Water hydrolysis reaction

Cement was chosen for the present study because of its low cost, simplicity of use, and stability in most environments. It is, however, rather porous. Also, in the presence of water, hydrolysis reactions promoted by the high pH of the cement can cause conversion reactions resulting in the release of iodine from many compounds. Type III Portland cement was chosen because of its early strength (curing time 8 days). 

The reverse of the reactions in Eqns 2.3 and 2.4 is achieved by hydrolysis, so named because it involves the splitting of the molecule with the addition of water. Hydrolysis reactions can be speeded up (catalysed, see Box 2.6) by the presence of an acid or base (e.g. the alkalis NaOH and KOH). The alkaline hydrolysis of fatty esters is often termed saponification. 

Acidity of Amides, Imides, and Sulfonamides Characteristic Reactions Reaction with Water Hydrolysis Reaction with Alcohols Reactions with Ammonia and Amines Reaction of Acid Chiorides with Salts of Carboxylic Acids Interconversion of Functional Derivatives Reactions with Organometallic Compounds 18.10 Reduction... 

Gelation is initiated in aqueous silicate systems by pH changes, and in alkox-ide precursor systems by addition of water (hydrolysis reactions to generate Si-OH groups). 

Ions as Acids and Bases—In reactions between ions and water—hydrolysis reactions—the ions react as weak acids or weak bases. The pH of salt solutions depends on the anions and/or cations present. Anions from weak acids act as bases whereas cations from weak bases act as acids. 

The trichloride is obtained as a liquid, boiling point 349 K, when a jet of chlorine burns in phosphorus vapour. Care must be taken to exclude both air and moisture from the apparatus since phosphorus trichloride reacts with oxygen and is vigorously hydrolysed by water, fuming strongly in moist air. The hydrolysis reaction is ... 

The experimental procedure to be followed depends upon the products of hydrolysis. If the alcohol and aldehyde are both soluble in water, the reaction product is divided into two parts. One portion is used for the characterisation of the aldehyde by the preparation of a suitable derivative e.g., the 2 4-dinitrophenylhydrazone, semicarbazone or di-medone compound—see Sections 111,70 and 111,74). The other portion is employed for the preparation of a 3 5-dinitrobenzoate, etc. (see Section 111,27) it is advisable first to concentrate the alcohol by dis tillation or to attempt to salt out the alcohol by the addition of solid potassium carbonate. If one of the hydrolysis products is insoluble in the reaction mixture, it is separated and characterised. If both the aldehyde and the alcohol are insoluble, they are removed from the aqueous layer separation is generally most simply effected with sodium bisulphite solution (compare Section Ill,74),but fractional distillation may sometimes be employed. 

Pairwise hydrophobic interactions can be used to alter the reactivity of organic molecules in water. For instance, the rate of hydrolysis reactions may be influenced significantly by the presence of hydrophobic cosolutes. The effect on reactivity has been analysed by comparirg the interactions between initial state and cosolute with those between transition state and cosolute. ... 

The Lewis base that acts as the nucleophile often is but need not always be an anion Neutral Lewis bases can also serve as nucleophiles Common examples of substitutions involving neutral nucleophiles include solvolysis reactions Solvolysis reactions are substitutions m which the nucleophile is the solvent m which the reaction is carried out 8olvolysis m water (hydrolysis) converts an alkyl halide to an alcohol... 

When esterification is the objective water is removed from the reaction mixture to encourage ester formation When ester hydrolysis is the objective the reaction is carried out m the presence of a generous excess of water Both reactions illustrate the applica tion of Le Chatelier s principle (Section 6 10) to organic synthesis... 

In aqueous solution, OF2 oxidizes HCl, HBr, and HI (and thek salts), Hberating the free halogens. Oxygen difluoride reacts slowly with water and a dilute aqueous base to form oxygen and fluorine. The rate of this hydrolysis reaction has been determined (23). 

Figure 17 summarizes the avadable sol—gel processes (56). The process on the right of the figure involves the hydrolysis of metal alkoxides in a water—alcohol solution. The hydrolyzed alkoxides are polymerized to form a chemical gel, which is dried and heat treated to form a rigid oxide network held together by chemical bonds. This process is difficult to carry out, because the hydrolysis and polymerization must be carefully controlled. If the hydrolysis reaction proceeds too far, precipitation of hydrous metal oxides from the solution starts to occur, causing agglomerations of particulates in the sol. 

The hydrolysis of phosphoms sulfides has been studied quantitatively. A number of products are formed (Table 6). Whereas phosphoms(V) sulfide reacts slowly with cold water, the reaction is more rapid upon heating, producing mainly hydrogen sulfide and orthophosphoric acid, H2PO4. At high pH, P4S Q hydroly2es to a mixture of products containing thiophosphates and sulfides. 

Hydrolysis. Complexes formed by Pu ions with OH represent hydrolysis reactions. There is extensive interaction between Pu + and water. Pu(Ill) hydrolyzes at ca pH 7 (105) the first hydrolysis equiUbrium is as follows ... 

This is an example of an ammonolytic reaction ia which a chemical bond is broken by the addition of ammonia. It is analogous to the hydrolysis reactions of water. An impressive number of inorganic and organic compounds undergo ammonolysis. 

