JEE Main 2017 · 9 Apr · Shift 1 · Chemistry Q58

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ChemistrySingle correct+4 / -1Question 58 of 90

Which of the following compounds will show highest dipole moment ?

Four cyclic ketones: (I) cyclopropenone, (II) cyclobut-2-enone, (III) cyclopent-3-enone, (IV) p-benzoquinone.

(I)

(II)

(III)

(IV)

Answer and worked solution

Official answer: A

In cyclopropenone the polarised form $\ce{C+-O-}$ puts two π electrons in a cyclopropenyl cation, which is aromatic. That large charge separation gives it the highest dipole moment; p-benzoquinone has none by symmetry.

Topics:Aromaticity Bond parameters and dipole moment

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JEE Main 2017 · 9 Apr · Shift 1, Chemistry question 58