Compare the carbon-carbon double bond rotatio | vedclass

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Question

(B) The rotation around the carbon-carbon double bond requires the breaking of the $\pi$-bond. The energy required for this rotation depends on the st

Vedclass · Accepted Answer

$A > C > B$

Vedclass · Answer

(B) The rotation around the carbon-carbon double bond requires the breaking of the $\pi$-bond. The energy required for this rotation depends on the stability of the resulting zwitterionic species formed upon breaking the $\pi$-bond.In these molecules,the $\pi$-bond breaks to form two rings,one carrying a positive charge and the other a negative charge. The stability of these rings is governed by $H$ückel's rule (aromaticity).For $(A)$: Breaking the bond forms a $5$-membered cation (aromatic,$6\pi$ electrons) and a $3$-membered anion (antiaromatic,$4\pi$ electrons).For $(B)$: Breaking the bond forms a $5$-membered cation (aromatic,$6\pi$ electrons) and a $7$-membered anion (aromatic,$8\pi$ electrons,but actually $7$-membered ring with $8\pi$ electrons is antiaromatic). Wait,let's re-evaluate: $5$-membered ring with $6\pi$ electrons is aromatic. $7$-membered ring with $6\pi$ electrons is aromatic. In $(B)$,we get a $5$-membered aromatic cation and a $7$-membered aromatic anion.For $(C)$: Breaking the bond forms a $3$-membered cation (antiaromatic) and a $7$-membered anion (aromatic). Since $(B)$ forms two aromatic rings,the $\pi$-bond breaks most easily,requiring the least energy. $(C)$ forms an antiaromatic ring,making it the most difficult to break. Thus,the order of rotation energy is $C > A > B$.

Compare the carbon-carbon double bond rotation energy for the following compounds $A$,$B$,and $C$:

Similar Questions

Draw other resonance structures related to the following structure and find out whether the functional group present in the molecule is ortho,para directing or meta directing.

Which of the following is the most unstable resonating structure?

Identify the compound in which steric inhibition of resonance is present.

For the given compounds,the correct order of resonance energy is:
$(I)$ $CH_2=CH-CH=CH-OCH_3$
$(II)$ $CH_2=CH-C(OCH_3)=CH_2$
$(III)$ $CH_2=CH-OCH_3$

Which of the following species has a positive charge that is not involved in resonance?

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