Question

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

• A.
• B.
• C. $H_2C=C=0$
• D. $H_2C=C=CH_2$

Answer 1

Answer: (C)

$H_2C=C=0$

Answer 2

In both (b) and (c), all the atoms are present in one single plane
In (a) 1, 3-butadiene, conformational change is possible
between $C_2-C_3$ bond in which atoms will be present in more
than one single plane.
In (d) allene, the terminals H-C-H planes are perpendicular
to one another.