Propose a mechanism for the entire reaction of pent-1-yne with 2 moles of HBr. Show why Markovnikov's rule should be observed in both the first and second additions of HBr.

Using hex-1-ene as your starting material, show how you would synthesize the following compounds. (Once you have shown how to synthesize a compound, you may use it as the starting material in any later parts of this problem.)

a. 1,2-dibromohexane

b. hex-1-yne

c. 2,2-dibromohexane

Predict the products of reaction of pent-1-yne with the following reagents.

a. 1 equivalent of HCl

b. 2 equivalents of HCl

c. excess H₂, Ni

Predict the major product(s) of the following reactions:

a. phenylacetylene + 2 HBr

b. hex-1-yne + 2 HCl

For the alkynes shows here, show the product(s) expected to form when treated under the following conditions: (iv) HBr (1 equiv.). 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: (v) HCl (2 equiv.). If you expect two products, show both.

(c)

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)

HBr and peroxides are also used to generate 1-bromo-1-alkenes. Suggest a starting reactant that would successfully undergo this reaction.