A semiempirical MO calculation on the two structures below indicated that
one would be expected to have a dipole moment of 3D, while the other
would have a dipole moment of 1.4D. Which structure should have the
larger dipole moment, and why?
a) Draw the structure and number the carbons of the allyl carbanion.
b) Set up, but do not solve the Huckel secular determinant equation for this conjugated
c) Calculate the electron density at each carbon of the allyl carbanion. The LCAO MO's
for this system are given below.
43 = 0.5 01 - 0.7 02 + 0.5 03
W1 = 0.501 + 0.7 02 + 0.5 03
Using the indicated atom numbers, write the Huckel secular determinant equation for each of
the following structures.
Set up, but do not solve the Huckel secular determinant equation for the following system.
Ordinarily the barrier to rotation about a Carbon-Carbon double bond is quite high, but the
compound below was observed by NMR to have a rotational barrier of only 20 kcal/mole.
Explain this result.
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