What is the difference between cis- and trans- isomers?

Answer 1

In cis-isomers, the carbon bonds are on the same side, and in the trans-isomers, the carbons are on the opposite side.

Or put another way...

In cis-isomers, the substituents bound to the C=C are on the same side, and the trans-isomer, the substituents bound to the C=C are on opposite sides.

Answer 2

Cis and trans isomers are positional isomers of a molecule.

Consider something such as PtCl2Br2 which is a square planar complex Pt sits in the middle with each of the ligands (in this case the chlorine and bromine atoms) attached in a cross shaped fashion.

. Cl

. |

Cl--Pt--Br

. |

. Br

This is the cis isomer as the bromine and chlorine atoms are adjacent to one another.

. Br

. |

Cl--Pt--Cl

. |

. Br

This is the trans isomer where similar ligands are opposite one another.

It won't let me draw it but the vertical lines are meant to be attached to Pt.

If your talking about octahedral complexes then the terms mer and fac are used where fac has the same ligands all on one side and mer has alternating ligands (a little too complicated to draw on here though)

The trans isomer are usually referred to as being E and the cis Z.

Answer 3

Z isomer are cis isomer it has the tow groups at the same side around the double bond but the E isomer are trance isomer it has the tow groups at opposite side around the double bond.

Answer 4

When there is a double bond (C=C), substituents on those carbons can be on the same side (cis) or on opposite sides (trans).