Organic Chemistry

Marc Loudon, Jim Parise

Chapter 10

The Chemistry of Alcohols and Thiols - all with Video Answers

Educators

Chapter Questions

Problem 1

Give the structure of each of the following compounds.
(a) sodium isopropoxide
(b) potassium tert-butoxide
(c) magnesium 2,2 -dimethyl-I-butanolate

Aadit Sharma

Aadit Sharma

Numerade Educator

Problem 2

Name the following compounds.
(a) $\mathrm{Ca}\left(\mathrm{OCH}_{3}\right)_{2}$
(b) $\mathrm{CuSCH}_{2} \mathrm{CH}_{3}$

Aadit Sharma

Numerade Educator

Problem 3

In each of the following sets, arrange the compounds in order of increasing acidity (decreasing $\left.\mathrm{p} K_{\mathrm{d}}\right)$. Explain your choices.
(a) $\mathrm{ClCH}_{2} \mathrm{CH}_{2} \mathrm{OH}, \mathrm{Cl}_{2} \mathrm{CHCH}_{2} \mathrm{OH}, \mathrm{Cl}\left(\mathrm{CH}_{2}\right)_{3} \mathrm{OH}$
(b) ClCH $_{2} \mathrm{CH}_{2} \mathrm{SH}, \mathrm{ClCH}_{2} \mathrm{CH}_{2} \mathrm{OH}, \mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{OH}$
(c) $\mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{CH}_{2} \mathrm{CH}_{2} \mathrm{OH}, \mathrm{CH}_{3} \mathrm{OCH}_{2} \mathrm{CH}_{2} \mathrm{OH}$

Aadit Sharma

Numerade Educator

Problem 4

What alkene(s) are formed in the acid-catalyzed dehydration of each of the following alcohols?
(a) 3-methyl-3-heptanol
(b)
<smiles>CC(C)O</smiles>

Aadit Sharma

Numerade Educator

Problem 5

Write the curved-arrow mechanism for the reaction in Problem 10.4 a. (Abbreviate the catalyzing acid as $\mathrm{H}-$ A.) In each step, identify all Bronsted acids and bases, all electrophiles and nucleophiles, and all leaving groups.

Aadit Sharma

Numerade Educator

Problem 6

Write the structure of the carbocation intermediate involved in the acid-catalyzed dehydration of 3 -ethyl-3-pentanol.

Aadit Sharma

Numerade Educator

Problem 7

Identify the major alkene product(s) in part (a) of Problem 10.4 .

Aadit Sharma

Numerade Educator

Problem 8

Draw the structures of two alcohols, one secondary and one tertiary, that could give each of the following alkenes as a major acid-catalyzed dehydration product. In each case, which alcohol would dehydrate most rapidly?
(a) 1 -methylcyclohexene
(b) 3 -methyl-2-pentene

Aadit Sharma

Numerade Educator

Problem 9

Write a curved-arrow mechanism for the reaction in Eq. 10.16 .

Aadit Sharma

Numerade Educator

Problem 10

A certain reaction is carried out in methanol with $\mathrm{H}_{2} \mathrm{SO}_{4}$ as a catalyst.
(a) What Brónsted acid is present in highest concentration in such a solution? (Hint: $\mathrm{H}_{2} \mathrm{SO}_{4}$ is completely dissociated in methanol, just as it is in water.)
(b) If a base is involved in the reaction mechanism, what is the basic species?

Aadit Sharma

Numerade Educator

Problem 11

Suggest an alcohol starting material and the conditions for the preparation of each of the following alkyl halides.

Aadit Sharma

Numerade Educator

Problem 12

Write a curved-arrow mechanism for the rearrangement shown in Eq. $10.22 .$

Aadit Sharma

Numerade Educator

Problem 13

Draw the structure of the alkyl halide product expected (if any) in each of the following reactions.
(a) 1 -propanol $+$ HBr in the presence of $\mathrm{H}_{2} \mathrm{SO}_{4}$ catalyst
(b) $\mathrm{HOCH}_{2} \mathrm{CH}_{2} \mathrm{CH}_{2} \mathrm{OH}+$ excess HI $\underset{\text { heat }}{-}$
(c)

Aadit Sharma

Numerade Educator

Problem 14

Draw both the complete structure and the abbreviated structure, and give another name for each of the following compounds.
(a) isopropyl methanesulfonate
(b) methyl $p$ -toluenesulfonate
(c) phenyl tosylate
(d) cyclohexyl mesylate

Aadit Sharma

Numerade Educator

Problem 15

Suggest a preparation of cyclohexyl mesylate from the appropriate alcohol.

