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

Options

A. `overset(Θ)(C)H_(2)-CH = CH-CH=overset(Θ)(O)-CH_(3)`
B. `CH_(2)=CH_(2)-overset(Θ)(C)H-CH=overset(Θ)(O)-CH_(3)`
C. `overset(Θ)(C)H_(2)-overset(Θ)(C)H - CH = CH-O-CH_(3)`
D. `CH_(2)=CH-overset(Θ)(C)H-overset(Θ)(C)H-O-CH_(3)`

Answer

C

Explanation

The octet of all atoms are complete in structures a and b. The molecule in which all the atoms have completed octet is more stable than atom which have incomplete octet. Larger the number of resonating structure, larger will be the stability, thus structures a and b stable.
In structure (d), the electron deficient of positive charged carbon is duly compensated by one pair electrons of adjacent oxygen atoms while such neighbor group support is not available in structure (c). Hence structure c is least stable in comparision to structure (d).