cis-1,4-Dichloro-2-butene
[CAS 1476-11-5]

Identification

• Classification: Chemical reagent >> Organic reagent >> Halogenated aliphatic hydrocarbon
• Name: cis-1,4-Dichloro-2-butene
• Synonyms: (Z)-1,4-dichlorobut-2-ene
• Molecular Formula: C₄H₆Cl₂
• Molecular Weight: 125.00
• CAS Registry Number: 1476-11-5
• EC Number: 216-021-5
• SMILES: C(/C=CCCl)Cl

Properties

• Density: 1.1±0.1 g/cm³ Calc.^*, 1.188 g/mL (Expl.)
• Melting point: -48 °C (Expl.)
• Boiling point: 155.5 °C 760 mmHg (Calc.)^*, 152.1 °C (Expl.)
• Flash point: 54.4 °C (Calc.)^*, 55 °C (Expl.)
• Index of refraction: 1.459 (Calc.)^*, 1.489 (Expl.)

^* Calculated using Advanced Chemistry Development (ACD/Labs) Software.

Safety Data

• Hazard Symbols: GHS02;GHS05;GHS06;GHS08;GHS09 DangerGHS02
• Risk Statements: H226-H301-H311-H314-H330-H350-H400-H410
• Safety Statements: P203-P210-P233-P240-P241-P242-P243-P260-P262-P264-P270-P271-P273-P280-P284-P301+P316-P301+P330+P331-P302+P352-P302+P361+P354-P303+P361+P353-P304+P340-P305+P354+P338-P316-P318-P320-P321-P330-P361+P364-P363-P370+P378-P391-P403+P233-P403+P235-P405-P501

Hazard Classification

Hazard	Class	Category Code	Hazard Statement
Skin corrosion	Skin Corr.	1B	H314
Acute toxicity	Acute Tox.	3	H301
Acute toxicity	Acute Tox.	3	H311
Acute hazardous to the aquatic environment	Aquatic Acute	1	H400
Carcinogenicity	Carc.	1B	H350
Acute toxicity	Acute Tox.	2	H330
Chronic hazardous to the aquatic environment	Aquatic Chronic	1	H410
Flammable liquids	Flam. Liq.	3	H226
Serious eye damage	Eye Dam.	1	H318
Carcinogenicity	Carc.	1A	H350
Acute toxicity	Acute Tox.	1	H330
Reproductive toxicity	Repr.	2	H361
Specific target organ toxicity - single exposure	STOT SE	1	H370
Specific target organ toxicity - repeated exposure	STOT RE	1	H372
Germ cell mutagenicity	Muta.	1B	H340

• Transport Information: UN 3390

chemBlink Chemical Story

cis-1,4-Dichloro-2-butene packs several synthetic instructions into four carbons. Two allylic chlorides provide substitution sites, while the central carbon-carbon double bond provides a separate reaction platform.

The cis double bond also stores three-dimensional information. Because rotation around a double bond is restricted, the terminal chloromethyl groups are fixed on the same side, giving a different starting geometry from the trans isomer. That can influence cyclization and stereochemical outcomes.

The molecule is therefore useful as a bifunctional linker and intermediate. Its value does not come from complexity but from information density: two leaving groups, one alkene, and one defined geometry are already present before the next reaction starts.

References:
NIST Chemistry WebBook. cis-1,4-Dichloro-2-butene, CAS 1476-11-5.
PubChem. (2Z)-1,4-Dichlorobut-2-ene.

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