HMPA

Hexamethylphosphoramide

Names
IUPAC name Hexamethylphosphoramide
Preferred IUPAC name Hexamethylphosphoric triamide
Other names Hexametapol HMPA Phosphoric tris(dimethylamide)
Identifiers
CAS Number	680-31-9 Y
3D model (Jmol)	Interactive image
ChEBI	CHEBI:24565 Y
ChemSpider	12158 Y
ECHA InfoCard	100.010.595
KEGG	C19250 N
PubChem CID	12679
InChI InChI=1S/C6H18N3OP/c1-7(2)11(10,8(3)4)9(5)6/h1-6H3 Y Key: GNOIPBMMFNIUFM-UHFFFAOYSA-N Y InChI=1/C6H18N3OP/c1-7(2)11(10,8(3)4)9(5)6/h1-6H3 Key: GNOIPBMMFNIUFM-UHFFFAOYAP
SMILES O=P(N(C)C)(N(C)C)N(C)C
Properties
Chemical formula	C6H18N3OP
Molar mass	179.20 g/mol
Appearance	clear, colorless liquid
Odor	aromatic, mild, amine-like
Density	1.03 g/cm3
Melting point	7.20 °C (44.96 °F; 280.35 K)
Boiling point	232.5 °C (450.5 °F; 505.6 K) CRC
Solubility in water	miscible
Vapor pressure	0.03 mmHg (20°C)
Hazards
Main hazards	carcinogen
Safety data sheet	Oxford MSDS
EU classification (DSD)	T
Flash point	104.4 °C (219.9 °F; 377.5 K)
US health exposure limits (NIOSH):
PEL (Permissible)	none
REL (Recommended)	Ca
IDLH (Immediate danger)	Ca [N.D.]
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
N  (what is YN ?)
Infobox references

Hexamethylphosphoramide, often abbreviated HMPA, is a phosphoramide (i.e. an amide of phosphoric acid) with the formula [(CH₃)₂N]₃PO. This colorless liquid is a useful polar aprotic solvent and additive in organic synthesis.

HMPA is the oxide of the highly basic tertiary phosphine hexamethylphosphorous triamide (HMPT), P(NMe₂)₃. Like other phosphine oxides (e.g., triphenylphosphine oxide), the molecule has a tetrahedral core and a P-O bond that is highly polarized, with significant negative charge residing on the oxygen atom.

Compounds containing a nitrogen-phosphorus bond typically are degraded by hydrochloric acid to form a protonated amine and phosphate.

HMPA is a specialty solvent for polymers, gases, and organometallic compounds. It improves the selectivity of lithiation reactions by breaking up the oligomers of lithium bases such as butyllithium. Because HMPA selectively solvates cations, it accelerates otherwise slow S_N2 reactions by generating more "naked" anions. The basic nitrogen centers in HMPA coordinate strongly to Li⁺.

HMPA is a ligand in the useful reagents based on molybdenum peroxide complexes, e.g., MoO(O₂)₂(HMPA)(H₂O) is used as an oxidant in organic synthesis.

Dimethyl sulfoxide can often be used in place of HMPA as a solvent. Both are strong hydrogen bond acceptors, and their oxygen atoms bind metal cations. Other alternatives to HMPA include the tetraalkylureas and the cyclic alkylureas like DMPU.