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 .

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

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

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

75. The H-bonds formed in the tertiary structure of proteins can be differentiated from those formed in secondary structures. What is the major distinguishing factor? (A) The H-bonds in 3° structures are significantly stronger than those found in 2° structures. (B) The H-bonds in 3° structures are more random than those formed in 2° structures.(C) The H-bonds in 3° structures are formed by predictable interactions among the peptide backbone α-amine and α-carboxylate groups. (D) The H-bonds in 3° structures are formed by interactions involving the side chain R-groups. (E) Both B and D are correct.

76. Predict the outcome of the following sequence of reactions.  (A) I (B) II (C) III (D) IV (E) V

77. Which of the following compounds exhibits the pattern of m/z values: 41, 43, 57, 87, 101, 116? (A) n-butyl n-propyl ether (B) sec-butyl iso-propyl ether (C) 2-heptanol (D) hexanoic acid (E) None of the above

78. How many different β-hydroxyaldehydes and β-hydroxyketones, including constitutional isomers and stereoisomers, are formed upon treatment of a mixture of acetone and acetophenone with base? (A) 4 (B) 6 (C) 9 (D) 10 (E) 12 .