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Solutions for Aromatic Compounds
C
C
H
H
40
(a) No, biphenyl is not fused. The rings must share two atoms to be labeled "fused".
(b) There are 12 π electrons in biphenyl compared with 10 for naphthalene.
(c) Biphenyl has 6 "double bonds". An isolated alkene releases 120 kJ/mole upon hydrogenation.
predicted: 6 x 120 kJ/mole (28.6 kcal/mole) ≈ 720 kJ/mole (172 kcal/mole)
observed: 418 kJ/mole (100 kcal/mole)
resonance energy: 302 kJ/mole (72 kcal/mole)
(d) On a "per ring" basis, biphenyl is 302 ÷ 2 = 151 kJ/mole, the same as the value for benzene. 
Naphthalene's resonance energy is 252 kJ/mole (60 kcal/mole); on a "per ring" basis, naphthalene has only 
126 kJ/mole of stabilization per ring. This is consistent with the greater reactivity of naphthalene compared 
with benzene. In fact, the more fused rings, the lower the resonance energy per ring, and the more reactive 
the compound. (Refer to Problem 21.)
41 Two protons are removed from sp carbons to make sp carbons and to generate a 3 2 π system with 10 
π electrons.
42
(a)
H
H
C4H9Li
C H
aromatic
(b) OH
H2SO4
CH
aromatic
(c) Cl
Ag+
CH
aromatic
(d) N
H
H
NaOH
N H
aromatic
(e)
H H
C4H9Li
C
H
(f)
O
Cl
Ag+
C
H
O O
aromatic
aromatic
Li+
+ C4H10
HSO4
–
+ H2O
+ AgCl
+ H2O
+ Na+
Li+
+ C4H10
+ AgCl
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