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A single-displacement reaction, also known as single replacement reaction or exchange reaction, is an archaic concept in chemistry. It describes the stoichiometry of some chemical reactions in which one element or ligand is replaced by an atom or group. [1] [2] [3] It can be represented generically as:
The head of an ionic surfactant carries a net positive, or negative, charge. If the charge is negative, the surfactant is more specifically called anionic; if the charge is positive, it is called cationic. If a surfactant contains a head with two oppositely charged groups, it is termed zwitterionic, or amphoteric. Commonly encountered ...
A substitution reaction (also known as single displacement reaction or single substitution reaction) is a chemical reaction during which one functional group in a chemical compound is replaced by another functional group. [1] Substitution reactions are of prime importance in organic chemistry.
General scheme ionic propagation. Propagating center can be radical, cationic or anionic. In polymer chemistry, ring-opening polymerization (ROP) is a form of chain-growth polymerization in which the terminus of a polymer chain attacks cyclic monomers to form a longer polymer (see figure). The reactive center can be radical, anionic or cationic.
This reaction can be accelerated by acidic conditions, which make the carbonyl more electrophilic, or basic conditions, which provide a more anionic and therefore more reactive nucleophile. The tetrahedral intermediate itself can be an alcohol or alkoxide , depending on the pH of the reaction.
In both anionic and cationic polymerization, each charged chain end (negative and positive, respectively) is matched by a counterion of opposite charge that originates from the initiator. Because of the charge stability necessary in ionic polymerization, monomers which may be polymerized by this method are few compared to those available for ...
Polyelectrolytes that bear both cationic and anionic repeat groups are called polyampholytes. The competition between the acid-base equilibria of these groups leads to additional complications in their physical behavior. These polymers usually only dissolve when sufficient added salt screens the interactions between oppositely charged segments.
The second step is the loss of a sulfur dioxide molecule and its replacement by the chloride, which was attached to the sulphite group. The difference between S N 1 and S N i is actually that the ion pair is not completely dissociated , and therefore no real carbocation is formed, which else would lead to a racemisation.