Word: hydration Pinyin: shuǐhé English: [hydrate] Comment: denotes the general tendency of water to enter into a contraction with hydrophilic substances including cellular substances The degree and intensity of hydration depends on many factors including the nature of the non-aqueous component, the composition of the salts, the PH, and the temperature Hydration is an exothermic process
Editorial Hydration-Body
A reaction process in which water is chemically combined with a molecule of another substance to become a single molecule. The addition of water molecules with their hydrogen and hydroxyl groups to the unsaturated bonds of the molecules of a substance produces a new compound, and this synthesis is used in organic chemical production. Water in the form of water molecules with the molecular combination of substances to form complexes (such as salts of water-containing crystals, hydrocarbons, hydrates, etc.) of the process can also be broadly referred to as hydration. Hydration belongs to the chemical change hydration process in the organic chemical industry, the earliest application is 1913 in Germany with acetylene hydration system acetaldehyde. Currently the main applications in industry are the following four aspects: ① olefin hydration important method of preparing alcohols, widely used in industry is ethylene hydration of ethanol and propylene hydration of isopropanol: hydration
According to the Markovnikov rule, only the hydration of ethylene to generate primary alcohols, the other olefins can only be generated by the hydration of secondary alcohol or tertiary alcohols. Olefin hydration has a direct hydration and indirect hydration of two methods. Indirect hydration is the first sulfuric acid absorption of olefins into sulfate esters, which are then hydrolyzed. This is an older production method, which has now been replaced by the direct hydration method. The direct hydration method uses acidic catalysts (see Acid-Base Catalysts), such as phosphoric acid catalysts contained in diatomaceous earth, tungsten oxide, phosphotungstic acid, and strongly acidic ion-exchange resins. Olefin hydration is an exothermic reaction, and low temperatures are favorable for equilibrium, but the selection of the temperature is largely determined by the activity of the catalyst (see CATALYTIC ACTIVITY). Elevated pressure can increase the equilibrium conversion rate, but not to cause water vapor in the gas phase in the catalyst surface condensation limit. ② hydration of epoxides This is an important method of producing diols, mainly ethylene oxide hydration to ethylene glycol, and propylene oxide hydration to propylene glycol: hydration
With sulfuric acid as the catalyst the reaction can be carried out at atmospheric pressure, and can be carried out without a catalyst at pressurized pressure. ③ nitrile hydration This is an important method for the industrial production of amides, such as acrylonitrile hydration of acrylamide: hydration
The best catalysts are skeletal copper catalysts (see metal catalysts), and now biocatalysts have been developed. ④ acetylene hydration Mainly acetylene hydration to make acetaldehyde: CH gallon CH + H2O -→ CH3CHO industrially, mercury sulfate is used as a catalyst, and the reaction is carried out in a sulfuric acid solution. This method has a long history of industrial application, but due to problems such as mercury contamination, it has been changed to other methods. The hydration process is one of the organic synthesis methods, but as an important production method, it is still limited to a few types of products, such as ethanol and diols.
Scientific and technical terms defined
Chinese name: hydrolysis English name: hydrolysis Definition: the chemical process that causes a compound to cleave into two or more simpler compounds. The H and OH parts of the water molecule are involved in the reaction on either side of the cleaved chemical bond. For example, fat is hydrolyzed by acids, bases, and lipases to produce glycerol and fatty acids or smaller molecules. Disciplines: Biochemistry and molecular biology (first level); Lipids (second level) This content is validated and published by the National Committee for the Validation of Scientific and Technical Nomenclature
Encyclopedia Business Card
Hydrolysis is a chemical unit process in which water is used to break down a substance to form a new one. The reaction in which ions ionized by salt combine with H+ and OH- ionized by water to form weak electrolyte molecules. The reaction that occurs between a substance and water that results in the decomposition of the substance (not necessarily a complex decomposition reaction) can also be described as whether or not the substance reacts with hydrogen ions or hydroxide ions in the water.
