25. Describe a Claisen rearrangement.
(A) [3,3] sigmatropic rearrangement of a 1,5-diene
(B) [1,3] sigmatropic rearrangement of an alkene
(C) [3,3] sigmatropic rearrangement of an allyl vinyl ether
(D) [1,5] sigmatropic rearrangement of a 1,3-diene
(E) [2,3] sigmatropic rearrangement of an alkene

1. Using the following four data to estimate the ring strain in cyclobutane (ΔE₁) and cyclopentane (ΔE₂). If heat of combustion (in kJ/mol) of following four compounds are: What is the number of AE1 + AE2 (in kJ/mol)?(A) 400 (B) 450 (C) 500 (D) 550 (E) 600

2. Select the most acidic H in each of the following compounds (I and II), (A) Compound I: Hₐ, Compound II: Hₐ (B) Compound I: Hc, Compound II: Hc (C) Compound I: Hc, Compound II: Hₐ (D) Compound I: Hc, Compound II: He (E) Compound I: Hₐ, Compound II: He

3. Select the right configuration assignment (E or Z) for the following two alkenes. (A) Compound I: E, Compound II: E (B) Compound I: Z, Compound II: Z (C) Compound I: E, Compound II: Z (D) Compound I: Z, Compound II: E (E) None of above assignments is correct.

4. trans-1-tert-Butyl-4-isopropylcyclohexane has two conformers. Using the following data to calculate the strain in this two conformers, by how much kJ/mol that one is favored than the other?If, H-C-C-H eclipsed interaction strain: 4 kJ/mol;CH3-C-C-H eclipsed interaction strain: 6 kJ/molCH3-C-C-CH3 eclipsed interaction strain: 11 kJ/mol;CH3-C-C-CH3 gauche interaction strain: 3.8 kJ/mol     Each one      strain (S) of 1, 3-X-H diaxial interaction in monosubstitutedcyclohexane (kJ/mol):  (A) 9.2 (B) 22.8 (C) 32 (D) 16 (E) 11.4

5.  Select the right configuration assignment (R or S) for the following two compounds.  (A) None of below assignments is correct. (B) Compound I: S, Compound II: R (C) Compound I: R, Compound II: S (D) Compound I: R, Compound II: R (E) Compound I: S, Compound II: S

6. Select the right stability order for the following four Hexenes. Arrange the more stable alkene first.  ex: I (if it is your most stable one) > II > III > IV. (A) I ＞ II ＞ III ＞ IV (B) II ＞ III ＞ I ＞ IV (C) III ＞ II ＞ I ＞ IV (D) IV ＞ I ＞ II ＞ III (E) III ＞ II ＞ IV ＞ I

7. The optically pure tosylate of 2,2-dimethyl-1-phenyl-1-propanol ([α]D = -50°) was heated in acetic acid to yield the corresponding acetate ([α]D = +10°). If complete inversion had occurred, the optically pure acetate would have had [α]D = +50°. What percentage racemization occurred in this reaction? (A) 80% (B) 60% (C) 50% (D) 40% (E) 20%

8. For the following three compounds, select the      achiral      compound(s). (A) Compounds X and Y (B) Compounds X and Z (C) Compounds Y and Z (D) Only compound X (E) Only compound Z

9. Select the best fit chemical structure for compound X which with the following 1H NMR data.  (A) (B)(C) (D)(E)

10. If a H exhibits a triplet at δ 1.105, 1.085, and 1.065 ppm, data collected by a 300 MHz NMR. Where will this triplet peaks show up (δ:ppm) if this same sample was measured in a 600 MHz NMR? (A) 1.105, 1.085, 1.065 (B) 1.105, 1.095, 1.085 (C) 1.115, 1.085, 1.055 (D) 1.095, 1.085, 1.075 (E) 1.085, 1.075, 1.065

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