Aromatic, antiaromatic and non-aromatic rings

14 questions on Aromatic, antiaromatic and non-aromatic rings from the General Organic Chemistry I: Electronic Effects chapter: 3 NEET level, 6 JEE Main, 5 JEE Advanced. Each one opens with its answer and solution.

• The planar ion shown is NEET level, drawn structure
• How many pi electrons are present in the ring of the compound shown (counting the oxygen lone pair that is part of the cyclic conjugation)? NEET level, drawn structure
• If the ring of the compound shown is assumed planar and square, it is NEET level, drawn structure
• The compound shown is cyclopropene. Which of the planar species shown, derived from a three-membered ring, is aromatic? JEE Main level, drawn structure
• The compound shown is a far weaker base than pyridine mainly because JEE Main level, drawn structure
• If the ring of the anion shown were planar, it would have JEE Main level, drawn structure
• The compound shown is a hydrocarbon yet has a noticeable dipole moment. The best explanation is that JEE Main level, drawn structure
• The compound shown behaves as an ordinary polyene rather than as a cyclic conjugated antiaromatic system because JEE Main level, drawn structure
• The aromatic parent hydrocarbon is shown for comparison. Select all of the planar species shown that are antiaromatic. JEE Main level, drawn structure
• The compound shown reacts with two equivalents of potassium metal and each atom accepts one electron to form a planar dianion. How many pi electrons are in the ... JEE Advanced level, drawn structure
• The compound shown has a dipole moment much larger than that of a saturated cyclic ketone of similar size. The best explanation is JEE Advanced level, drawn structure
• The compound shown is treated with one equivalent of acid. Protonation occurs at which nitrogen, and how many pi electrons does the ring of the resulting cation... JEE Advanced level, drawn structure
• The aromatic reference compound is shown for comparison. Select all of the planar species shown that are aromatic. JEE Advanced level, drawn structure
• Select all correct statements about the compound shown. JEE Advanced level, drawn structure