Chapter 27

Describe what is meant by each of the following reaction types, and illustrate with an example: (a) nucleophilic substitution reaction; (b) electrophilic substitution reaction; (c) addition reaction; (d) elimination reaction; (e) rearrangement reaction.

Describe what is meant by each of the following reaction types, and illustrate with an example from the text: (a) dehydration; (b) hydrolysis; (c) solvolysis; (d) hydration of an alkene.

Write a balanced chemical equation for the reaction that is described and then classify the reaction as a substitution, an elimination, an addition, or a rearrangement reaction: (a) Ethene and \(\mathrm{Br}_{2}\) react in carbon tetrachloride to give 1,2 -dibromoethane. (b) Iodoethane reacts with KOH(aq) yielding ethene, water, and potassium bromide. (c) Chloromethane reacts with \(\mathrm{NaOH}(\) aq) to give methanol and sodium chloride.

Write a balanced chemical equation for the reaction that is described and then classify the reaction as a substitution, an elimination, an addition, or a rearrangement reaction. (a) 3,3 -dimethyl- 1 -butene reacts in acid solution to yield 2,3-dimethyl-2-butene. (b) 1 -iodo-2,2-dimethylpropane reacts with water, 2,2-dimethyl-1-propanol, and HI(aq). (c) 2-chloro-2-methylpropane reacts with NaOH(aq) to give 2 -methyl- 1 -propene, sodium chloride, and water.

Write equations for the substitution reaction of \(n\) -bromobutane, a typical primary haloalkane, with the following reagents: (a) \(\mathrm{NaOH} ;\) (b) \(\mathrm{NH}_{3} ;\) (c) \(\mathrm{NaCN}\) (d) \(\mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{ONa}\).

Write equations for the substitution reaction of \(n\) -bromopentane, a typical primary haloalkane with the following reagents: (a) \(\mathrm{NaN}_{3};\) (b) \(\mathrm{N}\left(\mathrm{CH}_{3}\right)_{3};\) (c) \(\mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{C} \equiv \mathrm{CNa};\) (d) \(\mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{SNa}\).

Answer the following questions for this \(S_{\mathrm{N}} 2\) reaction: $$\begin{aligned} \mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{CH}_{2} \mathrm{CH}_{2} \mathrm{Br}+\mathrm{NaOH} & \longrightarrow \mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{CH}_{2} \mathrm{CH}_{2} \mathrm{OH}+ \mathrm{NaBr} \end{aligned}$$ (a) What is the rate expression for the reaction? (b) Draw the reaction profile for the reaction. Label all parts. Assume that the products are lower in energy than the reactants. (c) What is the effect on the rate of the reaction of doubling the concentration of \(n\) -butyl bromide? (d) What is the effect on the rate of the reaction of halving the concentration of sodium hydroxide?

Answer the following questions for this \(\mathrm{S}_{\mathrm{N}}1\) reaction: (a) What is the rate expression for the reaction? (b) Draw the reaction profile for the reaction. Label all parts. Assume that the products are lower in energy than the reactants. (c) What is the effect on the rate of the reaction of doubling the concentration of 1-bromo-1-methylpentane? (d) The solvent for the reaction is ethanol. What is the effect on the rate of the reaction of adding more ethanol?

Answer the following questions for this E2 reaction: $$\begin{aligned} \mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{CH}_{2} \mathrm{Br}+\mathrm{NaOH} & \longrightarrow \mathrm{CH}_{3} \mathrm{CH}= \mathrm{CH}_{2}+\mathrm{NaBr}+\mathrm{H}_{2} \mathrm{O} \end{aligned}$$ (a) What is the rate expression for the reaction? (b) Draw the reaction profile for the reaction. Label all parts. Assume that the products are lower in energy than the reactants. (c) What is the effect on the rate of the reaction of doubling the concentration of \(\mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{CH}_{2} \mathrm{Br} ?\) (d) What is the effect on the rate of the reaction of halving the concentration of \(\mathrm{NaOH} ?\)

Answer the following questions for this E1 reaction: $$\begin{array}{c} \mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{C}\left(\mathrm{CH}_{3}\right)_{2} \mathrm{Br}+\mathrm{CH}_{3} \mathrm{OH} \longrightarrow \mathrm{CH}_{3} \mathrm{CH}=\mathrm{C}\left(\mathrm{CH}_{3}\right)_{2}+\mathrm{Br}^{-}+\mathrm{CH}_{3} \mathrm{OH}_{2}^{+} \end{array}$$ (a) What is the rate expression for the reaction? (b) Draw the reaction profile for the reaction. Label all parts. Assume that the products are lower in energy than the reactants. (c) What is the effect on the rate of the reaction of doubling the concentration of \(\mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{C}\left(\mathrm{CH}_{3}\right)_{2} \mathrm{Br} ?\) (d) What is the effect on the rate of the reaction of doubling the concentration of \(\mathrm{CH}_{3} \mathrm{OH} ?\)

