Chapter 7: Problem 154

Give structures and names of the organic products expected from the reaction of 1 -butyne with the following: (a) 1 mole \(\mathrm{H}_{2}, \mathrm{~N}\) i (b) 2 moles \(\mathrm{Br}_{2}\) (c) 2 moles \(\mathrm{HC} 1\)

Short Answer

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The organic products expected from the reaction of 1-butyne with the given reagents are: (a) Reaction with 1 mole \(\mathrm{H}_{2}, \mathrm{~N}\) i: cis-2-butene, with the structure: H H | | H-C=C-C-C-H | | H H (b) Reaction with 2 moles \(\mathrm{Br}_{2}\): 1,1,2,2-tetrabromoethane, with the structure: Br Br | | Br-C-C-C-C-Br | | Br Br (c) Reaction with 2 moles \(\mathrm{HCI}\): 1,1,2-trichloroethane, with the structure: CI CI | | CI-C-C-C-C-H | | CI H

Step by step solution

Reaction with \(\mathrm{H}_{2}, \mathrm{~N}\) i

First, we have to react 1-butyne with 1 mole of hydrogen gas in the presence of a nickel catalyst. This reaction is a hydrogenation reaction. Alkynes undergo hydrogenation to form alkenes. In this case, since only 1 mole of \(\mathrm{H}_{2}\) is supplied, it will undergo partial hydrogenation and form a cis-alkene. So in the presence of a nickel catalyst, the triple bond in 1-butyne will be reduced to a double bond. The structure of the product will be: H H | | H-C=C-C-C-H | | H H The name of the product is: cis-2-butene

Reaction with 2 moles of \(\mathrm{Br}_{2}\)

Next, we will react 1-butyne with 2 moles of bromine. This reaction is a halogenation reaction. Alkynes undergo halogenation to form dihalides. In this case, two moles of \(\mathrm{Br}_{2}\) are supplied, so the triple bond will be converted to a single bond with four bromine atoms attached to it. The structure of the product will be: Br Br | | Br-C-C-C-C-Br | | Br Br The name of the product is: 1,1,2,2-tetrabromoethane

Reaction with 2 moles of \(\mathrm{HCI}\)

Finally, we will react 1-butyne with 2 moles of hydrochloric acid. This reaction is a hydrohalogenation reaction. Alkynes undergo hydrohalogenation to form dihalides by breaking the triple bond. In this case, two moles of \(\mathrm{HCI}\) are supplied, so the triple bond will be converted to a single bond with one chlorine attached to the first carbon and two chlorines attached to the second carbon. The structure of the product will be: CI CI | | CI-C-C-C-C-H | | CI H The name of the product is: 1,1,2-trichloroethane

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Give structures and names of the organic products expected from the reaction of 1 -butyne with the following: (a) 1 mole \(\mathrm{H}_{2}, \mathrm{~N}\) i (b) 2 moles \(\mathrm{Br}_{2}\) (c) 2 moles \(\mathrm{HC} 1\)

Short Answer

Step by step solution

Reaction with \(\mathrm{H}_{2}, \mathrm{~N}\) i

Reaction with 2 moles of \(\mathrm{Br}_{2}\)

Reaction with 2 moles of \(\mathrm{HCI}\)

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