| Phenylmagnesium bromide | |
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Phenylmagnesium bromide dietherate
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bromido(phenyl)magnesium |
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Other names
PMB |
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| Identifiers | |
| CAS number | 100-58-3 |
| Jmol-3D images | Image 1 |
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| Properties | |
| Molecular formula | C6H5MgBr |
| Molar mass | 181.31 g mol−1 |
| Appearance | Colorless crystals |
| Density | 1.14 g cm−3 |
| Solubility in water | Reacts violently |
| Basicity (pKb) | strong base |
| Hazards | |
| MSDS | External MSDS |
| R-phrases | R12 R14 R15 R20 R22 R35 R41 |
| S-phrases | S16 S26 S30 S33 S36 S37 S39 S43 S45 |
| Main hazards | flammable |
| Flash point | −45 °C |
| Related compounds | |
| Related compounds | Phenyllithium Magnesium bromide Methylmagnesium chloride |
| (verify) (what is: /?) Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa) |
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| Infobox references | |
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.
Contents |
Phenylmagnesium bromide is commercially available as solutions of diethyl ether or 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.[1]
Coordinating solvents such as ether or THF, are required to solvate (complex) the magnesium(II) center. The solvent must be aprotic since alcohols 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 201 and 206 pm whereas the Mg–C and Mg–Br distances are 220 pm and 244 pm, respectively.[2]
Phenylmagnesium bromide is a strong nucleophile as well as a strong base. It can abstract even mildly acidic protons, thus the substrate must be protected where necessary. It often adds to carbonyls, such as ketones, aldehydes.[1][3] With carbon dioxide, it reacts to give benzoic acid after an acidic workup.