Everything about Hydrolytic totally explained
Hydrolysis is a
chemical reaction or process in which a
chemical compound is broken down by reaction with
water. It is the type of reaction that's used to break down certain
polymers, especially those made by
step-growth polymerization. Such
polymer degradation is usually catalysed by either
acid or
alkali, attack often increasing with strength or
pH.
Types
In
organic chemistry, hydrolysis can be considered as the reverse or opposite of
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
inorganic chemistry, the word is often applied to solutions of salts and the reactions by which they're converted to new ionic species or to precipitates (oxides, hydroxides, or salts). The addition of a molecule of water to a chemical compound, without forming any other products is usually known as
hydration, rather than
hydrolysis.
In
biochemistry, hydrolysis is considered the reverse or opposite of
dehydration synthesis. In hydrolysis, a water molecule (H
2O), is added, whereas in dehydration synthesis, a molecule of water is removed.
In
electrochemistry, hydrolysis can also refer to the
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.
In
polymer chemistry, hydrolysis of
polymers can occur during high-temperature processing such as
injection moulding leading to chain degradation and loss of product integrity. Polymers most at risk include
PET,
polycarbonate,
nylon and other polymers made by
step-growth polymerization. Such materials must be dried prior to moulding.
Hydrolysis of amide links
In other hydrolysis reactions, such as hydrolysis of an
amide link into a
carboxylic acid and an
amine product or
ammonia, only the carboxylic acid product has a hydroxyl group derived from the water. The amine product (or ammonia) gains the remaining hydrogen ion. A more specific case of the hydrolysis of an amide link is hydrolyzing the
peptide links of
amino acids.
Many
polyamide polymers such as
nylon 6,6 are attacked and hydrolysed by strong acids. Such attack leads to
depolymerization and nylon products fail by fracturing when exposed to even small amounts of acid. The reaction is essentially the reverse of the synthesis from monomers:
step-growth polymerization are susceptible to similar
polymer degradation reactions. The problem is known as
stress corrosion cracking.
Hydrolysis of metal salts
(As noted above, hydrolysis of metal salts is more commonly known as hydration.) Many metal ions are strong
Lewis acids, and in water they may undergo hydrolysis to form
basic salts. Such salts contain a
hydroxyl group that's directly bound to the metal ion in place of a water
ligand. The positive charge on metal ions creates an attraction to water, a
Lewis base with a non-binding electron pair on the
oxygen atom, and alters water's electron density. This in turn increases the
polarity of the O-H bond, which now acts as a proton donor under
Brønsted-Lowry acid-base theory to release the hydrogen as a H+ ion, increasing the acidity of the solution. For example,
aluminium chloride undergoes extensive hydrolysis in water such that the solution becomes very acidic.
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 anhydrous pyrophosphate bonds.
Further Information
Get more info on 'Hydrolytic'.
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