In chemistry, a nucleophile (literally nucleus lover as in nucleus and phile) is a reagent that forms a chemical bond to its reaction partner (the electrophile) by donating both bonding electrons. Chemistry (from Egyptian kēme (chem meaning "earth") is the Science concerned with the composition structure and properties The nucleus of an Atom is the very dense region consisting of Nucleons ( Protons and Neutrons, at the center of an atom A reagent or reactant is a substance or compound consumed during a Chemical reaction. A chemical bond is the physical process responsible for the attractive interactions between Atoms and Molecules and which confers stability to diatomic and polyatomic In Chemistry, an electrophile (literally electron-lover) is a Reagent attracted to Electrons that participates in a chemical reaction by accepting The electron is a fundamental Subatomic particle that was identified and assigned the negative charge in 1897 by J ^[1] Because nucleophiles donate electrons, they are by definition Lewis bases (see acid-base reaction theories). All molecules or ions with a free pair of electrons can act as nucleophiles, although negative ions (anions) are more potent than neutral reagents. In Chemistry, a molecule is defined as a sufficiently stable electrically neutral group of at least two Atoms in a definite arrangement held together by An ion is an Atom or Molecule which has lost or gained one or more Valence electrons giving it a positive or negative electrical charge An ion is an Atom or Molecule which has lost or gained one or more Valence electrons giving it a positive or negative electrical charge Neutral nucleophilic reactions with solvents such as alcohols and water are named solvolysis. In Chemistry, an alcohol is any Organic compound in which a Hydroxyl group ( - O[[hydrogen H]]) is bound to a Carbon Solvolysis is a special type of Nucleophilic substitution or elimination where the Nucleophile is a Solvent molecule

Nucleophiles may take part in nucleophilic substitution, whereby a nucleophile becomes attracted to a full or partial positive charge on an element and displaces the group it is bonded to. In organic and Inorganic chemistry, nucleophilic substitution is a fundamental class of Substitution reaction in which an "electron rich"

Nucleophilic is an adjective that describes the affinity of a nucleophile to the nuclei, while nucleophilicity or nucleophile strength refers to the nucleophilic character. In Grammar, an adjective is a word whose main syntactic role is to modify a Noun or Pronoun, giving more information about the Nucleophilicity is often used to compare an atom's relative affinity to another's.

In general, in a row across the periodic table, the more basic the ion (the higher the pK_a of the conjugate acid), the more reactive it is as a nucleophile. In a given group, polarizability is more important in the determination of the nucleophilicity: the easier it is to distort the electron cloud around an atom or molecule, the more readily it will react. Polarizability is the relative tendency of a charge distribution like the Electron cloud of an Atom or Molecule, to be distorted from its normal shape e. g. , the iodide ion (I⁻) is more nucleophilic than the fluoride ion (F⁻). An iodide Ion is an iodine atom with a &minus1 charge. Compounds with iodine in formal Oxidation state &minus1 are called iodides Fluoride is the reduced form of Fluorine. Both organic and Inorganic compounds containing the element fluorine are considered fluorides

An ambident nucleophile is one that can attack from two or more places, resulting in two or more products. For example, the thiocyanate ion (SCN⁻) may attack from either the S or the N. Thiocyanate (also known as sulphocyanate or thiocyanide or rhodanide) is the anion − Sulfur or sulphur (ˈsʌlfɚ see spelling below) is the Chemical element that has the Atomic number 16 Nitrogen (ˈnaɪtɹəʤɪn is a Chemical element that has the symbol N and Atomic number 7 and Atomic weight 14 For this reason, the S_N2 reaction of an alkyl halide with SCN⁻ often leads to a mixture of RSCN (an alkyl thiocyanate) and RNCS (an alkyl isothiocyanate). The SN2 reaction (also known as bimolecular nucleophilic substitution) is a type of Nucleophilic substitution, where a lone pair from a Nucleophile Isothiocyanate is the Chemical group - N = C = S, formed by substituting Sulfur for Oxygen in the Isocyanate Similar considerations apply in the Kolbe nitrile synthesis. The Kolbe nitrile synthesis is a method for the preparation of alkyl nitriles by reaction of the corresponding alkylhalide with a metal Cyanide.

