Chemistry 122

1. Chemistry 122 isomers

2. Isomers • The prefix “iso-” means same parts. How does this help with the definition of the term isotope? • Some hydrocarbons only differ in their structural arrangement, not their structural formula • Ex. C4H8 has three structural arrangements • When the arrangements are different but the formula is the same, the molecules are referred to as structural isomers • They have different physical characteristics

3. Stereoisomers – Geometric Isomers • Stereoisomers exist when the order of the atoms is identical but their positions in space is different - bond angles are different • Geometric isomers are joined in the same order but differ in the orientation of groups around a double bond • There are two configurations – trans (opposite sides) and cis (same sides) • They are possible whenever each carbon of the double bond has at least one substituent

5. Stereoisomers – Optical Isomers Optical isomers exist when a carbon atom has four different atoms or groups attached, the molecule is asymmetric They are mirror images of each other – such as in looking at yourself in the mirror The mirror images will never be identical unless bonds are broken Conceptual Problem 22.4

6. For the remainder of class… • Questions 18 – 19, page 706, 25 on page 707 • Guided reading – up to section 22.3 • Quick Lab – Page 707 • To be passed in Thursday • Complete questions 1 – 3 under the analyze and conclude section • Draw and name the nine structural isomers of heptane (C7H16) • Bonus Assignment (add 5 points to your Chapter 19 Test), draw and name the 18 isomers of octane – due Thursday