Buta-1,3-diene (simply called butadiene thereafter) is a diene of chemical formula C4H6, which was i — Physical Chemistry — Electrochemistry Chemistry Question
Butadiene π-electron system
Buta-1,3-diene (simply called butadiene thereafter) is a diene of chemical formula C4H6, which was isolated for the first time in 1863 by the French chemist E. Caventou and identified in 1886 by the English chemist H. E. Armstrong. It is a key reagent in the... 𝛹3 = 0.6015 𝜑1 − 0.3717 𝜑2 − 0.3717 𝜑3 + 0.6015 𝜑4 ; E3 = α − 0.62 β 𝛹4 = 0.3717 𝜑1 − 0.6015 𝜑2 + 0.6015 𝜑3 − 0.3717 𝜑4 ; E4 = α − 1.62 β
We consider the formation of the butadiene π-electron system, starting from four...
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Model Answer
Butadiene possesses 4 π-electrons.
Draw and fill in the MO diagram of butadiene. Draw schematically each MO and identify its nature (bonding or anti-bonding).
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Model Answer
ΔEf = 2 E1 + 2 E2 – 4 α = 4.48 β
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Model Answer
ΔEc = 2 E1 + 2 E2 – 2 × 2(α + β) = 0.48 β < 0
Correct statement: Butadiene
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Model Answer
q1 = q2 = 0; q3 = q2 = 0 and q1 = q4 = 0
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Model Answer
I12 = 0.8943; I23 = 0.4473; I34 = 0.8943
Strongest double-bond character: bonds C1C2 and C3C4.
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Fill in the MO diagram of cyclobutadiene.
Using the provided diagram and considering the symmetry of the molecule, determine the missing coefficients (cij) in the following MO expressions.
𝛹1 = 0.500 𝜑1 + c12 𝜑2 + c13 𝜑3 + c14 𝜑4
𝛹2 = 0.707 𝜑1 + c22 𝜑2 + c23 𝜑3 + c24 𝜑4
𝛹3 = c31𝜑1 + 0.707 𝜑2 + c33 𝜑3 + c34 𝜑4
𝛹4 = 0.500 𝜑1 + c42 𝜑2 + c43 𝜑3 + c44 𝜑4
Model Answer
c12 = c13 = c14 = 0.5
c22 = c24 = 0; c23 = –0.707
c31 = c33 = 0; c34 = –0.707
c42 = c44 = –0.5; c43 = 0.5
Calculate the formation and conjugation energies, ΔEf’ and ΔEc’, for cyclobutadiene.
Model Answer
ΔEf’ = 2 E1 + 2 E2 – 4 α = 4 β
ΔEc’ = 2 E1 + 2 E2 – 2 × 2(α + β) = 0
Correct answer: Both are equally stable
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Model Answer
ΔEf (butadiene) < ΔEf’(cyclobutadiene)
Correct statement: Butadiene
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Model Answer
Correct statements:
This deformation stabilizes C=C double bonds. (shortening of the double bonds,