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Short answer: n-pentane (C5H12, CAS 109-66-0) boils at about 36 °C (309.2 K, about 97 °F) at normal atmospheric pressure. NIST gives 309.2 ± 0.2 K; the CRC Handbook value cited in PubChem is 36.06 °C. It melts at about −129.7 °C (143.4 K), is lighter than water (0.626 g/cm³ at 20 °C), and is highly volatile at room temperature. Values read 2026-11-07.
Definition and scope
Pentane is a five-carbon alkane solvent. “Pentane” and “n-pentane” name the same straight-chain compound; the branched C5H12 isomers carry their own names, 2-methylbutane (isopentane) and 2,2-dimethylpropane (neopentane). This page is a datasheet-style reference for the properties a bench scientist uses most: boiling point, melting point, density and vapor pressure. For the next alkane up, see the hexane boiling point reference.
Pentane boiling point and melting point
The boiling point of n-pentane is 36 °C at 1 atm. Different reference works round it differently, so the spread in published numbers is rounding and unit conversion, not disagreement about the chemistry.
| Source | Boiling point |
|---|---|
| NIST Chemistry WebBook (SRD 69) | 309.2 ± 0.2 K (about 36.05 °C), average of 81 of 94 values |
| CRC Handbook of Chemistry and Physics, 94th ed., p. 3-438 (via HSDB in PubChem) | 36.06 °C |
| ILO-WHO ICSC 0534 | 36 °C |
| PAC (US DOE), via PubChem | 36.1 °C at 760 mmHg |
| CAMEO / NTP 1992, OSHA, NIOSH Pocket Guide, via PubChem | 97 °F |
The Fahrenheit entries are the same number: 36.06 °C is 96.9 °F. NIST reports a melting (fusion) temperature of 143.4 ± 0.7 K (about −129.75 °C), a triple point of 143.46 ± 0.05 K and a critical temperature of 469.8 ± 0.5 K.
n-Pentane vs pentane vs its isomers
There is no difference between pentane and n-pentane; the “n” (normal) marks the unbranched chain, and the IUPAC name of that compound is pentane. The distinction matters because the isomers behave differently. PubChem lists neopentane (2,2-dimethylpropane) with a melting point of −16.37 °C (HSDB) or −16.6 °C (ICSC, PAC), roughly 113 °C higher than n-pentane’s −129.75 °C.
Why is the melting point of neopentane higher than n-pentane?
The numbers above are sourced; the explanation is the usual textbook one and is an editorial interpretation rather than a claim from those data sheets: neopentane’s compact, nearly spherical shape packs into a crystal lattice more efficiently than the flexible straight chain of n-pentane, so more thermal energy is needed to disrupt the solid.
Pentane density
HSDB (via PubChem) gives 0.6262 g/cm³ at 20 °C; ICSC, NIOSH and OSHA give a relative density of 0.63, and PAC gives 0.62 at 20 °C. CAMEO notes it is less dense than water and floats on it, so pentane forms the upper layer over an aqueous phase.
Pentane vapor pressure: check the temperature
Published vapor-pressure figures look contradictory until you read the temperature attached to each:
| Reported value | Condition | Source |
|---|---|---|
| 514 mmHg | 25 °C | HSDB, PAC |
| 426 mmHg | 68 °F (20 °C) | CAMEO / NTP |
| 53.3 kPa (about 400 mmHg) | 18.5 °C | ICSC |
| 420 mmHg | temperature not stated | OSHA, NIOSH |
The figures are consistent: vapor pressure rises steeply with temperature, and at 25 °C pentane’s is already about two-thirds of atmospheric pressure (760 mmHg). Always record the temperature when quoting a vapor pressure; a figure without one cannot be compared.
What the numbers mean at the bench
These points are inferences from the sourced numbers, not procedures.
- Evaporation: with a boiling point of 36 °C, pentane can boil from a flask warmed by hand or sunlight. In a rotary evaporator it needs little or no heat, and the condenser must be cold enough to recover it.
- Containment: a vapor pressure near 500 mmHg at 25 °C means vapor fills container headspace quickly. A fume hood and the general guidance in Prudent Practices in the Laboratory apply; use the supplier’s safety data sheet for hazard data.
- Extraction: density near 0.63 g/cm³ places pentane above water.
- Chromatography: see column chromatography solvent selection for how solvent choice is made.
- Comparison with hexane: hexane boils at about 68.7 °C according to the hexane reference page, roughly 32 °C higher than pentane.
Common misunderstandings
- “Pentane boils at 97”: that is °F, not °C.
- “Vapor pressure is 420, 426 or 514”: all can be correct; they refer to different temperatures.
- “Pentane and n-pentane are different solvents”: they are the same compound; check the supplier’s specification when isomer identity matters.
FAQ
What is n-pentane vs pentane?
They are the same unbranched five-carbon alkane. “n-” means normal (straight chain); isopentane and neopentane are the branched isomers.
What is the melting point and boiling point of pentane?
About −129.7 °C (143.4 K) and 36 °C (309.2 K) respectively, per the NIST WebBook.
What is the IUPAC name of pentane?
Pentane. Its isomers are 2-methylbutane (isopentane) and 2,2-dimethylpropane (neopentane).
What is the boiling point of pentane in Celsius, Kelvin and Fahrenheit?
About 36 °C, 309.2 K and 97 °F.
Sources
- NIST Chemistry WebBook, SRD 69, n-Pentane: webbook.nist.gov (read 2026-11-07).
- PubChem, Pentane (CID 8003), experimental properties citing HSDB/CRC Handbook 94th ed., ILO-WHO ICSC 0534, PAC, CAMEO, NIOSH, OSHA: pubchem.ncbi.nlm.nih.gov (read 2026-11-07).
- PubChem, Neopentane (CID 10041), melting point: pubchem.ncbi.nlm.nih.gov (read 2026-11-07).
