Phenylpropylammonium bromide
[CAS# 120375-53-3]

Identification

• Classification: Chemical reagent >> Organic reagent >> Amine salt (ammonium salt)
• Name: Phenylpropylammonium bromide
• Synonyms: PPABr; 3-phenylpropan-1-amine;hydrobromide
• Molecular Formula: C₉H₁₄BrN
• Molecular Weight: 216.12
• CAS Registry Number: 120375-53-3
• SMILES: C1=CC=C(C=C1)CCCN.Br

Safety Data

• Hazard Symbols: GHS07 Warning
• Hazard Statements: H315-H319-H335
• Precautionary Statements: P261-P305+351+338-P302+352

Discovory and Applicatios

Phenylpropylammonium bromide is a quaternary ammonium salt derived from phenylpropylamine, consisting of a phenylpropyl moiety bound to an ammonium center, with bromide serving as the counterion. Compounds of this type belong to a broader class of ammonium salts that have attracted attention due to their roles in synthetic chemistry, materials science, and occasionally pharmacological research. The structural core of phenylpropylammonium bromide combines a hydrophobic aromatic group with a positively charged ammonium cation, creating a bifunctional chemical entity with distinct physicochemical properties.

The discovery and use of ammonium salts such as phenylpropylammonium bromide can be traced back to early investigations into quaternary ammonium compounds in the late 19th and early 20th centuries. Researchers were particularly interested in the ability of these salts to act as surfactants, phase-transfer agents, and stabilizers, since their ionic and hydrophobic features enable interactions across polar and non-polar media. Phenylpropylammonium derivatives were later synthesized as part of systematic explorations of substituted ammonium compounds to evaluate how variations in alkyl or aryl substituents influence solubility, reactivity, and biological effects.

From a synthetic chemistry perspective, phenylpropylammonium bromide can be prepared by quaternization of phenylpropylamine with an alkylating agent in the presence of hydrobromic acid or bromide sources. The introduction of the bromide counterion ensures charge balance and contributes to the crystalline stability of the compound. Such ammonium salts are often highly soluble in water and polar solvents, where the ionic interactions dominate, while the hydrophobic aromatic side chain may facilitate solubilization in certain organic systems.

Applications of phenylpropylammonium bromide are primarily associated with its function as an intermediate and auxiliary reagent in research. In organic synthesis, ammonium salts are useful as phase-transfer catalysts, helping to mediate reactions between reactants located in immiscible phases. While tetraalkylammonium salts are the most common in this role, derivatives bearing aromatic substituents, such as phenylpropyl groups, provide alternative steric and electronic properties that can influence catalytic performance. The balance of hydrophobic and ionic features also makes such salts relevant for studying micelle formation and aggregation phenomena, contributing to physical chemistry and colloid science.

In materials science, phenylpropylammonium bromide and similar organic ammonium salts have been employed as templating agents and surface modifiers. In particular, quaternary ammonium salts have found roles in controlling crystal growth, stabilizing nanoparticles, and modifying the surface chemistry of layered materials. The phenylpropyl group introduces additional aromatic interactions, which can be useful in systems where π-π stacking contributes to self-assembly or material stabilization.

Pharmacologically, ammonium salts of this class have been examined to some extent, although phenylpropylammonium bromide itself does not appear to be widely used as a therapeutic compound. In general, phenylpropylamine derivatives are studied for their structural similarity to naturally occurring amines that interact with neurotransmitter systems, but the conversion to quaternary ammonium salts typically limits their ability to cross lipid membranes such as the blood-brain barrier. This property can, however, be advantageous in applications where peripheral selectivity is desired, preventing central nervous system effects.

The study of phenylpropylammonium bromide contributes to a broader understanding of how structural modifications of ammonium salts affect their solubility, stability, and functional properties. Such knowledge has ongoing relevance in developing new phase-transfer catalysts, ionic liquids, and functional organic salts for applications across synthetic chemistry, materials research, and potential biomedical uses.

In summary, phenylpropylammonium bromide is a representative example of an aromatic-substituted ammonium salt. Its discovery arose from systematic investigations into quaternary ammonium chemistry, and its applications span synthesis, catalysis, and materials science. While not a prominent pharmaceutical compound, it remains an instructive molecule for understanding the interplay between ionic character and aromatic substitution in the design and function of ammonium-based chemicals.