The correct statement(s) concerning the structures $\mathbf{E}$, $\mathbf{F}$ and $\mathbf{G}$ is (are)

(B) E, $\mathbf{F}$ and E, $\mathbf{G}$ are tautomers; (C) $\mathbf{F}$ and $\mathbf{G}$ are geometrical isomers; (D) $\mathbf{F}$ and $\mathbf{G}$ are diastereomers

(A) E, F and G are resonance structures

JEE Advanced · 2008 · 13 Apr 2008 · Paper 1 · General Organic Chemistry

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The correct statement(s) concerning the structures

E

F

and

G

is (are)

(A)E, F and G are resonance structures
(B)E, $F$ and E, $G$ are tautomers✓ Correct
(C) $F$ and $G$ are geometrical isomers✓ Correct
(D) $F$ and $G$ are diastereomers✓ Correct

Answer: (B), (C), (D)

Solution

Structure E is a ketone (pentan-3-one), while structures F and G are enols (pent-2-en-3-ol in different geometric forms).

E and F, and E and G are tautomers (keto-enol tautomerism).
F and G are geometrical isomers (cis-trans isomers about the C=C double bond).
Since F and G are geometrical isomers, they are also diastereomers (stereoisomers that are not mirror images).
E, F, and G are not resonance structures because they differ in the position of atoms (hydrogen has moved).

Therefore, statements (B), (C), and (D) are correct.

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JEE Advanced · 2008 · 13 Apr 2008 · Paper 1 · General Organic Chemistry

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