsilanol 4 polymerizes to hexamethyldisiloxane 7. Compound 111 is readily converted into dimethylsilanone 110 and MesSil 17 [46] (Scheme 3.6). 

The preparation of diphenylphosphine oxide normally involves the controlled hydrolysis of chlorodiphenylphosphine, but the product has a significant amount of diphenylphosphinic acid impurity. This problem... 

The purified tetraethyl pyrophosphate is a colorless, odorless, water-soluble, hygroscopic liquid (24, 4 )- It possesses a very high acute toxicity (28), exceeding that of parathion, and is rapidly absorbed through the skin. There is no spray-residue problem, however, for tetraethyl pyrophosphate hydrolyzes even in the absence of alkali to nontoxic diethyl phosphoric acid. Hall and Jacobson (24) and Toy (47) have measured its rate of hydrolysis, which is a first-order reaction. Its half-life at 25° C. is 6.8 hours and at 38° C. is 3.3 hours. Coates (10) determined the over-all velocity constant at 25° C. k = 160 [OH-] + 1.6 X 10 3 min.-1 Toy (47) has described an elegant method for preparing this ester as well as other tetraalkyl pyrophosphates, based upon the controlled hydrolysis of 2 moles of dialkyl chlorophosphate ... 

The chloride (60 1) and 2 volumes of water were mixed ready for subsequent addition of alkali to effect controlled hydrolysis. Before alkali was added, the internal temperature rose from 15 to 25° during 30 min, and then to 35°C in 5 min, when gas was suddenly evolved. This was attributed to the effect of liberated hydrochloric acid causing autocatalytic acceleration of the hydrolysis and then rapid release of carbon dioxide arising from decarboxylation of the carbamic acid. Hydrolysis by addition of the chloride to excess alkali would prevent the gas evolution. 

It ignites in air, explodes dining uncontrolled hydrolysis [1], and chars during controlled hydrolysis [2], When isolated as the etherate, attempts to remove solvent ether caused violent decomposition [3],... 

Although uncontrolled reaction of xenon hexafluoride and moisture produces explosive xenon trioxide, controlled action by progressive addition of limited amounts of water vapour with agitation to a frozen solution of the hexafluoride in anhydrous hydrogen fluoride at —196° C to give xenon oxide tetrafluoride or xenon dioxide difluoride is safe [1], Controlled hydrolysis in solution in hydrogen fluoride is, however, described as hazardous [2],... 

Controlled hydrolysis of Fe(III) complexes, using for example the [Fe20]4+ unit, in aqueous or non-aqueous solvents in the presence of appropriate ligands has been carried out to give a variety of products. These have been shown to contain di-, tri- and tetranuclear and even deca-, undeca-, dodeca-, heptadeca-, octadeca- and nonadecanuclear Fe(III) core structures (Gorin and Lippard, 1986 Micklitz etal, 1994 Heath et al., 1996 Lippard and Berg, 1994 Powell, 1998). 

Reports on the sensitivity of many neutral and cationic NHP derivatives towards air and moisture reveal in most cases pronounced reactivity even with traces of H20 causing P-X bond hydrolysis whereas genuine oxidation processes appear to play a role only for P-H and P-alkyl NHPs [71]. Controlled hydrolysis proceeds at low temperature as depicted in Scheme 9 to give secondary phosphine oxides 17 as initial product which may react further with excess NHP to phosphinous acid anhydrides 18.3 Both products may be obtained as isolable products starting from P-chloro NHPs [48], Hydrolysis at ambient temperature may be unselective and... 

Scheme 9 Products formed by controlled hydrolysis of P-substituted NHPs (X=H, PR2, Halogen)...

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