CHEM 0320 Lecture Notes - Lecture 4: Osmium Tetroxide, Naphthalene, Fluorobenzene
Document Summary
Mo(cid:374)osu(cid:271)stituted (cid:271)e(cid:374)ze(cid:374)es are (cid:374)a(cid:373)ed (cid:271)(cid:455) addi(cid:374)g a su(cid:271)stitue(cid:374)t prefi(cid:454) to the word (cid:862)(cid:271)e(cid:374)ze(cid:374)e(cid:863) fluorobenzene. There are three possible arrangements of disubstituted benzenes: 1,2 (o) for adjacent substitutents, 1,3 (m) for 1,3 disubstitution, 1,4 (p) for 1,4 disubstitution. Alternatively, the ring is numbered, and substitutents labeled with these numbers are named in alphabetic order. The generic term for substituted benzenes are arene - an arene as a substituent is an aryl group (ar) Benzene is unusually unreactive the reason for this poor reactivity is that the cyclic six-electron arrangement imparts a special stability in the form of a large resonance energy. The benzene ring contains six equally overlapping p orbitals. All carbons are sp2 hybridized, and each p orbital overlaps to an equal extent with its two neighbors. The resulting delocalized electrons form circular pi clouds above and below the ring. The symmetric structure of benzene is a consequence of the interplay between the sigma and pi electrons in the molecule.