Use Cases Hydrolysis Reactions
Substitution Reactions
Hydrolysis of Lye
The hydrolysis of salts consisting of weak acid radicals or weak base ions can occur in two ways: Stepwise hydrolysis of carbonate ions
① Weak acid radicals combine with H+ in water to form a weak acid, and the solution becomes alkaline, e.g., an aqueous solution of sodium acetate: CH3COO- + H2O ←═→ CH3COOH + OH- ② weak base ions combined with OH- in water, the solution is acidic, such as aqueous solution of ammonium chloride: NH4+ + H2O ← ═→ NH3-H2O + H+ The weaker the acid (or base) to produce weak acids (or bases), the weaker the weak acid (or base), the weaker the acidic root (or weak base ions), the stronger the tendency to hydrolyze. (The weaker the more hydrolyzed, who is weak who hydrolyzed) Weak cation hydrolyzed to generate H+, weak anion hydrolyzed to generate OH-. For example, sodium borate has a stronger tendency to hydrolyze than sodium acetate, and the pH value of the former is greater when the concentration of the solution is the same. The acidity or alkalinity of weak acid and weak base salt solutions depends on the strength of the hydrolysis tendency of weak acid radicals[1] and weak base ions. For example, ammonium bicarbonate has a stronger tendency to hydrolyze weak acids than weak base ions, and the solution is alkaline; ammonium fluoride has a stronger tendency to hydrolyze weak base ions, and the solution is acidic; if the two have the same tendency to hydrolyze, the solution is neutral, which is an individual case, such as ammonium acetate. The hydrolysis of weak acid and weak base salts has a greater degree of hydrolysis and the pH of the solution is closer to 7 (at room temperature) than the hydrolysis of the corresponding strong acid and weak base salts or strong base and weak acid salts. For example, 0.10 mol/L Na2CO3 hydrolysis is 4.2%, pH 11.6, while the same concentration of (NH4)2CO3 hydrolysis is 92%, pH 9.3. Esters, polysaccharides, proteins, etc. and water to generate a simpler substance, but also hydrolysis: CH3COOC2H5 + H2O -→ CH3COOH + C2H5OH (C6H105OH). C2H5OH (C6H10O5)n + nH2O -→ nC6H12O6 Certain salts that can be hydrolyzed are used as acids (e.g. aluminum sulfate) or bases (e.g. sodium carbonate).
Editor's introduction
The reaction process in which water reacts with another compound and the compound decomposes into two parts, with hydrogen atoms in the water added to one of the hydrolyzed
parts and hydroxyl groups added to the other, thus giving two or more new compounds. More industrial applications are the hydrolysis of organic substances, mainly the production of alcohols and phenols. Hydrolysis is the reverse of neutralization or esterification. The hydrolysis of most organic compounds is difficult to be carried out with water alone. Depending on the nature of the hydrolyzed substance, the hydrolyzing agent can be an aqueous solution of sodium hydroxide, dilute or concentrated acid, or sometimes an aqueous solution of potassium hydroxide, calcium hydroxide, sodium bisulfite, etc. This is called alkaline hydrolysis. This is the so-called alkali hydrolysis and acid hydrolysis. Hydrolysis can be intermittent or continuous operation, the former is often carried out in the kettle reactor, the latter is mostly used in the tower reactor. There are four typical types of hydrolysis.
