Phenylmagnesium bromide: Difference between revisions

| verifiedrevid = 293939474

| Name = Phenylmagnesium bromide

| ImageFile1=PhMrBrL2.png

| ImageSize1 = 150px

| ImageName1 = Phenylmagnesium bromide, OR₂ = ether or THF

| ImageFile2 = Phenylmagnesium-bromide-dietherate-from-1964-xtal-3D-balls.png

| ImageSize2 = 150px

| ImageName2 = PhMgBr THF adduct

| IUPACName = bromido(phenyl)magnesium

| OtherNames = PMB

| Section1 = {{Chembox Identifiers

| SMILES = Br[Mg]c1ccccc1

| CASNo_Ref = {{cascite|correct|CAS}}

| RTECS =

| Section2 = {{Chembox Properties

| Formula = C₆H₅MgBr

| MolarMass = 181.31 g/mol

| Appearance = Colorless crystals

| Density = 1.14 g/cm³

| Solubility = Reacts violently

| pKb = strong base

| Section7 = {{Chembox Hazards

| ExternalMSDS = [http://physchem.ox.ac.uk/MSDS/PH/phenylmagnesium_bromide_in_ether.html External MSDS]

| MainHazards = flammable

| FlashPt = -45°C

| RPhrases = {{R12}} {{R14}} {{R15}} {{R20}} {{R22}} {{R35}} {{R41}}

| SPhrases = {{S16}} {{S26}} {{S30}} {{S33}} {{S36}}<br />{{S37}} {{S39}} {{S43}} {{S45}}

| Section8 = {{Chembox Related

| OtherCpds = [[Phenyllithium]]<br />[[Magnesium bromide]]<br /> [[Methylmagnesium chloride]]

'''Phenylmagnesium bromide''', with the simplified formula C₆H₅MgBr, is a [[magnesium]]-containing [[organometallic compound]]. It is so commonly used that it is commercially available as a solution in [[diethyl ether]] or [[tetrahydrofuran]] (THF). Phenylmagnesium bromide is a [[Grignard reagent]]. It is often used as a synthetic equivalent for the [[phenyl]] "Ph⁻" [[synthon]].

Phenylmagnesium bromide is commercially available as solutions of [[diethyl ether]] or [[tetrahydrofuran|THF]]. It may be prepared in the laboratory by treating [[bromobenzene]] with [[magnesium]] metal, usually in the form of turnings. A small amount of [[iodine]] may be used to activate the magnesium to initiate the reaction.<ref name = robertson>{{cite web | publisher = [[MiraCosta College]] | author = Donald L. Robertson | date = 2007-01-03 | title = Grignard Synthesis: Synthesis of Benzoic Acid and of Triphenylmethanol | accessdate = 2008-01-25 | url = http://www.miracosta.edu/home/dlr/211exp2.htm}}</ref>

Coordinating solvents such as ether or THF, are required to solvate (complex) the magnesium(II) center. The solvent must be [[aprotic solvent|aprotic]] since [[alcohol]]s and water react with phenylmagnesium bromide to give [[benzene]]. Carbonyl-containing solvents such as acetone and ethyl acetate are incompatible with the reagent.

Although phenylmagnesium bromide is routinely represented as C₆H₅MgBr, the molecule is more complex. The compound invariably forms an [[adduct]] with two OR₂ ligands from the ether or THF solvent. Thus, the Mg is tetrahedral and obeys the [[octet rule]]. The Mg-O distances are 2.01 and 2.06 Å whereas the Mg-C and Mg-Br distances are 2.2 and 2.44 Å, respectively.<ref>{{cite journal | author = Stucky, G. D.; Rundle, R. E. | title = The Structure of Phenylmagnesium Bromide Diethyletherate and the Nature of Grignard Reagents | journal = [[J. Am. Chem. Soc.]] | year = 1963 | volume = 85 | pages = 1002 | doi = 10.1021/ja00890a039}}</ref>

Phenylmagnesium bromide is a strong [[nucleophile]] as well as a strong [[base (chemistry)|base]]. It can abstract even mildly acidic protons, thus the substrate must be protected where necessary. It often adds to [[carbonyl]]s, such as ketones, aldehydes.<ref name = robertson/><ref>{{OrgSynth | author = W. E. Bachmann and H. P. Hetzner | title = Triphenylcarbinol | collvol = 3 | collvolpages = 839 | prep = cv3p0839}}</ref> With carbon dioxide, it reacts to give [[benzoic acid]] after an acidic workup.

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[[de:Phenylmagnesiumbromid]]

[[nl:Fenylmagnesiumbromide]]

[[pt:Brometo de fenilmagnésio]]