Hydrolysis

Hydrolysis is a chemical reaction or process in which a polymers. Water is added in this reaction.

In condensation, a reaction in which two molecular fragments are joined for each water molecule produced. As hydrolysis may be a reversible reaction, condensation and hydrolysis can take place at the same time, with the position of equilibrium determining the amount of each product.

In hydration, rather than hydrolysis.

In dehydration synthesis. In hydrolysis, a water molecule (H₂O), is added. Where as in dehydration synthesis, a molecule of water is removed.

In electrolysis of water. In hydrolysis, a voltage is applied across an aqueous medium, which produces a current and breaks the water into its constituents, hydrogen and oxygen.

Examples

Hydrolysis of metal salts

(As noted above, hydrolysis of metal salts is more commonly known as hydration.) Many metal ions are strong aluminium chloride undergoes extensive hydrolysis in water such that the solution becomes very acidic.

$[Al(H_2 O)_6]^{3+} \overset{H_2 O}{\rightleftharpoons} \underset{+\ H_3 O^+}{[Al(OH)(H_2 O)_5]^2+}$

This implies that TiO₂.

Hydrolysis of an ester link

In a hydrolysis reaction that involves breaking an carboxylic acid functional group.

The carbonyl is attacked by a hydroxide anion (or a water molecule, which is rapidly deprotonated). The resulting carboxylic acid again. In a basic solution, the carboxylic acid is deprotonated, such that the basic hydrolysis is irreversible, while acidic hydrolysis is not.

There are two main methods for hydrolysing esters, NaOH or KOH. Once the reaction is complete, the carboxylate salt is acidified to release the free carboxylic acid.

An important example of this reaction is the release of saponification.

Hydrolysis of amide links

In other hydrolysis reactions, such as hydrolysis of an amino acids.

Hydrolysis of cellulose (Cellulolysis)

Main article: Cellulase

Cellulolytic is relating to or causing the hydrolysis of enzymes).

The hydrolysis into glucose (i.e. of cellulose or starch) is called saccharification.

Irreversibility of hydrolysis under physiological conditions

Under physiological conditions (i.e. in dilute aqueous solution), a hydrolytic cleavage reaction, where the concentration of a metabolic precursor is low (on the order of 10^-3 to 10^-6 molar), is essentially thermodynamically irreversible. To give an example:

A + H₂O → X + Y

$K_d = \frac{\left[X\right] \left[Y\right]} {\left[H_2O\right] \left[A\right]}$

Assuming that x is the final concentration of products, and that C is the initial concentration of A, and W = [H₂O] = 55.5 molar, then x can be calculated with the equation:

$\frac{x \times x}{W\left(C - x\right)} = K_d$

let K_d×W = k:

then $x = \frac {-k + \sqrt {k^2 + 4kC} } {2}.$

For a value of C = 0.001 molar, and k = 1 molar, x/C > 0.999. Less than 0.1% of the original reactant would be present once the reaction is complete.

This theme of physiological irreversibility of hydrolysis is used consistently in metabolic pathways, since many biological processes are driven by the cleavage of pyrophosphate bonds.

References

^ Compendium of Chemical Terminology, hydrolysis, accessed 2007-01-23.
^ Compendium of Chemical Terminology, solvolysis, accessed 2007-01-23.

Chemical processes

This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Hydrolysis". A list of authors is available in Wikipedia.