Triethyloxonium tetrafluoroborate
| Triethyloxonium tetrafluoroborate | |
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Triethyloxonium tetrafluoroborate |
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| Identifiers | |
| CAS number | 368-39-8  |
| PubChem | 2723982 |
| ChemSpider | 2006158  |
| UN number | 3261 |
| Beilstein Reference | 3598090 |
| Jmol-3D images | Image 1 |
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| Properties | |
| Molecular formula | C6H15BF4O |
| Molar mass | 189.99 g mol−1 |
| Exact mass | 190.115208388 g mol-1 |
| Melting point |
91-92 °C, 364-365 K, 196-198 °F |
| Solubility in water | Reacts |
| Hazards | |
| EU classification |  C |
| R-phrases | R14, R34 |
| S-phrases | S22, S26, S36/37/39 |
 (verify) (what is:  / ?)Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa) |
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| Infobox references | |
Triethyloxonium tetrafluoroborate is the organic oxonium compound with the formula [(CH3CH2)3O]BF4. It is often called Meerwein's reagent after its discoverer Hans Meerwein.[1] Also well known and commercially available is the related trimethyloxonium tetrafluoroborate. The compounds are exceptionally strong alkylating agents. Aside from the BF4− salt, many related derivatives are available with varying solubilities and stabilities.[2]
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[edit] Synthesis
Triethyloxonium tetrafluoroborate is prepared from boron trifluoride, diethyl ether, and epichlorohydrin:[3]
- 4 Et2O·BF3 + 2 Et2O + 3 C2H3(O)CH2Cl → 3 Et3O+BF4− + B[(OCH(CH2Cl)CH2OEt]3
The trimethyloxonium salt is available from dimethyl ether via an analogous route.[4] These salts do not have long shelf-lives at room temperature. These salts degrade by hydrolysis:
- [(CH3CH2)3O]+BF4− + H2O → (CH3CH2)2O + CH3CH2OH + HBF4
The propensity of trialkyloxoniums to undergo alkyl-exchange may be utilized to the chemists' advantage. For example, trimethyloxonium tetrafluoroborate, which reacts sluggishly due to low solubility in most compatible solvents may be converted in-situ to higher alkyl/more soluble oxoniums, thereby speeding up alkylation reactions.[5]
[edit] Structure
The compound features pyramidal oxonium cation and a tetrahedral fluoroborate anion. Reflecting its ionic character, the salt dissolves in polar but inert solvents such as dichloromethane, sulfur dioxide, and nitromethane.
[edit] Safety
Triethyloxonium tetrafluoroborate is a strong alkylating agent, although the hazards are diminished because it is non-volatile. It releases strong acid upon contact with water. The properties of the methyl derivative are similar.
[edit] Use
Alkylating agent for nucleophilic functional groups in organic synthesis.
[edit] References
- ^ H. Meerwein, G. Hinz, P. Hofmann, E. Kroning, and E. Pfeil (1937). "Über Tertiäre Oxoniumsalze, I". Journal für Praktische Chemie 147 (10-12): 257. doi:10.1002/prac.19371471001.H. Meerwein, E. Bettenberg, H. Gold, E. Pfeil, and G. Willfang (1940). "Über Tertiäre Oxoniumsalze, II". Journal für Praktische Chemie 154 (3-5): 83. doi:10.1002/prac.19391540305.
- ^ Hartwig Perst, Dave G. Seapy "Triethyloxonium Tetrafluoroborate" in Encyclopedia of Reagents for Organic Synthesis John Wiley & Sons, New York, 2008. doi:10.1002/047084289X.rt223.pub2 . Article Online Posting Date: March 14, 2008
- ^ H. Meerwein (1973), "Triethyloxonium fluoroborate", Org. Synth., http://www.orgsyn.org/orgsyn/orgsyn/prepContent.asp?prep=cv5p1080; Coll. Vol. 5: 1080
- ^ T. J. Curphey (1988), "Trimethyloxonium tetrafluoroborate", Org. Synth., http://www.orgsyn.org/orgsyn/orgsyn/prepContent.asp?prep=CV6P1019; Coll. Vol. 6: 1019
- ^ Vartak A.P. and Crooks P.A. (2009). "A Scalable Enantioselective synthesis of the alpha2-adrenergic Agonist, Lofexidine". Org. Process. Res. Dev. 13 (3): 415–419. doi:10.1021/op8002689.
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