Hexamethylphosphoramide

Last updated
Hexamethylphosphoramide
HMPA-2D-skeletal.png
Hexamethylphosphoramide-from-xtal-3D-balls.png
Names
Preferred IUPAC name
Hexamethylphosphoric triamide [1]
Other names
  • Hexamethylphosphoramide
  • Hexametapol
  • HMPA
  • Phosphoric tris(dimethylamide) [2]
  • HMPT [3]
Identifiers
3D model (JSmol)
1099903
ChEBI
ChEMBL
ChemSpider
ECHA InfoCard 100.010.595 OOjs UI icon edit-ltr-progressive.svg
EC Number
  • 211-653-8
3259
KEGG
PubChem CID
RTECS number
  • TD0875000
UNII
UN number 2810 3082
  • InChI=1S/C6H18N3OP/c1-7(2)11(10,8(3)4)9(5)6/h1-6H3 Yes check.svgY
    Key: GNOIPBMMFNIUFM-UHFFFAOYSA-N Yes check.svgY
  • InChI=1/C6H18N3OP/c1-7(2)11(10,8(3)4)9(5)6/h1-6H3
    Key: GNOIPBMMFNIUFM-UHFFFAOYAP
  • O=P(N(C)C)(N(C)C)N(C)C
Properties
C6H18N3OP
Molar mass 179.20 g/mol
Appearanceclear, colorless liquid [4]
Odor aromatic, mild, amine-like [4]
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 [5]
miscible [4]
Vapor pressure 0.03 mmHg (4.0 Pa) at 20 °C [4]
Hazards
Occupational safety and health (OHS/OSH):
Main hazards
Suspected Carcinogen [4]
GHS labelling:
GHS-pictogram-silhouette.svg
Danger
H340, H350
P201, P202, P281, P308+P313, P405, P501
Flash point 104.4 °C (219.9 °F; 377.5 K)
NIOSH (US health exposure limits):
PEL (Permissible)
none [4]
REL (Recommended)
Ca [4]
IDLH (Immediate danger)
Ca [N.D.] [4]
Safety data sheet (SDS) Oxford MSDS
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
X mark.svgN  verify  (what is  Yes check.svgYX mark.svgN ?)

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

Contents

Structure and reactivity

HMPA is the oxide tris(dimethylamino)phosphine, P(NMe2)3. Like other phosphine oxides (such as 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.

It dissolves alkali metal salts [6] and alkali metals, forming blue solutions which are stable for a few hours. Solvated electrons are present in these blue solutions. [7]

Applications

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 SN2 reactions by generating more bare anions. The basic nitrogen centers in HMPA coordinate strongly to Li+. [8]

HMPA is a ligand in the useful reagents based on molybdenum peroxide complexes, for example, MoO(O2)2(HMPA)(H2O) is used as an oxidant in organic synthesis. [9]

Alternative reagents

Dimethyl sulfoxide can often be used in place of HMPA as a cosolvent. Both are strong hydrogen bond acceptors, and their oxygen atoms bind metal cations. Other alternatives to HMPA include the N,N′-tetraalkylureas DMPU (dimethylpropyleneurea) [10] [11] or DMI (1,3-dimethyl-2-imidazolidinone). [12] Tripyrrolidinophosphoric acid triamide (TPPA) has been reported to be a good substitute reagent for HMPA in reductions with samarium diiodide [13] and as a Lewis base additive to many reactions involving samarium ketyls. [14]

Toxicity

HMPA is only mildly toxic but has been shown to cause cancer in rats. [8] HMPA can be degraded by the action of hydrochloric acid.

Related Research Articles

<span class="mw-page-title-main">Alkylation</span> Transfer of an alkyl group from one molecule to another

Alkylation is a chemical reaction that entails transfer of an alkyl group. The alkyl group may be transferred as an alkyl carbocation, a free radical, a carbanion, or a carbene. Alkylating agents are reagents for effecting alkylation. Alkyl groups can also be removed in a process known as dealkylation. Alkylating agents are often classified according to their nucleophilic or electrophilic character. In oil refining contexts, alkylation refers to a particular alkylation of isobutane with olefins. For upgrading of petroleum, alkylation produces a premium blending stock for gasoline. In medicine, alkylation of DNA is used in chemotherapy to damage the DNA of cancer cells. Alkylation is accomplished with the class of drugs called alkylating antineoplastic agents.

<span class="mw-page-title-main">Organolithium reagent</span> Chemical compounds containing C–Li bonds

In organometallic chemistry, organolithium reagents are chemical compounds that contain carbon–lithium (C–Li) bonds. These reagents are important in organic synthesis, and are frequently used to transfer the organic group or the lithium atom to the substrates in synthetic steps, through nucleophilic addition or simple deprotonation. Organolithium reagents are used in industry as an initiator for anionic polymerization, which leads to the production of various elastomers. They have also been applied in asymmetric synthesis in the pharmaceutical industry. Due to the large difference in electronegativity between the carbon atom and the lithium atom, the C−Li bond is highly ionic. Owing to the polar nature of the C−Li bond, organolithium reagents are good nucleophiles and strong bases. For laboratory organic synthesis, many organolithium reagents are commercially available in solution form. These reagents are highly reactive, and are sometimes pyrophoric.

