cis-But-2-ene

Overview

The Z stereoisomer of but-2-ene, with both methyl groups on the same side.

Each double-bond carbon has a hydrogen and a methyl group. Restricted rotation around the carbon–carbon double bond keeps the cis and trans arrangements distinct. The two isomers share connectivity, so the difference is stereoisomerism rather than positional isomerism.

Identifiers

Formula

C4H8

Functional group

Alkenes

Molar mass

56.11 g/mol

Also known as

(Z)-but-2-ene, cis-2-Butene, cis-Butene, beta-cis-Butylene, (2Z)-but-2-ene, cis-1,2-Dimethylethylene

Properties

Melting Point

-138.89 °C

Boiling Point

3.72 °C

Density

0.616 g/cu cm at 25 °C

Water solubility

In water, 658 mg/L at 25 °C

Related compounds

• Alkenes

  The Z stereoisomer of but-2-ene, with both methyl groups on the same side.

Connected reactions

• Partial hydrogenation: But-2-yne → cis-But-2-ene

  The alkyne binds to the catalyst surface and receives both hydrogen atoms from the same face. This syn addition gives cis-but-2-ene; the deactivated Lindlar catalyst helps limit further reduction to butane.

References

1. PubChem Compound Summary: cis-But-2-ene (CID 5287573)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): cis-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/5287573#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): cis-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/5287573#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): cis-But-2-ene — densityHazardous Substances Data Bank (HSDB)

   Retrieved through PubChem PUG View on 2026-09-08. https://pubchem.ncbi.nlm.nih.gov/compound/5287573#section=Density. Source value, complete property clause or compact miscibility statement retained; absent pressure, temperature or phase conditions are not inferred. Original reference: Lide, D.R., G.W.A. Milne (eds.). Handbook of Data on Organic Compounds. Volume I. 3rd ed. CRC Press, Inc. Boca Raton ,FL. 1994., p. V2: 1950

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

   Retrieved through PubChem PUG View on 2026-09-08. https://pubchem.ncbi.nlm.nih.gov/compound/5287573#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)