trans-But-2-ene

Overview

The E stereoisomer of but-2-ene, with methyl groups on opposite sides.

Its atom connectivity matches cis-but-2-ene, but the arrangement around the double bond differs. E/Z assignment compares priorities separately at each alkene carbon; for this simple example, the methyl groups have higher priority than hydrogen.

Identifiers

Formula

C4H8

Functional group

Alkenes

Molar mass

56.11 g/mol

Also known as

(E)-but-2-ene, trans-2-Butene, trans-Butene, 2-BUTENE, (E)-, 2-trans-Butene, beta-trans-Butylene

Properties

Melting Point

-105.52 °C

Boiling Point

0.88 °C

Density

0.6042 g/cu cm at 20/4 °C

Water solubility

Solubility in water, 511 mg/L at 25 °C

Related compounds

• Alkenes

  The E stereoisomer of but-2-ene, with methyl groups on opposite sides.

Connected reactions

• Dissolving metal reduction: But-2-yne → trans-But-2-ene

  Successive electron transfers and protonations convert the triple bond into a double bond. The intermediate sequence favours the less crowded arrangement that gives trans-but-2-ene, so this is not the same process as hydrogen delivery on a metal surface.

References

1. PubChem Compound Summary: trans-But-2-ene (CID 62695)National Center for Biotechnology Information · PubChem

   Identity, molecular formula, molecular weight and aliases retrieved via PUG REST on 2026-09-08.

2. OpenStax Organic Chemistry: Cis–trans isomerism in alkenesJohn McMurry · OpenStax · 2023

   Supports the qualitative structural interpretation of the recorded molecular structure; no new physical measurement or verified preparative yield is claimed.

3. Hazardous Substances Data Bank (HSDB): trans-But-2-ene — melting pointHazardous Substances Data Bank (HSDB)

   Retrieved through PubChem PUG View on 2026-09-08. https://pubchem.ncbi.nlm.nih.gov/compound/62695#section=Melting-Point. Source value, complete property clause or compact miscibility statement retained; absent pressure, temperature or phase conditions are not inferred. Original reference: Haynes, W.M. (ed.). CRC Handbook of Chemistry and Physics. 95th Edition. CRC Press LLC, Boca Raton: FL 2014-2015, p. 3-78

4. Hazardous Substances Data Bank (HSDB): trans-But-2-ene — boiling pointHazardous Substances Data Bank (HSDB)

   Retrieved through PubChem PUG View on 2026-09-08. https://pubchem.ncbi.nlm.nih.gov/compound/62695#section=Boiling-Point. Source value, complete property clause or compact miscibility statement retained; absent pressure, temperature or phase conditions are not inferred. Original reference: Haynes, W.M. (ed.). CRC Handbook of Chemistry and Physics. 95th Edition. CRC Press LLC, Boca Raton: FL 2014-2015, p. 3-78

5. Hazardous Substances Data Bank (HSDB): trans-But-2-ene — densityHazardous Substances Data Bank (HSDB)

   Retrieved through PubChem PUG View on 2026-09-08. https://pubchem.ncbi.nlm.nih.gov/compound/62695#section=Density. Source value, complete property clause or compact miscibility statement retained; absent pressure, temperature or phase conditions are not inferred. Original reference: Larranaga, M.D., Lewis, R.J. Sr., Lewis, R.A.; Hawley's Condensed Chemical Dictionary 16th Edition. John Wiley & Sons, Inc. Hoboken, NJ 2016., p. 217

6. Hazardous Substances Data Bank (HSDB): trans-But-2-ene — solubilityHazardous Substances Data Bank (HSDB)

   Retrieved through PubChem PUG View on 2026-09-08. https://pubchem.ncbi.nlm.nih.gov/compound/62695#section=Solubility. Source value, complete property clause or compact miscibility statement retained; absent pressure, temperature or phase conditions are not inferred. Original reference: Suzuki T; J Computer-Aided Molecular Design 5: 149-66 (1991)