Diethylphosphite
Chemical compound
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Preferred IUPAC name
Diethyl phosphonate
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Other names
diethyl phosphonite; DEP; Phosphonic acid, diethyl ester
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Identifiers | |
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3D model (
JSmol
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4-01-00-01329 | |
ChemSpider | |
ECHA InfoCard | 100.010.992 |
PubChem
CID
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UNII | |
CompTox Dashboard
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EPA
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Properties | |
C 4 H 11 O 3 P | |
Molar mass | 138.103 g·mol −1 |
Appearance | colorless liquid |
Density | 1.072 g/cm 3 |
Boiling point | 50-51 °C at 2 mm Hg |
Except where otherwise noted, data are given for materials in their
standard state
(at 25
°C [77
°F], 100
kPa).
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Diethyl phosphite is the organophosphorus compound with the formula (C 2 H 5 O) 2 P(O)H. It is a popular reagent for generating other organophosphorus compounds, exploiting the high reactivity of the P-H bond. Diethyl phosphite is a colorless liquid. [1] The molecule is tetrahedral .
Synthesis and properties
The compound was probably prepared in the 1850s by combining phosphorus trichloride and ethanol, but intentional preparations came later. It arises as follows: [2]
- PCl 3 + 3 C 2 H 5 OH → (C 2 H 5 O) 2 P(O)H + 2 HCl + C 2 H 5 Cl
Under similar conditions but in the presence of base, triethyl phosphite results: [3]
- PCl 3 + 3 EtOH + 3 R 3 N → P(OEt) 3 + 3 R 3 NH + 3 Cl −
Many analogues of diethyl phosphite can be prepared. [4] [5] Despite being named as a phosphite the compound exists overwhelmingly in its phosphonate form, (C 2 H 5 O) 2 P(O)H , a property it shares with its parent acid phosphorous acid . Nonetheless many of its reactions appear to proceed via the minor phosphorus(III) tautomer . [6]
- (C 2 H 5 O) 2 P III (OH) ⇌ (C 2 H 5 O) 2 P V (O)H, K = 15 x 10 6 (25°C, aqueous) [7]
Reactions
Hydrolysis and alcoholysis
Diethyl phosphite hydrolyzes to give phosphorous acid. Hydrogen chloride accelerates this conversion.: [2]
Diethyl phosphite undergoes transesterification upon treating with an alcohol. For alcohols of high boiling points, the conversion can be driven by removal of ethanol: [8]
- (C 2 H 5 O) 2 P(O)H + 2 ROH → (RO) 2 P(O)H + 2 C 2 H 5 OH
Similarly amines can displace ethoxide: [9]
- (C 2 H 5 O) 2 P(O)H + RNH 2 → (C 2 H 5 O)(RN(H)P(O)H + C 2 H 5 OH
P-alkylation
Diethyl phosphite undergoes deprotonation with potassium tert -butoxide . This reactivity allows alkylation at phosphorus: [10]
- (C 2 H 5 O) 2 P(O)H + KO t Bu → (C 2 H 5 O) 2 P(O)K + HO t Bu
- (C 2 H 5 O) 2 P(O)K + RBr → (C 2 H 5 O) 2 P(O)R + KBr
For converting aryl halides, palladium-catalysis can be employed. [1] The C-P coupling process is reminiscent of the Buchwald-Hartwig amination .
Reaction of diethyl phosphite with Grignard reagents results in initial deprotonation followed by displacement of the ethoxy groups . [11] [12] This reactivity provides a route to secondary phosphine oxides, such as dimethylphosphine oxide as shown in the following pair of idealized equations:
- (C 2 H 5 O) 2 P(O)H + CH 3 MgBr → (C 2 H 5 O) 2 P(O)MgBr + CH 4
- (C 2 H 5 O) 2 P(O)MgBr + 2 CH 3 MgBr → (CH 3 ) 2 P(O)MgBr + 2 MgBr(OC 2 H 5 )
- (CH 3 ) 2 P(O)MgBr + H 2 O → (CH 3 ) 2 P(O)H + MgBr(OH)
Hydrophosphonylation
Diethyl phosphite can add across unsaturated groups via a hydrophosphonylation reaction. For example, it adds to aldehydes in a manner similar to the Abramov reaction :
- (C 2 H 5 O) 2 P(O)H + RCHO → (C 2 H 5 O) 2 P(O)CH(OH)R
It can also add to imines in the Pudovik reaction and Kabachnik–Fields reaction , [13] in both cases forming aminophosphonates
See also
References
- 1 2 Green, Kenneth (2001). "Diethyl Phosphonite". Encyclopedia of Reagents for Organic Synthesis . doi : 10.1002/047084289X.rd211 . ISBN 0471936235 .