Aadit Sharma

Numerade Educator

Problem 16

Design a preparation of each of the following compounds from an alcohol using sulfonate ester methodology.

Aadit Sharma

Numerade Educator

Problem 17

Give the product that results from each of the following sequences of reactions.

Aadit Sharma

Numerade Educator

Problem 18

Phosphoric acid, $\mathrm{H}_{3} \mathrm{PO}_{4},$ has the following structure.
<smiles>O=P(O)(O)O</smiles>
(a) Draw the structure of trimethyl phosphate.
(b) Draw the structure of the monoethyl ester of phosphoric acid.

Aadit Sharma

Numerade Educator

Problem 19

Predict the products in the reaction of dimethyl sulfate with each of the following nucleophiles.
(a) $\mathrm{CH}_{3} \ddot{\mathrm{N}} \mathrm{H}_{2}$
(b) water
(c) sodium ethoxide
(d) sodium 1 -propanethiolate

Aadit Sharma

Numerade Educator

Problem 20

Give three reactions that illustrate the preparation of 1 -bromobutane from 1 -butanol.

Aadit Sharma

Numerade Educator

Problem 21

(a) According to the mechanism of the reaction shown in Eq. 10.34 , what would be the absolute configuration of the alkyl chloride obtained from the reaction of thionyl chloride with $(S)-\mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{CH}_{2} \mathrm{CHD}-\mathrm{OH} ?$ Explain.
(b) According to the mechanism shown in Eqs. $10.36 \mathrm{a}$ and $10.36 \mathrm{~b}$, what would be the absolute configuration of 2-bromopentane obtained from the reaction of $\mathrm{Ph}_{3} \mathrm{PBr}_{2}$ with the $R$ enantiomer of 2 -pentanol? Explain.

Aadit Sharma

Numerade Educator

Problem 22

An important class of substitution reactions that you will study in Chapter 21 is called nucleophilic acyl substitution. Substitution reactions of this type occur at the carbon of a carbonyl (C = O) group. An important laboratory example is the reaction of nucleophiles (ammonia in the example below) with acyl chlorides (also called acid chlorides).

Aadit Sharma

Numerade Educator

Problem 23

Suggest conditions for carrying out each of the following conversions to yield a product that is as free of isomers as possible.

Aadit Sharma

Numerade Educator

Problem 24

Give the structure of two secondary alcohols that could be converted by $\mathrm{HBr} / \mathrm{H}_{2} \mathrm{SO}_{4}$ into the corresponding alkyl bromide without rearrangement.

Aadit Sharma

Numerade Educator

Problem 25

Contrast the products expected when 2 -methyl-3-pentanol is treated with (a) $\mathrm{HBr} / \mathrm{H}_{2} \mathrm{SO}_{4}$ or (b) $\mathrm{Ph}_{3} \mathrm{PBr}_{2}$. Explain.

Aadit Sharma

Numerade Educator

Problem 26

Considering the organic compound, classify each of the following transformations, some of which may be unfamiliar, as an oxidation, a reduction, or neither. For those that are oxidations or reductions, tell how many electrons are gained or lost.

Aadit Sharma

Numerade Educator

Problem 27

Write the transformation in Problem $10.26 \mathrm{~b}$ as a balanced half-reaction. Complete the following sentence: This reaction is a (how many)-electron (oxidation or reduction).

Aadit Sharma

Numerade Educator

Problem 28

For each of the following balanced oxidation-reduction reactions, indicate which compound(s) are oxidized and which are reduced. (Hint: Consider the change in the organic compounds in each reaction first.)

Aadit Sharma

Numerade Educator

Problem 29

How many moles of permanganate are required to oxidize one mole of toluene to benzoic acid? (Use $\mathrm{H}_{2} \mathrm{O}$ and protons to balance the equation.)

