University:
Amherst College
Course:
CHEM 221 | Organic Chemistry I
Academic year:

2009
Views:

322

Pages:

4
Author:

Kathryn Duarte

Exam I KEY Chem 21 Oct 2, 2009 Name Ke page 1 (20) 2 (25) 3 (30) 4 (25) total (100) chk Please don't write in this space, 1. (15 points) Draw the Lewis structures of the following compounds, including lone pairs and formal charges where appropriate. Be sure to clearly show the bonding between heavy atoms. Read the formulas carefully! 6 (a) (CH3)2CC(CHO)CH2NHCOCH3 CH CH₂ H C-CH3 CH3 5 (b) CH3CCN(CH3)3C1 9H3 (C)4 CH3-CEC-N-CH3CO CH3 (c) KOCH(CH2F)2 -CH CH₂ CH₂-F 2. (5 points) Draw a molecule with the formula C2H2Cl2 that has no molecular dipole moment. CI all bond dipoles cancel H CI 20 3. (15 points) Draw the other important resonance structures of the cation below in skeletal form. Some structural templates are provided to make drawing easier. Add any atoms, bonds, lone pairs, and charges necessary to complete the structures. You may not need them all or you may need to add some of your own. It's up to you. Use curved arrows to show shifts of electrons. 12 (a) CHO- N CHO N Ne CH N 5 CHO N: 3 (b) Draw the actual structure (or "resonance hybrid") of the cation. CH 8+ S+ 4. (10 points) Add all the Hs, in their correct geometrical positions, to the skeletal structure shown. H HH 0: H H H 5. (16 points) For each compound below, state the number of electrons in the conjugated cycle, if any, and decide whether the compound is aromatic, antiaromatic, or non-aromatic. Assume each conjugated x-system is planar. aromatic B no conj. cle 10 es Gram, 8πος antiavan. 6. (14 points) The nitrogen of aniline (below left) is flattened considerably relative to the N in ammonia (NH3), but it is not quite planar. The N of para-acetylaniline (below right) is planar. Explain why aniline's N is not quite planar, but para-acetylaniline's N is planar. You are strongly encouraged to draw resonance structures.

Exam 1 Chemistry 21 Key

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