CHEM 2311 E3 practice-i (answered provided) 1. (32 points) Circle the letter on the right which corresponds to the answer to each question. There is only one correct answer for each question. (i) Which of the following statements is not true? A. The heterolysis of a bond between atoms which do not bear formal charges always produces a cation and an anion B. Carbocations are Lewis acids C. Carbon atoms of carbanions have a complete octet of valence shell electrons D. Nucleophiles seek centers of high electron density (e.g., a negative charge). (ii) What is the approximate equilibrium constant (Keq) at 25 °C for a reaction with a ΔG° value of +10 kcal/mole. [hmmmm, you do not need a calculator for this!!] E. –1 F. 4x10–8 G. 1 H. 4x108 (iii) Which of the following is the correct order of decreasing basicity (more basic > less basic)? I. NH3 > MeNH2 > H2O > HF J. MeNH2 > NH3 > MeOH >CH4 K. NH3 > Me3N > H2O > MeOH L. CH3COONa > NaOH > NaOMe > NaNMe2 (iv) Which of the following reactions corresponds to an addition reaction M. 2° alkyl halide → alkene N. 3°alkyl halide → 3° alcohol O. ketone → 2° alcohol P. 2° alcohol → alkene (v) Which of the following is not a characteristic of SN2 reactions? Q. rate is independent of the concentration of nucleophile R. chiral electrophiles undergo inversion S. alkyl fluorides are relatively unreactive T. iodide is a relatively good nucleophile (vi) Which of the following is a characteristic of the reaction of 3° alkyl halides with water (hydrolysis)? U. chiral electrophiles undergo inversion V. alkyl fluorides are relatively unreactive W. the rate will be slower in a polar solvent X. the rate will be slower at higher temperatures (vii) Which of the following is the strongest nucleophile? Y. tert-butyl cation Z. water AA. Hydrogen sulphide, H2S BB. ethylene (viii) Which of the following is the strongest electrophile CC. tert-butyl cation DD. di-tert-butyl ether, (CH3)3C-O-C(CH3)3 EE. ethylene FF. 2,3-dimethylbutane A B C D E F G H I J K L M N O P Q R S T U V W X Y Z AA BB CC DD EE FF2. (32 points). Give answers for each part of the question in the spaces provided. (a) Provide an energy – reaction coordinate diagram for the reaction of tert-butyl bromide with water to give tert-butanol. The diagram should accurately reflect the relative energy of starting materials, intermediates products, and transition states. Draw the structures of the two intermediates in this reaction (b) (i) Place curved arrows on the structures of the starting materials to account for the bonding changes in the following proposed reaction. (ii) The reaction does not proceed. Provide two reasons to explain why the reaction does not proceed - - (c) Provide the major organic product expected from each of the following reactions. (d) Although it is a tertiary alkyl bromide, 1-bromobicyclo[2.1.1]hexane is unreactive in SN1 reactions. Explain. + HO––:CH2CH2CH2CH2OHenergy (CH3)3CClHHKI50 °C, acetone(CH3)3CBrNaOMe50 °C, MeOHNaOMe50 °C, MeOHCH3CH2CH2CH2Clreaction coordinate Br3. (32 points). Give answers for each part of the question in the spaces provided. (a) Explain, with the aid of structures and a sentence (or two), why compound A is a stronger acid than a simple diol. A (b) Show curved arrows to account for the changes in bonding which take place in each of the following elementary reaction steps (note: you will need to add lone pairs to the structures as appropriate). (c) Draw the chemical equation which represents the acid-base reaction involved when each of the following are mixed. Indicate whether K>1 or K<1. (i) aqueous NaOH + CH3COOH (d) With reference to structure, explain why the acetylide anion, HC≡C:– is a weaker base than the ethyl anion, CH3CH2:– (e) Circle all of the electrophilic atoms in the following molecule. HBrBrH3COHH3COH2HClClOOHOHO