CHE 24, Fall 1998
October 26, 1998
1. Multiple choiceŚchoose the one BEST answer for each of the following: (2 points each)
Which of the following structures is an enantiomer of lactic acid, shown below?
Which of the following accurately describes (+)-glucose?
Which of the following is not true of enantiomers?
Which of the following intermediates is formed during the Markovnikov addition of HBr to 1-methylcyclohexene?
Which is the best method to accomplish the transformation shown?
2. (a) Label each hydrogen in the following molecule with a letter to designate which hydrogens are alike and which are different. For each type of hydrogen, indicate the relative integral sizes. (5 points)
(b) Consider a sample that is a mixture composed of naphthalene, benzoic acid, and benzyl bromide, with the structures shown below. Predict the order of elution of the components in this mixture. Assume that the chromatography uses a silica column, and the solvent system is based on acetone, with an increasing proportion of isopropanol being added as a function of time. Explain why the compounds elute in the order that you predict. (5 points)
3. Provide the major products for the following reactions, showing stereochemistry where appropriate. (4 points each reaction)
4. Synthesize the following compound, using acetylene, alkyl halides, and any inorganic reagents as starting materials. Show all reagents and the product formed in each step of your synthetic scheme. (20 points)
5. Reaction of cis-2-butene with OsO4 (followed by reaction with NaHSO3) yields a different product than reaction of trans-2-butene. (20 points)
(a) Draw the structures of the starting material and products for both of these reactions, showing the stereochemistry of each compound.
(b) Which of the products is a meso compound? Explain briefly.
6. When cyclohexene is allowed to react with bromine (Br2) in an aqueous solution of sodium chloride, the products are trans-1,2-dibromocyclohexane, trans-2-bromocyclohexanol, and trans-1-bromo-2-chlorocyclohexane. (20 points)
(a) Write a mechanism that explains how each of these products can be formed, using arrows to show the flow of electrons.
(b) Explain why no products have cis stereochemistry.
(c) Explain why no dichloro or diol (two alcohol) products are formed.