The physical and chemical properties of 2-methyltetrahydrofuran (2-MeTHF) - boiling point 80.2°C, density 0.854 g/mL, molecular weight 86.13 g/mol, water solubility around 14% - are not just data points on a safety data sheet. Each value carries real engineering implications: how the solvent distills, how it phase-separates, how it stores, how it reacts. This article walks through the key 2-MeTHF properties one by one and explains why each one matters for the chemist, process engineer, and procurement specialist working with this solvent in 2026.

1. Property Snapshot Table

Before diving into individual properties, the table below collects the most-cited 2-MeTHF physical and chemical data in one place. Values are at standard atmospheric pressure unless noted otherwise.

2. 2-MeTHF Boiling Point (80.2°C) and Distillation Implications

The 2-MeTHF boiling point sits at 80.2°C at atmospheric pressure - about 14 degrees higher than tetrahydrofuran (66°C) and around 45 degrees higher than diethyl ether (35°C). This middle-temperature reflux range is one of the most consequential numbers on the property list.

2.1 What the higher 2-MeTHF bp means in practice

The 80.2°C boiling point allows reactions to be run at a noticeably higher reflux temperature without resorting to pressurized equipment. For magnesium activation in Grignard chemistry, palladium-catalyzed couplings, or sluggish hydrogenations, that extra thermal headroom often makes the difference between a smooth conversion and a stalled reaction. The detailed reaction case studies appear in our Grignard & organometallic article.

2.2 Distillation and recovery

For solvent recovery from process streams, the methf bp at 80.2°C means a single-stage atmospheric distillation easily separates 2-MeTHF from higher-boiling impurities such as residual reagents, salt byproducts, or product oils. The relatively low latent heat of vaporization (around 35 kJ/mol) keeps energy consumption per kilogram of recovered solvent modest, and standard stainless-steel distillation columns work well without exotic materials.

2.3 Reduced-pressure distillation

For temperature-sensitive products, vacuum distillation can be used to drive 2-MeTHF off well below 80°C. At 100 mbar, for example, 2-MeTHF distills at roughly 30°C, allowing complete solvent removal from heat-sensitive APIs without thermal degradation.

3. 2-MeTHF Density (0.854 g/mL) and Process Design

The 2-MeTHF density of 0.854 g/mL at 20°C is significantly lower than water's 1.000 g/mL, and somewhat higher than typical hydrocarbons (heptane ≈ 0.68, toluene ≈ 0.87). This single number drives several engineering decisions.

3.1 Phase-separation geometry

In aqueous workups, the methf density of 0.854 g/mL means the 2-MeTHF layer floats on top of the aqueous layer. This is the same orientation as toluene, ether, or ethyl acetate, so process operators do not need to retrain workup intuition when switching from THF (which is fully miscible with water and therefore does not separate at all). The clean upper-layer organic phase enables straightforward decanting or pumping in industrial separators.

3.2 Mass-volume conversions for procurement

Procurement specifications often quote 2-MeTHF in metric tons by weight, while users measure in liters by volume. The 2 methyl thf density of 0.854 g/mL gives an easy conversion: 1 metric ton = 1,170 L; 1 cubic meter = 854 kg. Standard 200 L drums hold approximately 170 kg of 2-MeTHF; 1000 L IBC totes hold about 854 kg.

3.3 Pump and pipework sizing

Combined with the relatively low viscosity of about 0.46 cP at 20°C, the moderate density allows standard centrifugal pumps and stainless-steel pipework sized for organic solvents to handle 2-MeTHF without modification. Pressure-drop calculations track closely with toluene-style hydraulics.

4. Water Solubility & Azeotrope Behavior

2-MeTHF dissolves about 14 grams of water per 100 mL at room temperature (and water dissolves a similar amount of 2-MeTHF), making it a solvent with limited but non-trivial mutual solubility. This intermediate behavior is one of the molecule's defining characteristics and the engineering foundation for many of its industrial advantages.

4.1 Why limited miscibility matters

Full miscibility (as with THF) means the two phases never separate, forcing the chemist to add salt or other workup tricks. Complete immiscibility (as with hexane and water) means very poor partition for polar products. 2-MeTHF's intermediate solubility hits a sweet spot: it dissolves polar organic products well, but still phase-separates from water cleanly enough for direct industrial workup.

4.2 The 2-MeTHF / water azeotrope

2-MeTHF forms a binary azeotrope with water that boils at approximately 71°C, with a composition near 90% 2-MeTHF and 10% water by weight. This azeotrope is exploited in some drying procedures: distilling the 2-MeTHF/water mixture removes the water-rich vapor, condenses it, and allows phase separation in the receiver to recover dry 2-MeTHF.

4.3 Drying for sensitive reactions

For Grignard and organolithium reactions, 2-MeTHF must be dried below 50 ppm water. Common drying agents include molecular sieves (4Å), sodium-benzophenone (in research-scale settings), or column drying with neutral alumina. The relevant procedures are detailed in our handling, storage & safety article.

5. Peroxide Formation Kinetics

Like all cyclic ethers, 2-MeTHF can undergo autoxidation in the presence of atmospheric oxygen and light to form organic peroxides. Concentrated peroxides are explosive when distilled to dryness - one of the most serious safety hazards associated with ether solvents.

5.1 Mechanism in brief

Oxidation begins by abstraction of a hydrogen atom alpha to the ether oxygen - the position in the ring most stabilized by resonance with the lone pair. The resulting carbon-centered radical reacts with O₂ to form a peroxyl radical, which abstracts another hydrogen to propagate the chain. The methyl substituent in 2-MeTHF sterically hinders this initial hydrogen abstraction at the substituted alpha-carbon, slowing the reaction relative to THF.

