Chemical Reaction

A chemical reaction is a process that results in the interconversion of chemical substances . The substance or substances initially involved in a chemical reaction are called reactants. Chemical reactions are characterized by a chemical change, and they yield one or more products which are, in general, different from the reactants. Classically, chemical reactions encompass changes that strictly involve the motion of electrons in the forming and breaking of chemical bonds, although the general concept of a chemical reaction, in particular the notion of a chemical equation, is applicable to transformations of elementary particles, as well as nuclear reactions. On the classical definition, therefore, there are only two types of chemical reaction: redox reactions and acid-base reactions. The former involve the motion of lone electrons and the latter of an electron pair.

Different chemical reactions are used in combinations in chemical synthesis in order to get a desired product. In biochemistry, series of chemical reactions form metabolic pathways, since straight synthesis of a product would be energetically impossible in conditions within a cell. Chemical reactions are also divided into organic reactions and inorganic reactions.

Some reaction are:

• Isomerisation, in which a chemical compound undergoes a structural rearrangement without any change in its net atomic composition; see stereoisomerism
• Direct combination or synthesis, in which two or more chemical elements or compounds unite to form a more complex product:

N₂ + 3H₂ → 2NH₃

• Chemical decomposition or analysis, in which a compound is decomposed into smaller compounds or elements:

2H₂O → 2H₂ + O₂

• Single displacement or substitution, characterized by an element being displaced out of a compound by a more reactive element:

2Na + 2HCl → 2NaCl + H₂

• Double displacement or coupling substitution , in which two compounds in aqueous solution (usually ionic) exchange elements or ions to form different compounds:

NaCl + AgNO₃ → NaNO₃ + AgCl

• Combustion, in which any combustible substance combines with an oxidizing element, usually oxygen, to generate heat and form oxidized products. The term combustion is used usually only large-scale oxidation of whole molecules, i.e. a controlled oxidation of a single functional group is not combustion.

C₁₀H₈+ 12O₂ → 10CO₂ + 4H₂O

CH₂S + 6F₂ → CF₄ + 2 HF + SF₆