hydrolysis

[shuǐ jiě]

A decomposition technique

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Water has the dual characteristics of decomposition and fusion materials. Hydrolysis is a decomposition technology. hydrolysis Is a kind of Chemical unit process Is to use water to decompose substances formation The process of new substances. Hydrolysis is the combination of ions ionized by salt with hydrogen ions and hydroxyl ions ionized by water Weak electrolyte Molecular reactions. Hydrolysis is the reaction between a substance and water that results in the decomposition of a substance (not necessarily Metathesis reaction ）It can also be said that material And hydrogen ion in water or Hydroxyl ion React.

Chinese name: hydrolysis
Foreign name: Hydrolysis
Substantive: Chemical unit process
Process: Water will decompose Form new material

Reaction: Not necessarily Metathesis reaction
Classification: halide Hydrolysis amine Hydrolysis of
influence factor: Salt concentration humidity 、 acidity 、 temperature
Time of publication: 1991^[2]
See publications: Chemical Terms Science Press

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hydrolysis Is a kind of Chemical unit process Is the process of using water to decompose substances into new substances. Usually refers to salt Of Hydrolysis equilibrium 。

hydrolysis of salts It refers to the hydrogen ion or Hydroxyl ion Combination Weak electrolyte Process.

Hydrolysis reaction That is, the reaction of salt in solution and water to change the acidity of solution needs to be carried out under certain temperature conditions.

brief introduction

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hydrolysis

Water reacts with another compound, which is decomposed into two parts, and hydrogen ions in water are added to one part, while hydroxyl The reaction process of adding to another part to obtain two or more new compounds is called hydrolysis. Hydrolysis of organic matter is widely used in industry, mainly producing alcohol and phenol. Hydrolysis reaction Is neutralizing or esterification The reverse reaction of. majority Organic compound It is difficult to carry out the hydrolysis with water only. According to the nature of the hydrolysate, sodium hydroxide can be used as the hydrolysate aqueous solution , dilute acid or concentrated acid, sometimes available Potassium hydroxide 、 calcium hydroxide 、 Sodium bisulfite And other aqueous solutions. This is called alkali hydrolysis and acid hydrolysis. Hydrolysis can use Intermittent or continuous operation Tower reactor The latter is more useful Kettle reactor 。 There are five typical types of hydrolysis.

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Hydrolysis of organic matter

There are five types of typical hydrolysis^[1] 。

① halide Hydrolysis of

Usually used sodium hydroxide The general formula of the reaction is as follows:

R-X+NaOH─→R-OH+NaX

Ar-X+2NaOH─→Ar-ONa+NaX+H two O

Where R, Ar and X respectively represent alkyl 、 Aryl group 、 halogen 。 Aliphatic chain Halogens on are generally active and can be hydrolyzed under mild conditions, such as from benzyl chloride Benzyl alcohol ； Aromatic halogen cover Adjacency Or alignment Nitro During activation, hydrolysis is easy, such as Nitrochlorobenzene system P-Nitrophenol Sodium.

② Hydrolysis of aromatic sulfonates

Generally, it is not easy to carry out. It needs to be alkali fused first, that is, molten sodium hydroxide reacts with sodium arylsulfonate at high temperature to generate sodium phenolate, which can be hydrolyzed by adding acid to generate phenol. For example, 2-naphthol is obtained by hydrolysis of sodium naphthalene-2-sulfonate after normal pressure alkali melting at 300-340 ℃. some Aromatic sulfonate Sodium hydroxide and Potassium hydroxide Of Mixed alkali As a reagent for alkali melting. When aromatic sulfonates are more active, sodium hydroxide aqueous solution can be used for alkali melting at a lower temperature.

