Hexamethylphosphoramide
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| Hexamethylphosphoramide | |
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| Chemical name | Hexamethylphosphoramide |
| Other names | Hexametapol HMPA |
| Chemical formula | C6H18N3OP |
| Molecular mass | 179.20 g/mol |
| CAS number | [680-31-9] |
| Density | 1.03 g/cm3 |
| Melting point | 7.20 °C |
| Boiling point | 235 °C |
| SMILES | CN(C)P(=O)(N(C)C)N(C)C |
| Disclaimer and references | |
Hexamethylphosphoramide (abbreviated HMPA) is a colorless organic liquid with the formula [(CH3)2N]3PO. It is used as a polymer solvent, as a selective solvent for gases, stabilizer in polystyrene against thermal degradation, as a laboratory solvent for organometallic and organic reactions, and other applicatons. It has been tested as a fire retardant and as an insect chemosterilant, but there is no known current use of HMPA for these applications. It is useful for improving the selectivity of certain organic reactions, for instance in some deprotonation reactions it is used as an additive to break up the oligomers of lithium bases such as butyl lithium. Also because HMPA solvates cations so well, while not solvating anions it has been used as a solvent for some difficult SN2 reactions where an electrophilic substrate is being reacted with a nucleophile. The basic oxygen atom in HMPA coordinates strongly to lithium cation. A molybdenum peroxide complex of HMPA is used in synthetic chemistry as an oxidant.
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[edit] Alternatives
Many of the reactions which are best conducted in HMPA can also be done using dimethyl sulfoxide in place of the HMPA. Both DMSO and HMPA are very strong hydrogen bond acceptors, also their oxygen atoms are able to bind to metals. Other alternatives such as tetraalkyl ureas have also been used.
[edit] Toxicity
HMPA is reasonably anticipated to be a human carcinogen according to the eleventh edition of the report on carcinogens. HMPA is therefore nicknamed Liquid Cancer by practicing organic chemists, and it is generally unused in pharmaceutical process chemistry.
HMPA can be degraded to less toxic compounds by the action of hydrochloric acid. In phosphorus chemistry it is the case in general that the treatment of a compound containing a nitrogen phosphorus single bond with hydrogen chloride will form a protonated amine and a P-chloro compound. For example if P-dimethylamino-P, P-diphenyl phosphine is treated with hydrogen chloride then P-chloro-P, P-diphenyl phosphine and dimethylamine HCl salt will be obtained.
[edit] Reference
- Merck Index, 12th Edition, 4761.
