Acetylene
C2H2, 26.038 g/mol. Its structure, the values that were measured, the values that were calculated, and where each one came from.
Identifiers
- Molecular formula
- C₂H₂
- Molecular weight
- 26.038 g/mol
- Exact mass
- 26.01565 g/mol
- IUPAC name
- acetylene
- C#C
- InChI=1S/C2H2/c1-2/h1-2H
- HSFWRNGVRCDJHI-UHFFFAOYSA-N
Measured properties
Values somebody obtained from a sample and published. Where two sources report the same property they are both shown, in the units each used — a disagreement between them is information, and averaging it away would be inventing a number neither one gave.
- Boiling Point
- -119 °F at 760 mmHg (USCG, 1999)
- -84.7 °C (sublimation point)
- Melting Point
- -119 °F (Sublimes) (NIOSH, 2024)
- -80.7 °C (triple point)
- Density
- 0.613 at -112 °F (USCG, 1999) - Less dense than water; will float
- 0.377 g/cu cm (pressure >1 atm)
- Solubility
- 2 % (NIOSH, 2024)
- In water, 1200 mg/L at 25 °C
- Vapor Pressure
- 44.2 atm (NIOSH, 2024)
- Vapor pressure = 40 atm at 16.8 °C
- LogP
- log Kow = 0.37
- 0.37
- Flash Point
- 0 °F
- Closed cup: -18.15 °C (-0.7 °F).
Calculated properties
Derived from the structure rather than from a sample. These are reproducible and they are not measurements: a calculated partition coefficient and a measured one can differ by a long way, and where both exist they are listed apart on purpose.
- Molecular weight
- 26.04 g/mol
- Exact mass
- 26.0156500638 Da
- XLogP3
- 0.4
- Polar surface area
- 0 Ų
- Complexity
- 8
- H-bond donors
- 0
- H-bond acceptors
- 0
- logP
- 0.2494
- Topological polar surface area
- 0 Ų
- H-bond donors
- 0
- H-bond acceptors
- 0
- Rotatable bonds
- 0
- Molar refractivity
- 9.89 cm³/mol
- Fraction sp³ carbons
- 0
- QED drug-likeness
- 0.3329
What it is made of
Elements
Structure
- Heavy atoms, hydrogen excluded
- 2
- Total atoms, hydrogen included
- 4
- Rings
- 0
- Aromatic rings
- 0
- Stereocentres
- 0
- Formal charge
- 0
Functional groups
Alkyne
The molecule in three dimensions
The drawing above is a diagram of what is bonded to what. A molecule is not flat, and the model here is one low-energy shape generated from the connectivity — useful for seeing which groups can reach each other, and not a measured structure. A real sample is a population of conformations, interconverting.
Reactions it appears in
Other names for it
The systematic name on this record is acetylene.
The sources also call it Ethyne, Narcylen, Ethine, Acetylen, Vinylene, acetylene;ethyne.
Structurally related
Seen alongside it in reaction records
Molecules that appear in the same recorded reactions as Acetylene. This says nothing about structure: most of them are the bases, solvents, ligands and catalysts the chemistry needed, and they are here because somebody put them in the same flask.
Where these values came from
chemistry engine
What this page does not claim
The identifiers are what the source record holds, copied rather than recomputed. Measured values are reported as their source gave them, units and all; calculated values are marked as calculated and are not measurements. Where a field is absent the page says so, because a blank cell reads as a zero and a guessed value reads as a fact.
Nothing here is a hazard assessment, a purity statement or advice about handling a sample. A flash point quoted from a safety database is a number somebody published, not a judgement by us about whether this molecule is safe for what you intend.