Hydrolysis reactions involving

Hydrolysis reactions involving tetrahedral intermediates are subject to steric and electronic effects. Electron-withdrawing substituents faciUtate, but electron-donating and bulky substituents retard basic hydrolysis. Steric effects in acid-cataly2ed hydrolysis are similar to those in base-cataly2ed hydrolysis, but electronic effects are much less important in acid-cataly2ed reactions. Higher temperatures also accelerate the reaction. 

Hydrolysis Reactions. Hydrolysis reactions involve cleavage of a single bond by reaction with water, a hydronium, or a hydroxide ion (78). The bond is typically polarized between an electron-deficient atom (C in carbonyl, P in organophosphates) and an electron-rich atom (0, Cl, Br). The reaction may be neutral, base-, or acid-promoted, depending on the substrate properties and the reaction conditions, such as pH, temperature, and ionic strength (78, 79). 

Hydrolysis reactions involve the oxidation reaction of chemical hydrides with water to produce hydrogen. The reaction of sodium borohydride has been the most studied to date ... 

Structural modifications of the drug may be employed to retard hydrolysis. The most frequently encountered hydrolysis reaction involves the ester. Substituents can have an effect on these reaction rates. Flansch and Taft [14] and Hammett [15] provide excellent reviews of the topic. Additionally, a compound may be stabilized by reducing its solubility. This can be accomplished by the addition of lipophilic substituents to side chains or aromatic rings. Often less soluble salts or esters have been employed to aid in product stability. 

A more complete description of the hydrolysis reactions involving these and other chemical agents and of... 

There have been a few reports of first generation coordination complex structural models for the phosphatase enzyme active sites (81,82), whereas there are some examples of ester hydrolysis reactions involving dinuclear metal complexes (83-85). Kim and Wycoff (74) as well as Beese and Steitz (80) have both published somewhat detailed discussions of two-metal ion mechanisms, in connection with enzymes involved in phosphate ester hydrolysis. Compared to fairly simple chemical model systems, the protein active site mechanistic situation is rather more complex, because side-chain residues near the active site are undoubtedly involved in the catalysis, i.e, via acid-base or hydrogenbonding interactions that either facilitate substrate binding, hydroxide nucleophilic attack, or stabilization of transition state(s). Nevertheless, a simple and very likely role of the Lewis-acidic metal ion center is to... 

The most common hydrolysis reactions involve drugs that have ester or amide functional groups. Esters are most commonly those of carboxylic acids but can also include those of phosphoric acid and sulfuric acid. Drugs that have hydrolyzable ester... 

Solvolysis is the reaction of a substance with the solvent in which it is dissolved. The solvolysis reactions that we will consider in this chapter occur in aqueous solutions so they are called hydrolysis reactions. Hydrolysis is the reaction of a substance with water. Some hydrolysis reactions involve reaction with H3O+ or OH ions. One common kind of hydrolysis involves reaction of the anion of a weak add with water to form nonionized acid molecules and OH ions. This upsets the H30 /0H balance in water and produces basic solutions. This reaction is usually represented as... 

The second common kind of hydrolysis reaction involves the reaction of the cation of a weak base with water to form nonionized molecules of the weak base and H3O+ ions. This upsets the H3O+/OH- balance in water, giving an excess of H3O+, and making such solutions acidic. Consider a solution of ammonium chloride, NH Cl, the salt of aqueous NH3 and HCl. 

Outside the scope of coverage of this contribution are Zn(II)-promoted carboxy-ester hydrolysis reactions involving multinuclear zinc complexes or systems wherein the first step involves transesterification.98,100-102,105,109-114... 

On the other hand, phosphorane intermediates are not expected to be involved in the hydrolysis of phosphate monoesters, so the effective observed catalysis by the carboxyl group of salicyl phosphate 3.21 [51] (Scheme 2.26) is presumed to be concerted vith nucleophilic attack. (The hydrolysis reaction involves the less abundant tautomer 3.22 of the dianion 3.21, and the acceleration is >10 -fold relative to the expected rate for the pH-independent hydrolysis of the phosphate monoester dianion of a phenol of pK 8.52.) However, this system differs from the methoxy-methyl acetals discussed above, in that there is a clear distinction between neutral nucleophiles, which react through an extended transition structure similar to 3.16 in Scheme 2.23, and anions, which do not react at a significant rate, presumably because of electrostatic repulsion. This distinction is well-established for the dianions of phosphate monoesters with good leaving groups (p-nitrophenyl [52] and... 

A general mechanism that has been proposed for the effect of a metal ion or metal chelate on the hydrolysis reaction involves the combination of salicyl phosphate with the metal ion or metal chelate in such a manner that an intramolecular nucleophilic attack of the phosphate group by the carboxylic acid group can take place (14%)-... 

Hydrolysis involves the chemical reaction with water, without regard to redox conditions, dissolved minerals, or the presence of soil microbes. For the reaction to take place, the organic compound needs to be dissolved in water, and the reaction can be modified by pH and/or temperature. The general hydrolysis reaction, involves the exchange of some functional group X (e.g. chloride, CT) with the hydroxide group in water ... 

Triethyltin hydride reduces chlorodimethylarsine quantitatively to dimethylarsine 283a). Substituted arsenic hydrides are also produced by coupling and by hydrolysis reactions involving metal derivatives of arsenic hydrides 163, 284). 

While deriving the dynamic batch-reactor models in Tables 7.3 and 7.4, the equal-reactivity-of-functional-groups assumption was made, so that kp is the rate constant for all forward linear polyamidation reactions and Ay is the rate constant for all reverse hydrolysis reactions involving amide links on linear chains. Let the rate constant for the forward cychzation reaction be Ay and the rate constant for hydrolysis of an amide link on cyclic oligomers be A . In practice all of these rate constants depend on the reactor temperature and... 

The aluminum speciation and precipitation equilibria play an important role both in its state in the soil solution (and soil acidity) and in the presence of aluminum minerals in soil environments hence, we will devote some discussion to this point. Al(III) in aqueous solution undergo the following hydrolysis reactions involving aqueous mononuclear species ... 

Hydrolysis reactions involve the oxidation reaction of chemical hydrides with water to produce hydrogen. The reaction of sodium borohydride has been the most studied to date. In the first embodiment, a slurry of an inert stabilizing liquid protects the hydride from contact with moisture and makes the hydride pumpable. At the point of use, the slurry is... 

The small boron (III) atom forms no simple cations in solution [10]. The least hydrolyzed form of boron in aqueous solution is boric acid, B(OH)3 [10]. The principal hydrolysis reaction involving boric acid is the rapid and... 

It should be obvious that a hydrolysis reaction involves water and in fact some water is used up during the reaction. However, if the concentration of the methyl acetate is less than IM the loss of 1 mol of water out of a concentration of 55 M will hardly be missed and further 1 mol of water is only about 18 mL. Thus, on the basis of moles and volume, the amount of water in the 1 M HCl solution seems almost constant. The rate constant really should be... 

Hydrolysis reactions involving alkyl or activated aryl halides, and sulfonates, or diazonium compounds afford alcohols in good yields. The products in some cases may be contaminated by olefin byproducts. The Bucherer reaction of an aromatic amine can be consid-... 

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