-
1
2
Malowan, J. E. (1953).
Diethyl Phosphite
. pp.
58–60.
doi
:
10.1002/9780470132357.ch19
.
ISBN
9780470132357
.
{{ cite book }}
:| journal=
ignored ( help ) - ↑ Ford-Moore, A. H.; Perry, B. J. (1951). "Triethyl Phosphite". Org. Synth . 31 : 111. doi : 10.15227/orgsyn.031.0111 .
- ↑ Pedrosa, Leandro (March 20, 2011). "Esterification of Phosphorus Trichloride with Alcohols; Diisopropyl phosphonate" . ChemSpider Synthetic Pages . Royal Society of Chemistry . SyntheticPage 488. doi : 10.1039/SP488 . Retrieved July 10, 2017 .
- ↑ Fakhraian, H.; Mirzaei, A. (2004). "Reconsideration of the Base-Free Batch-Wise Esterification of Phosphorus Trichloride with Alcohols". Org. Process Res. Dev. 8 (3): 401–404. doi : 10.1021/op049958v .
- ↑ Doak, G. O.; Freedman, Leon D. (1961). "The Structure and Properties of the Dialkyl Phosphonates". Chem. Rev. 61 (1): 31–44. doi : 10.1021/cr60209a002 .
- ↑ Guthrie, J. Peter (1979). "Tautomerization Equilibria for Phosphorous Acid and its Ethyl Esters, Free Energies of Formation of Phosphorous and Phosphonic Acids and their Ethyl Esters, and p Ka Values for Ionization of the P—H Bond in Phosphonic Acid and Phosphonic Esters" . Canadian Journal of Chemistry . 57 (2): 236–239. doi : 10.1139/v79-039 .
-
↑
Malowan, John E. (1953). "Dioctyl phosphite".
Inorganic Syntheses
. pp.
61–62.
doi
:
10.1002/9780470132357.ch20
.
ISBN
9780470132357
.
{{ cite book }}
:| journal=
ignored ( help ) -
↑
John M. Read, Yu-Pu Wang, Rick L. Danheiser (2015).
"Synthesis of Phosphoryl Ynamides by Copper-Catalyzed Alkynylation of Phosphoramidates. Preparation of Diethyl Benzyl(oct-1-yn-1-yl)phosphoramidate"
.
Org. Synth
.
92
: 156.
doi
:
10.15227/orgsyn.092.0156
.
{{ cite journal }}
: CS1 maint: multiple names: authors list ( link ) - ↑ Boeckman, Robert K.; Perni, Robert B.; Macdonald, James E.; Thomas, Anthony J. (1988). "6-Diethylphosphonomethyl-2,2-dimethyl-1,3-dioxen-4-one (Phosphonic acid, [ (2,2-dimethyl-4-oxo-4 H -1,3-dioxin-6-yl)methyl ] -, diethyl ester)" . Organic Syntheses . 66 : 194. doi : 10.15227/orgsyn.066.0194 . ; Collective Volume , vol. 8, p. 192
- ↑ Hays, Hugh R. (1968). "Reaction of diethyl phosphonate with methyl and ethyl Grignard reagents". J. Org. Chem. 33 (10): 3690–3694. doi : 10.1021/jo01274a003 .
- ↑ Busacca, Carl A.; Lorenz, Jon C.; Sabila, Paul; Haddad, Nizar; Senanyake, Chris H. (2007). "Synthesis of Electron-Deficient Secondary Phosphine Oxides and Secondary Phosphines: Bis [ 3,5-bis(trifluoromethyl)phenyl ] phosphine Oxide and Bis [ 3,5-bis(trifluoromethyl)phenyl ] phosphine" . Organic Syntheses . 84 : 242. doi : 10.15227/orgsyn.084.0242 .
- ↑ Keglevich, György; Bálint, Erika (1 November 2012). "The Kabachnik–Fields Reaction: Mechanism and Synthetic Use" . Molecules . 17 (11): 12821–12835. doi : 10.3390/molecules171112821 . PMC 6268146 . PMID 23117425 .