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Hexamethylphosphoramide

 

 
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Hexamethylphosphoramide
 
 
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Hexamethylphosphoramide, often abbreviated HMPA, is an organophosphorus compound having the formula
Chemical formula

A chemical formula is a way of expressing information about the atoms that constitute a particular chemical compound, and how the relationship between those atoms changes in chemical reactions....
 [(CH3)2N]3PO. This colorless liquid is a useful polar aprotic solvent and additive in organic synthesis
Organic synthesis

Organic synthesis is a special branch of chemical synthesis and is concerned with the construction of organic compounds via organic reactions. Organic_chemistry molecules can often contain a higher level of complexity compared to purely Inorganic_chemistry compounds, so the synthesis of organic compounds has developed into one of the most im...
.

is the oxide of the highly basic tertiary phosphine hexamethylphosphorous triamide (HMPT), P(NMe2)3. Like other phosphine oxides (e.g., triphenylphosphine oxide
Triphenylphosphine oxide

Triphenylphosphine oxide is the chemical compound with the formula OP3. Often chemists abbreviate the formula by writing Ph3PO or PPh3O ....
), 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
Nitrogen

Nitrogen is a chemical element that has the symbol N and atomic number 7 and atomic mass 14.00674?. Elemental nitrogen is a colorless, odorless, tasteless and mostly inert diatomic gas at standard conditions, constituting 78% by volume of Earth's atmosphere....
-phosphorus bond typically are degraded by hydrochloric acid
Hydrochloric acid

Hydrochloric acid is the solution of hydrogen chloride in water. It is a highly corrosive, strong acid mineral acid and has major industrial uses....
 to form a protonated amine and phosphate.

is used as a solvent
Solvent

A solvent is a liquid or gas that dissolves a solid, liquid, or gaseous solute, resulting in a solution.The most common solvent in everyday life is water....
 for polymer
Polymer

A polymer is a large molecule composed of repeating structural units typically connected by covalent chemical bonds. While polymer in popular usage suggests plastic, the term actually refers to a large class of natural and synthetic materials with a variety of properties....
s, gases, and organometallic compounds.






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Hexamethylphosphoramide, often abbreviated HMPA, is an organophosphorus compound having the formula
Chemical formula

A chemical formula is a way of expressing information about the atoms that constitute a particular chemical compound, and how the relationship between those atoms changes in chemical reactions....
 [(CH3)2N]3PO. This colorless liquid is a useful polar aprotic solvent and additive in organic synthesis
Organic synthesis

Organic synthesis is a special branch of chemical synthesis and is concerned with the construction of organic compounds via organic reactions. Organic_chemistry molecules can often contain a higher level of complexity compared to purely Inorganic_chemistry compounds, so the synthesis of organic compounds has developed into one of the most im...
.

Structure and reactivity

HMPA is the oxide of the highly basic tertiary phosphine hexamethylphosphorous triamide (HMPT), P(NMe2)3. Like other phosphine oxides (e.g., triphenylphosphine oxide
Triphenylphosphine oxide

Triphenylphosphine oxide is the chemical compound with the formula OP3. Often chemists abbreviate the formula by writing Ph3PO or PPh3O ....
), 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
Nitrogen

Nitrogen is a chemical element that has the symbol N and atomic number 7 and atomic mass 14.00674?. Elemental nitrogen is a colorless, odorless, tasteless and mostly inert diatomic gas at standard conditions, constituting 78% by volume of Earth's atmosphere....
-phosphorus bond typically are degraded by hydrochloric acid
Hydrochloric acid

Hydrochloric acid is the solution of hydrogen chloride in water. It is a highly corrosive, strong acid mineral acid and has major industrial uses....
 to form a protonated amine and phosphate.

Applications

HMPA is used as a solvent
Solvent

A solvent is a liquid or gas that dissolves a solid, liquid, or gaseous solute, resulting in a solution.The most common solvent in everyday life is water....
 for polymer
Polymer

A polymer is a large molecule composed of repeating structural units typically connected by covalent chemical bonds. While polymer in popular usage suggests plastic, the term actually refers to a large class of natural and synthetic materials with a variety of properties....
s, gases, and organometallic compounds. It usefully improves the selectivity of lithiation reactions, because it breaks up the oligomers of lithium
Lithium

Lithium is a chemical element with the symbol Li and atomic number 3. It is a soft alkali metal with a silver-white color. Under standard conditions for temperature and pressure, it is the lightest metal and the least dense solid element....
 bases such as butyllithium. Because HMPA solvates cations so well, while not solvating anions, it accelerates some difficult SN2 reactions. The basic oxygen
Oxygen

Oxygen no O2 produced; 2) O2 produced, but absorbed in oceans & seabed rock; 3) O2 starts to gas out of the oceans, but is absorbed by land surfaces and formation of ozone layer; 4-5) O2 sinks filled and the gas accumulates]]...
 atom in HMPA coordinates strongly to Li+. A molybdenum
Molybdenum

Molybdenum , is a Group 6 element chemical element with the symbol Mo and atomic number 42. It has the List of elements by melting point melting point of any element....
 peroxide
Peroxide

A peroxide is a compound containing an oxygen-oxygen chemical bond. The simplest stable peroxide is hydrogen peroxide. Superoxides, dioxygenyls, ozones and ozonides compound are considered separately....
 complex of HMPA is used as an oxidant in organic synthesis.

Alternative reagents

Dimethyl sulfoxide
Dimethyl sulfoxide

Dimethyl sulfoxide is the chemical compound with the chemical formula 2SO. It was first synthesized in 1866 by the Russian scientist Alexander Saytzeff, who reported his findings in a German chemistry journal in 1867....
 can often be used in place of HMPA as a solvent. Both are strong hydrogen bond
Hydrogen bond

A hydrogen bond is the attractive force between one electronegative atom and a hydrogen covalently bonded to another electronegative atom. It results from a dipole-dipole force with a hydrogen atom bonded to nitrogen, oxygen or fluorine ....
 acceptors, and their oxygen atoms bind metal cations. Other alternatives to HMPA include the tetraalkylurea
Urea

Urea is an organic compound with the chemical formula 2carbonoxygen.Urea is also known by the International Nonproprietary Name carbamide, as established by the World Health Organization....
s and the cyclic alkylurea
Urea

Urea is an organic compound with the chemical formula 2carbonoxygen.Urea is also known by the International Nonproprietary Name carbamide, as established by the World Health Organization....
s like DMPU
DMPU

1,3-Dimethyl-3,4,5,6-tetrahydro-2-pyrimidinone is a cyclic urea sometimes used as a polar, aprotic organic solvent. In 1985, Dieter Seebach showed that it is possible to substitute the relatively toxic hexamethylphosphoramide with DMPU....
.

Toxicity

HMPA is only mildly toxic but has been shown to cause nasal cancers in rats. HMPA can be degraded to less toxic compounds by the action of hydrochloric acid
Hydrochloric acid

Hydrochloric acid is the solution of hydrogen chloride in water. It is a highly corrosive, strong acid mineral acid and has major industrial uses....
.

External links

  • Merck Index, 12th Edition, 4761.