44.Carboxylic acids exist in the vapor state as:
(A)Monomeric species
(B)Cyclic esters
(C)Cyclic dimers
(D)Cyclic trimers
(E)None of these

40.Which of the following is least able to serve as a nucleophile in a chemical reaction? (A)Br- (B)OH- (C)NH3 (D)CH3+ (E)I-

41.Thiols are alcohol analogs in which the oxygen has been replaced by sulfur (e.g., CH3SH). Given the fact that the S-H bond is less polar than the O-H bond, which of the following statements comparing thiols and alcohols is correct? (A)Hydrogen bonding forces are weaker in thiols. (B)Hydrogen bonding forces are stronger in thiols (C)Hydrogen bonding forces would be the same. (D)No comparison can be made without additional information. (E)None of these.

42.Rank the transition states which occur during the following reaction steps in order of increasing stability (least→most stable): (a)CH3 - OH2+→CH3 + +H2O (b)(CH3)3C - OH2+→(CH3)3C + + H2O (c)(CH3)2CH - OH2+→(CH3)2CH+ + H2O (A)a < b < c (B)b < c < a (C)a < c < b (D)b < a < c (E)c < b < a

43.An alkane with a molecular formula C6H14 reacts with chlorine in the presence of light and heat. Four constitutionally isomeric monochlorides of molecular formula C6H13Cl are formed (along with a mixture of dichlorides, trichlorides, and so on). What is the most reasonable structure for the starting alkane? (A)CH3CH2CH2CH2CH2CH3 (B)(CH3)2CHCH2CH2CH3 (C)CH3CH(CH2CH3)2 (D)(CH3)3CCH2CH3 (E)(CH3)2CHCH(CH3)2

45.The product from the reaction of 1-pentene with Cl2 in H2O is named: (A)1-Chloro-2-pentanol (B)2-Chloro-2-pentanol (C)1-Chloro-1-pentanol (D)2-Chloro-1-pentanol (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

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.