5.2 Practical inhibition with BHT

Commercial 2-MeTHF is supplied with BHT (butylated hydroxytoluene) stabilizer at 150–250 ppm. BHT scavenges peroxyl radicals before they can propagate the chain, dramatically extending the practical shelf life of the solvent. Stabilizer-free grades are available on request for applications where even trace BHT cannot be tolerated, but they require shorter expiration dating and more frequent peroxide testing.

5.3 Testing and threshold values

Peroxide content is typically measured with potassium iodide test strips or by titration. A common safety threshold for distillation is 100 ppm peroxide; above this level, the solvent should be either treated to remove peroxides (with reducing agents such as ferrous sulfate or sodium metabisulfite) or disposed of as hazardous waste rather than distilled to dryness.

6. Vapor Pressure & Flash Point

The vapor pressure of 2-MeTHF at room temperature (~13 kPa at 20°C) is meaningfully lower than that of THF (~21 kPa at 20°C), reducing evaporative loss during handling and lowering the working VOC concentration in process areas. The Antoine equation parameters published in NIST and DDBST databases allow vapor pressure to be calculated at any practical temperature.

The flash point of −11°C (closed cup) classifies 2-MeTHF as an NFPA Class IB flammable liquid - the same category as ethanol, gasoline, and most ether solvents. Standard flammable-liquid storage practices apply: bonded and grounded transfers, explosion-proof electrical equipment in handling areas, and dedicated solvent storage rooms with appropriate ventilation.

6.1 Vapor density and ventilation

2-MeTHF vapor is heavier than air (vapor density ~3.0, relative to air = 1), so it tends to accumulate at floor level and travel along low points to ignition sources. Ventilation systems for 2-MeTHF handling areas should pull air from low vents, not just ceiling exhaust.

6.2 Auto-ignition temperature

The auto-ignition temperature of approximately 270°C is well above typical process temperatures, but hot surfaces such as steam pipes, hot oil systems, or motor housings should still be evaluated for ignition risk in case of leak or spill.

7. Molecular Weight, Refractive Index & Polarity Parameters

A few additional 2-MeTHF properties round out the engineering picture.

7.1 2 methyl tetrahydrofuran molecular weight (86.13 g/mol)

The 2 methyl tetrahydrofuran molecular weight of 86.13 g/mol is useful for stoichiometry calculations and for converting between mass and molar quantities. Compared to THF (MW 72.11), the methyl group adds 14 g/mol, so a kilogram of 2-MeTHF contains slightly fewer moles than the same mass of THF.

7.2 Refractive index for purity verification

The refractive index n_D = 1.405 at 20°C is a quick and reliable purity check for 2-MeTHF. Deviations from this value can indicate contamination with water (lower n_D), THF (lower n_D), or oxidation products. Standard Abbe refractometers are sufficient.

7.3 Dielectric constant and dipole moment

The dielectric constant of about 6.97 and dipole moment of about 1.38 D place 2-MeTHF in the moderate-polarity aprotic category - comparable to THF, less polar than acetone, more polar than diethyl ether. These values explain why 2-MeTHF dissolves a wide range of organic compounds while still coordinating Lewis-acidic metal centers in organometallic chemistry.

7.4 Hansen solubility parameters

Hansen solubility parameters (dispersion ~16.9, polar ~5.0, hydrogen bonding ~4.3 MPa^0.5) make 2-MeTHF a useful solvent for resins, oils, and many active pharmaceutical ingredients. Formulators predicting compatibility for coatings, adhesives, or pharmaceutical excipients can use these parameters with the standard Hansen sphere method.

8. Frequently Asked Questions

Q1. What is the 2-MeTHF boiling point compared to THF?

2-MeTHF boils at 80.2°C; THF boils at 66°C. The 14°C difference enables higher reflux temperatures, less evaporative loss during handling, and easier separation of 2-MeTHF from low-boiling impurities during distillation.

Q2. What is the 2-MeTHF density at room temperature?

2-MeTHF density is 0.854 g/mL at 20°C. This means the 2-MeTHF layer floats on water in aqueous workups, similar to ether, ethyl acetate, or toluene. Density decreases slightly at higher temperatures (about 0.001 g/mL per °C).

Q3. Is 2-MeTHF miscible with water?

Only partially. About 14 grams of water dissolve in 100 mL of 2-MeTHF at room temperature, and a similar amount of 2-MeTHF dissolves in water. Above these limits, two phases separate. Full miscibility (as with THF) does not occur.

Q4. What is the 2-MeTHF molecular weight?

The 2 methyl tetrahydrofuran molecular weight is 86.13 g/mol, corresponding to the molecular formula C₅H₁₀O. The CAS number is 96-47-9 and the IUPAC name is 2-methyloxolane.

Q5. How quickly does 2-MeTHF form peroxides during storage?

In commercial BHT-stabilized 2-MeTHF stored properly (sealed, dark, cool, with intact stabilizer), peroxide accumulation is slow - typically months to a year before measurable peroxide content develops. In stabilizer-free or improperly stored material, peroxides can form within weeks. Always test before distillation to dryness, regardless of stabilizer status.

Q6. Where can I find authoritative reference data for 2-MeTHF properties?

The NIST WebBook and DDBST databases publish thermophysical data for 2-MeTHF, including vapor pressure equations, heat capacities, and azeotropic data. Supplier COAs typically report a smaller subset focused on purity, water content, peroxide level, and BHT concentration.