Chemistry 2311 Homework Problems- Chapter 6 (1) Indicate True (T) or False (F) for each of the following statements. (a) Increasing the concentration of the nucleophilic species in an SN2 reaction increases the rate of reaction. (b) Carbocations are Lewis bases while nucleophiles are Lewis acids. (c) The SN2 reaction occurs by a back-side attack of the nucleophile on the carbon bearing the leaving group. (d) The difference in free energy between the reactants and the products is defined as the free energy of activation. (e) The smaller the free energy of activation the faster the reaction. (f) The overall rate in a multi-step reaction is controlled primarily by the slowest step in the reaction sequence. (g) The first step in the SN1 reaction of tert-butyl chloride is the homolytic cleavage of the carbon-chlorine bond. (h) Carbocations have a trigonal planar geometry at the carbon bearing the positive charge. (i) Carbon-hydrogen and carbon-carbon bonds located beta to a carbocationic center stabilize the cationic species by hyperconjugative electron delocalization. (j) The Hammond-Leffler postulate states that the structure of a transition state resembles the stable species that is nearest it in free energy. (k) Nucleophilicities are related to rates of reaction while basicities are related to equilibria. (l) Dimethylsulfoxide and N,N-dimethylformamide are dipolar protic solvents. (m) The SN2 reaction is an example of a one step concerted reaction. (n) The tert-butyl cation is less stable than the isopropyl cation. (o) The reaction of tert-butyl chloride with methanol is an example of a methanolysis reaction. (p) Secondary alkyl halides undergo SN2 reactions more readily than primary alkyl halides. (q) Neopentyl halides, even though they are primary halides, are very unreactive in an SN2 nucleophilic displacement due to steric effects. (r) In polar, aprotic solvents such as dimethylsulfoxide, fluoride is a poorer nucleophile than iodide. (s) In substitution reactions triflate is a better leaving group than p-toluenesulfonate. (t) Vinyl chloride is a molecule where the chloride is attached to an sp2 hybridized carbon. (u) A secondary carbocation is more stable than a vinyl carbocation. (v) In an SN2 reaction bromide is a better leaving group compared to iodide. (w) In an SN2 reaction bromide is a better nucleophile compared to iodide. (x) tert-Butyl chloride undergoes an SN1 process at a faster rate than sec-butyl chloride. (y) Nucleophiles are species with at least one unshared electron pair. (z) Nucleophiles are Lewis bases. (aa) In general, SN2 reactions are characterized by first-order kinetics.(bb) Cyanide ion is both a nucleophile and a base. (cc) An E2 elimination process is characterized by 2nd-order kinetics. (dd) A concerted reaction is one in which there is a single energy barrier between the reactants and products. (ee) SN2 reactions at a chiral center always occurs with retention of configuration. (ff) The reaction of tert-butyl chloride with sodium methoxide in methanol leads to the formation of tert-butyl methyl ether. (gg) 1-Bromo[2.2.1]bicycloheptane, a tert halide, undergoes rapid ethanolyis. (2) Complete each of the following reactions. (a) CF3CH2ClH2O, OH- (b) H2CCOCH2OCH3Na+ I-AcetoneBr (c) O BrNa+ CN-Ethanol-Water (d) CH2BrNO2CH3CO- Na+Acetic AcidO(e) H3CCHCH2OCCH2ClOCH3Na+ N3-Acetone-Water (f) OOCH3CH3H2CHOO2SNa+ I-Acetone (g) OCH2S- Na+OCH2Br (h)(3) Circle the correct answer. (a) Which compound undergoes substitution by the SN1 mechanism at the fastest rate? (b) Which compound undergoes substitution by the SN2 mechanism at the fastest rate? Br(1)BrBrBr(3)(2)(4) (4) Write the structure of the principal organic product to be expected from the reaction of 1-bromopropane with each of the following: (a) Sodium iodide in acetone (b) Sodium ethoxide in ethanol(c) Sodium cyanide in dimethyl sulfoxide (5) In each of the following circle which reaction will occur faster. (a) 1-Bromobutane or 1-Iodobutane with sodium cyanide in dimethyl sulfoxide. (b) 1-Chloro-2-methylbutane or 1-chloropentane with sodium iodide in acetone. (c) 1-chlorohexane or cyclohexyl chloride with sodium azide in aqueous ethanol. (d) Solvolysis of 1-bromo-2,2-dimethylpropane or tert-butyl bromide in ethanol. (e) Solvolysis of isobutyl bromide or sec-butyl bromide in aqueous formic acid. (6) Give the mechanistic symbols (SN1, SN2, E1, E2) that are most consistent with each of the following statements. (1) Methyl halides react with sodium ethoxide in ethanol only by this mechanism. (2) Unhindered primary halides react with sodium ethoxide in ethanol mainly by this mechanism. (3) The substitution product obtained by solvolysis of tert-butyl bromide reacts mainly by this mechanism. (7) Identify the product in each of the following reactions:(8) What is the effect of doubling the concentration of sodium bromide on the following SN2 reaction? (1) The rate constant, k, doubles. (2) The rate of the reaction doubles. (3) The products of reaction change. (4) There is no effect. (9) Which of the following is a polar aprotic solvent? (1) Methanol (2) Acetic acid (3) Hexane (4) N,N-dimethylformamide (10) Which of the following ions has the most nucleophilic reactivity in methanol. (1) Fluoride ion (2) Iodide ion (3) Potassium ion (4) Tetrafluoroborate ion, BF4- (11) Which of the following structures is consistent with the IR