Question

Starting with acetylene use a sequence of reagents to show how you could make each of the following products. Note that some steps will be redundant so please just start from a common intermediate once you have shown its synthesis. For example, all of the other products can be made from either 1-butyne or 2-hexyne. You may not use any other source of C other than methyl bromide, calcium carbide, chloroform and the products you can make from these sources. Note the stereochemistry. Ethene (see 19.5- you'll need to use catalytic hydrogenation a number of times) bromoethane 1-butvne (You must make haloethane to make 1-butyne)

Answer 1

Ethylene (C2H4) is a gas with a low boiling. It is formed in large amounts during the cracking of petroleum and is an important and common industrial chemical. Ethene or ethane can be produced from acetylene by the addition of hydrogen in the presence of a noble metal catalyst such as platinum (Pt) or palladium (Pd). For preparing Ethene we supply H2 gas in limited quantity.

Bromoethane can be prepared from acetylene catalytic hydrogenation to form ethene and then by photochemical reaction with bromine.

1-butyne can be prepared using sodium amide in ammonia through sn1 reaction.

2 H2 Pd limited supply of H2 Acetylene Ethene 2 H2 Br2 Pd light Acetylene ethane or heat Bromoethane Photochemical reaction NaNH3 C Na NH3 Acetylene Bromoethane Acetvlide anion NaBr l-butyne