Warm-Up: Resonance v. Constitutional Isomer

Which of the following are constitutional isomers?

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Answer explanation

Three of the of the four share the formula: C3H6O whereas one has the formula: C2H6O.

Which of the following is the best resonance structure?

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Answer explanation

The BEST structure contains no formal charges if possible. In this case, it was possible.

Which of the following is the worst resonance structure?

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Answer explanation

The WORST resonance structure places a formal charge on the least electronegative atom. In this case, it was Carbon.

Which of the following is NOT from the same structure?

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Answer explanation

If you look closely at the position of the lone pair in the last problem; it's closer (and more restricted) than the other three.

Which of the following is the BEST resonance structure?

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Answer explanation

Even though it is not desirable for oxygen to have a positive formal charge, it is the most electronegative atom AND all octets are filled in this structure.