<span class="mw-page-title-main">Samarium(II) iodide</span> Chemical compound

Samarium(II) iodide is an inorganic compound with the formula SmI2. When employed as a solution for organic synthesis, it is known as Kagan's reagent. SmI2 is a green solid and solutions are green as well. It is a strong one-electron reducing agent that is used in organic synthesis.

<span class="mw-page-title-main">Sodium borohydride</span> Chemical compound

Sodium borohydride, also known as sodium tetrahydridoborate and sodium tetrahydroborate, is an inorganic compound with the formula NaBH4. It is a white crystalline solid, usually encountered as an aqueous basic solution. Sodium borohydride is a reducing agent that finds application in papermaking and dye industries. It is also used as a reagent in organic synthesis.

<span class="mw-page-title-main">Chromium(III) chloride</span> Chemical compound

Chromium(III) chloride (also called chromic chloride) is an inorganic chemical compound with the chemical formula CrCl3. It forms several hydrates with the formula CrCl3·nH2O, among which are hydrates where n can be 5 (chromium(III) chloride pentahydrate CrCl3·5H2O) or 6 (chromium(III) chloride hexahydrate CrCl3·6H2O). The anhydrous compound with the formula CrCl3 are violet crystals, while the most common form of the chromium(III) chloride are the dark green crystals of hexahydrate, CrCl3·6H2O. Chromium chlorides find use as catalysts and as precursors to dyes for wool.

<span class="mw-page-title-main">1,10-Phenanthroline</span> Heterocyclic organic compound

1,10-Phenanthroline (phen) is a heterocyclic organic compound. It is a white solid that is soluble in organic solvents. The 1,10 refer to the location of the nitrogen atoms that replace CH's in the hydrocarbon called phenanthrene.

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<span class="mw-page-title-main">1,4-Benzoquinone</span> Chemical compound

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Potassium <i>tert</i>-butoxide Chemical compound

Potassium tert-butoxide (or potassium t-butoxide) is a chemical compound with the formula [(CH3)3COK]n (abbr. KOtBu). This colourless solid is a strong base (pKa of conjugate acid around 17), which is useful in organic synthesis. The compound is often depicted as a salt, and it often behaves as such, but its ionization depends on the solvent.

A solvated electron is a free electron in a solution, in which it behaves like an anion. An electron's being solvated in a solution means it is bound by the solution. The notation for a solvated electron in formulas of chemical reactions is "e". Often, discussions of solvated electrons focus on their solutions in ammonia, which are stable for days, but solvated electrons also occur in water and many other solvents – in fact, in any solvent that mediates outer-sphere electron transfer. The solvated electron is responsible for a great deal of radiation chemistry.

<span class="mw-page-title-main">Disodium tetracarbonylferrate</span> Chemical compound

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<span class="mw-page-title-main">DMPU</span> Chemical compound

N,N′-Dimethylpropyleneurea (DMPU) is a cyclic urea sometimes used as a polar, aprotic organic solvent. In 1985, Dieter Seebach showed that it is possible to replace the suspected carcinogen hexamethylphosphoramide (HMPA) with DMPU.

<span class="mw-page-title-main">Diphosphorus tetraiodide</span> Chemical compound

Diphosphorus tetraiodide is an orange crystalline solid with the formula P2I4. It has been used as a reducing agent in organic chemistry. It is a rare example of a compound with phosphorus in the +2 oxidation state, and can be classified as a subhalide of phosphorus. It is the most stable of the diphosphorus tetrahalides.

<span class="mw-page-title-main">Diethylaluminium chloride</span> Chemical compound

Diethylaluminium chloride, abbreviated DEAC, is an organoaluminium compound. Although usually given the chemical formula (C2H5)2AlCl, it exists as a dimer, [(C2H5)2AlCl]2 It is a precursor to Ziegler-Natta catalysts employed for the production of polyolefins. The compound is also a Lewis acid, useful in organic synthesis. The compound is a colorless waxy solid, but is usually handled as a solution in hydrocarbon solvents. It is highly reactive, even pyrophoric.

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<span class="mw-page-title-main">Reductions with samarium(II) iodide</span>

Reductions with samarium(II) iodide involve the conversion of various classes of organic compounds into reduced products through the action of samarium(II) iodide, a mild one-electron reducing agent.

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<span class="mw-page-title-main">Tetramethylurea</span> Chemical compound

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<span class="mw-page-title-main">Samarium(II) bromide</span> Chemical compound

Samarium(II) bromide is an inorganic compound with the chemical formula SmBr
2
. It is a brown solid that is insoluble in most solvents but degrades readily in air.