Aadit Sharma

Numerade Educator

Problem 30

Give the product expected when each of the following alcohols reacts with pyridinium chlorochromate $(\mathrm{PCC})$.

Aadit Sharma

Numerade Educator

Problem 31

From which alcohol and by what method would each of the following compounds best be prepared by an oxidation?

Aadit Sharma

Numerade Educator

Problem 32

Write a curved-arrow mechanism for the following oxidation of 2 -heptanol, which proceeds in $82 \%$ yield.

Aadit Sharma

Numerade Educator

Problem 33

For each of the following molecules, state whether the groups indicated by italic letters are constitutionally equivalent or nonequivalent. If they are constitutionally equivalent, classify them as homotopic, enantiotopic, or diastereotopic. (For cases in which more than two groups are designated, consider the relationships within each pair of groups.)

Aadit Sharma

Numerade Educator

Problem 34

In each of the following cases, imagine that the two reactants shown are allowed to react in the presence of alcohol dehydrogenase. Tell whether the ethanol formed is chiral. If the ethanol is chiral, draw a line-and-wedge structure of the enantiomer that is formed.

Aadit Sharma

Numerade Educator

Problem 35

How many electrons are involved in the oxidation of 1 -propanethiol to each of the following compounds. (See Fig. 10.3 for detailed Lewis structures.)
(a) 1-propanesulfonic acid, $\mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{CH}_{2} \mathrm{SO}_{3} \mathrm{H}$
(b) 1-propanesulfenic acid, $\mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{CH}_{2} \mathrm{~S}-\mathrm{OH}$

Aadit Sharma

Numerade Educator

Problem 36

(a) How many electrons are involved in the oxidation of triphenylphosphine $\left(\mathrm{Ph}_{3} \mathrm{P}:\right)$ to triphenylphosphine oxide $\left(\mathrm{Ph}_{3} \mathrm{P}=\mathrm{O}\right)$ ? Show your reasoning.
(b) Draw a resonance structure for triphenylphosphine oxide in which phosphorus obeys the octet rule.
(c) Draw a Lewis structure for trimethylamine oxide $\left(\mathrm{Me}_{3} \mathrm{NO}\right)$. How is the bond order of the $\mathrm{N}-\mathrm{O}$ bond in this compound different from the bond order of the $\mathrm{P}-\mathrm{O}$ bond in the phosphorus analog, trimethylphosphine oxide? Justify your answer with appropriate resonance structures.

Aadit Sharma

Numerade Educator

Problem 37

The rates of the reactions in Eqs. $10.71 \mathrm{a}-\mathrm{b}$ are increased when the thiol is ionized by a base such as sodium ethoxide. Suggest a mechanism for Eq. 10.71 a that is consistent with this observation, and explain why the presence of base makes the reaction faster.

Aadit Sharma

Numerade Educator

Problem 38

Outline a synthesis of each of the following compounds from the indicated starting material. Begin each synthesis with a retrosynthetic analysis.

Aadit Sharma

Numerade Educator

Problem 39

Give the product expected, if any, when 1 -butanol (or other compound indicated) reacts with each of the following reagents.
(a) concentrated aqueous $\mathrm{HBr}, \mathrm{H}_{2} \mathrm{SO}_{4}$ catalyst, heat
(b) cold aqueous $\mathrm{H}_{2} \mathrm{SO}_{4}$
(c) pyridinium chlorochromate $(\mathrm{PCC})$ in $\mathrm{CH}_{2} \mathrm{Cl}_{2}$
(d) $\mathrm{NaH}$
(e) product of part (d) $+\mathrm{CH}_{3} \mathrm{I}$ in DMSO
(f) $p$ -toluenesulfonyl chloride in pyridine
(g) PrMgBr in anhydrous ether
(h) $\mathrm{SOCl}_{2}$ in pyridine
(i) $\mathrm{Ph}_{3} \mathrm{PBr}_{2}$ in DMF
(j) product of part (a) $+\mathrm{Mg}$ in dry ether
(k) product of part (f) $+\mathrm{K}^{+}\left(\mathrm{CH}_{3}\right)_{3} \mathrm{C}-\mathrm{O}^{-}$ in $\left(\mathrm{CH}_{3}\right)_{3} \mathrm{COH}$
(l) triflic anhydride and pyridine
(m) product of (l) followed by anhydrous $\mathrm{K}^{+} \mathrm{F}^{-}$ in acetonitrile

