Amongst the given options, the compound in which all the atoms are in one plane in all the possible conformations (if any ), is (are)

Amongst the given options, the compound in which all the atoms are in

1.	Amongst the given options, the compound in which all the atoms are in one plane in all the possible conformations (if any ), is (are)
Answer» `H_2C=C=O` `H_2C=C=CH_2` SOLUTION :Along C-C single bond, numerous CONFORMATIONS are possible in 1,3-butadiene (a) . In some of these conformations , all the atoms may not lie in the same plane. In `CH_2=C=CH_2` (d), due to sp-hybridization of the central carbon, H-atoms on the terminal `CH_2` groups lie in perpendicular planes . However, in `CH_2=C=O` (c ), due to replacement of `CH_2` by O the two H-atoms on the `sp^2`-HYBRIDIZED `CH_2` group lie in the same plane in which the two carbon and the oxygen atoms lie. In compound (B), due to linear structure of H-C`-=`C- PORTION of the molecule , the three H-atoms on -HC =`CH_2` portion always lie in the same plane. Thus, options (b) and (c ) are correct.