The terms nucleophile and electrophile were introduced by Christopher Kelk Ingold in 1929,^[2] replacing the terms cationoid and anionoid proposed earlier by A. J. Lapworth in 1925. Sir Christopher Kelk Ingold ( October 28 1893 - December 8 1970, Edgware) was a British Chemist based in Leeds Arthur Lapworth ( October 10 1872 - April 5 1941) was a Scottish Chemist born in Galashiels, Scotland son of Charles Lapworth ^[3]

Contents 1 Common examples 1.1 Carbon nucleophiles 1.2 Oxygen nucleophiles 1.3 Sulfur nucleophiles 1.4 Nitrogen nucleophiles 2 Nucleophilicity scales 2.1 Swain-Scott equation 2.2 Richie equation 2.3 Mayr-Patz equation 2.4 Unified equation 3 See also 4 References

Common examples

In the example below, the oxygen of the hydroxide ion donates an electron to bond with the carbon at the end of the bromopropane molecule. Oxygen (from the Greek roots ὀξύς (oxys (acid literally "sharp" from the taste of acids and -γενής (-genēs (producer literally begetteris the Carbon (kɑɹbən is a Chemical element with the symbol C and its Atomic number is 6 The haloalkanes (also known as halogenoalkanes or alkyl halides) are a group of Chemical compounds consisting of Alkanes such as Methane The bond between the carbon and the bromine then undergoes heterolytic fission, with the bromine atom taking the donated electron and becoming the bromide ion (Br⁻): The picture is incorrect, because a Sn2 reaction occurs by backside attack. In Chemistry, heterolysis or heterolytic fission (from Greek ἑτερος heteros "different" and λυσις lusis "loosening" A bromide Ion is a Bromine atom with charge of −1 Compounds with bromine in formal Oxidation state −1 are called bromides This means that the hydroxide ion attacks the carbon atom from the other side, exactly opposite the bromine ion.

Carbon nucleophiles

Carbon nucleophiles are alkyl metal halides found in the Grignard reaction, Blaise reaction, Reformatsky reaction, and Barbier reaction, organolithium reagents and anions of a terminal alkyne. The Grignard reaction, named for the French chemist François Auguste Victor Grignard, is an organometallic Chemical reaction in which Alkyl - The Blaise reaction is an Organic reaction that forms a β-ketoester from the reaction of Zinc metal with a α-bromoester and a Nitrile. The Reformatsky reaction (sometimes spelled Reformatskii reaction) is an Organic reaction which condenses Aldehydes 1 (or Ketones The Barbier reaction is an Organic reaction between an Alkyl halide and a Carbonyl group as an Electrophilic substrate in the presence of An organolithium reagent is an Organometallic compound with a direct bond between a Carbon and a Lithium atom An ion is an Atom or Molecule which has lost or gained one or more Valence electrons giving it a positive or negative electrical charge A polymer is a large Molecule ( Macromolecule) composed of repeating Structural units typically connected by Covalent Chemical bonds Alkynes are Hydrocarbons that have at least one Triple bond between two Carbon atoms with the formula CnH2n-2.

Enols are also carbon nucleophiles. The formation of an enol is catalyzed by acid or base. Enols are ambident nucleophiles, but generally nucleophilic at the alpha carbon atom. Enols are commonly used in condensation reactions, including the Claisen condensation and the aldol condensation reactions.

Oxygen nucleophiles

Examples of oxygen nucleophiles are Water (H₂O) and Alcohols. Water is a common Chemical substance that is essential for the survival of all known forms of Life. In Chemistry, an alcohol is any Organic compound in which a Hydroxyl group ( - O[[hydrogen H]]) is bound to a Carbon

Sulfur nucleophiles

Sulfur nucleophiles are Thiols (HS⁻). In Organic chemistry, a thiol is a compound that contains the functional group composed of a Sulfur atom and a Hydrogen atom (-SH

Sulfur is generally very nucleophilic because of its large size, which makes it easily polarizable, and its lone pairs of electrons (in some cases).

Nitrogen nucleophiles

Nitrogen nucleophiles are Ammonia, Azide and Amines. Ammonia is a compound with the formula N[[hydrogen H3]] It is normally encountered as a Gas with a characteristic pungent Odor Azide is the anion with the formula N3− It is the Conjugate base of Hydrazoic acid. Amines are Organic compounds and Functional groups that contain a basic Nitrogen Atom with a Lone pair.

