Name ______________KEY___________________________
Throughout this exam, give answers only in the provided spaces (boxes or lines). Answers not in these spaces will not be graded, even if correct.
1. (12 pts) Give acceptable names for the following compounds,
being sure to address alkene geometry and R/S configuration where appropriate.
2. (14 pts) For each of the following four molecules, list the properties from the list on the right which best describe it. Each item on the list can be used as often as necessary, or not at all. DON'T GUESS!!
| a. contains a chiral carbon | |
| b. SN1 reaction very probable | |
| CH3Br ____c e k_____________ | c. incapable of an elimination reaction |
| d. reacts with Br2 (uncatalyzed) | |
| PhBr ______c f i j___________ | e. SN2 reaction very probable |
| f. contains no sp3 carbons | |
| CH3CH2Br _____e h k______________ | g. capable of E1 reaction to form an alkene |
| h. capable of E2 reaction to form an alkene | |
| 2-bromo-2-
methylpropane _____b g h____________ |
i. reacts with CH3Cl/AlCl3 |
| j. completely planar (all atoms) | |
| k. reacts with NaOH to form an alcohol | |
| l. a meso compound |
3. (30 pts) Complete the following reactions (provide either the starting molecule, the reagent(s), or product(s). If more than one product is produced, draw them all. If one product predominates, circle it.
4. (16 pts) Indicate a synthesis of any TWO (2) of the following four molecules from the indicated starting materials. You may use any inorganic reagents you like, but all carbon atoms must come from the starting materials provided. Please fill in the letter of your choices in the spaces provided.
a. methoxybenzene (anisole, PhOCH3) from phenol and methanol
b. phenylethene (styrene, PhCH=CH2) from benzene and ethanol
c. 2-bromopropane from 1-bromopropane
d. t-butyl methyl ether (2-methoxy-2-methylpropane) from 2-methylpropene and iodomethane
5. (16 pts) Explain the following observations.
a. Phenol is about a million times more acidic than ethanol (pKa of about 10 vs. about 16, respectively). Use resonance structures in your answer.
The strength of an acid is determined by the stability of its conjugate base - the more stable the conjugate base, the stronger the acid. The conjugate base of phenol is resonance- stabilized, as shown, while the conjugate base of ethanol (CH3CH2O-) has no such stabilization. Thus, phenol is many times more acidic than ethanol.
b. (R)-2-bromohexane, when treated with sodium bromide, yields racemic 2-bromohexane as the product. This is true irrespective of the solvent.
In polar solvents, a carbocation is formed which can then be attacked
with equal probability by bromide on either of its two faces. Since attack
on one face yields one enantiomer, and attack on the other yields the opposite
enantiomer, racemization occurs. In nonpolar solvents, SN2 displacement
occurs, yielding the opposite enantiomer. This process will eventually
give an equal mixture of both enantiomers.
6.(8 pts) Outline the mechanism of the reaction (diagrammed in the box) of t-butyl iodide and methanol to form methyl t-butyl ether as the major product, with 2-methylpropene (isobutylene) as a by-product. A complete mechanism will account for both products.
7. (4 pts) Circle the aromatic molecules or ions in the following selection:
An alternative method for forming alkyl benzene derivatives is via the acid-catalyzed reaction of alkenes with aromatics. Provide a mechanism which accounts for the transformation illustrated in the box.
