Question

How are alkene obtained?

Answer 1

First of all we have to know about alkenes, so alkene are the hydrocarbons in which at least one double bond is present between two carbon atoms and its general formula is denoted as ${{\text{C}}_{\text{n}}}{{\text{H}}_{{\text{2n}}}}$, where n is the number of carbon atoms present in that molecule.

Complete answer:
The path which we have to follow to obtain alkene will depend upon the species from which we have to find out the alkene. In chemistry many mechanism and reactions are present to obtain alkenes and some processes are given below:
-Through reduction
When we have to obtain alkene from alkyne then we have to follow the process of reduction of alkyne in the following way:
${{\text{C}}_{\text{2}}}{{\text{H}}_{\text{2}}}{\text{ + }}{{\text{H}}_{\text{2}}} \to {{\text{C}}_{\text{2}}}{{\text{H}}_4}$
-Through oxidation
When we have to obtain alkene from alkanes then we have to follow the process of oxidation of alkane in the following way:
${{\text{C}}_{\text{2}}}{{\text{H}}_6} \to {{\text{C}}_{\text{2}}}{{\text{H}}_4}{\text{ + }}{{\text{H}}_{\text{2}}}$
-Through dehydration
When we have to obtain alkene from alcohol then we have to follow the process of dehydration of alcohol in the presence of strong acid in the following way:
${\left( {{\text{C}}{{\text{H}}_{\text{3}}}} \right)_{\text{2}}}{\text{CH - CH}}\left( {{\text{C}}{{\text{H}}_{\text{3}}}} \right)\left( {{\text{OH}}} \right)\xrightarrow[{ - {H_2}O}]{{{H_2}S{O_4}}}{\left( {{\text{C}}{{\text{H}}_{\text{3}}}} \right)_{\text{2}}}{\text{C = CHC}}{{\text{H}}_{\text{3}}}$
-Through de-hydro-halogenation:
When we have to obtain alkene from alkyl halide then we have to follow the process of de-hydro-halogenation of alkyl halides in the presence of alcoholic ${\text{KOH}}$, in the following manner:
${\text{RC}}{{\text{H}}_{\text{2}}}{\text{C}}{{\text{H}}_{\text{2}}}{\text{X}} \to {\text{RCH = C}}{{\text{H}}_{\text{2}}}{\text{ + HX(X = Cl,Br,I)}}$

Note:
Please keep in mind that above given processes are not only restricted mechanisms to obtain alkenes from different compounds in chemistry, beside these many processes are also present.