9 • Additional Problems
9 • Additional Problems
The following cycloalkyne is too unstable to exist. Explain.
Reaction of acetone with D3O+ yields hexadeuterioacetone. That is, all the hydrogens in acetone are exchanged for deuterium. Review the mechanism of mercuric-ion-catalyzed alkyne hydration, and then propose a mechanism for this deuterium incorporation.
Reactions of Alkynes
Terminal alkynes react with Br2 and water to yield bromo ketones. For example:
Propose a mechanism for the reaction. To what reaction of alkenes is the process analogous?
Predict the products of the following reactions:
Identify the reagents a–c in the following scheme:
How would you carry out the following multistep conversions? More than one step may be needed in some instances.
How would you carry out the following multistep transformation?
How would you carry out the following multistep conversions?
The sex attractant given off by the common housefly is an alkene named muscalure. Propose a synthesis of muscalure starting from acetylene and any alkyl halides needed. What is the IUPAC name for muscalure?
Organometallic reagents such as sodium acetylide undergo an addition reaction with ketones, giving alcohols:
How might you use this reaction to prepare 2-methyl-1,3-butadiene, the starting material used in the manufacture of synthetic rubber?
The oral contraceptive agent Mestranol is synthesized using a carbonyl addition reaction like that shown in Problem 9-50. Draw the structure of the ketone needed.
1-Octen-3-ol, a potent mosquito attractant commonly used in mosquito traps, can be prepared in two steps from hexanal, CH3CH2CH2CH2CH2CHO. The first step is an acetylide-addition reaction like that described in Problem 9-50. What is the structure of the product from the first step, and how can it be converted into 1-octen-3-ol?
Hydrocarbon A has the formula C9H12 and absorbs 3 equivalents of H2 to yield B, C9H18, when hydrogenated over a Pd/C catalyst. On treatment of A with aqueous H2SO4 in the presence of mercury(II), two isomeric ketones, C and D, are produced. Oxidation of A with KMnO4 gives a mixture of acetic acid (CH3CO2H) and the tricarboxylic acid E. Propose structures for compounds A–D, and write the reactions.
A cumulene is a compound with three adjacent double bonds. Draw an orbital picture of a cumulene. What kind of hybridization do the two central carbon atoms have? What is the geometric relationship of the substituents on one end to the substituents on the other end? What kind of isomerism is possible? Make a model to help see the answer.
Which of the following bases could be used to deprotonate 1-butyne?
(a) (b) (c) (d)