In chemistry, nucleophilic substitution is a class of substitution reaction in which an electron-rich nucleophile attacks a molecule and replaces a group or atom, called the leaving group. It is a fundamental class of reaction in organic chemistry, where the reaction occurs at a carbon centre, but nucleophilic substitutions are also well known in inorganic covalent compounds too. Chemistry (in Greek: χημεία) is the science of matter that deals with the composition, structure, and properties of substances and with the transformations that they undergo. ... In a substitution reaction, a group of a particular compound is replaced by another group. ... In chemistry, a nucleophile (literally nucleus lover) is a reagent which is attracted to centres of positive charge. ... A leaving group is an atom or molecule that detaches from an organic molecule, which, after detachment, is called the residual or main part. ... Jump to: navigation, search Organic chemistry is the scientific study of the structure, properties, composition, reactions, and synthesis of organic compounds that by definition contain carbon. ... Jump to: navigation, search General Name, Symbol, Number carbon, C, 6 Chemical series nonmetals Group, Period, Block 14, 2, p Appearance black (graphite) colorless (diamond) Atomic mass 12. ... Inorganic chemistry is the branch of chemistry concerned with the properties and reactions of inorganic compounds. ... Covalent bonding is a form of chemical bonding characterized by the sharing of one or more pairs of electrons between atoms, in order to produce a mutual attraction, which holds the resultant molecule together. ... An inorganic compound is a chemical compound not containing carbon and hydrogen atoms bonded to each other. ...

If we ignore formal charges, the most general form for the reaction may be given as In chemistry, a formal charge (FC) on an atom in a molecule is defined as FC = number of valence electrons of the atom - number of Lone pair electrons on this atom - half the total number of electrons participating in covalent bonds with this atom When determining the correct Lewis structure...

Nuc: + R-LG → R-Nuc + LG:

The electron pair (:) from the nucleophile (Nuc) attacks the substrate (R-LG) forming a new bond, while the leaving group (LG) departs with an electron pair. The principal product in this case is R-Nuc. The nucleophile may be electrically neutral or negatively charged, whereas the substrate is typically neutral or positively charged.

An example of nucleophilic substitution is the hydrolysis of an alkyl bromide, R-Br, under alkaline conditions, where the attacking nucleophile is the OH⁻ and the leaving group is Br^-. An Alkyl is a univalent radical containing only carbon and hydrogen atoms arranged in a chain. ... A bromide is a phrase, or person who uses phrases, which have been used and repeated so many times as to become either insincere in their meaning, or seem like an attempt at trying to explain the obvious. ... An Alkyl is a univalent radical containing only carbon and hydrogen atoms arranged in a chain. ... Jump to: navigation, search Hydroxide is a polyatomic ion consisting of oxygen and hydrogen: −O−H It has a charge of −1. ... A leaving group is an atom or molecule that detaches from an organic molecule, which, after detachment, is called the residual or main part. ... A bromide is a phrase, or person who uses phrases, which have been used and repeated so many times as to become either insincere in their meaning, or seem like an attempt at trying to explain the obvious. ...

R-Br + OH⁻ → R-OH + Br⁻

Nucleophilic substitution reactions are commonplace in organic chemistry, and they can be broadly categorised as taking place at an aliphatic (saturated) carbon or at (less often) an aromatic or other unsaturated carbon centre.^[1] In chemistry, non-aromatic and non-cyclic (acyclic) organic compounds are called aliphatic. ... In chemistry, saturation has three different meanings: In physical chemistry, saturation is the point at which a solution of a substance can dissolve no more of that substance. ... In chemistry, an aromatic molecule is one in which electrons are free to cycle around circular arrangements of atoms, which are alternately singly and doubly bonded to one another. ...

Nucleophilic substitution at saturated carbon centres^[2]

In chemistry, saturation has three different meanings: In physical chemistry, saturation is the point at which a solution of a substance can dissolve no more of that substance. ...