Aadit Sharma

Numerade Educator

Problem 40

Give the product expected, if any, when 2 -methyl-2propanol (or other compound indicated) reacts with each of the following reagents.
(a) concentrated aqueous $\mathrm{HCl}$
(b) $\mathrm{CrO}_{3}$ in pyridine
(c) $\mathrm{H}_{2} \mathrm{SO}_{4},$ heat
(d) $\mathrm{Br}_{2}$ in $\mathrm{CH}_{2} \mathrm{Cl}_{2}$ (dark)
(e) potassium metal
(f) methanesulfonyl chloride in pyridine
(g) product of part (f) $+\mathrm{NaOH}$ in DMSO
(h) product of part (e) + product of part (a)

Aadit Sharma

Numerade Educator

Problem 41

Give the structure of a compound that satisfies the criterion given in each case. (There may be more than one correct answer.)
(a) a seven-carbon tertiary alcohol that yields a single alkene after acid-catalyzed dehydration
(b) an alcohol that, after acid-catalyzed dehydration, yields an alkene that, in turn, on ozonolysis and treatment with $\left(\mathrm{CH}_{3}\right)_{2} \mathrm{~S},$ gives only benzaldehyde, $\mathrm{Ph}-\mathrm{CH}=\mathrm{O}$
(c) an alcohol that gives the same product when it reacts with $\mathrm{KMnO}_{4}$ as is obtained from the ozonolysis of trans -3,6 -dimethyl- 4 -octene followed by treatment with $\mathrm{H}_{2} \mathrm{O}_{2}$

Raghvendra Singh

Raghvendra Singh

Numerade Educator

Problem 42

The following triester is a powerful explosive, but is also a medication for angina pectoris (chest pain). From what inorganic acid and what alcohol is it derived?

Aadit Sharma

Numerade Educator

Problem 43

In each compound, identify (1) the diastereotopic fluorines, (2) the enantiotopic fluorines, (3) the homotopic fluorines, and (4) the constitutionally nonequivalent fluorines.

Aadit Sharma

Numerade Educator

Problem 44

How many chemically nonequivalent sets of hydrogens are in each of the following structures?

Aadit Sharma

Numerade Educator

Problem 45

When tert-butyl alcohol is treated with $\mathrm{H}_{2}{ }^{18} \mathrm{O}$ (water containing the heavy oxygen isotope ${ }^{18} \mathrm{O}$ ) in the presence of a small amount of acid, and the tert-butyl alcohol is re-isolated, it is found to contain ${ }^{18} \mathrm{O} .$ Write a curvedarrow mechanism consisting of Brónsted acid-base reactions, Lewis acid-base associations, and Lewis acid-base dissociations that explains how the isotope is incorporated into the alcohol.

Aadit Sharma

Numerade Educator

Problem 46

Arrange the compounds or ions within each set in order of increasing acidity (decreasing $\mathrm{pK}_{\mathrm{a}}$ ) in solution. Explain your reasoning.
(a) propyl alcohol, isopropyl alcohol, tert-butyl alcohol, 1-propanethiol
(b) 2 -chloro-1-propanethiol, 2 -chloroethanol, 3-chloro-1-propanethiol
(c)
$$
\mathrm{CH}_{3} \ddot{\mathrm{NH}}-\mathrm{CH}_{2} \mathrm{CH}_{2}-\ddot{\mathrm{O}} \mathrm{H}, \mathrm{CH}_{3} \ddot{\mathrm{N}} \mathrm{H}-\mathrm{CH}_{2} \mathrm{CH}_{2} \mathrm{CH}_{2}-\ddot{\mathrm{O}} \mathrm{H}
$$
$\left(\mathrm{CH}_{3}\right)_{3} \mathrm{~N}^{+}-\mathrm{CH}_{2} \mathrm{CH}_{2}-\ddot{\mathrm{O}} \mathrm{H}$
(d)
$$
\begin{array}{l}
\mathrm{CH}_{3} \ddot{\mathrm{O}}-\mathrm{CH}_{2} \mathrm{CH}_{2}-\ddot{\mathrm{O}} \mathrm{H}, \quad \mathrm{CH}_{3} \mathrm{O}-\mathrm{CH}_{2} \mathrm{CH}_{2} \mathrm{CH}_{2}-\mathrm{O}_{\mathrm{O}}^{+} \mathrm{H} \\
\because \mathrm{O}-\mathrm{CH}_{2} \mathrm{CH}_{2}-\ddot{\mathrm{O}} \mathrm{H}, \quad \mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{CH}_{2}-\ddot{\mathrm{O}} \mathrm{H}
\end{array}
$$
(e)

