Organic Chemistry

John McMurry

Chapter 9

Alkynes: An Introduction to Organic Synthesis - all with Video Answers

Educators

Chapter Questions

Problem 1

Name the following compounds:
a.(FIGURE CAN'T COPY)
b.(FIGURE CAN'T COPY)
c.(FIGURE CAN'T COPY)
d.(FIGURE CAN'T COPY)
e.(FIGURE CAN'T COPY)
f.(FIGURE CAN'T COPY)

Brittany Carnathan

Brittany Carnathan

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Problem 2

There are seven isomeric alkynes with the formula $\mathrm{C}_{6} \mathrm{H}_{10}$. Draw and name them.
(FIGURE CAN'T COPY)

Brittany Carnathan

Brittany Carnathan

Numerade Educator

Problem 3

What products would you expect from the following reactions?
a.(FIGURE CAN'T COPY)
b.(FIGURE CAN'T COPY)
c.(FIGURE CAN'T COPY)

Brittany Carnathan

Brittany Carnathan

Numerade Educator

Problem 4

What product would you obtain by hydration of the following alkynes?
a.(FIGURE CAN'T COPY)
b.(FIGURE CAN'T COPY)

Brittany Carnathan

Brittany Carnathan

Numerade Educator

Problem 5

What alkynes would you start with to prepare the following ketones?
a.(FIGURE CAN'T COPY)
b.(FIGURE CAN'T COPY)

Brittany Carnathan

Brittany Carnathan

Numerade Educator

Problem 6

What alkyne would you start with to prepare each of the following compounds by a hydroboration-oxidation reaction?
a.(FIGURE CAN'T COPY)
b.(FIGURE CAN'T COPY)

Brittany Carnathan

Brittany Carnathan

Numerade Educator

Problem 7

How would you prepare the following carbonyl compounds starting from an alkyne (reddish brown $=B r) ?$
a.(FIGURE CAN'T COPY)
b.(FIGURE CAN'T COPY)

Tom Rutherford

Numerade Educator

Problem 8

Using any alkyne needed, how would you prepare the following alkenes?
(a) trans-2-Octene
(b) cis-3-Heptene
(c) 3-Methyl-1-pentene

Brittany Carnathan

Brittany Carnathan

Numerade Educator

Problem 9

The $p K_{a}$ of acetone, $C H_{3} C O C H_{3}$, is $19.3 .$ Which of the following bases is strong enough to deprotonate acetone?
(a) $\mathrm{KOH}\left(\mathrm{pK}_{2} \text { of } \mathrm{H}_{2} \mathrm{O}=15.7\right)$
(b) $\mathrm{Na}^{+}-\mathrm{C}=\mathrm{CH}\left(\mathrm{p} K_{\mathrm{a}} \text { of } \mathrm{C}_{2} \mathrm{H}_{2}=25\right)$
(c) $\mathrm{NaHCO}_{3}\left(\mathrm{p} K_{\mathrm{a}} \text { of } \mathrm{H}_{2} \mathrm{CO}_{3}=6.4\right)$
(d) $\mathrm{NaOCH}_{3}\left(\mathrm{pK}_{\mathrm{a}} \text { of } \mathrm{CH}_{3} \mathrm{OH}=15.6\right)$

Brittany Carnathan

Brittany Carnathan

Numerade Educator

Problem 10

Show the terminal alkyne and alkyl halide from which the following products can be obtained. If two routes look feasible, list both.
a.(FIGURE CAN'T COPY)
b.(FIGURE CAN'T COPY)
c.(FIGURE CAN'T COPY)

Brittany Carnathan

Brittany Carnathan

Numerade Educator

Problem 11

How would you prepare cis-2-butene starting from propyne, an alkyl halide, and any other reagents needed? This problem can't be worked in a single step. You'll have to carry out more than one reaction.

