Tetrabutylammonium tribromide
[CAS# 38932-80-8]

Identification

• Classification: Chemical reagent >> Organic reagent >> Amine salt (ammonium salt)
• Name: Tetrabutylammonium tribromide
• Synonyms: Tetra-n-butylammonium tribromide; TBABr3
• Molecular Formula: C₁₆H₃₆Br₃N
• Molecular Weight: 482.18
• CAS Registry Number: 38932-80-8
• EC Number: 609-598-3
• SMILES: CCCC[N+](CCCC)(CCCC)CCCC.Br[Br-]Br

Properties

• Melting point: 73 °C (Expl.)
• Water solubility: insoluble

Safety Data

• Hazard Symbols: GHS05;GHS07 Danger
• Risk Statements: H314-H315-H319-H335
• Safety Statements: P260-P261-P264-P264+P265-P270-P271-P272-P280-P284-P301+P330+P331-P302+P352-P302+P361+P354-P304+P340-P305+P354+P338-P308+P316-P316-P317-P319-P320-P321-P333+P317-P362+P364-P363-P403+P233-P405-P501

Hazard Classification

Hazard	Class	Category Code	Hazard Statement
Eye irritation	Eye Irrit.	2	H319
Specific target organ toxicity - single exposure	STOT SE	3	H335
Skin irritation	Skin Irrit.	2	H315
Skin corrosion	Skin Corr.	1C	H314
Serious eye damage	Eye Dam.	1	H318
Skin corrosion	Skin Corr.	1B	H314

Discovery and Applications

Tetrabutylammonium tribromide is a quaternary ammonium salt with the formula C16H36Br3N. It consists of a tetrabutylammonium cation (C16H36N+) paired with three bromide anions (Br−). This compound is a member of the larger family of ammonium salts, which are well-known for their solubility in both polar and non-polar solvents, making them versatile reagents in various chemical applications. It is primarily used in organic synthesis and phase transfer catalysis, and its properties have made it a valuable reagent in a variety of chemical reactions.

Tetrabutylammonium tribromide was first synthesized as part of research into quaternary ammonium salts and their role in facilitating reactions between immiscible phases. Quaternary ammonium salts, which contain a positively charged nitrogen atom bound to four alkyl groups, have been studied extensively for their utility in organic chemistry. The particular structure of tetrabutylammonium tribromide, which incorporates large butyl groups and three bromide ions, provides it with both lipophilic and hydrophilic properties that are particularly useful in facilitating phase transfer reactions.

One of the primary applications of tetrabutylammonium tribromide is in phase transfer catalysis (PTC), a technique used to drive reactions between two phases that do not readily mix, such as an aqueous phase and an organic phase. In these types of reactions, tetrabutylammonium tribromide serves as a catalyst to transport an anionic reactant, like a halide, from the aqueous phase to the organic phase, where it can undergo a reaction. The tetrabutylammonium cation is highly soluble in the organic phase, while the bromide anions can react with substrates in that phase, increasing the efficiency of reactions like nucleophilic substitutions.

Tetrabutylammonium tribromide also plays a role in organic synthesis, particularly in reactions that involve bromination or other substitutions. In bromination reactions, tetrabutylammonium tribromide can act as a source of bromide ions, which are used to introduce a bromine atom into organic compounds. This is useful for the synthesis of a wide range of brominated organic compounds, which have applications in pharmaceuticals, agrochemicals, and materials science. The presence of bromide ions also helps stabilize reaction intermediates, promoting more efficient reaction pathways.

Another significant application of tetrabutylammonium tribromide is in the extraction and solubilization of certain compounds. The large, hydrophobic butyl groups attached to the nitrogen atom make tetrabutylammonium tribromide soluble in non-polar solvents, while the bromide ions provide a means of extracting metal ions and organic molecules from aqueous solutions. This makes it useful in solvent extraction processes, which are often employed in the purification of metals or in the removal of organic contaminants from water.

In electrochemical processes, tetrabutylammonium tribromide is used as an electrolyte in certain systems. Its bromide anions can participate in electrochemical reactions, and the compound has been employed in electroplating, where metal ions are reduced onto a surface, as well as in the study of metal halide complexes. The salt can also be used in experiments that involve the electrochemical behavior of halides in solution, as it provides a stable source of bromide ions under various conditions.

Despite its usefulness, tetrabutylammonium tribromide, like other quaternary ammonium salts, can present safety concerns. It is generally considered safe when handled with proper precautions, but direct contact with the skin, eyes, or respiratory system should be avoided. It is important to use gloves, goggles, and work in well-ventilated areas when handling this compound. Additionally, the compound should be stored in a cool, dry place to maintain its stability over time.

In conclusion, tetrabutylammonium tribromide is a versatile and useful compound in a range of chemical applications, particularly in organic synthesis and phase transfer catalysis. Its ability to facilitate reactions between immiscible phases and its role as a bromine source make it valuable in the synthesis of various organic compounds, while its solubility properties also enable its use in extraction processes. Its diverse applications and relatively simple synthesis process have made it an important reagent in both academic and industrial chemistry.

References

2004 Chemoselective thioacetalisation and transthioacetalisation of carbonyl compounds catalysed by tetrabutylammonium tribromide (TBATB). Org. Biomol. Chem., 2, 1677.
DOI: 10.1039/B402648A

2015 Tetrabutylammonium tribromide impregnated MCM-48 as a heterogeneous catalyst for selective oxidation of sulfides. RSC Adv., 5, 38047.
DOI: 10.1039/C5RA04573H

2017 PEG-600 mediated one-pot reaction of 3-acetyl-2H-chromen-2-one with heterylthiols and phenylthioureas using tetrabutylammonium tribromide as an efficient green reagent. New J. Chem., 41, 5175.
DOI: 10.1039/C7NJ00504K