IIT-JEE 2011 · Paper 1 · Chemistry Q11

ChemistryMultiple correct+4Question 11 of 69

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)

\ce{H2C=CH-CH=CH2}

\ce{HC#C-CH=CH2}

\ce{H2C=C=O}

\ce{H2C=C=CH2}

Answer and worked solution

Official answer: B, C

(A) Buta-1,3-diene: rotation about the central single bond gives non-planar (gauche) conformations.
(B) But-1-en-3-yne: the C≡C-H part is linear, so rotation about the single bond does not take any atom out of the vinyl plane. Always planar.
(C) Ketene: H₂C=C=O is planar; no conformers.
(D) Allene: the two CH₂ groups lie in perpendicular planes.

(B), (C)

Topics:Hybridisation Conformations

IIT-JEE 2011 · Paper 1, Chemistry question 11