Phenylmagnesium bromide
From Wikipedia, the free encyclopedia
| Phenylmagnesium bromide | |
|---|---|
 
OR2 = ether or THF |
|
| General | |
| Systematic name | ? |
| Other names | PMB |
| Molecular formula | C6H5MgBr |
| SMILES | Br[Mg]c1ccccc1 |
| Molar mass | 181.31 g/mol |
| Appearance | Usually a colorless solution in ether or tetrahydrofuran |
| CAS number | [100-58-3] |
| Properties | |
| Density and phase | Solution |
| Solubility in water | Reacts violently |
| Basicity (pKb) | ? |
| Viscosity | ? cP at ?°C |
| Structure | |
| Hazards | |
| MSDS | External MSDS |
| Main hazards | Highly flammable, corrosive, harmful |
| NFPA 704 | |
| Flash point | ?°C |
| R/S statement | R: R12 R14 R15 R20 R22 R35 R41 S: S16 S26 S30 S33 S36 |
| RTECS number | ? |
| Supplementary data page | |
| Structure and properties |
n, εr, etc. |
| Thermodynamic data |
Phase behaviour Solid, liquid, gas |
| Spectral data | UV, IR, NMR, MS |
| Related compounds | |
| Related compounds | ? |
| Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa) Infobox disclaimer and references |
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Phenylmagnesium bromide, with the simplified formula C6H5MgBr, is a 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 "Ph−" phenyl synthon.
Contents |
[edit] Preparation and structure
Phenylmagnesium bromide can be prepared in the laboratory by treating bromobenzene with magnesium metal, usually in the form of ribbon. A polar solvent is required to solvate the magnesium portion of the molecule, hence the use of ether or THF. Protic solvents such as alcohols and water react with phenylmagnesium bromide to give benzene, and halogenated solvents are also incompatible with the synthesis. A small amount of iodine may be used to activate the magnesium by removing the oxide surface.
Although in organic synthesis it is convenient to represent this species as C6H5MgBr, the molecule is more complex as shown in the figure. 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.
[edit] Chemistry
Phenylmagnesium bromide is a strong nucleophile as well as a strong base. It can abstract many labile protons, thus the substrate must be protected where necessary. It often adds to carbonyls, which are electron-deficient, such as in the laboratory synthesis of benzoic acid and triphenylmethanol.
[edit] References
- Oxford University, Phenylmagnesium bromide in ether, Aug 19 2005. Accessed 28 Oct 2006.
