Predict the product of the following alkyne reductions.

(b)

Predict the product of the following alkyne reductions.

(c)

Suggest alkynes that might be used to make the following trans-alkenes.

(a)

Suggest alkynes that might be used to make the following trans-alkenes.

(b)

Suggest alkynes that might be used to make the following trans-alkenes.

(c)

The following deprotonation step occurs during the trans reduction of an alkyne. Calculate K_eq for this reaction.

When sodium generates electrons in the presence of ammonia, these electrons persist in solution, giving the blue color. However, electrons do not persist when sodium is added to water. Why?

Sodium amide, the base we use to deprotonate terminal alkynes, is synthesized by reducing ammonia via a mechanism similar to the reduction of alkynes in Figure 10.21. Suggest a mechanism for this reaction.

Long, polarized bonds are also reducible in the same way that the C―C π bond of an alkyne is. Show a mechanism by which a C―Br bond might be reduced by sodium metal.

We have studied the following reactions in previous chapters. For each, (i) indicate which reaction sheets they should appear on, (ii) show the best structure to use to represent them, and (iii) write the notes you could put in the margin so that the mechanism is implied.

(b) Radical halogenation of an alkane

The alkyl carbocation is estimated to be 15 kcal/mol more stable than the alkenyl carbocation. If this is also the difference in the energies of the transition state leading to each, what is the expected rate difference? 

<IMAGE>

Predict the major products resulting from the addition of one equivalent of HX to the following alkynes.

(b)

Predict the alkyne and reactants you might use to make the following haloalkenes. [Providing the reactant and the reagent is how we start thinking about synthesis.]

(a)

Predict the alkyne and reactants you might use to make the following haloalkenes. [Providing the reactant and the reagent is how we start thinking about synthesis.]

(b)

Draw the ketone(s) you would expect to form by reacting the following alkynes under the conditions of oxymercuration: (a) 6-methyloct-1-yne, (b) 1,10-dicyclohexyldec-5-yne, and (c) 5-phenylhex-2-yne.

Draw the ketone(s) you would expect to form by treating the following alkynes under the conditions of hydroboration–oxidation: (a) 6-methyloct-1-yne, (b) 1,10-dicyclohexyldec-5-yne, and (c) 5-phenylhex-2-yne.

<IMAGE>

For each of the following ketones/aldehydes, indicate whether it is possible to synthesize it from an alkyne as the only compound in good ( > 50%) yield. If so, how would you do it?

(a)

For each of the following ketones/aldehydes, indicate whether it is possible to synthesize it from an alkyne as the only compound in good (> 50%) yield. If so, how would you do it?

(d)

When doing synthesis, you will often find yourself repeating the same series of steps. To see this in action, synthesize the following aldehydes beginning with an organic molecule containing three carbons or fewer.

(b)

When doing synthesis, you will often find yourself repeating the same series of steps. To see this in action, synthesize the following aldehydes beginning with an organic molecule containing three carbons or fewer.

(d)

Beginning with the molecules on the left of each chemical equation, synthesize the molecules shown. While there can be multiple ways of doing each synthesis, the minimum number of steps necessary is indicated over each reaction arrow.

(a)

Beginning with the molecules on the left of each chemical equation, synthesize the molecules shown. While there can be multiple ways of doing each synthesis, the minimum number of steps necessary is indicated over each reaction arrow.

(b)

Beginning with the molecules on the left of each chemical equation, synthesize the molecules shown. While there can be multiple ways of doing each synthesis, the minimum number of steps necessary is indicated over each reaction arrow.

(c)

Name the following alkynes according to the IUPAC rules of nomenclature.

(b)

Name the following alkynes according to the IUPAC rules of nomenclature.

(c)

Name the following alkynes according to the IUPAC rules of nomenclature.

(d)

Draw the molecular orbital picture of pent-1-en-3-yne.

To which carbon would you expect an electrophile to add (1, 3, or 4)? Explain your answer.

For the alkynes shows here, show the product(s) expected to form when treated under the following conditions: (i) H₂ , Pd/C; If you expect two products, show both.

(c)

For the alkynes shows here, show the product(s) expected to form when treated under the following conditions: (ii) H₂, Pd/C, Pb(OAc)₂ , CaCO₃ (Lindlar's catalyst). If you expect two products, show both.

(c)