<span class="mw-page-title-main">MoOPH</span> Chemical compound

MoOPH, also known as oxodiperoxymolybdenum(pyridine)-(hexamethylphosphoric triamide), is a reagent used in organic synthesis. It contains a molybdenum(VI) center with multiple oxygen ligands, coordinated with pyridine and HMPA ligands. It is an electrophilic source of oxygen that reacts with enolates and related structures, and thus can be used for alpha-hydroxylation of carbonyl-containing compounds. Other reagents used for alpha-hydroxylation via enol or enolate structures include Davis oxaziridine, oxygen, and various peroxyacids. This reagent was first utilized by Edwin Vedejs as an efficient alpha-hydroxylating agent in 1974 and an effective preparative procedure was later published in 1978.

References

  1. "Front Matter". Nomenclature of Organic Chemistry: IUPAC Recommendations and Preferred Names 2013 (Blue Book). Cambridge: The Royal Society of Chemistry. 2014. pp. P001–P004. doi:10.1039/9781849733069-FP001. ISBN   978-0-85404-182-4.
  2. Not recommended: see Blue Book reference.
  3. This name is also used to refer to tris(dimethylamino)phosphine
  4. 1 2 3 4 5 6 7 8 NIOSH Pocket Guide to Chemical Hazards. "#0321". National Institute for Occupational Safety and Health (NIOSH).
  5. Haynes, William M. (2010). Handbook of Chemistry and Physics (91 ed.). Boca Raton, Florida, USA: CRC Press. p. 3-280. ISBN   978-1-43982077-3.
  6. Luehrs, Dean C.; Kohut, John P. (1974). "Hexamethylphosphoramide solvates of alkali metal salts". Journal of Inorganic and Nuclear Chemistry. 36 (7): 1459–1460. doi:10.1016/0022-1902(74)80605-6.
  7. Gremmo, Norberto; Randles, John E. B. (1974). "Solvated electrons in hexamethylphosphoramide. Part 1.—Conductivity of solutions of alkali metals". Journal of the Chemical Society, Faraday Transactions 1: Physical Chemistry in Condensed Phases. 70: 1480–1487. doi:10.1039/F19747001480.
  8. 1 2 Dykstra, R. R. (2001). "Hexamethylphosphoric Triamide". Hexamethylphosphoric Triamide. Encyclopedia of Reagents for Organic Synthesis. New York, NY: John Wiley & Sons. doi:10.1002/047084289X.rh020. ISBN   978-0471936237.
  9. Dickman, Michael H.; Pope, Michael T. (1994). "Peroxo and Superoxo Complexes of Chromium, Molybdenum, and Tungsten". Chemical Reviews. 94 (3): 569–584. doi:10.1021/cr00027a002.
  10. Mukhopadhyay, T.; Seebach, D. (1982). "Substitution of HMPT by the Cyclic Urea DMPU as a Cosolvent for highly Reactive Nucleophiles and Bases". Helvetica Chimica Acta . 65 (1): 385–391. doi:10.1002/hlca.19820650141.
  11. Beck, A. K.; Seebach, D. (2001). "N,N′-Dimethylpropyleneurea". N,N′-Dimethylpropyleneurea. Encyclopedia of Reagents for Organic Synthesis. New York: John Wiley & Sons. doi:10.1002/047084289X.rd366. ISBN   978-0471936237.
  12. Lo, Chi-Chu; Chao, Pei-Min (1990). "Replacement of carcinogenic solvent HMPA by DMI in insect sex pheromone synthesis". Journal of Chemical Ecology. 16 (12): 3245–3253. doi:10.1007/BF00982095. PMID   24263426. S2CID   9859086.
  13. McDonald, Chriss E.; Ramsey, Jeremy D.; Sampsell, David G.; Butler, Julie A.; Cecchini, Michael R. (2010). "Tripyrrolidinophosphoric Acid Triamide as an Activator in Samarium Diiodide Reductions". Organic Letters. 12 (22): 5178–5181. doi:10.1021/ol102040s. PMID   20979412.
  14. Berndt, Mathias; Hölemann, Alexandra; Niermann, André; Bentz, Christoph; Zimmer, Reinhold; Reissig, Hans-Ulrich (2012). "Replacement of HMPA in Samarium Diiodide Promoted Cyclizations and Reactions of Organolithium Compounds". European Journal of Organic Chemistry. 2012 (7): 1299–1302. doi:10.1002/ejoc.201101830. ISSN   1099-0690. Tripyrrolidinophosphoric acid triamide (TPPA) can replace carcinogenic HMPA as a Lewis basic additive in many reactions involving samarium ketyls. In most cases, yields and selectivities of cyclizations of (het)aryl, alkenyl, and alkynyl ketones are similar.