50.A compound having a molecular formula of C₂₀H₃₆ is inert to catalytic hydrogenation. Which of the following statements is true?
(A)The substance has at least one double bond and two rings.
(B)The substance is acyclic (i.e., no rings are present)
(C)The substance has two rings.
(D)The substance has three rings.
(E)None of these.

46.In the traction of a reagent such as HBr with an alkene, the frist step of the reaction is the to ______the alkene.(A)Fast addition of an electrophile(B)Fast addition of a nuclephile(C)Slow addition of an electrophile(D)Slow addition of a nuclephile(E)none of these

47.Markovnikov’s rule “works” because: (A)The most stable transition state is the one leading to the more substituted carbocation. (B)The nucleophile adds during the second step of the ionic reaction. (C)The electrophile adds to the less substituted end of the double bond. (D)All of these are true. (E)All of these are not true.

48.Treatment of 2-methyl-2-butene with HBr in the presence of peroxide yields (A)A primary alkyl bromide (B)A secondary alkyl bromide (C)A tertiary alkyl bromide (D)A vicinal dibromide (E)None of these

49.The strongest evidence for the formation of a bridged bromonium ion as an intermediate in the addition of Br2 to an alkene is: (A)Markovnikov’s rule (B)Zaitsev’s rule (C)The regioselectivity of the reaction (D)The stereospecificity of the reaction (E)None of these

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

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

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