Mirror, Mirror, on the Wall A Study in Chirality
Do You Know... what an isomer is? how many kinds of isomers there are? (Hint – use your textbook index.) Isomers are different compounds that have the same molecular formula. There are conformational, constitutional (structural), and stereoisomers.
Conformational Isomers Parts of the molecule rotate freely around a single bond but do not change location on the molecule. These isomers will not have different physical or chemical properties, since they can change their shape easily.
Conformational Isomers All of these images are 1-propanol arranged in different conformations. The order of attachment is the same in all.
Constitutional Isomers Constitutional isomers have the same molecular formula, but the groups and/or atoms are attached to the molecule in a different order. Constitutional isomers may also have different kinds of bonds within the molecules.
Constitutional Isomers C 3 H 7 Cl can be either 1-chloropropane or 2- chloropropane. H H H | | | ClCCCH | | | H H H H Cl H | | | HCCCH | | | H H H
Constitutional Isomers C 3 H 6 O can have two different structures. What are the names of these compounds? H H | | O=CCCH | | | H H H H H \ | C=CCOH / | | H H H The first compound is called propanal. The second compound is 2-propen-1-ol.
Stereoisomers In stereoisomers the atoms and/or groups are attached to the molecule in the same order, but they have a different orientation in space. There are several different types of stereoisomers. We have already studied one type.
Cis and Trans Isomers Recall from Chapter 12 (Section 12.2) that alkenes can exist as cis and trans isomers. Cis and trans isomers are one type of stereoisomer. They have the same atoms and/or groups, but they are attached to different sides of the double bond.
This structure is a cis isomer, with the groups both on the same side of the double bond in the molecule.
And this is a trans isomer, with the groups on opposite sides of the double bond.
Can You Match These? Trans-2-pentene ___ Trans-2-methyl-3- hexene ___ Cis-2-butene ___ Cis-2-pentene ___ A D C B A B C D
Stereoisomers We will now begin to explore isomers based on the groups around specific carbon atoms within a molecule. YOU This chapter will be taught by YOU using Power Point presentations!
Your Group Tasks You will work in groups of three students, with each member of the group contributing to the presentation. Each group will be assigned a different concept from within this chapter.
Your Group Tasks You will use your textbook and Internet resources to gather information on your assigned topic. Each group will make and photograph molecular models illustrating your topic. You may also use images from other sources with appropriate permission.
Your Group Tasks Each group will create and present a Power Point presentation that teaches about their assigned topic. Complete details for the project will be found on your handout.
Individual Responsibilities Each student is responsible for learning the vocabulary from the entire chapter. Each student is responsible for learning the material presented by their group and by the other groups.
Individual Responsibilities Each student is responsible for learning any material presented by the teacher. Each student will be individually assessed by written and manipulative tests.