Question

In which of the following compounds, all the atoms are in one plane in all the possible conformations.

• A.

  

• B.

  

• C.

  

• D.

  

Answer 1

Answer: (B), (C)

Explanation for correct options:

(b)

Due to the linear structure of the $\mathrm{H}-\mathrm{C}\equiv \mathrm{C}-$ portion of the molecule, the three H-atoms on $-\mathrm{HC}={\mathrm{CH}}_2$ portion always lie in the same plane.

(c)

In ${\mathrm{CH}}_2=\mathrm{C}=\mathrm{O}$, due to the replacement of ${\mathrm{CH}}_2$ by Oxygen and the two Hydrogen atoms on the ${\mathrm{sp}}^2-$hybridized ${\mathrm{CH}}_2$ group lie in the same plane in which the two carbon and the oxygen atoms lie.

Explanation for incorrect options:

(a)

All the atoms may not lie in the same plane, as the single bond between two Carbon atoms can rotate. So, this option is incorrect

(d)

Here, due to sp-hybridization of the central Carbon atom, Hydrogen atoms on the terminal ${\mathrm{CH}}_2$ groups lie in perpendicular planes.

So, the correct options are (b) and (c).