Rank the following in order of decreasing importance as a contributing resonance structure to the molecular structure of acetone, CH₃COCH₃ (more important less important)

Question

Rank the following in order of decreasing importance as a contributing resonance structure to the molecular structure of acetone, CH₃COCH₃ (more important > less important)

Quizplus · Accepted Answer

1) O=C-CH3 
This is the most important structure as it contains a full octet on both carbon and oxygen atoms.
2) 
   H3C-C=O
   |
   H

This structure is the 2nd most important contributor with a positive charge on carbon but still contains a full octet on oxygen.
3) 
   H3C-C-O
   |
   H

This structure has a negative charge on the oxygen while the carbon has only 6 electrons, making it the least important contributor to the resonance hybrid structure of acetone.

Rank the Following in Order of Decreasing Importance as a Contributing