Nucleophilicity scales

Many schemes have been devised attempting to quantify relative nucleophilic strength. The following empirical data have been obtained by measuring reaction rates for a large number of reactions involving a large number of nucleophiles and electrophiles and linear regression. A central concept in Science and the Scientific method is that all Evidence must be empirical, or empirically based that is dependent on evidence The reaction rate or rate of reaction for a Reactant or product in a particular reaction is intuitively defined as how fast a reaction takes In statistics linear regression is a form of Regression analysis in which the relationship between one or more Independent variables and another variable called Nucleophiles displaying the so-called alpha effect are usually omitted in this type of treatment. The alpha effect refers to the increased nucleophilicity of a Molecule due to the presence of an adjacent (alpha Atom with Lone pair Electrons

Swain-Scott equation

The first such attempt is found in the so-called Swain-Scott equation^[4][5] derived in 1953:

This free-energy relationship relates the pseudo first order reaction rate constant (in water at 25°C), k, of a reaction, normalized to the reaction rate, k₀, of a standard reaction with water as the nucleophile, to a nucleophilic constant n for a given nucleophile and a substrate constant s that depends on the sensitivity of a substrate to nucleophilic attack (defined as 1 for methyl bromide). In Physical organic chemistry, a free-energy relationship or linear Gibbs energy relation relates the Logarithm of a Reaction rate constant The rate law or rate equation for a Chemical reaction is an equation which links the Reaction rate with concentrations or pressures of reactants and constant In Chemical kinetics a reaction rate constant k or \lambda quantifies the speed of a Chemical reaction. The Chemical compound bromomethane, commonly known as methyl bromide, is an organic Halogen compound with formula C[[Hydrogen

This treatment results in the following values for typical nucleophilic anions: acetate 2. An acetate, or ethanoate, is either a salt or Ester of Acetic acid. 7, chloride 3. The chloride Ion is formed when the element Chlorine picks up one Electron to form an Anion (negatively-charged ion Cl&minus 0, azide 4. Azide is the anion with the formula N3− It is the Conjugate base of Hydrazoic acid. 0, hydroxide 4. In Chemistry, hydroxide is the most common name for the diatomic Anion OH− consisting of Oxygen and Hydrogen 2, aniline 4. Aniline, phenylamine or aminobenzene is an Organic compound with the formula C6H7N 5, iodide 5. An iodide Ion is an iodine atom with a &minus1 charge. Compounds with iodine in formal Oxidation state &minus1 are called iodides 0 and thiosulfate 6. Thiosulfate (S2O32&minus is an Oxyanion of Sulfur produced by the reaction of Sulfite ions with elemental sulfur 4. Typical substrate constants are 0. 66 for ethyl tosylate, 0. A tosyl group (abbreviated Ts or Tos) combines the Toluene and Sulfonyl Functional groups. 77 for β-propiolactone, 1. lactone is a cyclic Ester in Organic chemistry. It is the condensation product of an Alcohol group and a Carboxylic acid 00 for 2,3-epoxypropanol, 0. An epoxide is a cyclic Ether with only three ring atoms This ring approximately is an Equilateral triangle, i 87 for benzyl chloride and 1. Benzyl chloride, or α-chlorotoluene is an Organic compound consisting of a phenyl group substituted with a chloromethyl group 43 for benzoyl chloride. Benzoyl chloride, also known as benzenecarbonyl chloride is a colourless fuming liquid C6H5COCl with an irritating odour

The equation predicts that in a nucleophilic displacement on benzyl chloride, the azide anion reacts 3000 times faster than water. In organic and Inorganic chemistry, nucleophilic substitution is a fundamental class of Substitution reaction in which an "electron rich" Benzyl chloride, or α-chlorotoluene is an Organic compound consisting of a phenyl group substituted with a chloromethyl group Azide is the anion with the formula N3− It is the Conjugate base of Hydrazoic acid.

Richie equation

The Richie equation named after its creator and derived in 1972 is another free-energy relationship:^[6][7][8]

or

where N⁺ is the nucleophile dependent parameter and k₀ the reaction rate constant for water. In Physical organic chemistry, a free-energy relationship or linear Gibbs energy relation relates the Logarithm of a Reaction rate constant In Chemical kinetics a reaction rate constant k or \lambda quantifies the speed of a Chemical reaction. In this equation a substrate dependent parameter like s in the Swain-Scott equation is absent. The equation states that two nucleophiles react with the same relative reactivity regardless of the nature of the electrophile which is in violation of the Reactivity–selectivity principle. In Chemistry the reactivity–selectivity principle or RSP states that a more reactive Chemical compound or Reactive intermediate is less selective For this reason this equation is also called the constant selectivity relationship.

