D. A. Evans, K. Scheidt Carbonium lon X-ray Structures: A Summary Chem 206 1442A 1446A 1408A 2.092A 1739A 439A 1432A A 1508A 1668A 1342A 422A 1725A 1481421A 1467A1495A 1855A 1621A 1622A 1608A Nomenclature: classical vs nonclassical 1503A 1551A hyperconjugation unsymmetrical symmetrical no bridging bridging bridging creasing nonclassical character classical nonclassicalD. A. Evans, K. Scheidt Carbonium Ion X-ray Structures: A Summary Chem 206 1.467 Å 1.855 Å 1.503 Å 1.495 Å 1.467 Å 1.442 Å 2.092 Å 1.739 Å + + + 1.408 Å 1.371 Å 1.432 Å 1.446 Å 1.439 Å 1.442 Å + 1.621 Å 98.2 ° 1.466 Å + 1.551 Å 1.608 Å 1.622 Å 1.421 Å 1.432 Å 1.422 Å 1.725 Å 1.668 Å Cl Cl + 1.508 Å 1.342 Å (ref 1.513 Å)Ph–C(Me)=CH2 1.491 Å C C C Å C C C Å C C C Å C C C Å open trivalent hyperconjugation no bridging unsymmetrical bridging symmetrical bridging classical nonclassical increasing nonclassical character Nomenclature: classical vs nonclassical