Triphenylphosphine Molecular Weight: 262.29 g/mol, Formula & Uses Explained

Triphenylphosphine Molecular Weight: The Short Answer

Triphenylphosphine has a molecular weight of 262.29 g/mol (262.292 g/mol when calculated from standard atomic weights). Its molecular formula is C₁₈H₁₅P, which means each molecule contains eighteen carbon atoms, fifteen hydrogen atoms, and one phosphorus atom. That formula fixes the molar mass at this value regardless of supplier, grade, or batch. It is also the number every chemist, purchasing manager, and scale-up engineer needs when converting mass into moles.

Searches for "triphenylphosphine molecular weight" usually come from one of three places: a lab notebook being filled, a quotation being checked, or a reaction being scaled. That is appropriate, because this reagent is not a trace catalyst. In the Mitsunobu and Appel reactions it is consumed in roughly equimolar amounts — typically 1.0 to 1.5 equivalents — so a weighing mistake or an unaccounted impurity shifts yields and forces extra purification. Understanding the molecular weight is the first step to controlling those variables.

How 262.29 g/mol Is Calculated from the Formula

Molecular weight is the sum of the atomic weights of every atom in the formula. For triphenylphosphine (C₁₈H₁₅P) the arithmetic is straightforward:

• Carbon: 18 × 12.011 = 216.198
• Hydrogen: 15 × 1.008 = 15.120
• Phosphorus: 1 × 30.974 = 30.974
• Total: 216.198 + 15.120 + 30.974 = 262.292 g/mol

Most suppliers and reference databases round the value to 262.29 g/mol. The nominal mass, using whole numbers (C = 12, H = 1, P = 31), is 262. For everyday synthesis the rounded and exact values are interchangeable; the 0.002 g/mol difference only matters in high-precision gravimetric work. If you see 262.28 or 262.3 quoted somewhere else, those are simply different rounding conventions of the same number.

A more practical numeric neighbor is triphenylphosphine oxide (Ph₃P=O), which has a molecular weight of 278.28 g/mol. Triphenylphosphine slowly oxidizes in air, and once oxide forms, a batch carries a higher average molar mass than 262.29. If you assume the sample is pure, you will weigh out fewer active moles than planned — a quiet cause of failed replicates and stalled reactions.

Physical Properties That Matter Alongside Molecular Weight

Molecular weight rarely acts alone in practice. The following values are what chemists and procurement teams check when qualifying a batch or planning a process.

The melting point is a fast diagnostic: a value near 79-81 °C generally indicates low oxide content, while a broad or depressed range points to oxidation or residual solvent. Molecular weight, melting point, and solubility together give a reliable picture of batch quality before the reagent ever reaches a reaction flask.

Why Molecular Weight Drives Everyday Lab Calculations

Three routine calculations dominate practical use once the molecular weight is fixed: stoichiometric weighing, solution preparation, and per-mole cost comparison.

Stoichiometric Weighing in Synthesis

Because 1 mmol of triphenylphosphine weighs 262.29 mg, a 10 mmol reaction with 1.2 equivalents requires 10 × 1.2 × 262.29 = 3.15 g of pure material. The same arithmetic applies to phosphonium salt preparation and to ligand screening. If the reagent is 98% pure rather than 99%+, divide by the purity fraction: 3.15 ÷ 0.98 = 3.21 g. That small correction is exactly where molecular weight knowledge prevents underdosing.

Preparing Standard Solutions

A 0.1 mol/L solution in 1 L of THF requires 26.23 g of pure triphenylphosphine. Solubility is generally good in aromatic and ethereal solvents, so the molecular weight, rather than solubility, is the factor that sets the target mass. Weigh directly into a volumetric flask and make up to the mark with freshly dried solvent for reproducible stock solutions.