In the original publication the data were obtained by reactions of selected nucleophiles with selected electrophilic carbocations such as tropylium cations:

or diazonium cations:

or (not displayed) ions based on Malachite green. A carbocation (ˌkɑrboʊˈkætaɪɒn is an Ion with a positively-charged Carbon Atom. In Organic chemistry, the tropylium ion is an Aromatic species with a formula of + Diazonium compounds or diazonium salts are a group of Organic compounds sharing a common Functional group with the characteristic structure of R-N2+ Malachite green, also called aniline green, basic green 4, diamond green B, or victoria green B, IUPAC name 4--NN-dimethyl-aniline Subsequently many other reaction types were described.

Typical Richie N⁺ values (in methanol) are: 0. Methanol, also known as methyl alcohol, carbinol, wood alcohol, wood naphtha or wood spirits, is a Chemical compound 5 for methanol, 5. Methanol, also known as methyl alcohol, carbinol, wood alcohol, wood naphtha or wood spirits, is a Chemical compound 9 for the cyanide anion, 7. A cyanide is any Chemical compound that contains the cyano group (C≡N which consists of a Carbon Atom triple-bonded to a 5 for the methoxide anion , 8. Methoxide is an Organic salt, and the simplest Alkoxide. In Organic chemistry, the methoxide ion has a formula of CH3O- 5 for the azide anion and 10. Azide is the anion with the formula N3− It is the Conjugate base of Hydrazoic acid. 7 for the thiophenol anion. Thiophenol is a Chemical compound with the formula C6H5SH and sometimes abbreviated as PhSH The values for the relative cation reactivities are -0. 4 for the malachite green cation, +2. 6 for the benzenediazonium cation and +4. 5 for the tropylium cation.

Mayr-Patz equation

In the Mayr-Patz equation (1994):^[9]

The second order reaction rate constant k at 20°C for a reaction is related to a nucleophilicity parameter N, an electrophilicity parameter E and a nucleophile-dependent slope parameter s. The rate law or rate equation for a Chemical reaction is an equation which links the Reaction rate with concentrations or pressures of reactants and constant In Chemical kinetics a reaction rate constant k or \lambda quantifies the speed of a Chemical reaction. The constant s is defined as 1 with 2-methyl-1-pentene as the nucleophile.

Many of the constants have been derived from reaction of so-called benzhydrylium ions as the electrophiles:^[10] and a diverse collection of π-nucleophiles:

. In Chemistry, an electrophile (literally electron-lover) is a Reagent attracted to Electrons that participates in a chemical reaction by accepting

Typical E values are +6. 2 for R = chlorine, +5. Chlorine (ˈklɔriːn from the Greek word 'χλωρóς' ( khlôros, meaning 'pale green' is the Chemical element with Atomic number 17 and 90 for R = hydrogen, 0 for R = methoxy and -7. Hydrogen (ˈhaɪdrədʒən is the Chemical element with Atomic number 1 In Chemistry (particularly Organic chemistry) methoxy refers to the Functional group consisting of a Methyl group bound to Oxygen 02 for R = dimethylamine. Dimethylamine is an Organic compound with the formula (CH32NH

Typical N values with s in parenthesis are -4. 47 (1. 32) for electrophilic aromatic substitution to toluene (1), -1. Electrophilic aromatic substitution or EAS is an Organic reaction in which an atom usually Hydrogen, appended to an aromatic system is replaced Toluene, also known as methylbenzene or phenylmethane, is a clear water -insoluble liquid with the typical smell of Paint thinners redolent of 41 (1. 12) for electrophilic addition to 1-phenyl-2-propene (2) and 0. In Organic chemistry, an electrophilic addition reaction is an Addition reaction where in a Chemical compound, a Pi bond is removed by the creation 96 (1) for addition to 2-methyl-1-pentene (3), -0. 13 (1. 21) for reaction with triphenylallylsilane (4), 3. 61 (1. 11) for reaction with 2-methylfuran (5), +7. Furan, also known as furane and furfuran, is a heterocyclic Organic compound. 48 (0. 89) for reaction with isobutenyltributylstannane (6) and +13. 36 (0. 81) for reaction with the enamine 7. An enamine is an unsaturated compound derived by the reaction of an Aldehyde or Ketone with a Secondary amine followed by loss of H2O ^[11]

The range of organic reactions also include SN2 reactions:^[12]

With E = -9. The SN2 reaction (also known as bimolecular nucleophilic substitution) is a type of Nucleophilic substitution, where a lone pair from a Nucleophile 15 for the S-methyldibenzothiophenium ion, typical nucleophile values N (s) are 15. 63 (0. 64) for piperidine, 10. Piperidine is an Organic compound with the molecular formula (CH25NH 49 (0. 68) for methoxide and 5. Methoxide is an Organic salt, and the simplest Alkoxide. In Organic chemistry, the methoxide ion has a formula of CH3O- 20 (0. 89) for water. In short: nucleophilicities towards sp₂ or sp₃ centers follow the same pattern.

