Single Choice

Which of the following resonating strictures of l-methoxy 1, 3 -butadiene is least stable?

A$$ \overset { \oplus} CH_2 -CH=CH-CH = \overset { \oplus} O -CH_3 $$
B$$ CH_2=CH - \overset { \ominus} CH -CH = \overset { \oplus}O -CH_3 $$
C$$ \overset { \ominus} CH_2 - \overset { \oplus} CH-CH =CH -O-CH_3 $$
Correct Answer
D$$ CH_2 =CH - \overset { \ominus} CH - \overset { \oplus} CH -O-CH_3 $$

Solution

The octet of all atoms are complete in structures (A) and (B). the molecule in which all the atoms have complete octet is more stable than the atom having incomplete octet. Larger the number of resonating structures , larger will be stability.thus, structures (A) and (B) are stable.
In structure (D) , the electron deficiency of positive charged carbon is duly compensated by lone pair electrons of adjacent oxygen atoms, while such neighbour group support is not available in structure (C).
Hence, structure (C) is less stable in comparision to structure (D).

SIMILAR QUESTIONS

Organic Chemistry

For 1-methoxy-1,3-butadiene, which of the following resonating structure is the least stable?

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Resonance structures can be written for:

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In which of the following compound, resonance is not possible:

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Which of the following molecules is least resonance stabilized?

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Which of the following conditions is not correct for resonating structures?

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A solid has a structure in which, atoms of W, O and Na are located respectively at the corners, centre of the edge and at the centre of the cubic lattice. Name the compound.

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Write the resonance structures of (1) $$ CH_3COO^{\ominus }$$ and (2) $$ CH_2=CH-CHO $$. Indicate the relative stability of the contributing structures.

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Explain why the following two structures (i) and (ii) cannot be the major contributors to the real structures of $$ CH_3COOCH_3 $$.

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Draw the resonance structures for $$CH_3CH = CH\overset{+}CH_2$$. Show the electron shift using curved-arrow notation.

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What is resonance effect ? What are its various types ? In what respects, does the resonance effect differ from inductive effect ?

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