③ Hydrolysis of amine

Aliphatic amines and aromatic amines are generally difficult to hydrolyze. The aromatic primary amine is usually first mixed in dilute sulfuric acid Diazotization generate Diazonium salt And reheat to hydrolyze the diazonium salt. The general reaction formula is as follows:

Ar-NH two +NaNO two +2H two SO four ─→Ar-N two HSO four +NaHSO four +2H two O

Ar-N two HSO four +H two O─→ArOH+H two SO four +N two

As from O-Aminoanisole system O-hydroxyanisole ( Guaiacol )。 Aromatic amino Direct hydrolysis, mainly used for preparation 1-Naphthol Derivatives, because they are not easy to be prepared by other synthetic routes. According to the structure of aromatic primary amine Alkaline water Solution and addition Acid water Solution or Sodium bisulfite Hydrolysis of aqueous solution. E.g. from 1-naphthylamine-5- sulfonic acid system 1-Naphthol-5-sulfonic acid It is hydrolyzed with sodium bisulfite.

④ Hydrolysis of esters

Hydrolysis of protein

Oil can be hydrolyzed with alkali to obtain high carbon Fatty acid sodium (Soap) and glycerol ； Fatty acid is produced by adding acid, emulsification and hydrolysis. Alkyl sulfate obtained by the reaction of low-carbon olefins with concentrated sulfuric acid is obtained by acid addition and hydrolysis Low-carbon alcohol 。

⑤ Hydrolysis of protein

Under the action of enzymes, proteins have specific hydrolysis sites, which are used for primary structure and peptide analysis. Under the action of acid, protein, Tryptophan destruction, Asparagine and glutamine Deamidation.

Hydrolysis of inorganic salts

There are four categories:

I Strong acid and alkali salt Hydrolysis does not occur because they ionization The anions and cations coming out cannot destroy the ionization balance of water, so they are neutral.

II Strong acid weak base salt We call the weak alkali part weak cation, weak alkali ions are ionized from water Hydroxyl ion , which destroys the ionization balance of water and makes the ionization of water move forward. As a result, the concentration of hydrogen ion in the solution is higher than that of hydroxyl ion, making the aqueous solution acidic.

III Strong base weak acid salt We call the weak acid part weak anion. Similarly, weak anion combines with hydrogen ions ionized from water to make the concentration of hydroxyl ions in the solution greater than that of hydrogen ions, making the solution alkaline.

IV Weak acid and weak base salt , weak acid partially combines with hydrogen, and weak base partially combines with hydroxyl to generate two kinds of Weak electrolyte And then compare their ionization constants Ka and Kb (not the degree of hydrolysis). At a temperature, the ionization constant of weak electrolyte (also called Ionization equilibrium constant ）It is a fixed value. This comparison can show what the salt is like and who is stronger. The ionization constant is the negative logarithm at the base of 10, and whoever is less negative will be greater. In a word, the anion and cation in the salt solution combine with the hydrogen ion ionized from the water or Hydroxyl ion The reaction that can generate weak electrolyte is called salt hydrolysis.

influence factor

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1. Salt concentration: the smaller the salt concentration, the greater its degree of hydrolysis.

2. Temperature: in analytical chemistry and inorganic preparation, it is often used to raise the temperature to make hydrolysis complete separate And synthetic purposes.

3、 acidity : According to equilibrium equation The hydrolysis balance can be controlled by controlling the acidity.

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Inorganic reaction

(1) Hydrolysis of salts containing weak acid anions and weak base cations, such as: Fe 3+ +3H two O=Fe(OH) three +3H + ，CO three 2- +H two O=HCO 3- +OH -

(2) Metal nitrides Hydrolysis of, for example: Mg three N two +6H two O=3Mg(OH) two +2NH three ↑

（3） metal sulfide Hydrolysis of, for example: Al two S three +6H two O=2Al(OH) three +3H two S

(4) Metal carbide Hydrolysis of, for example: CaC two +2H two O=Ca(OH) two +C two H two ↑

(5) Nonmetal halide Hydrolysis of, for example: PCl three +3H two O=H three PO three +3HCl

Such reactions are mostly water molecules attacking halogen atoms, but there are exceptions, such as NCl three Hydrolysis:

NCl three +3H two O=NH three +3HClO

The reaction involves water molecules attacking nitrogen atoms.