Identify the nucleophile, electrophile, and leaving group in each of the following substitution reactions. Predict whether equilibrium favors the reactants or products: (a) \(\mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{ONa}+\mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{CH}_{2} \mathrm{I} \rightleftharpoons\) \(\mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{CH}_{2} \mathrm{OCH}_{2} \mathrm{CH}_{3}+\mathrm{NaI}\) (b) \(\mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{NH}_{3}^{+}+\mathrm{KI} \rightleftharpoons\) \(\mathrm{NH}_{3}+\mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{I}+\mathrm{K}^{+}\)

Identify the nucleophile, electrophile, and leaving group in each of the following substitution reactions. Predict whether equilibrium favors the reactants or products: (a) \(\mathrm{CH}_{3} \mathrm{OH}+\mathrm{I}^{-} \rightleftharpoons \mathrm{CH}_{3} \mathrm{OH}+\mathrm{NaOH}\) (b) \(\left(\mathrm{CH}_{3}\right)_{2} \mathrm{CHCl}+\mathrm{KCN} \rightleftharpoons\left(\mathrm{CH}_{3}\right)_{2} \mathrm{CHCN}+\mathrm{KCl}\)

A sample of \((S)-\mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{CH}\left(\mathrm{CH}_{3}\right) \mathrm{Cl}\) is hydrolyzed by water, and the resulting solution is optically inactive. (a) Write the formula of the product. (b) By which nucleophilic substitution reaction mechanism does this reaction occur?

A sample of \((R)-\mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{CH}\left(\mathrm{CH}_{3}\right) \mathrm{Cl}\) reacts with \(\mathrm{CH}_{3} \mathrm{O}^{-}\) in dimethyl sulfoxide, \(\left(\mathrm{CH}_{3}\right)_{2} \mathrm{SO},\) a convenient solvent for organic reactions. The resulting solution is optically active. (a) Write the formula of the product. (b) By which mechanism does this nucleophilic substitution reaction occur?

A sample of \((R)-\mathrm{CH}_{3} \mathrm{CH}(\mathrm{Cl}) \mathrm{CH}_{2} \mathrm{CH}_{3}\) reacts with \(\mathrm{CH}_{3} \mathrm{S}^{-}\) in dimethyl sulfoxide, and the resulting solution is optically active. (a) Write the formula of the product. (b) By which mechanism does this nucleophilic substitution reaction occur?

Predict the major organic product obtained in each of the following reactions. Assume that [O] represents \(\mathrm{Na}_{2} \mathrm{Cr}_{2} \mathrm{O}_{7}\) in \(\mathrm{H}_{2} \mathrm{SO}_{4}\) (a) \(\left(\mathrm{CH}_{3}\right)_{2} \mathrm{CHCH}_{2} \mathrm{OH}+\mathrm{HBr} \longrightarrow\) (b) \(\left(\mathrm{CH}_{3}\right)_{3} \mathrm{COH}+\mathrm{K} \longrightarrow\) (c) \(\left(\mathrm{CH}_{3}\right)_{2} \mathrm{CHOH} \stackrel{[\mathrm{O}]}{\longrightarrow}\) (d) \(\mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{CH}_{2} \mathrm{OH}+\mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{I} \longrightarrow\)

Predict the products of the following reactions. Assume that \([\mathrm{O}]\) represents \(\mathrm{Na}_{2} \mathrm{Cr}_{2} \mathrm{O}_{7}\) in \(\mathrm{H}_{2} \mathrm{SO}_{4}:\) (a) \(\left(\mathrm{CH}_{3}\right)_{2} \mathrm{CHCH}_{2} \mathrm{OH} \stackrel{[\mathrm{O}]}{\longrightarrow}\) (b) \(\mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{OH}+\left(\mathrm{CH}_{3}\right)_{2} \mathrm{CHCOOH} \frac{\mathrm{H}^{+}}{\Delta}\) (c) 3 -methyl- 2 -butanol \(+\mathrm{NaCl} \stackrel{\mathrm{H}_{2} \mathrm{SO}_{4}}{\longrightarrow}\) (d) \(\mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{CH}_{2} \mathrm{OH} \frac{\mathrm{H}_{2} \mathrm{SO}_{4}}{\Delta}\)

Draw the structures of the products of each of the following reactions: (a) propene + hydrogen (Pt, heat) (b) 2 -butanol \(+\) heat (in the presence of sulfuric acid)