Aadit Sharma

Numerade Educator

Problem 47

(a) When 1-propanol containing deuterium (D, or ${ }^{2} \mathrm{H}$ ) rather than hydrogen at the oxygen, PrOD, is treated with an excess of $\mathrm{H}_{2} \mathrm{O}$ containing a catalytic amount of $\mathrm{NaOH},$ l-propanol is formed rapidly. Write a curved-arrow mechanism for this reaction. Where does the deuterium go?
(b) How would one prepare PrOD from 1-propanol?

Aadit Sharma

Numerade Educator

Problem 48

Indicate whether each of the following transformations is an oxidation, a reduction, or neither, and how many electrons are involved in each oxidation or reduction process.

Ian Kaigh

Numerade Educator

Problem 49

Outline a synthesis for the conversion of enantiomerically pure $(R)-\mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{CHD}-\mathrm{OH}$ into each of the following isotopically labeled compounds. Assume that $\mathrm{Na}^{18} \mathrm{OH}$ or $\mathrm{H}_{2}{ }^{18} \mathrm{O}$ is available as needed.
(a) $(S)-\mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{CHD}-{ }^{18} \mathrm{OH}$
(b) $(R)-\mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{CHD}-{ }^{18} \mathrm{OH}$ (Hint: Two inversions of con-
figuration correspond to a retention of configuration.)

Lottie Adams

Numerade Educator

Problem 50

Outline a synthesis for each of the following compounds from the indicated starting material and any other
reagents.
(a)
<smiles>CCCC(C)(C)O</smiles> from 2 -methyl-1-pentanol
(b)
<smiles>O=C(O)CC1CCCC1</smiles>
<smiles>C=CC1CCCC1</smiles> from
cyclopentylethylene
(c)
<smiles>O=CCC1CCCC1</smiles> from cyclopentylethylene
(d)
<smiles>O=C(O)C1CCCC1</smiles> from cyclopentylethylene
(e)
<smiles>CC1CCCC1CNC1CCCC1</smiles>
<smiles>CC1=CCCC1</smiles>
<smiles>ClC(Cl)Cl</smiles> from
(f) ethylcyclopentane from cyclopentylethylene

Lottie Adams

Numerade Educator

Problem 51

Ethyl triflate is much more reactive than ethyl mesylate toward nucleophiles in $\mathrm{S}_{\mathrm{N}} 2$ reactions.
(a) Give the structures of all of the products formed when each compound reacts with potassium iodide in acetone (a polar aprotic solvent).
(b) Explain in detail why the triflate anion is a much weaker base than the mesylate anion.
(c) Explain why the relative reactivities of ethyl mesylate and ethyl triflate correlate inversely with the relative basicities of the two anions in (b).

Aadit Sharma

Numerade Educator

Problem 52

How many grams of $\mathrm{CrO}_{3}$ are required to oxidize $10 \mathrm{~g}$ of 2-heptanol to the corresponding ketone?

Susan Hallstrom

Susan Hallstrom

Numerade Educator

Problem 53

The primary alcohol 2 -methoxyethanol, $\mathrm{CH}_{3} \mathrm{O}-\mathrm{CH}_{2} \mathrm{CH}_{2}-\mathrm{OH},$ can be oxidized to the corre-
sponding carboxylic acid with aqueous nitric acid $\left(\mathrm{HNO}_{3}\right)$. The by-product of the oxidation is nitric oxide, NO. How many moles of $\mathrm{HNO}_{3}$ are required to oxidize 0.1 mole of the alcohol?

