Geometric isomerism Occurs when atoms

In geometric isomers, or cis-trans isomers, of coordination compounds, the same ligands are arranged in different orders within the coordination sphere. Geometric isomerism occurs when atoms or groups of atoms can be arranged on two sides of a rigid structure. Cis means adjacent to and trans means on the opposite side of. Cis- and trans-diamminedichloroplatinum(II) are shown below. 

CH3 c= CH3 / C i Geometric isomerism occurs when there is a C=C in the molecule, and both carbon atoms have two different atoms or groups attached. 

Cis-trans isomerism (or geometrical isomerism) occurs when there is restricted rotation about a bond between two atoms. Groups attached to each atom may be on the same side of the bond (the cis isomer) or opposite sides (the trans isomer). See also E-Z convention. 

The carbon chains of samrated fatty acids form a zigzag pattern when extended, as at low temperamres. At higher temperatures, some bonds rotate, causing chain shortening, which explains why biomembranes become thinner with increases in temperamre. A type of geometric isomerism occurs in unsaturated fatty acids, depending on the orientation of atoms or groups around the axes of double bonds, which do not allow rotation. If the acyl chains are on the same side of the bond, it is cis-, as in oleic acid if on opposite sides, it is tram-, as in elaidic acid, the tram isomer of oleic acid (Fig-... 

Geometric, or cis-trans, isomerism is common among alkenes. It occurs when both of the double-bonded carbon atoms are joined to two different atoms or groups. The other two structural isomers of C4H8 shown under (1) on page 597 do not show cis-trans isomerism. In both cases the carbon atom at the left is joined to two identical hydrogen atoms. 

Maleic acid and its esters are isomerized by irradiation of their solutions in the presence of various alkyl bromides, sometimes bromine itself. The C-Br (or Br-Br) bond is sonolyzed to bromine atoms, which add reversibly to the double bond.56 Geometric stabilization of the adduct radical and then elimination of bromine produces fumaric compounds (Fig. 13). When the initiator is bromine, oxygen inhibits the reaction (R = H or CH3), an argument in favor of a radical chain process with the initiation step, the cleavage of the Br2 molecule, occurring in the cavitation bubble. The lifetime of the bromine atoms is s, which at the... 

---