Acetylene

An alkyne, C2H2, 26.038 g/mol. Boiling point -84.7 °C (sublimation point), melting point -80.7 °C (triple point), as published.

verified recordOrganic — alkyne7 measured properties

Identifiers

Molecular formula: C₂H₂
Molecular weight: 26.038 g/mol
Exact mass: 26.01565 g/mol
IUPAC name: acetylene
SMILES: C#C
InChI: InChI=1S/C2H2/c1-2/h1-2H
InChIKey: HSFWRNGVRCDJHI-UHFFFAOYSA-N

Open in ReactionLens Use in reaction prediction

Measured properties

Published measurements, each with its source. Two readings of one property are both shown, in the units each used.

Boiling Point: -119 °F at 760 mmHg (USCG, 1999)measured · CAMEO Chemicals; -84.7 °C (sublimation point)measured · Hazardous Substances Data Bank (HSDB)
Melting Point: -119 °F (Sublimes) (NIOSH, 2024)measured · CAMEO Chemicals; -80.7 °C (triple point)measured · Hazardous Substances Data Bank (HSDB)
Density: 0.613 at -112 °F (USCG, 1999) - Less dense than water; will floatmeasured · CAMEO Chemicals; 0.377 g/cu cm (pressure >1 atm)measured · Hazardous Substances Data Bank (HSDB)
Solubility: 2 % (NIOSH, 2024)measured · CAMEO Chemicals; In water, 1200 mg/L at 25 °Cmeasured · Hazardous Substances Data Bank (HSDB)
Vapor Pressure: 44.2 atm (NIOSH, 2024)measured · CAMEO Chemicals; Vapor pressure = 40 atm at 16.8 °Cmeasured · Hazardous Substances Data Bank (HSDB)
LogP: log Kow = 0.37measured · Hazardous Substances Data Bank (HSDB); 0.37measured · ILO-WHO International Chemical Safety Cards (ICSCs)
Flash Point: 0 °Fmeasured · Haz-Map, Information on Hazardous Chemicals and Occupational Diseases; Closed cup: -18.15 °C (-0.7 °F).measured · Hazardous Substances Data Bank (HSDB)

Calculated properties

Derived from the structure, not from a sample; kept apart from the measurements above.

Molecular weight: 26.04 g/molcalculated · reference compound database; Average mass of one molecule, from reference compound database.
Exact mass: 26.0156500638 Dacalculated · reference compound database; Mass of the most common isotopic form.
XLogP3: 0.4calculated · reference compound database; Estimated oil/water partition, computed by reference compound database.
Polar surface area: 0 Å²calculated · reference compound database; Polar surface area as computed by reference compound database.
Complexity: 8calculated · reference compound database; A rough measure of how intricate the structure is.
H-bond donors: 0calculated · reference compound database
H-bond acceptors: 0calculated · reference compound database
logP: 0.2494calculated · chemistry engine; Estimated preference for oil over water. Higher means more oil-like.
Topological polar surface area: 0 Å²calculated · chemistry engine; Surface area from polar atoms; relates to how easily a molecule crosses membranes.
H-bond donors: 0calculated · chemistry engine; Atoms that can donate a hydrogen bond.
H-bond acceptors: 0calculated · chemistry engine; Atoms that can accept a hydrogen bond.
Rotatable bonds: 0calculated · chemistry engine; Single bonds the molecule can freely twist around.
Molar refractivity: 9.89 cm³/molcalculated · chemistry engine; Relates to the molecule's polarisability.
Fraction sp³ carbons: 0calculated · chemistry engine; Share of carbon atoms with tetrahedral bonding.
QED drug-likeness: 0.3329calculated · chemistry engine; Quantitative estimate of drug-likeness (0–1).

What it is made of

Elements

C Carbon2 atoms · 92.3% by mass
H Hydrogen2 atoms · 7.7% by mass

Percentages are of the molecular weight above, worked out the same way the molar mass calculator does it.

Structure

Heavy atoms, hydrogen excluded: 2
Total atoms, hydrogen included: 4
Rings: 0
Aromatic rings: 0
Stereocentres: 0
Formal charge: 0

Functional groups

Alkyne
A carbon–carbon triple bond.

Matched by structural pattern, not by a measurement.

The molecule in three dimensions

Rotate and inspect the atoms. Loaded only when you ask, so the page stays light.

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

No documented reaction with a written procedure and a source involves Acetylene yet.

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

Nothing structurally close to Acetylene has a page here yet.

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.

1,1,3,3-Tetrachloro-2-trichlorosilyl-1,3-disilacyclopent-4-ene

formed as a product

C₃H₃Cl₇Si₃, 371.486 g/mol.

1,1,3,3-Tetrachloro-2-dichlorosilyl-1,3-disilacyclopent-4-ene

formed as a product

C₃H₄Cl₆Si₃, 337.041 g/mol.

Where these values came from

reference compound database6326
compound record
chemistry engine
structure perception

compound record.

What this page does not claim

Identifiers are copied from the source record, measured values are reported as published, and calculated values are marked as calculated. Nothing here is a hazard, purity or handling assessment — how the library is checked.