Brittany Carnathan

Brittany Carnathan

Numerade Educator

Problem 12

Beginning with 4 -octyne as your only source of carbon, and using any inorganic reagents necessary, how would you synthesize the following compounds?
(a) cis-4-Octene
(b) Butanal
(c) 4 -Bromooctane
(d) 4-Octanol
(e) 4,5 -Dichlorooctane
(f) Butanoic acid

Brittany Carnathan

Brittany Carnathan

Numerade Educator

Problem 13

Beginning with acetylene and any alkyl halide needed, how would you synthesize the following compounds?
(a) Decane
(b) $2,2-$ Dimethylhexane
(c) Hexanal
(d) 2 -Heptanone

Brittany Carnathan

Brittany Carnathan

Numerade Educator

Problem 14

Name the following alkynes, and predict the products of their reaction with
(1) $\mathrm{H}_{2}$ in the presence of a Lindlar catalyst and (2) $\mathrm{H}_{3} \mathrm{O}^{+}$ in the presence of $\mathrm{HgSO}_{4}:$
a.(FIGURE CAN'T COPY)
b.(FIGURE CAN'T COPY)

Brittany Carnathan

Brittany Carnathan

Numerade Educator

Problem 15

From what alkyne might each of the following substances have been made? (Green = Cl.)
a.(FIGURE CAN'T COPY)
b.(FIGURE CAN'T COPY)

Brittany Carnathan

Brittany Carnathan

Numerade Educator

Problem 16

How would you prepare the following substances, starting from any compounds having four carbons or fewer?
a.(FIGURE CAN'T COPY)
b.(FIGURE CAN'T COPY)

Zubair Abdulla

Numerade Educator

Problem 17

The following cycloalkyne is too unstable to exist. Explain.
(FIGURE CAN'T COPY)

Brittany Carnathan

Brittany Carnathan

Numerade Educator

Problem 18

Give IUPAC names for the following compounds:
a.(FIGURE CAN'T COPY)
b.(FIGURE CAN'T COPY)
c.(FIGURE CAN'T COPY)
d.(FIGURE CAN'T COPY)
e.(FIGURE CAN'T COPY)
f.(FIGURE CAN'T COPY)

Brittany Carnathan

Brittany Carnathan

Numerade Educator

Problem 19

Draw structures corresponding to the following names:
(a) 3,3 -Dimethyl- 4 -octyne
(b) 3-Ethyl-5-methyl-1,6,8-decatriyne
(c) 2,2,5,5 - Tetramethyl- 3 -hexyne
(d) $3,4-$ Dimethylcyclodecyne
(e) $3,5-$ Heptadien-1-yne
(f) 3 -Chloro- 4,4 -dimethyl-1-nonen-6-yne
(g) $3-$ sec-Butyl-1-heptyne
(h) 5 -tert-Butyl- 2 -methyl-3-octyne

Brittany Carnathan

Brittany Carnathan

Numerade Educator

Problem 20

The following two hydrocarbons have been isolated from various plants in the sunflower family. Name them according to IUPAC rules.
a.(FIGURE CAN'T COPY)
b.(FIGURE CAN'T COPY)

Brittany Carnathan

Brittany Carnathan

Numerade Educator

Problem 21

Predict the products of the following reactions:
a.(FIGURE CAN'T COPY)
b.(FIGURE CAN'T COPY)

Brittany Carnathan

Brittany Carnathan

Numerade Educator

Problem 22

Predict the products from reaction of 1 -hexyne with the following reagents:
(a) 1 equiv HBr
(b) 1 equiv $\mathrm{Cl}_{2}$
(c) $\mathrm{H}_{2},$ Lindlar catalyst
(d) $\mathrm{NaNH}_{2}$ in $\mathrm{NH}_{3},$ then $\mathrm{CH}_{3} \mathrm{Br}$
(e) $\mathrm{H}_{2} \mathrm{O}, \mathrm{H}_{2} \mathrm{SO}_{4}, \mathrm{HgSO}_{4}$
(f) 2 equiv HCl