S_N1 and S_N2 reactions

In 1935, Edward D. Hughes and Sir Christopher Ingold studied nucleophilic substitution reactions of alkyl halides and related compounds. They proposed a theory proposing that there were two main mechanisms at work, both of them competing with each other. The two main mechanisms are the S_N1 reaction and the S_N2 reaction. S stands for chemical substitution, N stands for nucleophilic, and the number represents the kinetic order of the reaction. In chemistry, an alkyl halide is an organic molecule of the form R_X, where X is a halide and R contains a carbon atom bonded to other functional groups or hydrogens. ... The SN1 reaction is an organic reaction in chemistry. ... SN2 is a kind of nucleophilic substitution. ... Order in the context of a chemical reaction is a concept of reaction kinetics, a subdiscipline of physical chemistry. ...

In the S_N2 reaction, the addition of the nucleophile and the elimination of leaving group take place simultaneously. S_N2 occurs where the central carbon atom is easily accessible to the nucleophile. By contrast the S_N1 reaction involves two steps. S_N1 reactions tend to be important when the central carbon atom of the substrate is surrounded by bulky groups, both because such groups interfere sterically with the S_N2 reaction (discussed above) and because a highly substituted carbon forms a stable carbocation. A carbocation is an ion with a positively-charged carbon atom. ...

Initially, the rate of the nucleophilic substitution was a little puzzling as the rate followed the pattern :

CH₃X > primary > secondary < tertiary Ordinal adjectives: Primary first, first hand. ... Secondary can mean: An ordinal adjective indicating Second or second hand, see Primary The secondary in American football refers to the group of (usually four) defensive backs. ... The Tertiary period was previously one of the major divisions of the geologic timescale, from the end of the Cretaceous period about 65. ...

The reaction kinetics changed from second order to first order. Chemical substances in a system may increase or decrease in concentration with time due to chemical reactions. ...

The S_N1 and S_N2 reactions are influenced by different factors

S_N1 reactivity rates follow the trend CH₃X < primary < secondary < tertiary

S_N2 reactivity rates follow the trend CH₃X > primary > secondary > tertiary

The total reactivity is the sum of the two rates.

Jump to: navigation, search Image File history File links Sn2_Sn1_Graph. ...

A graph showing the relative reactivities of the different alkyl halides towards S_N1 and S_N2 reactions. Also see Table 1.

There are many reactions in organic chemistry that involve this type of mechanism. Common examples include The SN1 reaction is an organic reaction in chemistry. ... SN2 is a kind of nucleophilic substitution. ... In physical chemistry, chemical kinetics or reaction kinetics study reaction rates in a chemical reaction. ... An elimination reaction is a type of organic chemical reaction in which two groups are removed from a molecule in either a one or two-step mechanism. ... A leaving group is an atom or molecule that detaches from an organic molecule, which, after detachment, is called the residual or main part. ... In chemistry, a nucleophile (literally nucleus lover) is a reagent which is attracted to centres of positive charge. ... A solvent is a liquid that dissolves a solid, liquid, or gaseous solute, resulting in a solution. ... Stereochemistry, a subdiscipline of chemistry, involves the study of the relative spatial arrangement of atoms within molecules. ... An elimination reaction is a type of organic chemical reaction in which two groups are removed from a molecule in either a one or two-step mechanism. ...

• organic reductions with hydrides, for example

R-X → R-H using LiAlH₄   (S_N2)

• hydrolysis reactions such as

R-Br + OH⁻ → R-OH + Br⁻ (S_N2) or

R-Br + H₂O → R-OH + HBr   (S_N1)

• Williamson ether synthesis

R-Br + OR'⁻ → R-OR' + Br⁻   (S_N2)

