Greenia reagent is called Grignard reagent for short.It contains magnesium halideOrganometallic compound, because it containsCarbonium anion, therefore belonging toNucleophile, byFrancechemistVictor Grignard (Franç ois Auguste Victor Grignard).Grignard reagents are very useful in organic synthesis.[1]
It was founded by French chemist Greenia in 1901.From organic halogen compounds（Haloalkane, active halogenated aromatics) and magnesium in absolute anhydrous ether to form organic compoundsMagnesium reagent, called "Greenia reagent", referred to as "Grignard reagent".[1]In 1953, the post French chemist Normanfuran(THF) was used as solvent to obtain Grignard reagent.This improvement is called the "Greenia Norman reaction".[1]
Halogenated hydrocarbon and magnesium powder are commonly used inAnhydrous etherorTetrahydrofuran(THF), and the preparation process must be carried out under the condition of absolute anhydrous, carbon dioxide free, ethanol free and other substances with active hydrogen.It is usually represented by the general formula R-Mg-X.Grignard reagent is a kind of active organic synthesis reagent, which can occur many types of reactions, such as coupling, addition, substitution, etc., and has high application value in organic synthesis.[2]
There are two Grignard reagents, 1: chlorobenzenes (benzyl chloride) react with magnesium in the presence of ether (tetrahydrofuran), 2: bromocyclopentane reacts with magnesium (zinc) in the presence of ether (tetrahydrofuran).[3]
nature
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It is called Grignard reagent for short.A type of reagent with the general formula R-Mg-X, where R isAliphatic alkylorAromatic hydrocarbon group, X ishalogen(Cl, Br or I).Usually usedHalohydrocarbonAnd metallic magnesium in anhydrousEtherorTetrahydrofuranIn the production.It is extremely active and can be mixed with compounds with active hydrogen (such as HtwoO. ROH, RC ∨ CH...) Aldehydes, ketones, esters, acyl halides, nitrilesethylene oxide、Haloalkane, carbon dioxidePhosphorus trichloride、Boron trichloride、Silicon tetrachlorideAnd other reactions.It is an important organic synthetic reagent.[4]
structure
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Grignard reagent isCovalent compound, magnesiumatomDirectly connected with carbon to form polaritycovalent bondCarbon is the negative end, so Grignard reagent is extremely strongLewis baseIt can capture protons from water and other Lewis acids, so Grignard reagent cannot contact with water and carbon dioxide. The preparation of Grignard reagent and the reaction initiated by Grignard reagent need to be carried out under the conditions of anhydrous water and air isolation.[5]
preparation
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Grignard reagent cooled at 0 ℃
Grignard reagent is generally composed of halogenated hydrocarbon andMagnesium powderstayAnhydrous etherorTetrahydrofuran(THF).(Halogenated benzene must be reacted in THF) Grignard reagent can form complex with oxygen atom in ether or tetrahydrofuran, and the preparation process must be carried out under the condition of absolute anhydrous, carbon dioxide free, ethanol free and other substances with active hydrogen (such as water, alcohol, ammonia, hydrogen halide, terminal alkyne, etc.).[6]
In active hydrogen or THF: R-Br+Mg → R-Mg-X[1]
Due to the high price of iodoalkane, it is generally synthesized with bromoalkane.Bromoalkane is the halohydrocarbon most commonly used to prepare Grignard reagent. However, because chlorine and bromomethane are both gases, it is inconvenient to use them, and iodomethane is generally used to synthesize methyl magnesium iodide.The temperature and pressure must be controlled when preparing Grignard reagent for chlorobenzene.Allyl and benzyl Grignard reagents will be coupled with unreacted halohydrocarbons after synthesis, so the temperature needs to be strictly controlled.[6]
Preparation method
A 250mL three port flask is equipped with a stirrer, a constant pressure drip funnel and a CaCltwoReturn condenser pipe of drying pipe.Put 2.9g (0.12mol) of magnesium chips into a three necked flask and immerse it in 20mL of anhydrous ether.Under stirring, first drop 5mL of 25% halogenated hydrocarbon ether solution (prepared by 0.12mol halogenated hydrocarbon and anhydrous ether).If the reaction liquid appears cloudy and the temperature rises, the reaction has started.If the above phenomenon does not occur, 1-2 small iodine crystals need to be added and slightly heated.Moments later, the color of iodine began to fade, the solution became turbid, the reaction began, and the heating stopped.Drop the remaining halogenated hydrocarbon solution into the reaction bottle at a rate appropriate to maintain the stable boiling of the reaction solution.After addition, use warm water bath to heat and reflow for about half an hour to make the reaction complete, and then obtain Grignard reagent ether solution.[3][7]
(2) All instruments shall be dried.Both solvents and reagents must be dried.[7-8]
(3) Hot water bath can be used for heating, and open fire cannot be used for heating.[8]
(4) The oxygen in the air will slowly oxidize with Grignard reagent, and the ether solution of Grignard reagent will emit beautiful light in the dark room, which is why.Therefore, Grignard reagent can not be stored for a long time, and it is usually used when it is prepared.[7-8]
Grignard reaction
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Grignard reaction
Green's reagent and some active hydrogen compounds (water, alcohol, acid, etc.), COtwoThe reactions of carbonyl compounds, metal or nonmetal halides, etc. become Greenian reactions.It is often used to prepare hydrocarbons, alcohols, ketones, acids, etc.For example:[1]
Related research
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Chemical Reaction Creation Research Site (WPI-ICReDD) of Hokkaido University, JapanHokkaido UniversityA research team composed of scientific researchers from the Engineering Research Institute and other institutions has developed a simple method for preparing Grignard reagent ("Grignard reagent" for short) without using organic solvents.The research results were recently published in the journal Nature Communications, entitled "Mechanical Synthesis of Magnesium based Carbon Nucleophiles in Air and Their Use in Organic Synthesis".
Grignard reagent, as an important reagent in organic synthesis, is widely used. Its preparation usually needs to be carried out in an anhydrous and oxygen free reaction container. It needs to use high-purity organic solvents and strictly control the temperature. Not only is the preparation process cumbersome, but the organic solvents also produce waste and toxicity.
In order to explore a more simple and efficient preparation method, researchers can easily and efficiently prepare Grignard reagent in a short time by shaking the ball mill from left to right and mechanically stirring, and only adding a small amount of organic solvent.This preparation method can reduce the amount of organic solvent used to about one tenth of the original amount, without the use of high priced and high-purity organic solvents. Moreover, the preparation method is not easily affected by water and oxygen in the reaction vessel, and can be used for a variety of organic synthesis reactions.
This research achievement effectively controls the use of harmful organic solvents in the preparation of Grignard reagent, which can not only reduce the adverse effects of chemicals on the environment, but also help reduce the production costs of chemicals.[9-10]
