55.Which of the following statements is true concerning pK_a?
(A)The larger the pK_a value, the weaker the acid.
(B)Strong acids have small pK_a values.
(C)pK_a = -log K_a
(D)All the statements are correct.
(E)All the statements are incorrect.

51.The bimolecular subsittution reaction CH3Br + OH- →CH3OH + Br-is represented by the kinetic equation: (A)Rate = k[CH3Br]2 (B)Rate = k[CH3Br][OH- ] (C)Rate = k[CH3Br] + k[OH- ] (D)Rate = k/[CH3Br][OH- ] (E)Rate = k[CH3Br]2 + k[OH- ]

52.The solvoysis reactions of optically active halides generally proceed with (A)Complete racemization (B)Partial racemization (C)complete retention of configuration (D)Complete inversion of configuration (E)None of these

53.Which of the following statements pertaining to an SN2 reaction are true? 1.The rate of reaction is independent of the concertration of the nucleophile.2.The nucleophile attacks carbon on the side of the molecule opposite the group being displaced.3.The reaction proceeds with simultaneous bond formation and bond rupture.4.Partial racemization of an optically active substrate results. (A)1,4 (B)1,3,4 (C)2,3 (D)1,3 (E)All

54.Which of the following phrases are not correctly associated with SN1 reactions? 1.Rearrangements possible 2.Rate affected by solvent polarity 3.Strength of nucleophile important in determining rate 4.Reactivity series tertiary > secondary > primary 5.Proceed with complete inversion of configuration (A)3,5 (B)1,5 (C)2,3,5 (D)3 only (E)4,5

56.Referring to the following equilibrium (R=alkyl group)(A)K < 1 ; the equilibrium would lie the left. (B)K > 1 ; the equilibrium would lie the right. (C)K = 1 ; equal amounts of all species would be present. (D)Not enough information is given; the structure of R must be known. (E)None of these

57.Which alkyne yields butanoic acid (CH3CH2CH2CO2H) as the only organic product upon treatment with ozone followed by hydrolysis? (A)1-Butyne (B)4-Octyne (C)1-Pentyne (D)2-Hexyne (E)None of these ..

58.Which of the following produces a significant amount of acetylide ion on reaction with acetylene? (A)Conjugate base of CH3OH (pKa16) (B)Conjugate base of H2 (pKa35) (C)Conjugate base of H2O (pKa16) (D)Both {A} and {C} (E)Both {A} and {B}

59.Hydrogenation of cyclohexene releases 120kJ/mol of heat. Which of the following most likely represents the observed heat of hydrogenation of 1,3-cyclohexadiene? (A)232kJ/mol (B)239kJ/mol (C)247kJ/mol (D)120kJ/mol (E)142kJ/mol

60.Arrange the following intermediates in order of decreasing basicity (strongest→weakest): (A)B > A > D > (B)D > A > B > C (C)C > D > A > B (D)C > B > D >A (E)D > C >B >A

61.Give the major product of the following reaction: [E]-2-pentence+ CH2I2/Zn(Cu)→ ? (A)cis-1-Ethyl-2-methylcyclopropane (B)trans-1-Ethyl-2-methylcyclopropane (C)1-Ethyl-1-methylcyclopropane (D)An equimolar mixture of product {A} and {B}(E)None of these