hydrolysis

Examples of hydrolysis in the following topics:

• Overview of the Acid-Base Properties of Salt

  • Some salts, such as ammonium bicarbonate (NH4HCO3), contain cations and anions that can both undergo hydrolysis.
  • The following is a more complicated scenario in which a salt contains a cation and an anion, both of which are capable of participating in hydrolysis.
  • This video examines the hydrolysis of an acid salt, a basic salt, and a salt in which both ions hydrolyze.
  • Predict the pH of a solution of a salt containing cations and anions, both of which participate in hydrolysis.

• Preparation of Carboxylic Acids

  • Two other useful procedures for preparing carboxylic acids involve hydrolysis of nitriles and carboxylation of organometallic intermediates.
  • The hydrolysis may be either acid or base-catalyzed, but the latter give a carboxylate salt as the initial product.

• Strong Acids

  • For instance, strong acids can accelerate the synthesis and hydrolysis of carbonyl compounds.
  • With carbonyl compounds such as esters, synthesis and hydrolysis go through a tetrahedral transition state, where the central carbon has an oxygen, an alcohol group, and the original alkyl group.
  • Strong acids protonate the carbonyl, which makes the oxygen positively charged so that it can easily receive the double-bond electrons when the alcohol attacks the carbonyl carbon; this enables ester synthesis and hydrolysis.

• Polysaccharides

  • This is easily demonstrated by acid-catalyzed hydrolysis to the monosaccharide.
  • Since partial hydrolysis of cellulose gives varying amounts of cellobiose, we conclude the glucose units in this macromolecule are joined by beta-glycoside bonds between C-1 and C-4 sites of adjacent sugars.
  • Also, many enzymes catalyze its hydrolysis.
  • Hydrolysis of starch, usually by enzymatic reactions, produces a syrupy liquid consisting largely of glucose.
  • Furthermore, slow hydrolysis of pyroxylin yields nitric acid, a process that contributes to the deterioration of early motion picture films in storage.

• Disaccharides

  • Acid-catalyzed hydrolysis of these disaccharides yields glucose as the only product.
  • Enzyme-catalyzed hydrolysis is selective for a specific glycoside bond, so an alpha-glycosidase cleaves maltose and trehalose to glucose, but does not cleave cellobiose or gentiobiose.
  • Maltose, sometimes called malt sugar, comes from the hydrolysis of starch.
  • Cellobiose is obtained by the hydrolysis of cellulose.

• Multistep Transformations

  • Initial hydrolysis of the lactone to santoninic acid is followed by isomerism of the α,β-unsaturation to a β,ν-location and tautomerization.

• Acyl Group Substitution

  • If Nuc-H is water the reaction is often called hydrolysis, if Nuc–H is an alcohol the reaction is called alcoholysis, and for ammonia and amines it is called aminolysis.
  • Base catalyzed hydrolysis produces carboxylate salts.
  • Not only is the amine more nucleophilic than water, but the acylating reagent is generally not soluble in or miscible with water, reducing the rate of its hydrolysis.
  • The most important such reaction is hydrolysis, and this normally requires heat and strong acid or base catalysts.
  • Hydrolysis of nitriles to carboxylic acids was described earlier, and requires reaction conditions (catalysts and heat) similar to those needed to hydrolyze amides.

• Irreversible Addition Reactions

  • In the borohydride reduction the hydroxylic solvent system achieves this hydrolysis automatically.
  • The acid catalyzed hydrolysis of the aluminum salts also effects the removal of the acetal.
  • The product of this addition is a metal alkoxide salt, and the alcohol product is generated by weak acid hydrolysis of the salt.
  • The first two examples show that water soluble magnesium or lithium salts are also formed in the hydrolysis, but these are seldom listed among the products, as in the last four reactions.
  • Following acid-catalyzed hydrolysis of the acetal, the resulting 4-hydroxyaldehyde is in equilibrium with its cyclic hemiacetal.

• Radical Recombination Reactions

  • Subsequent tautomerism of the nitroso product, followed by hydrolysis, converts this function to a carbonyl group.
  • Hydrolysis of 3 by nitrous acid yields the corresponding aldehyde, which immediately forms the bis-hemiacetal, 4.

• Anomeric Forms of Monosaccharides

  • Acid-catalyzed hydrolysis of the pentamethyl ether derivatives, however, gave a tetramethyl derivative that was oxidized by Tollen's reagent and reduced by sodium borohydride, as expected for an aldehyde.
  • Acid hydrolysis of acetals regenerates the carbonyl and alcohol components, and in the case of the glucose derivative this will be a tetramethyl ether of the pyranose hemiacetal.