Organic substitution reaction

（ Hydrolysis (organic reaction)

1. Halogenated hydrocarbons are hydrolyzed in strong alkaline aqueous solution, such as: CH three CH two -Cl+H-OH—△→NaOH

CH three CH two OH+HCl→CH three CH two Cl+H two O

two Sodium alkoxide Hydrolysis of, for example: CH three CH two ONa+H two O=CH three CH two OH+NaOH

3. Esters are hydrolyzed in acid and alkali aqueous solutions, such as:

CH three COOCH two CH three +H two O—H△→CH three COOH+CH three CH two OH

CH three COOCH two CH three +NaOH+ H two O△=CH three COONa+CH three CH two OH

four Disaccharide Hydrolysis of polysaccharides, such as starch: （C six H ten O five ）n+n·H two O→n·C six H twelve O six

five Dipeptide Hydrolysis of polypeptides, such as H two NCH two CONHCH two COOH+H two O→2H two NCH two COOH

six Imine Hydrolysis of ArCH=N-Ph—H twenty H+ →ArCHO+PhNH two

Note: "=" in the above reactions are reversible symbols (except for ester hydrolysis reaction in alkali), and the amount of hydrolysis products is very small, so it is unnecessary to indicate precipitation or gas.

Alkali hydrolysis application

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Since human first walked on the earth remains It is usually buried or cremated. However, there is an innovative approach that is attracting people's interest - using Lye To hydrolyze the corpse and turn it into brown syrup sewer Just do it.

This process is called alkali hydrolysis. This technology was developed in the United States 16 years ago and is mainly used to treat animal carcasses. By putting a huge image pressure cooker The alkali in the stainless steel cylinder is heated to 300 degrees, and then boosted to 60 pounds per square inch pressure Then the corpse can be hydrolyzed. By 2013, only American medical centers in the world will use it to dispose of human bodies - all the remains of donors used for research.

Because this method has the advantage of environmental protection, some funeral homes say that it will one day be better than burial and cremation. However, getting the public to accept this approach may face the biggest challenge, which will make some people feel terrible. Because psychopaths and dictators use acid or alkali to torture or kill their victims. Therefore, the rise of this method has caused great controversy in American society, and some places in the United States prohibit the application of this method in law.

However, in the United States Minnesota And New Hampshire, alkaline hydrolysis is legal, and some funeral contractors are eager to promote this method. It is reported that the coffee colored liquid after hydrolysis has the consistency of engine oil and a strong smell of ammonia. But supporters said that it was sterilized, and if the operation was carried out according to the requirements, it could enter the sewer safely. Moreover, alkaline hydrolysis will not occupy as much space for burial and cremation, and it can also reduce the waste discharge problems most concerned by crematoria - including carbon dioxide and Mercury Discharge of.

U.S.A University of Florida The two school sites of the University started to dissolve animal carcasses with alkaline hydrolysis in 2005 and the mid-1990s, respectively. The American Biosafety Company is responsible for the production of this steel cylinder. They estimate that about 40-50 hospitals use their equipment to treat medical waste and animal carcasses. Users include veterinary colleges, universities, pharmaceutical companies, and U.S. government agencies.

Double hydrolysis

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Double hydrolysis reaction The double hydrosis reaction refers to weak acid anion and weak base cation mutual promotion hydrolysis , such as Al 3+ And HCO three - , until complete reaction. But in fact, aluminum ion and Bicarbonate Complete double hydrolysis does not necessarily occur. As long as the reaction conditions are slightly controlled, aluminum ions can react with bicarbonate to form basic aluminum carbonate. One of the conditions for the occurrence of double hydrolysis reaction is that the hydrolysate is a substance with very low solubility that is easy to separate from the reaction system, such as Al(OH)3 、 Fe(OH)3 or H2 、 O2 Such as extremely insoluble gases. Of course, if the degree of mutual promotion of hydrolysis is very large, the hydrolysis reaction can also be considered complete.

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