2-methyl-2-pentene from propyne and isomers, characteristics

Synthesis 2-methyl-2-pentene from propyne. You can use any organic reagents. But note that you have to start the conversion with propyne.


2-methyl-2-pentene is an alkene compound. A -CH3 group is attached as a substitution group. Five carbon atoms contain in the major branch.


Preparing 2-methyl-2-pentene

IUPAC name of 2-methyl-2-pentene demonstrates an alkene compound. We have synthesis 2-methyl-2-pentene from propyne. Propyne and 2-methyl-2-pentene contain 3 and 6 carbon atoms respectively. Number of carbon atoms of propyne is doubled when 2-methyl-2-pentene is prepared. But propyne is not straightly doubled to give 2-methyl-2-pentene.

propyne to 2-methyl-2-pentene

Preparing 2-methyl-2-pentene from propyne

Each stepes of preparing 2-methyl-2-pentene from propyne is explained below.

Propyne hydrolysis

Alkyne hydrolysis is done by HgSO4 and dilute H2SO4 and give aldehyde or ketone as products. Propyne hydrolysis gives propanone as the product. Here, HgSO4 and dilute H2SO4 behave as catalysts.

Propanone aldol condensation with dilute NaOH

Aldehyde or ketone react with dilute NaOH to give compounds with longer carbon chains. (Aqueous KOH also can be used instead of NaOH).

Heating the solution

Solution is heated with I2 or alone to dehydrate the -OH bond. A double bond forms. The carbonyl group exists without any change.

Clemmensen reduction

Aldehyde or ketone can be reduced to hydrocarbons using clemmensen reduction. This reaction is called clemmensen reduction. Zn(Hg) and concentrated HCl is used as the reagent. So given aldol product is reduced by Clemmensen reduction. Otherwise we can simply this by reducing -CHO to -CH2.

propyne to 2-methyl-2-pentene conversion

Physical properties of 2-methyl-2-pentene from propyne

  • 2-methyl-2-pentene is a liquid and from propyne is a gas at room temperature.
  • 2-methyl-2-pentene is an alkene and propyne is an alkyne.

Chemical properties of 2-methyl-2-pentene from propyne

  • Propyne reacts with Na. But 2-methyl-2-pentene does not.
  • Both compounds reacts with liquid Br2.
  • Alkyne hydration is more difficult than alkene.

Isomers of 2-methyl-2-pentene

There are no optical isomerism and geometric isomerism.

Organic conversions exercises