Hexamethylphosphoramide , often abbreviated HMPA , is a phosphoramide (an amide of phosphoric acid ) with the formula [(CH 3 ) 2 N] 3 PO. This colorless liquid is used as a solvent in organic synthesis .
5-512: HMPA is the oxide of tris(dimethylamino)phosphine , P(NMe 2 ) 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 and alkali metals, forming blue solutions which are stable for
10-531: A few hours. Solvated electrons are present in these blue solutions. 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 N 2 reactions by generating more bare anions. The basic nitrogen centers in HMPA coordinate strongly to Li. HMPA
15-446: A good substitute reagent for HMPA in reductions with samarium diiodide and as a Lewis base additive to many reactions involving samarium ketyls . HMPA is only mildly toxic but has been shown to cause cancer in rats. HMPA can be degraded by the action of hydrochloric acid . Tris(dimethylamino)phosphine Tris(dimethylamino)phosphine is an organophosphorus compound with the formula P(NMe 2 ) 3 (Me = methyl ). It
20-430: Is a colorless oil at room temperature, and is one of the most common aminophosphines . Its structure has been determined by X-ray crystallography . Tris(dimethylamino)phosphine acts as a base. It reacts with oxygen to give hexamethylphosphoramide , O=P(NMe 2 ) 3 , and with sulfur to give the corresponding compound hexamethylthiophosphoramide, S=P(NMe 2 ) 3 . It can also act as a ligand, forming complexes with
25-539: Is a ligand in the useful reagents based on molybdenum peroxide complexes, for example, MoO(O 2 ) 2 (HMPA)(H 2 O) is used as an oxidant in organic synthesis. 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) or DMI (1,3-dimethyl-2-imidazolidinone). Tripyrrolidinophosphoric acid triamide (TPPA) has been reported to be
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