Predict the product(s) of the reaction of: (a) HCl with 2-chloro-1-propene (b) HCN with \(\mathrm{CH}_{3} \mathrm{CH}=\mathrm{CH}_{2}\) (c) HCl with CH \(_{3} \mathrm{CH}=\mathrm{C}\left(\mathrm{CH}_{3}\right)_{2}\)

Give the major product that forms when (Z)-3-methyl2-pentene reacts with each of the following reagents: (a) \(\mathrm{HI} ;\) (b) \(\mathrm{H}_{2}\) in the presence of a platinum catalyst; (c) \(\mathrm{H}_{2} \mathrm{O}\) in \(\mathrm{H}_{2} \mathrm{SO}_{4} ;\) (d) \(\mathrm{Br}_{2}\) in \(\mathrm{CCl}_{4}\).

Give the major product that forms when 1 -ethylcyclohexene reacts with each of the following reagents: (a) \(\mathrm{HI} ;\) (b) \(\mathrm{H}_{2}\) in the presence of a platinum catalyst; (c) \(\mathrm{H}_{2} \mathrm{O}\) in \(\mathrm{H}_{2} \mathrm{SO}_{4} ;\) (d) \(\mathrm{Br}_{2}\) in \(\mathrm{CCl}_{4}\)

Alkylation of benzene can be accomplished by treating benzene with haloalkane (RX) in the presence of \(\mathrm{AlCl}_{3}\) The reaction is known as a Friedel-Crafts alkylation reaction. (The reaction is named after Charles Friedel, a French chemist, and James M. Crafts, an American chemist, who discovered this method of making alkylbenzenes in \(1877 .\) ) An example of a Friedel-Crafts alkylation reaction is shown below: The mechanism for this reaction involves the following steps. First, \(\left(\mathrm{CH}_{3}\right)_{2} \mathrm{CHCl}\) and \(\mathrm{AlCl}_{3}\) react in a Lewis acid-base reaction to form an adduct, \(\left(\mathrm{CH}_{3}\right)_{2} \mathrm{CH}-\mathrm{Cl}-\mathrm{AlCl}_{3},\) in which a chlorine atom is bonded to both carbon and aluminum. The adduct then dissociates to \(\left(\mathrm{CH}_{3}\right)_{2} \mathrm{CH}^{+},\) a carbocation, and \(\mathrm{AlCl}_{4}{^-}\). The carbocation acts as an electrophile in a reaction with benzene, forming an arenium ion. Finally, a proton is removed from the arenium ion by \(\mathrm{AlCl}_{4}{^-},\) yielding an alkylbenzene, \(\mathrm{HCl},\) and \(\mathrm{AlCl}_{3}\) Write chemical equations for the elementary processes involved in forming 1 -methyl-1-phenylethane and \(\mathrm{HCl}\) from \(\left(\mathrm{CH}_{3}\right)_{2} \mathrm{CHCl}\) and benzene. Use curved arrows to show the movement of electrons.

Predict the main product(s) of (a) the mononitration of chlorobenzene; (b) the monosulfonation of nitrobenzene; (c) the monochlorination of 1-methyl-2-nitrobenzene

Predict the main product(s) of (a) the mononitration of benzoic acid; (b) the monosulfonation of phenol; (c) the monobromination of 2 -nitrobenzaldehyde.

What is major product expected from the monobromination of 2,2,3 -trimethylpentane?

What is the major product expected from the monobromination of methylcyclohexane?

(a) Write the initiation, propagation, and termination steps involved in the monofluorination of 2,3-dimethylbutane to give 1-fluoro-2,3-dimethylbutane. (b) Explain why in the monofluorination of \(2,3-\) dimethylbutane the major product is \(1-\) fluoro- \(2,3-\) dimethylbutane, not 2-fluoro-2,3-dimethylbutane.

Write the initiation, propagation, and termination steps involved in the monobromination of \(2,3-\) dimethylbutane to give 2 -bromo- 2,3 -dimethylbutane.

In referring to the molecular mass of a polymer, we can speak only of the average molecular mass. Explain why the molecular mass of a polymer is not a unique quantity, as it is for a substance like benzene.

Explain why Dacron is called a polyester. What is the percent oxygen, by mass, in Dacron?

Nylon 66 is produced by the reaction of 1,6 -hexanediamine with adipic acid. A different nylon polymer is obtained if sebacyl chloride is substituted for the adipic acid. What is the basic repeating unit of this nylon structure?

Would you expect a polymer to be formed by the reaction of terephthalic acid with ethyl alcohol in place of ethylene glycol? With glycerol in place of ethylene glycol? Explain.

Starting with acetylene as the only source of carbon, together with any inorganic reagents required, devise a method to synthesize acetaldehyde.

