Question

Write short notes on Baeyer’s strain theory.

Answer 1

As we know that in organic chemistry, hydrocarbons are an important topic. The hydrocarbons are majorly classified as three groups. There are alkane, alkene and alkyne. The alkane means carbon-carbon single bond. The alkene has a carbon-carbon double bond. The alkyne means carbon-carbon having triple bond in the molecule.

Complete answer:
We must have to know that Baeyer strain theory is used to compare stability of cycloalkanes with cyclic saturated compounds. The hybridisation carbon atom is $s{p^3}$. Hence, the bond angle between carbon and other atoms in the structure is . But for cycloalkane angle calculated in different ways.
Bond angle is used to calculated as,
$= \dfrac{{180 - 360}}{n}$
Here, n is the number of carbon atoms used to make the ring.
Angle strain is nothing but the angle difference between original angles from coming angle. Angle strain is equal to the half of difference between original angles from coming angle.
The original angle is .
${\text{Angle strain}} = \dfrac{1}{2}\left( {109^\circ 28' - {\text{Bond angle in ring}}} \right)$
This theory is valued up to cyclopentane only. Because in cyclic compound angle strain increases stability of the ring will decrease. Cyclic compound angle strain decreases stability of the ring. Angle strain is inversely proportional to the ring stability.
${\text{Angle strain}} \propto \dfrac{1}{{{\text{Ring stability}}}}$
But cyclohexane and above members in cyclic compounds, if the angle strain increases, stability of the ring will increase.

Note:
We have to remember the conversion of one type of hydrocarbon to another hydrocarbon by oxidation and reduction. The oxidation of alkane to give alkene. The oxidation of alkene to give alkyne. The reduction of alkyne to give alkene. The reduction of alkene to give alkane. It has some general formulas. The general formula of alkane is ${{\text{C}}_{\text{n}}}{{\text{H}}_{{\text{2n + 2}}}}$. The general formula of alkene is ${{\text{C}}_{\text{n}}}{{\text{H}}_{{\text{2n}}}}$. The general formula of alkyne is ${{\text{C}}_{\text{n}}}{{\text{H}}_{{\text{2n - 2}}}}$.The general formula of cycloalkane is ${{\text{C}}_{\text{n}}}{{\text{H}}_{{\text{2n}}}}$. According to Baeyer's strain theory, the stability order is cyclopropane < cyclobutane