Brittany Carnathan

Brittany Carnathan

Numerade Educator

Problem 23

Predict the products from reaction of 5 -decyne with the following reagents:
(a) $\mathrm{H}_{2},$ Lindlar catalyst $\quad$ (b) $\mathrm{Li}$ in $\mathrm{NH}_{3}$
(c) 1 equiv $\mathrm{Br}_{2}$
(d) $\mathrm{BH}_{3}$ in THF, then $\mathrm{H}_{2} \mathrm{O}_{2}, \mathrm{OH}^{-}$
(e) $\mathrm{H}_{2} \mathrm{O}, \mathrm{H}_{2} \mathrm{SO}_{4}, \mathrm{HgSO}_{4}$
(f) Excess $\mathrm{H}_{2},$ Pd/C catalyst

Brittany Carnathan

Brittany Carnathan

Numerade Educator

Problem 24

Predict the products from reaction of 2-hexyne with the following reagents:
(a) 2 equiv $\mathrm{Br}_{2}$
(b) 1 equiv HBr
(c) Excess HBr
(d) Li in $\mathrm{NH}_{3}$
(e) $\mathrm{H}_{2} \mathrm{O}, \mathrm{H}_{2} \mathrm{SO}_{4}, \mathrm{HgSO}_{4}$

Brittany Carnathan

Brittany Carnathan

Numerade Educator

Problem 25

Propose structures for hydrocarbons that give the following products on oxidative cleavage by $\mathrm{KMnO}_{4}$ or $\mathrm{O}_{3}:$
a.(FIGURE CAN'T COPY)
b.(FIGURE CAN'T COPY)
c.(FIGURE CAN'T COPY)
d.(FIGURE CAN'T COPY)
e.(FIGURE CAN'T COPY)

Brittany Carnathan

Brittany Carnathan

Numerade Educator

Problem 26

Identify the reagents a-c in the following scheme:
a.(FIGURE CAN'T COPY)
b.(FIGURE CAN'T COPY)
c.(FIGURE CAN'T COPY)

Brittany Carnathan

Brittany Carnathan

Numerade Educator

Problem 27

How would you carry out the following conversions? More than one step may be needed in some instances.
(FIGURE CAN'T COPY)

Brittany Carnathan

Brittany Carnathan

Numerade Educator

Problem 28

How would you carry out the following reactions?
a.(FIGURE CAN'T COPY)
b.(FIGURE CAN'T COPY)
c.(FIGURE CAN'T COPY)
d.(FIGURE CAN'T COPY)
e.(FIGURE CAN'T COPY)
f.(FIGURE CAN'T COPY)

Brittany Carnathan

Brittany Carnathan

Numerade Educator

Problem 29

Each of the following syntheses requires more than one step. How would you carry them out?
a.(FIGURE CAN'T COPY)
b.(FIGURE CAN'T COPY)

Brittany Carnathan

Brittany Carnathan

Numerade Educator

Problem 30

How would you carry out the following transformation? More than one step is needed.
(FIGURE CAN'T COPY)

Brittany Carnathan

Brittany Carnathan

Numerade Educator

Problem 31

How would you carry out the following conversions? More than one step is needed in each case.
(FIGURE CAN'T COPY)

Brittany Carnathan

Brittany Carnathan

Numerade Educator

Problem 32

Synthesize the following compounds using 1 -butyne as the only source of carbon, along with any inorganic reagents you need. More than one step may be needed.
(a) 1,1,2,2 -Tetrachlorobutane
(b) $1,1-$ Dichloro- 2 -ethylcyclopropane

Brittany Carnathan

Brittany Carnathan

Numerade Educator

Problem 33

How would you synthesize the following compounds from acetylene and any alkyl halides with four or fewer carbons? More than one step may be needed.
a.(FIGURE CAN'T COPY)
b.(FIGURE CAN'T COPY)
c.(FIGURE CAN'T COPY)
d.(FIGURE CAN'T COPY)
e.(FIGURE CAN'T COPY)