The principal reactions are reversible and a mixture of products and reactants is found in the cmde sulfate. High propylene pressure, high sulfuric acid concentration, and low temperature shift the reaction toward diisopropyl sulfate. However, the reaction rate slows as products are formed, and practical reactors operate by using excess sulfuric acid. As the water content in the sulfuric acid feed is increased, more of the hydrolysis reaction (Step 2) occurs in the main reactor. At water concentrations near 20%, diisopropyl sulfate is not found in the reaction mixture. However, efforts to separate the isopropyl alcohol from the sulfuric acid suggest that it may be partially present in an ionic form (56,57). 

Carbon disulfide is essentially unreactive with water at room temperature, but above about 150°C in the vapor phase some reaction occurs forming carbonyl sulfide (carbon oxysulfide) [463-58-1] and hydrogen sulfide [7783-06-4]. Carbonyl sulfide is an intermediate in the hydrolysis reaction ... 

The equihbrium expressions for the hydrolysis reactions (eq. 1) foUow and are the ionisation constants of HOX and water, respectively. 

The mother Hquor from the cmde ferrous sulfate crystallisation contains neady all the chromium. It is clarified and aged with agitation at 30°C for a considerable period to reverse the reactions of the conditioning step. Hydrolysis reactions are being reversed therefore, the pH increases. Also, sulfate ions are released from complexes and the chromium is converted largely to the hexaaquo ion. Ammonium chrome alum then precipitates as a fine crystal slurry. It is filtered and washed and the filtrate sent to the leach circuit the chrome alum is dissolved in hot water, and the solution is used as cell feed. 

Acidic Hydrolysis. Hydrolysis of esters by use of water and a mineral acid leads to an equiUbrium mixture of ester, alcohol, and free carboxyHc acid. Complete reaction can only be achieved by removal of alcohol or acid from the equiUbrium. Because esters have poor solubiUty in water, the reaction rate in dilute acids is fairly low. Therefore, emulsifiers such as sulfonated oleic acid or sulfonated aromatic compounds (TwitcheU reagent) are added to facihtate the reaction. 

Carbides, which are binary compounds containing anionic carbon, occur as covalent and as salt-like compounds. The salt-like carbides are water-reactive and, upon hydrolysis, yield flammable hydrocarbons. Typical hydrolysis reactions include ... 

Ethyl aluminum dichloride (EADC) is used in the rnanufacmre of certain catalysts for making LDPE. Occasionally, the batch operation involving the catalyst production results in an off-spec lot. This off-spec lot is washed from the reactor (impregantor) with water and hexane, and must be sent to a waste disposal facility. The facility treats this waste in a hydrolysis reaction (i.e., with water and mild agitation). If the reaction is exothermic, what are the potential air pollution and fire problems associated with the waste treatment ... 

Imine formation is reversible. Show all the steps involved in the acid-catalyzed reaction of an imine with water (hydrolysis) to yield an aldehyde or ketone plus primary amine. 

Conversion of Acid Halides into Acids Hydrolysis Acid chlorides react with water to yield carboxylic acids. This hydrolysis reaction is a typical nucleophilic acyl substitution process and is initiated by attack of water on the acid chloride carbonyl group. The tetrahedral intermediate undergoes elimination of Cl and loss of H+ fo give the product carboxylic acid plus HC1. 

Acid-catalyzed ester hydrolysis can occur by more than one mechanism, depending on the structure of the ester. The usual pathway, however, is just the reverse of a Fischer esterification reaction (Section 21.3). The ester is first activated toward nucleophilic attack by protonation of the carboxyl oxygen atom, and nucleophilic addition of water then occurs. Transfer of a proton and elimination of alcohol yields the carboxylic acid (Figure 21.8). Because this hydrolysis reaction is the reverse of a Fischer esterification reaction, Figure 21.8 is the reverse of Figure 21.4. 

Conversion of Amides into Carboxylic Acids Hydrolysis Amides undergo hydrolysis to yield carboxylic acids plus ammonia or an amine on heating in either aqueous acid or aqueous base. The conditions required for amide hydrolysis are more severe than those required for the hydrolysis of add chlorides or esters but the mechanisms are similar. Acidic hydrolysis reaction occurs by nucleophilic addition of water to the protonated amide, followed by transfer of a proton from oxygen to nitrogen to make the nitrogen a better leaving group and subsequent elimination. The steps are reversible, with the equilibrium shifted toward product by protonation of NH3 in the final step. 

The most common reactions of carboxylic acid derivatives are substitution by water (hydrolysis) to yield an acid, by an alcohol (alcoholysis) to yield an ester, by an amine (aminolysis) to yield an amide, by hydride ion to yield an alcohol (reduction), and by an organometallic reagent to yield an alcohol (Grignard reaction). 

Interestingly, however, the mechanisms of the two phosphate hydrolysis reactions in steps 9 and 11 are not the same. In step 9, water is the nucleophile, but in the glucose 6-phosphate reaction of step 11, a histidine residue on the enzyme attacks phosphorus, giving a phosphoryl enzyme intermediate that subsequently reacts with water. 

It is interesting to determine which bond (the P—O bond marked a or the O—P bond marked b) is cleaved by hydrolysis (reaction with water). 

An important reaction of fats is the reverse of ester formation. They hydrolyze, or react with water, just as disaccharides do. Usually hydrolysis is carried out in aqueous Ca(OH)2, NaOH, or KOH solution. Because of long use in the preparation of soap from fats, the alkaline hydrolysis reaction (6) is called saponification. 

Employing silicon alkoxides, the hydrolysis has to be catalyzed by the addition of an acid or a base, and an excess of water is often used. Employing zirconium alkoxides, the hydrolysis reaction proceeds much faster than the condensation so that the product is obtained as a precipitate rather than a gel. 

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