Edit Classification of Hydrolysis
There are four types of typical hydrolysis. ① Halide hydrolysis Usually use aqueous sodium hydroxide as hydrolyzing agent, the reaction formula is as follows: Hydrolysis
R-X+NaOH-→R-OH+NaX Ar-X+2NaOH-→Ar-ONa+NaX+H2O The formula R, Ar, and X represent alkyl, aryl, and halogen, respectively. Halogen on the aliphatic chain is generally more active, can be hydrolyzed under milder conditions, such as benzyl chloride from benzyl benzoate; aryl ring halogen activated by the neighboring or para-nitro, hydrolysis is easier to carry out, such as p-nitrophenol from p-nitrochlorobenzene system sodium. ② arylsulfonate hydrolysis is usually not easy to carry out, must first be fused by alkali, that is, with molten sodium hydroxide at high temperatures and sodium arylsulfonate role of sodium phenol, the latter can be hydrolyzed to generate phenol by adding acid. Such as naphthalene - 2 - sodium sulfonate in 300 ~ 340 ℃ atmospheric pressure alkali melting and hydrolysis of 2 - naphthalene phenol. Some arylsulfonates also need to use a mixture of sodium hydroxide and potassium hydroxide as a reactant for alkaline fusion. When the arylsulfonate is more active, the aqueous solution of sodium hydroxide can be used at a lower temperature for alkali fusion. Hydrolysis of amines Fatty amines and aryl amines are generally not easy to hydrolyze. Aromatic amines are usually first diazotized in dilute sulfuric acid to generate diazonium salt, and then heated to make the diazonium salt hydrolysis. Reaction formula is as follows: Ar-NH2+NaNO2+2H2SO4-→Ar-N Sledge HSO+NaHSO4+2H2O Ar-N Sledge HSO+H2O-→ArOH+H2SO4+N2 For example, from the o-aminoanisole system of o-hydroxyanisole (guaiacol). Direct hydrolysis of the amino group on the aryl ring is mainly used for the preparation of 1-naphthol derivatives, because they are sometimes not easy to produce by other synthetic routes. According to the structure of the aryl amine can be hydrolyzed with base, acid or sodium bisulfite solution. For example, 1-naphthol-5-sulfonic acid from 1-naphthylamine-5-sulfonic acid is hydrolyzed by sodium bisulfite. Hydrolysis of ④ ester Hydrolysis of oil and grease by adding alkali hydrolysis can be obtained high-carbon fatty acid sodium (soap) and glycerol; the system of fatty acids to be added to the acid emulsion hydrolysis. Low-carbon olefin and concentrated sulfuric acid action of alkyl sulfate ester, by adding acid hydrolysis can get low carbon alcohol.
Edit positive salt
Positive salt is divided into four categories: First, strong acid and alkali salts do not hydrolyze, because they are ionized out of the anion and cationic ionization hydrolysis
Subcons can not disrupt the ionization equilibrium of the water, so it is neutral. Second, strong acid weak base salt, we call the weak base part of the weak Yang, weak base ions can hold the ionization of hydroxide ions from the water, destroying the ionization balance of water, making the ionization of water positively moving, as a result, the hydrogen ion concentration in the solution is greater than the concentration of hydroxide ions, so that the aqueous solution is acidic. Third, strong alkali weak acid salt, we call the weak acid part of the weak yin, the same weak yin holding the hydrogen ion ion ionized from the water, so that the concentration of hydroxide ions in the solution is greater than the concentration of hydrogen ions, so that the solution is alkaline. Fourth, weak acid weak base salt, weak acid part of the hold hydrogen, weak base part of the hold hydroxide, generate two weak electrolytes, and then compare the size of their ionization constants Ka, Kb value (not the size of the degree of hydrolysis), at a temperature of the weak electrolyte ionization constants (also known as the ionization equilibrium constant) is a fixed value, this comparison can be derived from the salt of what is presented to the sex of the person who is strong to present who is the sex of the ionization constants are based on the bottom of 10! The ionization constant is a negative logarithm, and whoever is less negative is greater. In a word, the salt solution of anions and cations holding the water from the ionization of hydrogen ions or hydroxide ions can generate a weak electrolyte reaction called hydrolysis of salts. There are also hydrolysis of organic substances, such as the hydrolysis of esters, ester and water reaction (under the condition of inorganic acid or alkali) to generate the corresponding carboxylic acid and alcohol reaction is called the hydrolysis of esters, there is also alkaline hydrolysis of halogenated hydrocarbons, the reaction of ethyl bromide and sodium hydroxide solution to generate ethanol and sodium bromide is called the hydrolysis of haloalkanes, as well as the hydrolysis of proteins, the end product of amino acids, and so on.
