CHE 230 Organic ChemistryExam 1, September 22, 1999
Before you begin this exam: First: You are allowed to have a calculator and a simple model set at your seat. Please put away all other materials. Second: Place your student identification on your desk. A proctor will come around to check everyone’s ID. Third: Read through the entire exam. Your goal, as always, is to score as many points as possible. Do not waste time on problems that you can’t do if there are others that look easy. Fourth: It is critically important that your answers be written in a clear, unambiguous manner. Answers in which your intentions are unclear will not receive credit. Fifth: READ THE INSTRUCTIONS FOR EACH PROBLEM.
You have until 8:50 to complete this exam. There will be no extensions, so budget your timecarefully.
(14 points) Assign the hybridization at the indicated atoms in the molecules below. Amoxicillin (a penicillin antibiotic) Viagra (a recreational drug)
(8 points) Give the Lewis dot structures for the following species:
(6 points) Which of the following molecules would have a net dipole moment? (Circlethem)
(10 points) Assign the formal charge at the central atom in each of the followingcompounds (assign the charge on B in a) and on N in b)). Charge is -1 Charge is +1
(8 points) Draw a 3-D drawing of an sp2 hybridized carbon atom. Please be sure to showthe lobed shaped of each of the orbitals present, and label each hybrid orbital (as sp3, sp2, orsp) and each atomic orbital (as s or p). It will help if you draw fairly large.
(8 points) Draw two additional resonance forms for the molecule shown below (more than 2are possible - just draw any two acceptable forms). Be sure to use the appropriate arrow todenote resonance forms.
(5 points) Peptides and proteins contain numerous amide groups, shown below. Thenitrogen in an amide is sp2 hybridized. Provide a brief explanation for why nitrogen adoptsthis hybridization rather than sp3. Please do not exceed the space provided, and aconvincing answer can be given in one or two sentences. Sometimes a picture helps a lottoo.
The N is sp2 hybridized because this places the lone pair in a p orbital where it can bedelocalized through resonance.
(3 points) How many π molecular orbitals are there in the allyl cation (below)?
(4 points) Draw the resonance hybrid for the allyl cation (one resonance form is shownbelow). Indicate partial π bonding (if any) with a dotted line and be sure you show anyfractional charges.
a) (5 points) Circle the favored side of the following equilibrium.
b) (5 points) What is the value of the equilibrium constant for this equilibrium? Note:you should not need a calculator. Simply writing the correct answer will earn full credit, butfor any partial credit, all of the work must be shown.
(6 points) Draw 3 different structural isomers for C H . If you give more than 3, I will
(8 points) For each of the compounds below, state that they are isomers or that they are thesame compound.
(10 points) Acetone (shown below) is much more acidic than a hydrocarbon like propane(also shown below). Provide a brief explanation for the relatively low pKa of acetone.
The conjugate base of acetone is stabilized by resonance, which places the anion on oxygen,an electronegative atom. The conjugate base of propane is not stabilized.
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