68. Which of the following compounds can adopt a chair conformation in which there are no axial methyl groups?

(A) 1,1-dimethylcyclohexane

(B) cis-1,2-dimethylcyclohexane

 
(C) trans-1,2-dimethylcyclohexane

 
(D) trans-1,3-dimethylcyclohexane

 
(E) everyone above have no axial methyl group

64. Which of the following sequences efficiently converts 2-methylpropene into 3-methylbutanal? (A) 1) HBr; 2) NaCCH; 3) O3; 4) H2O (B) 1) HBr; 2) NaCCH; 3) O3; 4) DMS(C) 1) HBr, ROOR; 2) NaCCH; 3) O3; 4) H2O (D) 1) HBr, ROOR; 2) NaCCH; 3) H2/Ni2B; 4) O3; 5) DMS (E) 1) NaCCH; 2) H2/Ni2B; 3) O3; 4) DMS  

65. How many positive and negative peaks appear in the DEPT-135 and in the DEPT-90 spectrum of 2-methylpentane? (A) DEPT-135: two positive and one negative, DEPT-90: one positive (B) DEPT-135: three positive and two negative, DEPT-90: one positive (C) DEPT-135: three positive and two negative, DEPT-90: no signals (D) DEPT-135: two positive and three negative, DEPT-90: two positive (E) None of the above is correct

66. The Fischer indole synthesis is the reaction of phenylhydrazine with a carbonyl compound to give the corresponding indole. For the preparation of the following indole, what carbonyl compound is needed?  (A) I (B) II (C) III (D) IV (E) V

67. What is the major product obtained from the following reaction sequence?  (A) I (B) II (C) III (D) IV (E) V

69. For the following reaction sequence, which molecule is an expected major product? 

70. Which of these is NOT a useful method for the synthesis of 1,3-pentadiene?(A) 1,4-pentanediol + H2SO4 at 180o C (B) 2,4-dibromopentane + (CH3)3COK , (CH3)3COH at 75o C (C) 2,4-pentanediol + H2SO4 at 180o C (D) HC=CCH=CHCH3 + H2, Ni2B (P-2)(E) 1,4-dibromopentane + CH3CH2ONa , CH3CH2OH at 75o C

71. Which of the following series of synthetic steps could be used to carry out the transformation shown below? (I) NaOH, (II) heat, (III) CH3COCH2COOEt, EtONa, (IV) NaOH, heat, then HCl, H2O (A) I → II → III → IV (B) IV → II → I → III (C) III →IV → II → I (D) II → IV → III → I (E) None of the above

72. What is the name of the following reaction? (A) Mixed Aldol condensation (B) Mixed Claisen condensation (C) Mixed Dieckmann condensation (D) Mixed Michael reaction (E) Mixed Knoevenagel reaction .

73. Which of the following represents the HOMO of pentadienyl anion? 

74. Predict the major product for the following reaction sequence. (A) I (B) II (C) III (D) IV (E) V