stability order: Cis-2-Butene, Trans-2-butene, 1-butene
Answers
HELLO THERE!
To determine the stability order of the given organic compounds, you need to know the phenomenon of Hypercojugation.
Hyperconjugation (also called no-bond resonance) is the phenomenon by which a compound stabilizes itself by drawing the electron pair from it's alpha-hydrogen (hydrogen attached to the nearest carbon, called alpha-carbon).
The more is the number of alpha hydrogen, more is the number of hyperconjugative structures, and more is the stability of the compound.
Now, consider the given compounds:
(i) Cis-2-butene
(ii) It's Geometrical Isomer, Trans-2-butene
(iii) 1-butene.
Let's start from the last.
(iii) 1-butene.
If you look at the structure, there are only two alpha hydrogens.
(ii) Trans-2-butene.
If you look at the structure, it has six alpha hydrogens.
(i) Cis-2-butene.
If you look at the structure, it has six alpha hydrogens. However, the two bulky methyl groups are present on the same side, due to which there is Steric Hindrance (repulsion), which decreases the stability. So, Stability of Trans > Cis.
Hence, what we get is:
Trans-2-butene > Cis-2-butene > 1-butene.
