Heptyltriphenylphosphonium Bromide: Properties & Lab Guide

Heptyltriphenylphosphonium Bromide is a lipophilic quaternary phosphonium salt widely employed in biomedical and synthetic chemistry research, particularly for mitochondria-targeting applications and as a reactive intermediate precursor in phosphonium-based reactions.

Chemical Class

Quaternary phosphonium salt (lipophilic cation)

SKU

H157315

Counter Ion

Bromide (Br⁻)

Lipophilic Alkyl Chain

Heptyl (C7) chain attached to phosphorus center

Typical Physical Form

Solid (powder or crystalline solid); exact melting point should be confirmed on product CoA

Solubility

Generally soluble in polar organic solvents (e.g., DMSO, methanol, dichloromethane); verify with CoA

Primary Application Areas

Mitochondria-targeting research; Wittig/phosphonium ylide chemistry; lipophilic cation studies

Chemical Identity and Structural Features

Heptyltriphenylphosphonium Bromide is a quaternary phosphonium salt consisting of a central phosphorus atom bearing three phenyl groups and one n-heptyl (C7) alkyl chain, with bromide as the counter-anion. The positive charge is permanently localized on the phosphorus center, conferring on the molecule a characteristic lipophilic cationic (LLC) nature.

This structural combination — a delocalized cationic phosphorus core with a medium-length aliphatic chain — endows the compound with amphiphilic character: the triphenylphosphonium (TPP) moiety provides membrane permeability driven by the large, hydrophobic aromatic surface and the delocalized positive charge, while the heptyl chain contributes additional hydrophobicity. These properties are central to its utility in biological membrane studies and organelle-targeting strategies.

Researchers should confirm the precise molecular weight, purity, and spectral data (e.g., ³¹P NMR) from the Certificate of Analysis (CoA) supplied with SKU H157315, as lot-specific values may vary.

Primary Laboratory Applications

Mitochondria-Targeting Research: Triphenylphosphonium (TPP) cations are well-established vehicles for delivering bioactive molecules selectively to mitochondria. The large, delocalized positive charge on the phosphorus center enables TPP-conjugated compounds to accumulate in the mitochondrial matrix, driven by the highly negative mitochondrial membrane potential (approximately −180 mV in energized mitochondria). Heptyltriphenylphosphonium Bromide, with its C7 alkyl chain, is used as a model lipophilic cation and as a synthetic building block for constructing mitochondria-targeted probes, antioxidants, or drug conjugates.

Phosphonium Ylide and Wittig-Type Chemistry: Quaternary phosphonium salts serve as precursors to phosphonium ylides upon treatment with a suitable base. These ylides are the active species in the Wittig reaction, enabling conversion of aldehydes and ketones to alkenes with defined geometry. The heptyl-substituted variant provides access to ylides with a medium aliphatic chain, useful in the synthesis of lipid-like molecules, surfactants, or biological probes.

Membrane Biophysics and Lipid Studies: As a lipophilic cation, Heptyltriphenylphosphonium Bromide is employed in studies of membrane potential, ion transport, and membrane partitioning. Its accumulation in lipid bilayers or membranes can be monitored using electrochemical or spectroscopic methods.

Note: Specific published protocols should be consulted for exact concentrations and conditions; researchers should validate each application in their own experimental system.

Handling, Storage, and Safety Guidelines

Personal Protective Equipment (PPE): When handling Heptyltriphenylphosphonium Bromide, wear appropriate PPE including chemical-resistant gloves, laboratory coat, and eye protection (safety glasses or goggles). Work in a well-ventilated area or fume hood to minimize inhalation of dust or aerosols.

Storage Conditions: Store the compound in a tightly sealed container, in a cool and dry location, away from direct light, moisture, and incompatible materials. For precise storage temperature recommendations (e.g., room temperature, 2–8 °C, or −20 °C), refer to the product label and CoA for SKU H157315, as storage requirements may be lot-specific.

Stability: Quaternary phosphonium salts are generally stable under ambient conditions when kept dry and away from strong bases (which can generate reactive ylides) and strong oxidizing agents. Avoid prolonged exposure to moisture, which may cause hygroscopic caking.

Waste Disposal: Dispose of waste material in accordance with local, institutional, and governmental regulations. Do not dispose of phosphonium salts via standard drain disposal without consulting your institution's environmental health and safety (EHS) office.

