In chemistry, an electrophile (literally electron-lover) is a reagent attracted to electrons that participates in a chemical reaction by accepting an electron pair in order to bond to a nucleophile. Because electrophiles accepts electrons, they are Lewis acids (see acid-base reaction theories). Most electrophiles are positively charged, have an atom which carries a partial positive charge, or have an atom which does not have an octet of electrons. Chemistry (from Greek χημεία khemeia[1] meaning alchemy) is the science of matter at the atomic to molecular scale, dealing primarily with collections of atoms, such as molecules, crystals, and metals. ... A reagent or reactant is any substance used in a chemical reaction. ... The Electron is a fundamental subatomic particle that carries an electric charge. ... A lone pair is an electron pair without bonding or sharing with other atoms. ... A chemical bond is the physical phenomenon (or phenomena) responsible for the attractive interactions betwen atoms that confers stability to di- and polyatomic chemical compounds. ... In chemistry, a nucleophile (literally nucleus lover) is a reagent which is attracted to centres of positive charge. ... In chemistry, a Lewis acid can accept a pair of electrons and form a coordinate covalent bond, after the American chemist Gilbert Lewis. ... An acid-base reaction is a chemical reaction between an acid and a base. ... Electric charge is a fundamental conserved property of some subatomic particles, which determines their electromagnetic interactions. ...

The electrophiles attack the most electron-populated part of a nuculeophile. The electrophiles frequently seen in the organic syntheses are cations such as H⁺ and NO⁺, polarlized neutral molecules such as HCl, alkyl halides, acyl halides, and carbonyl compounds, polarlizable neutral molecules such as Cl₂ and Br₂, oxidizing agents such as organic peracids, chemical species that do not satisfy the octet rule such as carbenes and radicals, and some of lewis acids such as BH₃ and DIBAL. Organic synthesis is the construction of organic molecules via chemical processes. ... R-phrases , S-phrases , , , , Flash point non-flammable Supplementary data page Structure and properties n, εr, etc. ... 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. ... An acyl halide (also known as an acid halide) is an organic compound containing a carbon atom which is double_bonded to an oxygen atom and singly bonded to a chlorine atom. ... In chemistry, a carbonyl group is a functional group composed of an atom of carbon double-bonded to an atom of oxygen. ... European Union Chemical hazard symbol for oxidizing agents Dangerous goods label for oxidising agents An oxidizing agent is a compound that oxidizes another substance in electrochemistry or redox chemical reactions. ... A peroxy acid (often spelt as one word ie. ... The bonding in carbon dioxide The octet rule is a simple chemical rule of thumb that states that atoms tend to combine in such a way that they each have eight electrons in their valence shells, similar to the electronic configuration of a noble gas. ... In chemistry a carbene is a short-lived and highly reactive organic molecule with a divalent carbon atom with only six valence electrons and the general formula: R1R2C: . The carbon atom is sp2 hybridised with an empty p-orbital extending above and below a plane containing R1 and R2 and... Look up Radical in Wiktionary, the free dictionary. ... A borane is an inorganic chemical compound of boron and hydrogen. ... DIBAH (diisobutylaluminium hydride) is a reducing agent with the formula iBu2AlH, where iBu represents an isobutyl group. ...

Electrophiles in organic chemistry

Alkenes

Electrophilic addition is one of the three main forms of reaction concerning alkenes. They consist of: An alkene is one of the three classes of unsaturated hydrocarbons that contain at least one carbon-carbon double bond and have the general molecular formula of CnH2n (the other two being alkynes and arenes). ...

• Hydrogenation by the addition of hydrogen over the double bond.
• Electrophilic addition reactions with halogens and sulfuric acid.
• Hydration to form alcohols.

Hydrogenation is a chemical reaction in which unsaturated bonds between carbon atoms are reduced by attachment of a hydrogen atom to each carbon. ... In organic chemistry, an electrophilic addition reaction is an addition reaction where in chemical compound a pi bond is removed by the creation of two new covalent bonds. ... In chemistry, hydration is the condition of being combined with water. ...

Addition of halogens

These occur between alkenes and electrophiles, often halogens. Common reactions include use of bromine water to titrate against a sample to deduce the number of double bonds present. For example, ethylene + bromine → 1,2-dibromoethane: Ethylene (or IUPAC name ethene) is the chemical compound with the formula CH2CH2. ... General Name, Symbol, Number bromine, Br, 35 Chemical series halogens Group, Period, Block 17, 4, p Appearance gas/liquid: red-brown solid: metallic luster Atomic mass 79. ... 1,2-Dibromoethane is a manufactured chemical. ...

