Question

Some compounds are given below.(Question no 45)

a. Which is the most stable?

b. Which is the least stable?

Short answer

a. Structure a is most stable.

b. Structure e is the least stable.

Step-by-step solution

Determination of stability

The stability of these compounds is determined by the presence of alpha H in Alpha carbon. The more alpha carbon, the more will be stability.

No of 𝜶-H = 7 No of 𝜶-H = 4.

No of 𝜶-H = 5 No of 𝜶-H = 5

No of 𝜶-H = 4 No of 𝜶-H = 5

So, from the above picture, we can say that structure 1 is the most stable one.

Now, both b and e have 4 alpha Hydrogens. So, the stability will be decided depending on the bulky groups and cis, trans, and geminal structures.

Between b and e, e has a geminal linkage whereas, b has trans linkage throughout the double bond. As the trans arrangement is more stable than the geminal, the geminal structure will be the least stable.