The types of chemical reactions

In modern science distinguish chemical and nuclear reactions in the interaction of the raw materials, which are called reagents.As a result, production of other chemicals, which are called products.All interactions occur under certain conditions (temperature, pressure, light, radiation, presence of catalysts, etc.).The nuclei of atoms reagents chemical reactions do not change.The nuclear transformations and the formation of new nucleus particles.There are several features, which define the types of chemical reactions.

The basis of classification can take a number of initial and produced materials.In this case, all types of chemical reactions are divided into five groups:

1. expansions (some new turns of a single substance), e.g., decomposition by heating potassium chlorate potassium chloride and oxygen: KCLO3 + 3O2 → 2KCL.
2. compounds (two or more compounds to form a new one), interacting with the water, the calcium oxide is converted to calcium hydroxide: CaO + H2O → Ca (OH) 2;
3. substitution (number of products equal to the number of the starting materials, which are substituted in one component part to another), iron sulfate, copper, replacing copper forms ferrous sulfate: Fe + CuSO4 + FeSO4 → Cu.
4. double exchange (molecules of the two substances exchanged leaves them parts), metals potassium iodide and silver nitrate anion exchange, forming the precipitated silver iodide and nitrate Qadi: KI + AgNO3 → AgI ↓ + KNO3.
5. polymorphous transformation (transition occurs substance from one form to another crystalline) iodide, mercury red when heated turns into yellow mercury iodide: HgI2 (red) ↔ HgI2 (yellow).

If chemical transformations considered on the basis of changes in the oxidation state of the reactants elements, then the types of chemical reactions can be divided into groups:

1. with the degree of oxidation - redox reactions.As an example, consider the interaction of iron with hydrochloric acid: Fe → HCL + FeCl2 + H2, as a result of oxidation of iron (a reducing agent loses electrons) changed from 0 to 2, and hydrogen (oxidant accepts electrons) from 1 to 0.
2. Without changing the degree of oxidation, such as reaction of the acid-base interaction of the hydrogen bromide with sodium hydroxide: HBr + NaOH → NaBr + H2O, as a result of such reactions to produce salt and water, and oxidation state chemical elements included in the raw materials is notchange.

If we look at the chemical equilibrium and the rate of flow in the forward and backward direction, then all types of chemical reactions can be divided into two groups as:

1. Reversible - those that take place simultaneously in two directions.Most reactions are reversible.In the Examples dissolution of carbon dioxide in water to form an unstable carbonic acid, which decomposes to starting materials: ↔ CO2 + H2O H2CO3.
2. Irreversible - flow only in the forward direction after a complete consumption of the starting materials are completed, after which there are only product and starting material, taken in excess.Typically, one of the products is either precipitated or precipitated insoluble substance gas.For example, by reacting sulfuric acid and barium chloride: H2SO4 + BaCl2 + → BaSO4 ↓ + 2HCl is precipitated insoluble barium sulfate.

types of chemical reactions in organic chemistry can be divided into four groups:

1. substituted (there is a replacement of one atom or group of atoms other), for example, by reacting chloroethane with sodium hydroxide produced ethanol and sodium chloride: C2H5Cl+ NaOH → C2H5OH + NaCl, i.e. a chlorine atom substituted by a hydrogen atom.
2. fitting (two molecules react and form one), for example, bromine joins at the break of the double bond in the molecule ethylene: Br2 + CH2 = CH2 → BrCH2-CH2Br.
3. Cleavage (molecule decomposes into two or more molecules), for example, under certain conditions, decomposes to ethylene ethanol and water: C2H5OH → CH2 = CH2 + H2O.
4. rearrangement (isomerization, when one molecule is converted to another, but a qualitative and quantitative composition of the atoms in it does not change), such as 3-hloruten-1 (C4H7CL) is converted into 1-chlorobutyl 2 (C4H7CL).Here, chlorine is passed from the third carbon atom in the hydrocarbon chain to the first, and the double bond connecting the first and second carbon atom, and then began to combine the second and third atoms.

There are other types of chemical reactions:

1. By thermal effect: reactions occurring with absorption (endothermic) or release of heat (exothermic).
2. By type of interacting reactants or products formed.Interaction with water - hydrolysis with hydrogen - hydrogenation with oxygen - oxidation or combustion.Cleavage of water - dehydration, hydrogen - dehydrogenation and so on.
3. Under interactions: in the presence of catalysts (catalytic) under the action of a low or high temperature, pressure changes, and the light etc.
4. On the mechanism of the reaction: ionic, radical-chain or chain reactions.