Advices For Studying Organic Chemistry

5. All atoms that are a part of the delocalized system must be in a plane or be
   nearly planar.

1. 2,3-Di-tert-butyl-1,3-butadiene behaves like a nonconjugated dienes because
   the bulky tert-butyl groups twist the structure and prevent the double bonds from
   lying in the same plane ⇒ the p orbitals at C2 and C3 do not overlap and
   delocalization (and therefore resonance) is prevented.

C C

CH 2

H 2 C C(CH^3 )^3

(H 3 C) 3 C

6. The energy of the actual molecule is lower than the energy that might be
   estimated for any contributing structure.

1. Structures 4 and 5 resembles 1° carbocations and yet the allyl cation is more
   stable than a 2° carbocation ⇒ resonance stabilization.

CH 2 CH CH+ 2 CH+ 2 CH CH 2

(^4 5)
or
Resonance structures
for benzene
Representation
of hybrid

7. Equivalent resonance structures make equal contributions to the hybrid, and
   a system described by them has a large resonance stabilization.


8. For nonequivalent resonance structures, the more stable a structure is the
   greater is its contribution to the hybrid.

1. Structures that are not equivalent do not make equal contributions.


2. Cation A is a hybrid of structures 6 and 7.
   i) Structure 6 makes greater contribution than 7 because 6 is a more stable 3°
   carbocation while 7 is a 1° cation.