Comparing Supplier Quotes on a Per-Mole Basis

Phosphines are usually quoted by weight, but reactions consume moles. Dividing a price per kilogram by 262.29 gives cost per mole and makes supplier comparisons meaningful. A 25 kg drum, for example, contains about 95.3 moles of triphenylphosphine — a useful frame for scale-up budgets and inventory planning.

The Reaction Chemistry Behind the Molecular Formula

Triphenylphosphine earns its place in the laboratory because the phosphorus lone pair makes it both a strong nucleophile and a mild reductant. The main reaction families are:

• Quaternization with alkyl or reactive halides to form phosphonium salts, which are then deprotonated to give Wittig reagents for alkene synthesis.
• The Mitsunobu reaction, where PPh₃ and an azodicarboxylate convert alcohols into esters, ethers, and related products under mild conditions.
• The Appel reaction, where PPh₃ and carbon tetrachloride or another halogen source convert alcohols into alkyl halides.
• The Staudinger reaction, where PPh₃ reacts with azides to give iminophosphoranes en route to amines and amides.
• Deoxygenation of epoxides, N-oxides, and ozonides, often as a final step in complex molecule synthesis.
• Ligand coordination to transition metals such as palladium, rhodium, and ruthenium in homogeneous catalysis.

The pattern is consistent: in nearly every application, triphenylphosphine is consumed in defined molar equivalents. Because these reactions consume one mole of phosphine per mole of substrate, process costs scale directly with molecular weight. A route using two equivalents adds 524.58 g of phosphine per mole of product before considering the oxide byproduct, which is why process chemists constantly look for ways to reduce phosphine loading or recycle the oxide. Whether you are assembling a palladium catalyst or scaling a Wittig route, 262.29 g/mol is the conversion factor that turns recipe moles into weighed masses.

From Phosphine to Phosphonium Ionic Liquids

The quaternization that converts triphenylphosphine into alkyltriphenylphosphonium salts is the same chemistry that produces quaternary phosphonium ionic liquids. Replace a phenyl group with an alkyl chain and pair the cation with a weakly coordinating anion, and the molecular phosphine becomes a salt that can be liquid near room temperature, thermally stable, and effectively non-volatile. Alkyltriphenylphosphonium salts themselves are known phase-transfer catalysts, and some members of that family behave as ionic liquids at moderate temperatures. These properties make the broader phosphonium family attractive in battery electrolytes, phase-transfer catalysis, and extraction processes.

For chemists who already think in molar equivalents, moving from a phosphine reagent to a phosphonium ionic liquid is conceptually simple: cation structure, anion identity, and molecular weight together control viscosity, conductivity, and thermal stability. Suppliers such as LETD now produce these materials at industrial scale, including tetraoctylphosphonium bis(trifluoromethylsulfonyl)imide, a hydrophobic, high-stability option for demanding electrochemical and separation applications. If you are new to the material class, an introduction to what ionic liquids are and how they work in industrial processes will clarify the terminology before you compare specific products.

Sourcing and Handling: A Practical Checklist

Triphenylphosphine is a commodity chemical, but the gap between a smooth campaign and a failed batch often comes down to grade selection and storage. Keep these points in mind:

1. Choose a grade that matches the application. Standard 98-99% grades are fine for most transformations; for ligand preparation or electrochemical studies, a higher purity grade or freshly recrystallized material is justified.
2. Check the melting point on receipt. A value near 79-81 °C indicates low oxide content, while a broad or elevated range signals oxidation.
3. Store under inert gas in a sealed container, away from light. Avoid prolonged air exposure while weighing.
4. Plan for the byproduct. Triphenylphosphine oxide is the unavoidable residue of most PPh₃-mediated reactions; factor its removal into your workup design.

If your project moves beyond molecular phosphines into formulated ionic liquids, LETD offers custom ionic liquid synthesis and industrial scale-up across phosphonium, imidazolium, pyridinium, and related families. The company's industrial application overview shows where these materials are already performing in antistatic treatment, white-oil extraction, and PET degradation chemistry.