Ahmed Ali

Numerade Educator

Problem 54

A police officer, Lawin Order, has detained a driver, Bobbin Weaver, after observing erratic driving behavior. Administering a breathalyzer test, Officer Order collects $52.5 \mathrm{~mL}$ of expired air from Weaver and finds that the air reduces $0.507 \times 10^{-6}$ mole of $\mathrm{K}_{2} \mathrm{Cr}_{2} \mathrm{O}_{7}$ to $\mathrm{Cr}^{3+}$. Assuming that $2100 \mathrm{~mL}$ of air contains the same amount of ethanol
as $1 \mathrm{~mL}$ of blood, calculate the "percent blood alcohol content" (BAC), expressed as (grams of ethanol per $\mathrm{mL}$ of blood) $\times 100 .$ If $0.08 \% \mathrm{BAC}$ is the lower limit of legal intoxication, should Officer Order make an arrest?

ES

Eugene Schneider

University of Minnesota - Twin Cities

Problem 55

Consider the following well-known reaction of glycols (vicinal diols).
(a) In this reaction, what species is oxidized? What species is reduced? Explain how you know.
(b) How many electrons are involved in the oxidation half-reaction? In the reduction half-reaction? Explain how you arrived at your answer.
(c) How many moles of periodate are required to react completely with 0.1 mole of a glycol?

Nicole Smina

Numerade Educator

Problem 56

Chemist Stench Thiall, intending to prepare the disulfide $A,$ has mixed one mole each of 1 -butanethiol and 2 -octanethiol with $\mathrm{I}_{2}$ and base. Stench is surprised at the low yield of the desired compound and has come to you for an explanation. Explain why Stench should not have expected a good yield in this reaction.

Dominique Jan Tan

Dominique Jan Tan

Numerade Educator

Problem 57

Compound $A, C_{7} H_{14},$ decolorizes $\mathrm{Br}_{2}$ in $\mathrm{CH}_{2} \mathrm{Cl}_{2}$ and reacts with $\mathrm{BH}_{3}$ in THF followed by $\mathrm{H}_{2} \mathrm{O}_{2} / \mathrm{OH}^{-}$ to yield compound $B$. When treated with $\mathrm{KMnO}_{4}$, then $\mathrm{H}_{3} \mathrm{O}^{+}, B$ is oxidized to a carboxylic acid $C$ that can be resolved into enantiomers. Compound $A$, after ozonolysis and workup with $\mathrm{H}_{2} \mathrm{O}_{2},$ yields the same compound $D$ as is formed by the oxidation of 3 -hexanol with chromic acid. Identify compounds $A, B, C,$ and $D$.

Niamat Khuda

Numerade Educator

Problem 58

In a laboratory are found two different compounds: $A$ (melting point $-4.7^{\circ} \mathrm{C}$ ) and $B$ (melting point $-1{ }^{\circ} \mathrm{C}$ ). Both compounds have the same molecular formula $\left(\mathrm{C}_{7} \mathrm{H}_{14} \mathrm{O}\right)$, and both can be resolved into enantiomers. Both compounds give off a gas when treated with NaH. Treatment of either $A$ or $B$ with tosyl chloride in pyridine yields a tosylate ester, and treatment of either tosylate with potassium tert-butoxide gives a mixture of the same two alkenes, $C$ and $D$. However, reaction of the tosylate of $A$ with potassium tert-butoxide to give these alkenes is noticeably slower than the corresponding reaction of the tosylate of
B. When either optically active $A$ or optically active $B$ is subjected to the same treatment, both alkene products $C$ and $D$ are optically active. Treatment of either $C$ or $D$ with $\mathrm{H}_{2}$ over a catalyst yields methylcyclohexane. Identify all unknown compounds and explain your reasoning.

