CHM 2201 Chapter 6 Sample Exam Answers

Chapter 6: Alkenes: Structure and Reactivity

Part A: Degree of Unsaturation 10 Points

Calculate the degree of unsaturation for the following formulas. For one or two problems below show variations with suggested isomer structures:

(1) C₄₀H₅₆ (β-carotene) 40x2+2=82 – 56(H) = 26/2= 13 degrees of unsaturation

(2) C₄H₆ 4x2+2=10 – 6(H) = 4/2= 2 degrees of unsaturation

(3) C₆H₅N 6x2+2=14 – 5(H) = 9 – 1 (for N) = 8/2 = 4 degrees of unsaturation

(4) C₆H₅NO₂ (oxygens are not double bonded)

6x2+2=12 – 5(H) = 7 – 1 (for N) = 6/2 (ignore oxygen) = 3 degrees of unsaturation

(5) C₈H₉Cl₃ 8x2+2=18 – [9(H) + 3 (for Cl)] = 6/2 = 3 degrees of unsaturation

(6) C₅H₆ 5x2+2=12 – 6(H) = 6/2= 3 degrees of unsaturation

(7) C₉H₁₆Br₂ 9x2+2=20 – [16(H) + 2 (for Br)] = 2/2 = 1 degree of unsaturation

(8) C₂₀H₃₂ClN 20x2+2=42 – [32(H) + 1 (for Cl)] = 9 – 1(for N) = 8/2 = 4 degrees of unsaturation

(9) C₃H₄ 3x2+2=8 – 4(H) = 4/2= 2 degrees of unsaturation

(10) C₆H₉N 6x2+2=14 – 9(H) = 5 – 1 (for N) = 4/2 = 2 degrees of unsaturation