Unified equation

In an effort to unify the above described equations the Mayr equation is rewritten as:^[12]

log(k) = s_Es_N(N + E)

with s_E the electrophile-dependent slope parameter and s_N the nucleophile-dependent slop parameter. This equation can be rewritten in several ways:

• with s_E = 1 for carbocations this equation is equal to the original Mayr-Patz equation of 1994,
• with s_N = 0. 6 for most n nucleophiles the equation becomes

log(k) = 0. 6s_EN + 0. 6s_EE

or the original Scott-Swain equation written as:

log(k) = log(k₀) + s_EN

• with s_E = 1 for carbocations and s_N = 0. 6 the equation becomes:

log(k) = 0. 6N + 0. 6E

or the original Ritchie equation written as:

log(k) − log(k₀) = N ⁺

See also

• Electrophile
• Lewis base

References

1. ^ Gold Book definition Link
2. ^ Ingold, C. In Chemistry, an electrophile (literally electron-lover) is a Reagent attracted to Electrons that participates in a chemical reaction by accepting Compendium of Chemical Terminology (ISBN 0-86542-684-8 is a book published by IUPAC containing internationally accepted definitions for terms in Chemistry. K. Recl. TraV. Chim. Pays-Bas 1929
3. ^ Lapworth, A. Nature 1925, 115, 625
4. ^ Quantitative Correlation of Relative Rates. Nature is a prominent Scientific journal, first published on 4 November 1869 Comparison of Hydroxide Ion with Other Nucleophilic Reagents toward Alkyl Halides, Esters, Epoxides and Acyl Halides C. Gardner Swain, Carleton B. Scott J. Am. Chem. Soc.; 1953; 75(1); 141-147. The Journal of the American Chemical Society (usually abbreviated as J Abstract
5. ^ Gold Book definition Link
6. ^ Gold Book definition Link
7. ^ Nucleophilic reactivities toward cations Calvin D. Compendium of Chemical Terminology (ISBN 0-86542-684-8 is a book published by IUPAC containing internationally accepted definitions for terms in Chemistry. Compendium of Chemical Terminology (ISBN 0-86542-684-8 is a book published by IUPAC containing internationally accepted definitions for terms in Chemistry. Ritchie Acc. Chem. Res. ; 1972; 5(10); 348-354. Abstract
8. ^ Cation-anion combination reactions. XIII. Correlation of the reactions of nucleophiles with esters Calvin D. Ritchie J. Am. Chem. Soc.; 1975; 97(5); 1170-1179. The Journal of the American Chemical Society (usually abbreviated as J Abstract
9. ^ Scales of Nucleophilicity and Electrophilicity: A System for Ordering Polar Organic and Organometallic Reactions Angewandte Chemie International Edition in English Volume 33, Issue 9, Date: May 18, 1994, Pages: 938-957 doi:10.1002/anie.199
10. ^ Reference Scales for the Characterization of Cationic Electrophiles and Neutral NucleophilesHerbert Mayr, Thorsten Bug, Matthias F. Angewandte Chemie is a weekly Peer-reviewed Chemistry journal that covers all disciplines of chemistry A digital object identifier ( DOI) is a permanent identifier given to an Electronic document. Gotta, Nicole Hering, Bernhard Irrgang, Brigitte Janker, Bernhard Kempf, Robert Loos, Armin R. Ofial, Grigoriy Remennikov, and Holger Schimmel J. Am. Chem. Soc.; 2001; 123(39) pp 9500 - 9512; (Article) doi:10.1021/ja010890y
11. ^ An internet database for reactivity parameters maintained by the Mayr group is available at http://www.cup.uni-muenchen.de/oc/mayr/
12. ^ ^{a b} Towards a General Scale of Nucleophilicity? Thanh Binh Phan, Martin Breugst, Herbert Mayr, Angewandte Chemie International Edition Volume 45, Issue 23 , Pages 3869 - 3874 2006 doi:10.1002/anie.200600542

The Journal of the American Chemical Society (usually abbreviated as J A digital object identifier ( DOI) is a permanent identifier given to an Electronic document. Angewandte Chemie is a weekly Peer-reviewed Chemistry journal that covers all disciplines of chemistry A digital object identifier ( DOI) is a permanent identifier given to an Electronic document.

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