Organic Chemistry> Preparation of 3-octyne from 1-hexyne ? S...

Preparation of 3-octyne from 1-hexyne ? Step by step

Ayan22 , 8 Years ago

Grade 12

1 Answers

Joy

Last Activity: 8 Years ago

Method 1enter image description here1) Reduction using sodium metal in pure ammonia to an alkene.2) Halohydrin formation; the -OH installs at the more substituted carbon due to its greater ability to stabilize positive charge (this always confused me; the more substituted carbon is both more positive in character and has more electron-donating methyl groups?)3) Conversion of OH to a good leaving group (-OTs) using a sulfonate ester and a weak base, pyridine.4) E2 elimination using NaOH and heat. Because of resonance and sheer bulk and negative induction the OTs(-) should make for a better leaving group than Br-. So the internal alkene is formed.5) Two-part one step ozonolysis; creation of aldehyde.6) Reduction of carbonyl with hydrogen and transition metal to terminal alcohol.7) Conversion of terminal alcohol to a better leaving group using tosyl chloride and pyridine again.8) Use of LDA to deprotonate and create the terminal alkene.Method 2Also we can take another route with the brominated alkene; we can use OsO4 and basic hydrogen peroxide to create a 1,2 (vic) diol, which can be cleaved by periodic acid, and this creates a primary alcohol, which we convert to a good leaving group using tosyl chloride and pyridine, and we can eliminate. Same number of steps, but just something different that I thought of. Well, perhaps slightly simpler since there isn`t a need for a two-step process (ozonolysis). After getting this you can replace 1-octyne it will help you in practice also