Molecules in Disguise

1. Molecules in Disguise Draw 5-propylheptane. What is its real name?

2. Cycloalkanes Alkanes with closed ring(s) of C atoms General formula: CnH2n (C3H6, C4H8, C5H10, etc.) Naming: use cyclo- prefix before alkane name

3. Fun Common Names

4. Teepee-ane

5. Dashes and Wedges Bonds

6. Stereoisomers Cycloalkane rings have two faces Stereoisomers: same connectivity, but different arrangement of atoms in space Geometric Isomers: type of stereoisomer involving rings or multiple bonds with substituents on two different carbons Designated as either cis or trans and must be included in the name

7. Conformational Analysis

8. Strain in Cycloalkanes What if cycloalkane rings were flat?

9. Cyclopropane and Cyclobutane

10. Cyclopentane

11. Cyclohexane

12. Cyclohexane �ring flip� Axial and equatorial positions can be swapped by ring flipping (Ea ~ 50 kJ/mol)

13. Drawing chairs from flat pictures

14. Optical Isomers Optical isomers are non-superimposable mirror images interact differently with polarized light type of stereoisomer

15. Chirality: Chiral vs. Achiral

16. Chirality �A carbon atom�s ability to bond to four other atoms (or groups of atoms) leads to an unusual property. If these t=four atoms or groups are all different, they can form two distinct molecules that are mirror images of each other. Although chemically identical, two such compounds behave differently when polarized light (where the light waves are in only one plane) is shone through them. They rotate the light in opposite directions and are said to be optically active. The polarimeter was introduced in 1840 to measure the optical activity. Sugars show this property; polarimeters were used routinely to analuze sugar syrups. After the 1860�s, they became valuable tools for collectors of excise duty to determine the strength of sugar solutions for taxation purposes.� - Eyewitness Science �Chemistry� , Dr. Ann Newmark, DK Publishing, Inc., 1993, pg 48 �A carbon atom�s ability to bond to four other atoms (or groups of atoms) leads to an unusual property. If these t=four atoms or groups are all different, they can form two distinct molecules that are mirror images of each other. Although chemically identical, two such compounds behave differently when polarized light (where the light waves are in only one plane) is shone through them. They rotate the light in opposite directions and are said to be optically active. The polarimeter was introduced in 1840 to measure the optical activity. Sugars show this property; polarimeters were used routinely to analuze sugar syrups. After the 1860�s, they became valuable tools for collectors of excise duty to determine the strength of sugar solutions for taxation purposes.� - Eyewitness Science �Chemistry� , Dr. Ann Newmark, DK Publishing, Inc., 1993, pg 48