Emergency Measures: In case of skin or eye contact, flush immediately with copious amounts of water and seek medical attention if irritation persists. Consult the Safety Data Sheet (SDS) for SKU H157315 for complete hazard information.

Solution Preparation and Quality Considerations

Solvent Selection: Heptyltriphenylphosphonium Bromide is typically soluble in polar organic solvents such as dimethyl sulfoxide (DMSO), methanol, and dichloromethane. Aqueous solubility may be limited due to the lipophilic nature of the compound; researchers should perform solubility tests before preparing aqueous stock solutions. Always verify solvent compatibility with the specific application (e.g., cell-based assays require consideration of solvent cytotoxicity).

Stock Solution Preparation: Weigh the compound accurately using a calibrated analytical balance. Dissolve in the chosen solvent to the desired concentration, vortex or sonicate gently to ensure complete dissolution. Filter through a 0.2 µm syringe filter if sterility is required for biological experiments. Prepare fresh solutions where possible; if storing stocks, use low-binding tubes and record preparation date and lot number.

Concentration Verification: For critical quantitative experiments, verify stock concentration using an appropriate analytical method (e.g., ³¹P NMR or UV-Vis spectrophotometry if applicable). Rely on the purity value stated on the CoA when calculating molar concentrations.

Quality Control: Each lot of SKU H157315 is accompanied by a Certificate of Analysis detailing purity (e.g., by HPLC or elemental analysis), identity confirmation (NMR, MS), and physical characteristics. Researchers should retain the CoA for experimental records and regulatory compliance.

Frequently asked questions

What is Heptyltriphenylphosphonium Bromide used for in research?

Heptyltriphenylphosphonium Bromide is primarily used as a lipophilic cationic building block for mitochondria-targeting studies, leveraging the large negative mitochondrial membrane potential to drive accumulation. It also serves as a precursor for phosphonium ylides in Wittig-type alkene synthesis and is employed in membrane biophysics research to study ion transport and membrane partitioning.

In which solvents is Heptyltriphenylphosphonium Bromide soluble?

Heptyltriphenylphosphonium Bromide is generally soluble in polar organic solvents such as DMSO, methanol, and dichloromethane. Aqueous solubility may be limited due to the compound's lipophilic character. Researchers are advised to perform preliminary solubility tests and to consult the product CoA for SKU H157315 for lot-specific data.

How should Heptyltriphenylphosphonium Bromide be stored to maintain stability?

The compound should be stored in a tightly sealed container in a cool, dry, and dark location, away from moisture, strong bases, and strong oxidizing agents. Specific temperature requirements should be confirmed from the product label and Certificate of Analysis for SKU H157315. Avoid repeated freeze-thaw cycles of stock solutions and record preparation dates on all aliquots.

Is Heptyltriphenylphosphonium Bromide suitable for cell-based mitochondria-targeting experiments?

Triphenylphosphonium salts are widely used as mitochondria-targeting moieties in cell-based studies. However, researchers must evaluate the cytotoxicity of Heptyltriphenylphosphonium Bromide and the solvent vehicle at the intended concentrations in their specific cell system before conducting targeting experiments. Published literature on analogous TPP salts can provide guidance on concentration ranges, but experimental validation is essential.

What precautions should be taken when generating a phosphonium ylide from this compound?

Generating a phosphonium ylide requires treatment with a strong base (e.g., n-BuLi, NaH, or KOtBu), which are highly reactive and hazardous reagents. These reactions should be performed under inert atmosphere (nitrogen or argon), using appropriate anhydrous solvents and standard air-free techniques. Operators must follow all relevant PPE guidelines and institutional safety protocols when handling strong bases and air-sensitive intermediates.

References

1. Murphy, M.P. (2008). Targeting lipophilic cations to mitochondria. Biochimica et Biophysica Acta (Bioenergetics). Review article on triphenylphosphonium-based mitochondria targeting.
2. Marechal, J.D. et al. General reference on Wittig reaction and phosphonium ylide chemistry. Standard organic chemistry textbook reference (e.g., March's Advanced Organic Chemistry).
3. Smith, R.A.J. et al. Delivery of bioactive molecules to mitochondria in vivo. Proceedings of the National Academy of Sciences. (General reference for TPP-based delivery strategies; specific volume and page to be confirmed.)

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