Nikhil Choudhary

Nikhil Choudhary

Numerade Educator

Problem 59

Complete each of the following reactions by giving the principal organic product(s) formed in each case. Explain your reasoning.(a)
(b)
(c)
(d)
(e)
(f)
$(\mathrm{g})$
(h)

Catherine Lemar

Catherine Lemar

Numerade Educator

Problem 60

(a) When the rate of oxidation of isopropyl alcohol to acetone is compared with the rate of oxidation of a deuterated derivative, a primary isotope effect (Sec. $9.5 \mathrm{D}$ ) is observed (see part (a) of Fig. P10.60). Assuming that the mechanism is the same as the one shown in Eqs. $10.52 \mathrm{a}-\mathrm{c}$ ( $\mathrm{p} .484$ ), which step of this mechanism is rate-limiting?
(b) When either $(S)$ - or $(R)-1$ -deuterioethanol is oxidized with $\mathrm{PCC}$ in $\mathrm{CH}_{2} \mathrm{Cl}_{2},$ the same product mixture results and it contains significantly more of the deuterated aldehyde $A$ than the undeuterated aldehyde $B$ (see part (b) of Fig. P10.60). Explain why the deuterated aldehyde is the major product.
(c) Explain why, in the oxidation of $(R)-1$ -deuterioethanol with alcohol dehydrogenase and $\mathrm{NAD}^{+},$ none of the deuterated aldehyde is obtained.

Emily Himsel

Numerade Educator

Problem 61

The Swern oxidation, shown in Fig. $\mathrm{P} 10.61$, is a very mild two-step procedure for the oxidation of primary and secondary alcohols.
(a) How many electrons are involved in this oxidation? Explain.
(b) What is the oxidizing agent?
(c) The following intermediate $A$ is formed prior to the addition of the base triethylamine.
<smiles>CCOC(C)C(C)Cl</smiles>
Triethylamine reacts with intermediate $A$ to give the product aldehyde and the by-product dimethyl sulfide. When an isotopically substituted alcohol $\mathrm{RCD}_{2} \mathrm{OH}$ is subjected to the Swern oxidation, a deuteriumsubstituted aldehyde $\mathrm{R}-\mathrm{CD}=\mathrm{O}$ is formed, and the by-product dimethyl sulfide contains one atom of deuterium per molecule, $\mathrm{H}_{3} \mathrm{C}-\mathrm{S}-\mathrm{CH}_{2} \mathrm{D} .$ Write a curved-arrow mechanism for the reaction of intermediate $A$ and the base triethylamine that accounts for the isotopic distribution in the products.

Zubair Abdulla

Numerade Educator

Problem 62

The enzyme aconitase catalyzes a reaction of the Krebs cycle (see Fig. P10.62), an important biochemical pathway. In this equation, ${ }^{*} \mathrm{C}={ }^{14} \mathrm{C},$ a radioactive isotope of carbon, and each $-\mathrm{CO}_{2}^{-}$ group is the conjugate base of a carboxylic acid group. Notice that the dehydration occurs toward the branch of citrate that does not contain the radioactive carbon. Imagine carrying out this dehydration in the laboratory using a strong acid such as $\mathrm{H}_{3} \mathrm{PO}_{4}$ or $\mathrm{H}_{2} \mathrm{SO}_{4}$. How would the product(s) of the reaction be expected to differ, if at all, from those of the enzymecatalyzed reaction, and why?

Lottie Adams

Numerade Educator

Problem 63

When the hydration of fumarate is catalyzed by the enzyme fumarase in $\mathrm{D}_{2} \mathrm{O},$ only $(2 S, 3 R)-3$ -deuteriomalate is formed as the product. (Each $-\mathrm{CO}_{2}^{-}$ group is the conjugate base of a carboxylic acid group.) This reaction can also be run in reverse. By applying the principle of microscopic reversibility, predict the product (if any) when each of the following compounds is treated with fumarase in $\mathrm{H}_{2} \mathrm{O}$ :
(a)
(b)
(c)

Emily Himsel

Numerade Educator

Problem 64

Monoamine oxidase (MAO) is an enzyme that catalyzes the oxidation of certain biologically important amines. One form of the enzyme catalyzes the following oxidationof serotonin, an important neurotransmitter (Fig. $\mathrm{P} 10.64 ;$ a number of antidepressants inhibit this reaction).
(a) How many electrons are lost in this oxidation?
(b) The pro- $R$ hydrogen is removed from carbon in this reaction. Give the product formed when each of the following compounds undergoes this oxidation.
(c) One of the compounds in part (b) reacts about 10 times faster than the other. Which compound reacts faster? Why?

