SME
Organic Chemistry II
Aromatic chemistry
Use this for “Is the cyclopropenyl cation, a flat three-carbon ring with 2 π electrons, aromatic, antiaromatic or nonaromatic?”
Sort
Which is each ring?
Tap a card, then tap its group.
Aromatic: a flat ring of p orbitals with 4n + 2 π electrons (2, 6, 10). Antiaromatic: the same with 4n (4, 8).
Assumptions
•
Count π electrons: 2 for each C=C in the ring, 2 for a carbanion or for an N or O lone pair the ring can use, 0 for a carbocation.
•
A lone pair already in an sp² orbital in the ring’s plane, as on pyridine’s N, is not part of the π count.
•
Hückel’s rule holds only for a ring that is cyclic, flat and has a p orbital on every atom.
•
A ring that could be antiaromatic but is able to pucker, as cyclooctatetraene does, bends out of plane and is nonaromatic.
Topic check
See what you know: 5 questions on this topic
New questions each time. Pass to mark it complete.