Why do the molecules that have the structures such as H2C=C=CH2 or HO-CH=CH2 are unstable?
Molecules with structures like H2C=C=CH2 or HO-CH=CH2 are considered unstable due to their high reactivity and tendency to undergo chemical reactions. There are two main reasons for their instability:
1. Lack of Saturation: In these structures, there are multiple carbon-carbon double bonds present, which result in unsaturation. Double bonds are more reactive than single bonds as they contain higher electron density, making them susceptible to attack by other species. This reactivity can lead to the molecule's decomposition or reaction with other compounds.
2. Electron Delocalization: In molecules like H2C=C=CH2 or HO-CH=CH2, the presence of double bonds allows for electron delocalization or resonance. Resonance occurs when electron pairs are able to move between different atoms within a molecule, resulting in stabilization. However, in highly unsaturated molecules, this electron delocalization can also lead to instability. The movement of electrons can generate reactive intermediates or species with high energy levels, increasing their reactivity and instability.
To understand the instability of such molecules, one can utilize the concept of electron counting and molecular orbital theory. By analyzing the electron distribution and bonding patterns, it becomes evident why molecules with structures like H2C=C=CH2 or HO-CH=CH2 are prone to reactivity and instability.