Question

a. Draw the condensed structures and give the systematic names for all the alkenes with molecular formula C₆H₁₂, ignoring stereoisomers.

(Hint:There are 13.)

b. Which of the alkenes have Eand Zisomers?

c. Which of the alkenes is the most stable?

d. Which of the alkenes is the least stable?

Short answer

a. All structures are drawn below.

b. Structure 3,7,9,11 has E and Z isomer.

c. Alkene no 5 is the most stable.

d. Alkene no 13 is the least stable.

Step-by-step solution

E, Z nomenclature

When a double bond has same priority number in the same side, the structure is called Z nomenclature.

When a double bond has same priority number in the Opposite side, the structure is called E nomenclature

Representation of structures

The common formula for C₆H₁₂ is C_nH_2n which makes it an alkene. So, all the possible structures of alkene except the geometrical isomers are,

b) Structure 3,7,9,11 has an E and Z isomer.

c) Stability of these alkenes is determined by calculating the alpha H. the more the alpha H, the more will be the stability. Here, in the case of structure 5, there is the highest no of Alpha Hydrogen (𝜶-H =12) which makes it the most stable isomer.

d) Similarly, like the previous, the compound with the least𝜶-H will be the least stable.

Structure 13 has no𝜶-H which makes it the least stable structure.