Partial answers : Lecture 2 : STEREOCHEMISTRY 1. Use Fig 2 2. C's are not chiral. 2 of the 4 groups (two H's) are identical. Same compound viewed from two different orientations. Different conformations require different twistings around single bonds. 3. Three below, plus 3 more by changing the second C from the bottom (put OH at the left). 4. Use Fig 10. For alanine, the sidechain is CH3. 5. There are only two different possible configurations. Racemic mixture = 50% of each type. Draw 2 identical structures of one configuration, and 2 more of the mirror image. 6. Use Fig-1 from Lecture 05 (Polar/Nonpolar) 7. Use Fig 13B 8. Use Fig 22 9. 10. Use Fig 14A, but note that rotation in the problem is the opposite from the classnotes.11. 12. Unwind the DNA double helix by twisting around single bonds -C-C-, -C-O-, -O-P- . Conformations : twisting around covalent bonds. Configurations : break covalent bonds and