CHCl (vinyl chloride, part of new car smell )

Transcription

1 ame Key 1) (20 points) Draw a Lewis dot structure for each of the following molecules; show all lone pairs. Indicate the hybridization at all atoms except hydrogen, chlorine, and fluorine. (a) 2 (b) C 2 CCl (vinyl chloride, part of new car smell ) C C Cl (c) CCC (A potent carcinogen) C C C sp sp 2) (20 points) Identify the functional groups indicated by the arrows. Carbonyl is not an acceptable answer. ether amide amine Melatonin (hormone) alkene alcohol Alprenolol (anitihypertensive) Chem 220, Fall 1999, Page 1

2 ame Key 3) (20 points) An incomplete structure of nitrobenzene(c 6 5 2, a neutral molecule) is shown below. (a) Complete the structure by showing all lone pairs and formal charges. (b) Provide two additional resonance structures for nitrobenzene. ote: do not increase the number of charges in your resonance forms. original 4) (20 points) The structure of K, a carcinogen from tobacco smoke, is shown below [see echt, S. S. J. atl. Cancer Inst. 91, (1999)]. (a) What is the molecular formula for this molecule? (b) give the hybridization of each nitrogen () atom. (a) C Chem 220, Fall 1999, Page 2

3 ame Key 5) (40 points) The following structure is part of a larger molecule that may serve as a anticancer compound [see Shao et al. rg. Lett. 1, (1999)]. (a) Redraw the structure below showing all bonds, lone pairs and formal charges in your new picture. (b) Indicate the hybridization at all carbon, and oxygen atoms. (c) Draw the orbitals (use a separate picture) which overlap to form the pi bonds in this molecule. Indicate the type of orbital in each case (sp,, p etc.) (d) ow many sigma bonds and pi bonds are there in this molecule? Indicate how many of each (a) C C C C C C (b) pi bonds (c) (d) 16 sigma bonds, 2 pi bonds Chem 220, Fall 1999, Page 3

4 ame Key 6) (40 points) Consider the molecule 2-methyl butane shown below. 2-methyl butane (a) Looking down the C2-C3 bond, draw a ewman projection for the highest energy conformer. Use one of the templates provided. Read part (b) before you answer this. C 3 C 3 C 3 (b) Is there more than one possible answer to the question in part (a)? If so, explain why. Present your answer in terms of eclipsing, gauche and anti interactions. Yes, there are two conformations that eclipse the methyl groups attached to C2 with the methyl group at C3. The other interactions in these conformations (the and C 3 eclipsing interactions) are also the same in these two conformers. These conformations are equal in energy. (c) Looking down the C2-C3 bond, draw a ewman projection for the lowest energy conformer. Use one of the templates provided. Read part (d) before you answer this. C 3 C 3 C 3 (d) Is there more than one possible answer to the question in part (c)? If so, explain why. Again, present your answer in terms of eclipsing, gauche and anti interactions. Yes, there are two conformations where one of the methyl groups at C2 is anti to the C3 methyl group and the other C2 methyl group is gauche to the C3 methyl group. These conformations are equal in energy. Chem 220, Fall 1999, Page 4

5 ame Key 7. (40 points) Consider the molecule shown below. C1 C5 C 2 C 3 C4 C 3 C2 (a) Use the ewman projection template given below to show the conformation of the above compound around the C4-C5 and C2-C1 bonds. Set up your drawing looking down the C4-C5 and C2-C1 bonds. C4-C5 Bond C2-C1 Bond C 3 C 2 C 3 (b) The above conformer is in equilibrium with a second chair conformer. Draw a ewman projection (again, around the C4-C5 and C2-C1 bonds) of this second conformer. Set up your drawing looking down the C4-C5 and C2-C1 bonds. C4-C5 Bond C2-C1 Bond C 2 C 3 C 3 (c) Which conformer is more stable, the structure in (a) or (b). Briefly explain why. Conformer (a) is more stable because the larger substituent, the ethyl group, is in the equatorial position. (d) Complete the below structure by adding the ethyl group to the approriate position. C 3 C 3 C 2 Chem 220, Fall 1999, Page 5