C

Cis

Quick Reference
Also Known AsCis isomer, Z-isomer (CIP rules), syn (in some naming systems)

What is Cis?

Cis is a Latin prefix meaning "on the same side", used in chemistry to describe geometric isomers in which identical or similar substituents are on the same side of a double bond or ring. In cis-2-butene, both methyl groups are on the same side of the C=C double bond, contrasting with the trans isomer where they are on opposite sides.

Properties & Characteristics

Cis refers to a geometric isomer in which identical or similar substituents are on the same side of a double bond, ring, or other restricted-rotation system. In alkenes, cis isomers (also called Z-isomers by the Cahn-Ingold-Prelog priority rules when priorities are on the same side) generally have higher dipole moments, lower melting points, but often higher boiling points than their trans counterparts. The prefix derives from Latin: "on this side."

Uses & Applications

The cis/trans distinction is critical in biochemistry: cis-fatty acids (unsaturated, kinked chains) are liquid at room temperature, while trans-fatty acids behave like saturated fats and are linked to cardiovascular disease. Cis-platinum (cisplatin) is an anticancer drug; its trans isomer is inactive.

Safety Information

Some cis isomers are significantly more toxic or pharmacologically active than their trans counterparts. Always verify the specific isomer when working with drugs, natural products, or environmental contaminants. Trans-fatty acid consumption is regulated in many countries.

Always consult the SDS/MSDS before handling any chemical. This information is for educational purposes only.

Key Facts

Term Cis
Synonyms Cis isomer, Z-isomer (CIP rules), syn (in some naming systems)

Frequently Asked Questions

Cis is a Latin prefix meaning "on the same side", used in chemistry to describe geometric isomers in which identical or similar substituents are on the same side of a double bond or ring. In cis-2-butene, both methyl groups are on the same side of the C=C double bond, contrasting with the trans isomer where they are on opposite sides.

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