Brittany Carnathan

Brittany Carnathan

Numerade Educator

Problem 34

How would you carry out the following reactions to introduce deuterium into organic molecules?
a.(FIGURE CAN'T COPY)
b.(FIGURE CAN'T COPY)
c.(FIGURE CAN'T COPY)
d.(FIGURE CAN'T COPY)

Brittany Carnathan

Brittany Carnathan

Numerade Educator

Problem 35

How would you prepare cyclodecyne starting from acetylene and any alkyl halide needed?

Brittany Carnathan

Brittany Carnathan

Numerade Educator

Problem 36

The sex attractant given off by the common housefly is an alkene named muscalure. Propose a synthesis of muscalure starting from acetylene and any alkyl halides needed. What is the IUPAC name for muscalure?
(FIGURE CAN'T COPY)

Brittany Carnathan

Brittany Carnathan

Numerade Educator

Problem 37

A hydrocarbon of unknown structure has the formula $\mathrm{C}_{8} \mathrm{H}_{10}$. On catalytic hydrogenation over the Lindlar catalyst, 1 equivalent of $\mathrm{H}_{2}$ is absorbed. On hydrogenation over a palladium catalyst, 3 equivalents of $\mathrm{H}_{2}$ are absorbed.
(a) How many degrees of unsaturation are present in the unknown?
(b) How many triple bonds are present?
(c) How many double bonds are present?
(d) How many rings are present?
(e) Draw a structure that fits the data.

Brittany Carnathan

Brittany Carnathan

Numerade Educator

Problem 38

Compound $A\left(C_{9} H_{12}\right)$ absorbed 3 equivalents of $H_{2}$ on catalytic reduction over
a palladium catalyst to give $\mathbf{B}\left(\mathrm{C}_{9} \mathrm{H}_{18}\right) .$ On ozonolysis, compound A gave, among other things, a ketone that was identified as cyclohexanone. On treatment with $\mathrm{NaNH}_{2}$ in $\mathrm{NH}_{3}$, followed by addition of iodomethane, compound $\mathrm{A}$ gave a new hydrocarbon, $\mathrm{C}\left(\mathrm{C}_{10} \mathrm{H}_{14}\right) .$ What are the structures of $\mathrm{A}, \mathrm{B},$ and $\mathrm{C} ?$

Brittany Carnathan

Brittany Carnathan

Numerade Educator

Problem 39

Hydrocarbon A has the formula $\mathrm{C}_{12} \mathrm{Hg}$. It absorbs 8 equivalents of $\mathrm{H}_{2}$ on catalytic reduction over a palladium catalyst. On ozonolysis, only two products are formed: oxalic acid (HO_CCO_AH) and succinic acid (HO_2CCH_CH_2CO_AH). Write the reactions, and propose a structure for A.

Brittany Carnathan

Brittany Carnathan

Numerade Educator

Problem 40

Occasionally, a chemist might need to invert the stereo-chemistry of an alkene that is, to convert a cis alkene to a trans alkene, or vice versa. There is no one step method for doing an alkene inversion, but the transformation can be carried out by combining several reactions in the proper sequence. How would you carry out the following reactions?
a.(FIGURE CAN'T COPY)
b.(FIGURE CAN'T COPY)

Brittany Carnathan

Brittany Carnathan

Numerade Educator

Problem 41

Organometallic reagents such as sodium acetylide undergo an addition reaction with ketones, giving alcohols:
(FIGURE CAN'T COPY)
How might you use this reaction to prepare 2-methyl-1,3-butadiene, the starting material used in the manufacture of synthetic rubber?

