Which is more Reactive, Alkane, Alkene, or Alkyne?

Read our take on the question of alkane vs alkene vs alkyne comparisons where we take into account their reactivities and factors influencing them.

Introduction：

The comparison of alkane vs alkene vs alkyne and the difference in their chemical properties demands a background knowledge of what these entities are. First of all, hydrocarbons, are extremely important to all life forms. Primarily found in fossil fuels, these compounds are commonly used in numerous industrial processes and as a fuel source.

These hydrocarbons exist in abundance and are extremely versatile compounds due to their carbon bonding scheme in the molecular structure. The ones that have single bonding in their molecular structure are called saturated hydrocarbons and the ones that have double or triple are called unsaturated hydrocarbons. Alkanes, alkenes, & alkynes are all subsets of hydrocarbons and differ due to their number of bonds between the carbon atoms.

Difference between alkane alkene and alkyne

Alkanes (also known as paraffin) are saturated hydrocarbons with single carbon bonds in their molecular structure. Represented by chemical formulae of C_nH_2n+2, this kind of hydrocarbon has a tree-shaped structure in which all the carbon–carbon bonding is with single bonds (sigma (σ) bonds) i.e a bond which is formed by two carbons combined in a way that their atomic orbitals are overlapped along the bond axis between the two atoms.

Alkenees on the other hand are a type of unsaturated hydrocarbons that have at least one carbon-to-carbon double bond in their molecular structure. These double bonds are one sigma bond (σ) and one pi bond (π). This pi bond forms due to the sideways overlapping of p-orbitals in a carbon atom. This unsaturation in alkenes is due to this double bond which can break and form new compounds when allowed to react with other chemical entities. Finally, alkynes are another unsaturated class of hydrocarbons with at least one triple bond between carbon atoms.

Which is more Reactive?

Comparing reactivities when putting alkane vs alkene vs alkyne in focus is directly related to their carbon bonding scheme in their molecular structure. Alkanes which are single-bonded have the least reactivity and alkynes which are triple-bonded have the highest reactivity in between these three. Alkynes’ greater reactivity as compared to the other two can be explained below reasons:

1. Presence of Multiple Pi Bonds:

Alkynes have three carbon-carbon bonds in which there is one sigma bond and two pi bonds. The sigma bonds result from direct overlapping of carbon orbitals while pi bonds are formed from sideways overlapping.

These two bonds are much weaker as compared to sigma bonds and provide an opportunity for alkynes to lose these electrons and bond with new compounds. This results in significantly greater reactivity as compared to alkanes and alkenes.

2. Electron Density

As a general rule, higher electron density means higher reactivity due to the increased nucleophilic nature. The triple bonds of carbon atoms in alkynes give them much more electron density as compared to alkenes and alkanes making them more nucleophilic and more reactive.

3. Unsaturated Bonds:

The most important factor is that alkynes have unsaturated bonds in their molecular structure. As a general rule of thumb, reactivity depends upon the degree of unsaturation in a molecule. Alkynes triple bonds have two pi bonds making them susceptible to being broken easily during reactions.

Applications:

The higher reactivity of alkynes makes it much more significant in the industries where they are commonly used to create complex molecules for pharmaceutical, agrochemical, and fine chemical industries. They are also used to introduce functional groups (carbonyl groups, hydroxyl, and halogens) into other important organic molecules.

They are also used in many polymerization processes to produce special polymers for various purposes. For example, it is used to create acetylene used to further commercially produce polyacetylene. This polymer is extremely important in materials sciences connected with electrical equipment. It is also frequently used to create certain copolymers used in making products where flexibility and strength are important.

Conclusion:

To conclude the activities in the comparison of alkane vs alkene vs alkyne, it can be stated that alkynes are much more reactive due to their pi bonds in the molecular structure. This increased reactivity makes them useful in our industry processes for making polymers and other complex compounds.