1-Bromobutane acetylene

Write a series of equations showing how to prepare cis 5 decene from acetylene and 1 bromobutane as the source of all its carbons using any nec essary organic or inorganic reagents Hint You may find it helpful to review Sec tion 9 6)... 

Alkyne alkylation is not limited to acetylene itself. Any terminal alkyne can be converted into its corresponding anion and then alkylated by treatment with an alkyl halide, yielding an internal alkyne. For example, conversion of 1-hexyne into its anion, followed by reaction with 1-bromobutane, yields 5-decyne. 

Solution The synthesis can be completed in four steps from acetylene and 1-bromobutane ... 

Silver fluoborate, reaction with ethyl bromide in ether, 46, 114 Silver nitrate, complexing with phenyl-acetylene, 46, 40 Silver oxide, 46, 83 Silver thiocyanate, 45, 71 Sodium amide, in alkylation of ethyl phenylacetate w ith (2-bromo-ethyl)benzene, 47, 72 in condensation of 2,4-pentanedione and 1 bromobutane to give 2,4-nonanedione, 47, 92 Sodium 2 ammobenzenesulfinate, from reduction of 2 mtrobenzenesul-finic acid, 47, 5... 

Dialkylation of acetylene with 1-bromobutane, prepared in part (/), gives the necessary ten-carbon chain. 

Problem 8.33 Show reagents and reactions needed to prepare the following compounds from the indicated starting compounds, (a) Acetylene to ethylidene iodide (1,1-diiodoethane). (b) Propyne to isopropyl bromide, (c) 2-Butyne to racemic 2,3-dibromobutane. (d) 2-Bromobutane to trans-2-butene. (e) n-Propyl bromide to 2-hexyne. (/) 1 -Pentene to 2-pentyne. ... 

What is an immediate precursor of 1-hexyne " Perhaps acetylene and l-bromobutane. 

The nucleophilic acetylide ion uses an electron pair to attack the positively, polarized, electrophilic carbon atom of bromomethane. As the new C-C bond forms, Br" departs, taking with it the electron pair from the former C-Br bond and yielding propyne as product. We call such a reaction an alkyla-l tion because a new alkyl group has become attached to the starting alkyne. Alkyne alkylation is not limited to acetylene itself, Any terminal alkyne s can be converted into its corresponding anion and then alkylated by treat-j ment with an alkyl halide, yielding an internal alkyne. For example, con/ version of 1-hexyne into its anion, followed by reaction with 1-bromobutane,] yields 5-decyne ... 

Starting with acetylene and 1-bromobutane as the only sources of carbon atoms, show how to synthesize the following. 

Using acetylene as your only source of carbon atoms, identify a synthetic route for the production of 2-bromobutane. 

The product is a tmns alkene, which can be made from an alkyne. So the last step of our synthesis might be a dissolving metal reduction to convert the alkyne below into the product. This alkyne can be made from acetylene and 1-bromobutane via alkylation processes ... 

Bromobutane can be made fiom 1-butyne, which can be made from acetylene and ethyl bromide via an alkylation process ... 

Now, let s draw out the forward scheme. Acetylene is reduced to ethylene using H2 and Lindlar s catalyst. HBr addition, followed by Sn2 substitution with an acetylide nucleophile (made by deprotonation of acetylene with sodium amide) gives 1-butyne. Reduction to 1-butene with H2 and Lindlar s catalyst followed by anrt-Markovnikov addition of HBr in the presence of peroxide produces 1-bromobutane. A substitution reaction with sodium acetylide gives 1-... 

Hexyne is made from an S]m2 reaction between acetylene (which must be deprotonated to form an acetyhde ion) and 1-bromobutane. 

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