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Unformatted text preview: CHAPTER I S-CONJUGATED SYSTEMS, ORBITAL SYMMETRY, AND ULTRAVIOLET SPECTROSCOPY 1 5 - 1 Look for: 1 ) the number of double bonds to be hydrogenated-the fewer the smaller the MI; 2) c onj ugation-the more conjugated, the more stable , the lower the � ; 3) degree of substitution of the a lkenes-the more substituted, the more stable, the lower the !1H
. C=C, ( a) � < � <�< � < == C � < �
b iggest !1H s mallest !1H <
s mallest !1H 1 5 -2 Reminder: conj ugate base. < HH
• < H
b i ggest !1H H H-B H i s used to symbolize the general fonn for an acid, that i s , a protonated base; H H H f"B H BH is the HH H H H H allylic The key step i s hydride shift from a 2° carbocation to a 2° a llyiic, resonance-stabilized carbocation, which can subsequently lose a proton to fonn a conjugated d iene. H ! B:
H H H H H H 3 17 ...
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This note was uploaded on 02/27/2010 for the course CHEM 140 taught by Professor Wade during the Spring '10 term at Whitman.
- Spring '10