Chemistry 22.3

Isomers The retinal molecule in the rod and cone cells of your eye has a hydrocarbon skeleton. When light strikes a cell containing retinal, it causes a change in the three-dimensional structure of the retinal molecule. The structures before and after the light strikes are examples of isomers. You will study different types of isomers.

Structural Isomers How do the properties of structural isomers differ?

Structural Isomers Compounds that have the same molecular formula but different molecular structures are called isomers. Structural isomers differ in physical properties such as boiling point and melting point. They also have different chemical reactivities.

Structural Isomers Structural isomers are compounds that have the same molecular formula, but the atoms are joined together in a different order.

Structural Isomers Both butane and 2-methylpropane have the molecular formula C4H10. The atoms in their molecules are arranged in a different order, so they are structural isomers. Both butane and 2-methylpropane have the molecular formula C4H10. But the atoms in their molecules are arranged in a different order. So these compounds are structural isomers.

Stereoisomers Stereoisomers What are the two types of stereoisomers?

Two types of stereoisomers are geometric isomers and optical isomers. Stereoisomers are molecules in which the atoms are joined in the same order, but the positions of the atoms in space are different.

Stereoisomers Geometric Isomers Geometric isomers have atoms joined in the same order, but differ in the orientation of groups around a double bond.

Stereoisomers In the trans configuration, the methyl groups are on opposite sides of the double bond. In the cis configuration, the methyl groups are on the same side of the double bond.

Stereoisomers There is a trans and a cis configuration of 2- butene because a methyl group is attached to each carbon of the double bond. There is a trans and a cis configuration of 2-butene because a methyl group is attached to each carbon of the double bond. Comparing and Contrasting How are the trans and cis configurations different?

Stereoisomers

Stereoisomers Optical Isomers A carbon with four different atoms or groups attached is an asymmetric carbon. Pairs of molecules that differ only in the way that four different groups are arranged around a central carbon atom are called optical isomers. In these models, four different atoms are attached to the same carbon atom, making the carbon atom an asymmetric carbon.

Play the isomer game of “Pick the Pairs.” Stereoisomers Simulation 28 Play the isomer game of “Pick the Pairs.”

for Conceptual Problem 22.4 Problem Solving 22.18 Solve Problem 18 with the help of an interactive guided tutorial.

22.3 Section Quiz 22.3.

22.3 Section Quiz 1. Structural isomers have different properties because they have a different number of bonds. different types of bonds. different substituents. a different order of atoms.

22.3 Section Quiz 2 Substituent groups on opposite sides of a double bond are said to be in the _______ configuration. If the groups are on the same side of the bond, then they are in the _______ configuration. cis, trans trans, cis trans, iso stereo, cis

22.3 Section Quiz 3. Geometric isomers have different arrangements of atoms and different molecular formulas. but only single bonds. around an asymetric carbon. around a double bond.

22.3 Section Quiz 4. A carbon atom that has four different substituents always forms an optical isomer. a saturated hydrocarbon. a geometric isomer. an unsaturated hydrocarbon.

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