C₂H₄ + Br₂ → BrCH₂CH₂Br

This takes the form of 3 main steps shown below^[1];

1. Forming of a π-complex

   The electrophilic Br-Br molecule interacts with electron-rich alkene molecure to form a π-complex 1.

2. Forming of a three-membered bromonium ion

   The alkene is working as an electron donor and bromine as an electrophile. The three-membered bromonium ion 2 consisted with two carbon atoms and a bromine atom forms with a release of Br⁻.

3. Attacking of bromide ion

   The bromonium ion is opened by the attack of Br⁻ from the back side. This yields the vicinal dibromide with an anti-periplanar configulation. When other nucleofiles such as water or alcohol are exsiting, these may attack 2 to give an alcohol or an ether.

This proccess is called Ad_E2 mechanism. Iodine (I₂), chlorine (Cl₂), sulfenyl ion (RS⁺), marcury cation (Hg²⁺), and dichlorocarbene (:CCl₂) also react through similar pathways. The direct convertion of 1 to 3 will appear when the Br⁻ is large excess in the reaction medium. A β-bromo carbenium ion intermediate may be predominant insted of 3 if the alkene has a cation-stabilizing substituent like phenyl group. There is an example of the isolation of the bromonium ion 2.^[2] Image File history File links Download high-resolution version (1241x325, 5 KB) Description: Mechanism for electrophilic addition of Bromine to alkenes. ...

Addition of hydrogen halides

Hydrogen harides such as hydrogen chloride (HCl) adds to alkenes to give alkyl halide. For exmaple, the reaction of HCl with ethylene furnishes chloroethane. The reaction proceeds with a cation intermediate, being different from the above halogen addition. An example shown below:

1. Proton (H⁺) adds (by working as an electrophile) to one of the carbon atoms on the alkene to form cation 1.
2. Chloride ion (Cl⁻) combines with the cation 1 to form the adducts 2 and 3.

In this manner, the stereoselectivity of the product, that is, from which side Cl⁻ will atack relies on the types of alkenes applied and conditions of the reaction. At least, which of the two carbon atoms will be atacked by H⁺ is usually decided by Markovnikov's rule. Thus, H⁺ atacks the carbon atom which carries the less number of substituents so as to the more stabilized carbocation (with the more stabilizing substituents) will form. Image File history File links Download high-resolution version (1186x265, 4 KB) Description: Mechanism for electrophilic addition of HCl to alkenes. ... In chemistry, Markovnikovs rule is an observation based on Zaitsevs rule. ...

This process is called A-S_E2 mechanism. Hydrogen fluoride (HF) and hydrogen iodide (HI) react with alkenes similary and Markovnikov-type products will be given. Hydrogen bromide (HBr) also takes this pathway, but sometimes a radical process competes and a mixture of isomers may form.

Hydration

One of the more complex reactions utilises sulfuric acid as a catalyst. This reaction occurs in a similar way to the addition reaction but has an extra step in which the OSO₃H group is replaced by an OH group, forming an alcohol: Sulfuric acid (British English: sulphuric acid), H2SO4, is a strong mineral acid. ... It has been suggested that this article or section be merged into Catalysis. ...

C₂H₄ + H₂O → C₂H₅OH

As you can see the H₂SO₄ does not take part in the overall reaction, however it does take part but remains unchanged so is clasified as a catalyst.

This is the reaction in more detail:

1. The H-OSO₃H molecule has a δ+ charge on the initial H atom, this is attracted to and reacts with the double bond in the same way as before.
2. The remaining (negatively charged) ⁻OSO₃H ion then attaches to the carbocation. Forming ethyl hydrogensulphate (upper way on the above scheme).
3. When water (H₂O) is added and the mixture headed ethanol is produced (C₂H₅OH) is produced, the "spare" hydrogen atom from the water goes into "replacing" the "lost" hydrogen and thus reproduces sulfuric acid. Another pathway in which water molecure combines directly to the intermediate carbocation (lower way) is also possible. This pathway become predominant when aqueous sulfuric acid is used.

Overall this process adds a molecule of water to a molecule of ethene. Image File history File links Download high-resolution version (1761x435, 16 KB) File links The following pages on the English Wikipedia link to this file (pages on other projects are not listed): Electrophile ...

This is an important reaction in industry as it produces ethanol, which is the alcohol having various purposes including fuels and starting material for other chemicals. Ethanol, also known as ethyl alcohol or grain alcohol, is a flammable, colorless, mildly toxic chemical compound with a distinctive perfume-like odor, and is the alcohol found in alcoholic beverages. ...

See also

• Nucleophile