Rabeya Zahid

Numerade Educator

Problem 65

Buster Bluelip, a student repeating organic chemistry for the fifth time, has observed that alcohols can be converted into alkyl bromides by treatment with concentrated HBr. He has proposed that, by analogy, alcohols should be converted into nitriles (organic cyanides, $\mathrm{R}-\mathrm{C} \equiv \mathrm{N}$ ) by treatment with concentrated $\mathrm{HC} \equiv \mathrm{N}$. Upon running the reaction, Bluelip finds that the alcohol does not react. Another student has suggested that the reason the reactionfailed is the absence of a strong acid catalyst. (HCN is a weak acid.) Following this suggestion, Bluelip runs the reaction in the presence of $\mathrm{H}_{2} \mathrm{SO}_{4}$ and again observes no reaction of the alcohol. Explain the difference in the reaction of alcohols with $\mathrm{HBr}$ and $\mathrm{HCN}-$ that is, why the latter fails but the former succeeds.

Nicholas Sacco

Numerade Educator

Problem 66

Primary alcohols, when treated with $\mathrm{H}_{2} \mathrm{SO}_{4}$, do not dehydrate to alkenes under the usual conditions. However, they do undergo another type of "dehydration" to form ethers if heated strongly in the presence of $\mathrm{H}_{2} \mathrm{SO}_{4}$. The reaction of ethyl alcohol to give diethyl ether is typical:Using the curved-arrow notation, show mechanistically how this reaction takes place.

Manik Pulyani

Numerade Educator

Problem 67

The reactions shown in Fig. $\mathrm{P} 10.67$ all involve conversion of the alcohol oxygen into a good leaving group, followed by the reaction of the resulting compound with a nucleophile provided by the reagent. Write curved-arrow mechanisms for each reaction. [Hints: In reaction (b), the phosphorus of triphenylphosphite is nucleophilic. Identify the intermediate $X$ and show how it leads to the products. In reaction (c), let triphenylphosphine act as a nucleophile and a bromine of $\mathrm{CBr}_{4}$ as the electrophile to form an ionic intermediate, which then reacts with the alcohol. Note that bromoform ( $\mathrm{HCBr}_{3}$ ) has $\left.\mathrm{p} K_{\mathrm{a}} \approx 24 .\right]$

Crystal Wang

Numerade Educator

Problem 68

Using the curved-arrow notation, give a mechanism for each of the known conversions shown in Fig. P10.68. (If necessary, re-read Study Problem 10.1, p. 461.)

The reaction given in part (c) of Fig. $\mathrm{P} 10.68$ is very important in the manufacture of high-octane gasoline. [Hint: If deuterated isobutane $\left(\mathrm{CH}_{3}\right)_{3} \mathrm{C}-\mathrm{D}$ is used, the product is $\left(\mathrm{CH}_{3}\right)_{2} \mathrm{CDCH}_{2} \mathrm{C}\left(\mathrm{CH}_{3}\right)_{3}$.]

Crystal Wang

Numerade Educator

Problem 69

(a) Describe the $\pi$ bond for the double bond in $\mathrm{Ph}_{3} \mathrm{P}=\mathrm{CH}_{2} ;$ that is, what orbitals are involved on carbon and phosphorus?
(b) Draw a resonance structure for the compound in part (a) that maintains the octet rule on both carbon and phosphorus.
(c) This compound is a strong base that reacts rapidly with water. Explain.

Kevin Chimex

Numerade Educator

Problem 70

The trichloromethyl anion, ${ }^{-}: \mathrm{CCl}_{3},$ which is the conjugatebase anion of chloroform $\left(\mathrm{HCCl}_{3}\right)$, is stabilized not only by the polar effect of the chlorines but also by resonance: Show the orbital overlap between carbon and chlorine that is implied by the resonance structures. (Hint: The chlorine provides the empty orbital.)

Lottie Adams

Numerade Educator