Starting with acetylene as the only source of carbon, together with any inorganic reagents required, devise a method to synthesize 1,1,2,2 -tetrabromoethane.

How would you synthesize \((E)\) - and \((Z)\) -3-heptene from acetylene and any other chemicals?

How would you synthesize ( \(R\) )-2-butanamine from (S)-2-butanol?

The azide anion is a nucleophile and when attached to a carbon atom, undergoes reduction to the amino group and free nitrogen. Suggest a method of preparation of the primary amine propanamine.

Draw a structure to represent the principal product of each of the following reactions: (a) 1 -pentanol \(+\) dichromate ion (acid solution) (b) butyric acid + ethanol (acid solution) (c) 2 -methyl-1-butene \(+\mathrm{HBr}\)

Predict the products of the monobromination of (a) \(m\) -dinitrobenzene; (b) aniline; (c) \(p\) -bromoanisole.

Write the formulas of the products formed from the reaction of propene with each of the following substances: (a) \(\mathrm{H}_{2} ;\) (b) \(\mathrm{Cl}_{2}\); (c) \(\mathrm{HCl} ;\) (d) \(\mathrm{H}_{2} \mathrm{O}\) (in acid).

Write the formulas of the products formed from the reaction of 2 -butene with each of the following substances: (a) \(\mathrm{H}_{2} ;\) (b) \(\mathrm{Cl}_{2} ;\) (c) \(\mathrm{HCl} ;\) (d) \(\mathrm{H}_{2} \mathrm{O}\) (in acid).

Write the formulas of the products expected to form in the following situations. If no reaction occurs, write N.R. (a) \(\mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{NH}_{2}(\mathrm{aq})+\mathrm{HCl}(\mathrm{aq}) \longrightarrow\) (b) \(\left(\mathrm{CH}_{3}\right)_{3} \mathrm{N}(\mathrm{aq})+\mathrm{HBr}(\mathrm{aq}) \longrightarrow\) (c) \(\mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{NH}_{3}^{+}(\mathrm{aq})+\mathrm{H}_{3} \mathrm{O}^{+}(\mathrm{aq}) \longrightarrow\) (d) \(\mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{NH}_{3}^{+}(\mathrm{aq})+\mathrm{OH}^{-}(\mathrm{aq}) \longrightarrow\)

To prepare methyl ethyl ketone, which of these compounds would you oxidize: 2 -propanol, 1 -butanol, 2-butanol, or tert-butyl alcohol? Explain.

Indicate the principal product(s) you would expect in (a) treating \(\mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{CH}=\mathrm{CH}_{2}\) with dilute \(\mathrm{H}_{2} \mathrm{SO}_{4}(\mathrm{aq})\) (b) exposing a mixture of chlorine and propane gases to ultraviolet light; (c) heating a mixture of isopropyl alcohol and benzoic acid; (d) oxidizing sec-butyl alcohol with \(\mathrm{Cr}_{2} \mathrm{O}_{7}^{2-}\) in acidic solution.

Write the structures of the isomers you would expect to obtain in the mononitration of \(m\) -methoxybenzaldehyde:

In the chlorination of \(\mathrm{CH}_{4},\) some \(\mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{Cl}\) is obtained as a product. Explain why this should be so.

The three isomeric tribromobenzenes, I, II, and III, when nitrated, form three, two, and one mononitrotribromobenzenes, respectively. Assign correct structures to I, II, and III.

Write the name and structure of the benzene derivatives described below. (a) Formula: \(\mathrm{C}_{8} \mathrm{H}_{10} ;\) forms three monochlorination products when treated with \(\mathrm{Cl}_{2}\) and \(\mathrm{FeCl}_{3}\) (b) Formula: \(\mathrm{C}_{9} \mathrm{H}_{12}\); forms one monochlorination product when treated with \(\mathrm{Cl}_{2}\) and \(\mathrm{FeCl}_{3}\) (c) Formula: \(\mathrm{C}_{9} \mathrm{H}_{12}\); forms four monochlorination products when treated with \(\mathrm{Cl}_{2}\) and \(\mathrm{FeCl}_{3}\)

For the monochlorination of hydrocarbons, the following ratio of reactivities has been found: \(3^{\circ}>2^{\circ}>\) \(1^{\circ}, \quad 4.3: 3: 1 . \quad\) How many different monochloro derivatives of 2 -methylbutane are possible, and what percentage of each would you expect to find?

The cyanide anion is a nucleophile and when attached to a carbon atom, undergoes hydrolysis under basic conditions to the carboxylate anion. Suggest a method of preparing sodium butanoate from chloropropane. How can sodium butanoate be converted into butanoic acid?