Hydrolytic stability, effects

Features Exc. hydrolytic stability effective at low levels in automatic dishwasher applies. 

Effect of acid number on the hydrolytic stability of urethanes made from polyftetramethylene adipate)... 

Because of their high degree of hydrolytic stability and the extended abilities and effectiveness of these novel chemistries, wherever phosphate-cycle or chelant programs are employed, the circumstances generally permit all-polymer/all-organic programs to be used as technically and economically viable alternatives. 

Consequently, when selecting and blending the various raw materials used in all-polymer/all-organic formulations, the questions of thermal and hydrolytic stability and ability to transport or otherwise control colloidal iron oxides (in addition to possible adverse effects such as copper corrosion) become increasingly important at higher boiler temperatures and pressures. 

It has been shown that the SF5 group has a similar but often enhanced effect on the lipophilicity of compounds, and on essentially any physical or chemical property that derives from its strong polar influence. It also has the advantage of greater hydrolytic stability than a trifluoromethyl group. 

Effect of Anionic Comonomers on the Hydrolytic Stability of Polyacrylamides at High Temperatures in Alkaline Solution... 

These synthetic pyrethroids mimic natural counterparts, of which the most important is pyrethrin 1 (10.265). Unfortunately, the natural products lack the photochemical and hydrolytic stability necessary for use as wool insect-resist agents. The synthetic products have the required stability, yet retain the low mammalian toxicity and low environmental retention of the natural products. Permethrin, however, is toxic to aquatic life and is therefore subject to increasingly severe discharge limits. There is some evidence that permethrin is less effective against larvae of a certain beetle. This can be compensated for by using a combination of permethrin with the hexahydropyrimidine derivative 10.264. Some possible alternative pyrethroids have been mentioned [517] as development products (10.266-10.269). 

K.A. Higginson, X. Zhang, and F. Papadimitrakopoulos, Thermal and morphological effects on the hydrolytic stability of Aluminum Tris(8-hydroxyquinoline) (Alq3), Chem. Mater., 10 1017— 1020 (1998). 

Solid lithium aluminium hydride can be solublized in non-polar organic solvents with benzyltriethylammonium chloride. Initially, the catalytic effect of the lithium cation in the reduction of carbonyl compounds was emphasized [l-3], but this has since been refuted. A more recent evaluation of the use of quaternary ammonium aluminium hydrides shows that the purity of the lithium aluminium hydride and the dryness of the solvent are critical, but it has also been noted that trace amounts of water in the solid liquid system are beneficial to the reaction [4]. The quaternary ammonium aluminium hydrides have greater hydrolytic stability than the lithium salt the tetramethylammonium aluminium hydride is hydrolysed slowly in dilute aqueous acid and more lipophilic ammonium salts are more stable [4, 5]. 

Niclosamide (4.158), which carries the three substituents, was hydrolyzed by neither mammalian liver nor helminth tissue preparations. The resistance of niclosamide to enzymatic hydrolysis was explained by steric hindrance caused by the two substituents adjacent to the amide bond [102], But, since monosubstitution also considerably reduced hydrolysis, one can postulate that H-bonding and electronic effects also contributed to the hydrolytic stability of niclosamide. 

This beneficial effect of fluorination on hydrolytic stability has also been demonstrated with the synthetic prostaglandin SC-46275 (Fig. 70). This compound possesses an anti-secretory activity that protects the stomach mucous membrane. However, its clinical development was too problematic because of the instability of the tertiary allyl alcohol in acidic medium (epimerisation, dehydration, etc.). A fluorine atom was introduced on the C-16 methyl to disfavour the formation of the allylic carbocation. This fluorinated analogue possesses the same biological activity, but does not undergo any degradation or rearrangement, and itepimerises only slowly [165]. 

Dialkyl Sulfosuccinates. Introduced in 1939 by the American Cyan amid Company under the Aerosol trademark, dialkyl sulfosuccinates have become widely used specialty surfactants (Table 8) (9). Within the limitations in hydrolytic stability imposed by the presence of the ester groups, sulfosuccinates are mild, versatile surfactants used when strong wetting, detergency, rewetting, penetration, and solubilization effectiveness is needed. 

It has been estimated that using available neutron intensities such as 102 neutrons / (cm2-s) concentrations of 10B from 10—30 Jg/g of tumor with a tumor cell to normal cell selectivity of at least five are necessary for BNCT to be practical. Hence the challenge of BNCT lies in the development of practical means for the selective delivery of approximately 109 10B atoms to each tumor cell for effective therapy using short neutron irradiation times. Derivatives of 10B-enriched Ww-borane anions and carboranes appear to be especially suitable for BNCT because of their high concentration of 10B and favorable hydrolytic stabilities under physiological conditions. 

A comparison of coatings formulations based on various glycols to determine the effects of the various glycol structures on the performance properties of the coatings has been made. Properties compared included degree of cure, flexibility, hardness, hydrolytic stability, processibility, chemical and stain resistance, and viscosity (18,19). 

These properties are still desired today in modem water treatment formulations. The phosphonates and newer organic polymers exhibit some or all of these effects, but modern inhibitors have considerably more hydrolytic stability, show a greater effectiveness in these properties, and have extended abilities, beyond that of controlling calcium carbonate crystalline scales. 

Kinetic studies show that hydrolysis of 1-organyl- and 1-alkoxysilatranes in neutral aqueous solutions is a first-order reaction catalyzed by the formed tris(2-hydroxyalkyl)amine13 294. As a rule, electron release and steric effects of the substituent X hinder the reaction. However, the hydrolytic stability of 1-methylsilatrane is just below that of 1-chloromethylsilatrane294. Successive introduction of methyl groups into the 3, 7 and 10 sites of the silatrane skeleton13,294 and substitution with ethyl group on C-459 retard sharply the hydrolysis rate. It was proposed294 that nucleophilic attack at silicon by water proceeds via formation of the four-centered intermediate 57 (equation 56). 

The nature of the organic diluent was proved to influence the stability of BTP molecules. Nitrobenzene and the chlorinated diluent C2H2C14 improved the hydrolytic stability of -PrBTP (236). For radiolysis, the same protective effect was observed in the presence of nitrobenzene. 

---