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Chapter 7: Problem 156

Outline all steps in the synthesis of (a) 1 -butyne and \(\quad\) (b) 2-butyne from acetylene using any needed organic or inorganic reagents.

Short Answer

Expert verified
(a) Synthesis of 1-butyne from acetylene: 1. Add HCl to acetylene to form chloroethene (C2H2 + HCl -> C2H3Cl) using a Pd(II) catalyst. 2. Perform Kumada-Corriu cross-coupling reaction with vinyl chloride and n-propylmagnesium bromide using a Pd(0) catalyst: C2H3Cl + CH3CH2CH2MgBr -> HC≡CCH2CH2CH3 + MgBrCl. (b) Synthesis of 2-butyne from acetylene: 1. Add Br2 to acetylene to form 1,2-dibromoethane (C2H2 + 2Br2 -> C2H2Br2) under UV light or heat. 2. Treat 1,2-dibromoethane with magnesium in dry ether to form ethylene(magnesium bromide) Grignard reagent (C2H2Br2 + Mg -> C2H2MgBr2). 3. React the formed Grignard reagent with acetylene to form 2-butyne (C2H2 + C2H2MgBr2 -> CH3C≡CCH3 + MgBr2).

Step by step solution

01

Formation of vinyl chloride (chloroethene) from acetylene

Add hydrogen chloride (HCl) to acetylene to form chloroethene. This reaction proceeds under palladium(II) catalyst. The reaction can be represented as: \[ C_2H_2 + HCl \rightarrow C_2H_3Cl \]
02

Kumada-Corriu cross-coupling reaction to form 1-butyne

Use the Kumada-Corriu cross-coupling reaction by reacting vinyl chloride with an organomagnesium reagent (Grignard reagent). For this, react vinyl chloride with n-propylmagnesium bromide, using a palladium(0) catalyst like "Pd(PPh3)4" (tetrakis(triphenylphosphine)palladium) and an appropriate solvent (e.g., ether) under inert atmosphere. This will form the desired 1-butyne. The reaction can be represented as: \[ C_2H_3Cl + CH_3CH_2CH_2MgBr \rightarrow HC \equiv CCH_2CH_2CH_3 + MgBrCl \] (b) Synthesis of 2-butyne from acetylene
03

Formation of 1,2-dibromoethane from acetylene

Add bromine (Br2) to acetylene to form 1,2-dibromoethane. This reaction proceeds under the UV light or in the presence of a heat source. The reaction can be represented as: \[ C_2H_2 + 2Br_2 \rightarrow C_2H_2Br_2 \]
04

Formation of a Grignard reagent

Treat 1,2-dibromoethane with magnesium in dry ether to form ethylene(magnesium bromide), which is a Grignard reagent. The reaction can be represented as: \[ C_2H_2Br_2 + Mg \rightarrow C_2H_2MgBr_2 \]
05

Formation of 2-butyne through Grignard reagent reaction with acetylene

React the formed Grignard reagent (ethylene(magnesium bromide)) with acetylene. This leads to the formation of 2-butyne. The reaction can be represented as: \[ C_2H_2 + C_2H_2MgBr_2 \rightarrow CH_3C \equiv CCH_3 + MgBr_2 \]

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Most popular questions from this chapter

You are given a mixture of 1 -butyne (bp \(8^{\circ}\) ) and 2 -butyne (bp \(27^{\circ}\) ). How could you separate, and then recover, each of these compounds using chemical means?

Give the equations and mechanisms for the reactions of sodium methyl acetylide with: (a) 1-bromobutane (b) 2-bromobutane.

Outline all steps in the synthesis of propyne from each of the following compounds, using any needed organic or inorganic reagents. (a) 1,2 -dibromopropane (e) n-propyl alcohol (b) propylene (f) 1,1 -dichloropropane (c) isopropy1 bromide (g) acetylene (d) propane (h) \(1,1,2,2\) -tetrabromopropane

Prepare an alkyne from each alkene precursor by the dehydrohalogenation of alky1 dihalides method.

Write equations for all steps in the manufacture of acetylene starting from limestone and coal.
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