Editing examples
Hydrolysis reactions
(1) the hydrolysis of salts containing weakly acidic anions and weakly alkaline cations, for example: Fe3++3H2O=Fe(OH)3+3H+, CO32-+H2O=HCO3-+OH- (2) the hydrolysis of metal nitrides, for example: Mg3N2+6H2O=3Mg(OH)2 +2NH3 (3) the hydrolysis of metal sulfides, for example: Al2S3 +6H2O = 2Al (OH) 3 +3H2S (4) the hydrolysis of metal carbides, for example: CaC2 +2H2O = Ca (OH) 2 + C2H2 (5) the hydrolysis of non-metallic halide, for example: PCl3 +3H2O = H3PO3 +3HCl Such reactions are mostly water molecules attack halogenated Atoms, but there are exceptions, such as the hydrolysis of NCl3: NCl3 + 3H2O = NH3 + 3HClO The reaction of water molecules attacking nitrogen atoms
Substitution reaction
(hydrolysis reaction) (organic reaction) 1. halogenated hydrocarbons in aqueous solutions of strong alkalis hydrolyzed, for example: CH3CH2-Cl + H-OH - △ → NaOH Hydrolysis of sodium alcohol, e.g. CH3CH2ONa+H2O=CH3CH2OH+NaOH 3. Hydrolysis of esters in aqueous solutions of acids and bases, e.g. CH3COOCH2CH3+H2O-∆H→CH3COOH+CH3CH2OH CH3COOCH2CH3+NaOH=∆ H2O=CH3CH2OH+H2O-∆H→NaOH NaOH=△ H2O=CH3COONa+CH3CH2OH 4. Hydrolysis of disaccharides and polysaccharides, e.g., hydrolysis of starch: (C6H10O5)n+nH2O→nC6H12O6(glucose) 5. Hydrolysis of dipeptides and polypeptides, e.g., H2NCH2CONHCH2COOH+H2O→2H2NCH2COOH 6. Hydrolysis of imines ArCH=N-Ph-H20 H+ →ArCHO+PhNH2 Note: The above reactions "=" are reversible symbols (except for the hydrolysis of lipids in alkali reaction), the hydrolysis product is very small, do not have to be labeled as a precipitate or gas.
Edit Lye Hydrolysis
Since man first walked the earth, human remains have usually been buried or cremated. However, there is now an innovative approach that is attracting interest - using lye to hydrolyze the body, turning it into a brown syrupy substance that can just be flushed down the drain. The process is called alkaline hydrolysis, and the technique was developed in the United States 16 years ago, primarily for the disposal of animal carcasses. By heating the lye in a huge stainless steel cylinder like a pressure cooker to 300 degrees, and then pressurizing it to 60 pounds per square inch, the carcass can be hydrolyzed. It is currently used only by U.S. medical centers to dispose of human corpses -- all the remains of donors used for research. Because of its environmental advantages, some funeral homes say it will one day trump burial and cremation. However, getting the public to accept the method may be the biggest challenge, and it can be scary for some. This is because psychopaths and dictators use acid or alkali to torture or kill their victims. As a result, the rise of this method has caused a lot of controversy in the American society, where some parts of the country have legally banned the use of this method. However, in the States of Minnesota and New Hampshire, where alkali hydrolysis is legal, some funeral directors are eagerly promoting the practice. The hydrolyzed coffee-colored liquid reportedly has the consistency of motor oil and a strong odor of ammonia. But proponents say it's decontaminated and safe to go down the drain if done properly. Moreover, alkaline hydrolysis does not take up as much space for burials and cremations, and reduces waste emissions - including carbon dioxide and mercury - that are a major concern for crematoriums. Two University of Florida sites have been using alkali hydrolysis to dissolve animal carcasses since 2005 and the mid-1990s, respectively. American Biosafety, which manufactures the cylinders, estimates that about 40-50 hospitals use their equipment to dispose of medical waste and animal carcasses. Users include veterinary colleges, universities, pharmaceutical companies, and U.S. government agencies.