Organic reductions or organic oxidations or organic redox reactions are redox reactions that take place with organic compounds. ... A hydride is a chemical compound of a hydrogen with other elements. ... In chemistry, an alkyl halide is an organic molecule of the form R_X, where X is a halide and R contains a carbon atom bonded to other functional groups or hydrogens. ... Jump to: navigation, search An alkane in organic chemistry simply put means that Reece has a severe Odour problem. ... Lithium Aluminium Hydride (LiAlH4), commonly abbreviated to LAH, is a powerful reducing agent used in organic chemistry. ... Hydrolysis is a chemical process in which a molecule is cleaved into two parts by the addition of a molecule of water. ... In general usage, alcohol (from Arabic al-khwl الكحول, or al-ghawl الغول) refers almost always to ethanol, also known as grain alcohol, and often to any beverage that contains ethanol (see alcoholic beverage). ... A bromide is a phrase, or person who uses phrases, which have been used and repeated so many times as to become either insincere in their meaning, or seem like an attempt at trying to explain the obvious. ... Hydrobromic Acid is a chemical compound, with the chemical formula HBr. ... Williamson ether synthesis was developed by Alexander Williamson in 1850. ... An alkoxide has an organic group bonded to a negatively charged oxygen atom, they are generally basic. ... Ether is the general name for a class of chemical compounds which contain an ether group — an oxygen atom connected to two (substituted) alkyl groups. ...

Other mechanisms

Besides S_N1 and S_N2, other mechanisms are known, although they are less common. The SNi mechanism is observed in reactions of thionyl chloride with alcohols, and it is similar to S_N1 except that the nucleophile is delivered from the same side as the leaving group. The National Intelligence Service (Serviço Nacional de Informações, or SNI) of Brazil was an intelligence agency formed by the Castelo Branco government in 1964. ... Thionyl chloride (or thionyl dichloride) is an inorganic compound with the formula S O Cl2. ... In general usage, alcohol (from Arabic al-khwl الكحول, or al-ghawl الغول) refers almost always to ethanol, also known as grain alcohol, and often to any beverage that contains ethanol (see alcoholic beverage). ...

Nucleophilic substitutions can be accompanied by an allylic rearrangement as seen in reactions such as the Ferrier rearrangement. This type of mechanism is called an S_N1' or S_N2' reaction (depending on the kinetics). With allylic halides or sulfonates, for example, the nucleophile may attack at the γ unsaturated carbon in place of the carbon bearing the leaving group. This may be seen in the reaction of 1-chloro-2-butene with sodium hydroxide to give a mixture of 2-buten-1-ol and 1-buten-3-ol: Jump to: navigation, search A allylic rearrangement or allylic shift is a organic reaction in which the double bond in an allyl chemical compound shifts to the next carbon atom. ... Jump to: navigation, search The Ferrier rearrangement is a organic reaction that involves a nucleophilic substitution reaction combined with an allylic shift in a 2,3-Unsaturated glycoside (see glycals). ... An allyl group is an alkene hydrocarbon group with the formula H2C=CH-CH2-. It is made up of a vinyl group, CH2=CH-, attached to a methylene -CH2. ... Jump to: navigation, search Flash point non flammable Supplementary data page Structure and properties n, εr, etc. ...

CH₃CH=CH-CH₂-Cl → CH₃CH=CH-CH₂-OH + CH₃CH(OH)-CH=CH2

References

1. ^  L. G. Wade, Organic Chemistry, 5th ed., Prentice Hall, Upper Saddle RIver, New Jersey, 2003.
2. ^  J. March, Advanced Organic Chemistry, 4th ed., Wiley, New York, 1992.
3. ^  J. P. Clayden, N. Greeves, S. Warren, P. D. Wothers, Organic Chemistry, Oxford University Press, Oxford, UK, 2001.
4. ^  S. R. Hartshorn, Aliphatic Nucleophilic Substitution, Cambridge University Press, London, 1973. [ISBN 0521098017]
5. ^  R. A. Rossi, R. H. de Rossi, Aromatic Substitution by the S_RN1 Mechanism, ACS Monograph Series No. 178, American Chemical Society, 1983. [ISBN 0841206481]