Ian Kaigh

Numerade Educator

Problem 42

The oral contraceptive agent Mestranol is synthesized using a carbonyl addition reaction like that shown in Problem $9.41 .$ Draw the structure of the ketone needed. (FIGURE CAN'T COPY)

Tom Rutherford

Numerade Educator

Problem 43

1-Octen-3-ol, a potent mosquito attractant commonly used in mosquito traps, can be prepared in two steps from hexanal, $\mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{CH}_{2} \mathrm{CH}_{2} \mathrm{CH}_{2} \mathrm{CHO}$. The first step is an acetylide-addition reaction like that described in Problem 9.41. What is the structure of the product from the first step, and how can it be converted into 1-octen-3-ol?
(FIGURE CAN'T COPY)

Brittany Carnathan

Brittany Carnathan

Numerade Educator

Problem 44

Erythrogenic acid, $\mathrm{C}_{18} \mathrm{H}_{26} \mathrm{O}_{2}$, is an acetylenic fatty acid that turns a vivid red on exposure to light. On catalytic hydrogenation over a palladium catalyst,
5 equivalents of $\mathrm{H}_{2}$ are absorbed, and stearic acid, $\mathrm{CH}_{3}\left(\mathrm{CH}_{2}\right)_{16} \mathrm{CO}_{2} \mathrm{H},$ is produced. Ozonolysis of erythrogenic acid gives four products: formaldehyde, $\mathrm{CH}_{2} \mathrm{O} ;$ oxalic acid, $\mathrm{HO}_{2} \mathrm{CCO}_{2} \mathrm{H} ;$ azelaic acid, $\mathrm{HO}_{2} \mathrm{C}\left(\mathrm{CH}_{2}\right)_{7} \mathrm{CO}_{2} \mathrm{H} ;$ and the aldehyde acid OHC(CH_) $_{4} \mathrm{CO}_{2} \mathrm{H}$. Draw two possible structures for erythrogenic acid, and suggest a way to tell them apart by carrying out some simple reactions.

Brittany Carnathan

Brittany Carnathan

Numerade Educator

Problem 45

Hydrocarbon A has the formula $\mathrm{C}_{9} \mathrm{H}_{12}$ and absorbs 3 equivalents of $\mathrm{H}_{2}$ to yield $\mathbf{B}, \mathrm{C}_{9} \mathrm{H}_{18},$ when hydrogenated over a Pd/C catalyst. On treatment of A with aqueous $\mathrm{H}_{2} \mathrm{SO}_{4}$ in the presence of mercury(il), two isomeric ketones, C and $\mathbf{D},$ are produced. Oxidation of A with KMnO, gives a mixture of acetic acid $\left(\mathrm{CH}_{3} \mathrm{CO}_{2} \mathrm{H}\right)$ and the tricarboxylic acid $\mathrm{E}$. Propose structures for compounds A-D, and write the reactions. (FIGURE CAN'T COPY)

Brittany Carnathan

Brittany Carnathan

Numerade Educator

Problem 46

Terminal alkynes react with Bra and water to yield bromo ketones. For example: (FIGURE CAN'T COPY)
Propose a mechanism for the reaction. To what reaction of alkenes is the process analogous?

Brittany Carnathan

Brittany Carnathan

Numerade Educator

Problem 47

A cumulene is a compound with three adjacent double bonds. Draw an orbital picture of a cumulene. What kind of hybridization do the two central carbon atoms have? What is the geometric relationship of the substituents on one end to the substituents on the other end? What kind of isomerism is possible? Make a model to help see the answer. (FIGURE CAN'T COPY)

Anish Wadhwa

Numerade Educator

Problem 48

Reaction of acetone with $\mathrm{D}_{3} \mathrm{O}^{+}$ yields hexadeuterioacetone. That is, all the hydrogens in acetone are exchanged for deuterium. Review the mechanism of mercuric ion-catalyzed alkyne hydration, and then propose a mechanism for this deuterium incorporation. (FIGURE CAN'T COPY)

Brittany Carnathan

Brittany Carnathan

Numerade Educator