Methyltriphenylphosphonium bromide
[CAS# 1779-49-3]

Identification

• Classification: Chemical reagent >> Organic reagent >> Phosphine ligand
• Name: Methyltriphenylphosphonium bromide
• Synonyms: Methyl(triphenyl)phosphonium bromide
• Molecular Formula: C₁₉H₁₈P.Br
• Molecular Weight: 357.23
• CAS Registry Number: 1779-49-3
• EC Number: 217-218-9
• SMILES: C[P+](C1=CC=CC=C1)(C2=CC=CC=C2)C3=CC=CC=C3.[Br-]

Properties

• Melting point: 230-233 °C (Expl.)
• Water solubility: 400 g/L (25 °C)

Safety Data

• Hazard Symbols: GHS06;GHS07;GHS09 Danger
• Risk Statements: H300-H301-H302-H312-H315-H319-H332-H411
• Safety Statements: P261-P264-P264+P265-P270-P271-P273-P280-P301+P316-P301+P317-P302+P352-P304+P340-P305+P351+P338-P317-P321-P330-P332+P317-P337+P317-P362+P364-P391-P405-P501

Hazard Classification

Hazard	Class	Category Code	Hazard Statement
Acute toxicity	Acute Tox.	4	H302
Acute toxicity	Acute Tox.	4	H312
Acute toxicity	Acute Tox.	4	H332
Acute toxicity	Acute Tox.	2	H300
Chronic hazardous to the aquatic environment	Aquatic Chronic	2	H411
Skin irritation	Skin Irrit.	2	H315
Eye irritation	Eye Irrit.	2	H319
Acute toxicity	Acute Tox.	3	H301
Specific target organ toxicity - single exposure	STOT SE	3	H335
Acute toxicity	Acute Tox.	3	H311
Acute toxicity	Acute Tox.	3	H331

Discovery and Applications

Methyltriphenylphosphonium bromide (C6H5)3PCH3Br is a quaternary ammonium salt composed of a methyl group attached to a triphenylphosphonium cation, with a bromide anion. It is typically synthesized by reacting triphenylphosphine with methyl bromide, resulting in the formation of this well-known phosphonium salt.

Methyltriphenylphosphonium bromide is widely utilized in organic chemistry, particularly in the Wittig reaction. In this reaction, it reacts with carbonyl compounds such as aldehydes or ketones to generate alkenes. This process involves the formation of a phosphonium ylide intermediate, which facilitates the creation of a carbon-carbon double bond. The Wittig reaction is crucial for the synthesis of a variety of alkenes, which have applications in the pharmaceutical, agrochemical, and material science industries.

Apart from its prominent role in the Wittig reaction, methyltriphenylphosphonium bromide is also employed in other synthetic processes involving phosphonium ylides. These ylides can participate in nucleophilic substitution reactions, where they react with electrophilic species to form new carbon-carbon bonds. The reactivity of methyltriphenylphosphonium bromide makes it a useful reagent in various organic synthesis protocols.

Methyltriphenylphosphonium bromide is also applied in the preparation of substituted phosphonium salts, which are important intermediates in numerous chemical reactions. Furthermore, it is utilized in the synthesis of other phosphonium compounds that find use in catalysis and other specialized applications in organic chemistry.

In conclusion, methyltriphenylphosphonium bromide is a versatile and valuable reagent in organic chemistry. Its key application in the Wittig reaction for alkene formation, along with its utility in the preparation of phosphonium ylides for various synthetic processes, makes it an important compound in chemical synthesis and industrial applications.

References

2014. Atom-economic threefold cross-couplings of triarylbismuth reagents with 2-halobenzaldehydes and pot-economic in situ Wittig functionalizations with phosphonium salts. RSC Advances, 4(104).
DOI: 10.1039/C4RA13348J

2015. Triphenylphosphonium Cations of the Diterpenoid Isosteviol: Synthesis and Antimitotic Activity in a Sea Urchin Embryo Model. Journal of Natural Products, 78(6).
DOI: 10.1021/acs.jnatprod.5b00124

1980. Effects of phosphonium compounds on Schistosoma mansoni. Journal of Medicinal Chemistry, 23(8).
DOI: 10.1021/jm00182a010