Organic Chemistry

John McMurry

Chapter 3

Organic Compounds: Alkanes and Their Stereochemistry - all with Video Answers

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Chapter Questions

Problem 1

Identify the functional groups in each of the following molecules:
(a) Methionine, an amino acid:
(b) Ibuprofen, a pain reliever:
(c) Capsaicin, the pungent substance in chili peppers:

Prashant Bana

Prashant Bana

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Problem 2

Propose structures for simple molecules that contain the following functional groups:
(a) Alcohol
(b) Aromatic ring
(c) Carboxylic acid
(d) Amine
(e) Both ketone and amine
(f) Two double bonds

Vishal Sharma

Numerade Educator

Problem 3

Identify the functional groups in the following model of arecoline, a veterinary drug used to control worms in animals. Convert the drawing into a linebond structure and a molecular formula (red $=\mathrm{O},$ blue $=\mathrm{N}$ ).

Anupa Sharad Medhekar

Anupa Sharad Medhekar

Numerade Educator

Problem 4

Draw structures of the five isomers of $\mathrm{C}_{6} \mathrm{H}_{14}$

Niamat Khuda

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Problem 5

Propose structures that meet the following descriptions:
(a) Two isomeric esters with the formula $\mathrm{C}_{5} \mathrm{H}_{10} \mathrm{O}_{2}$
(b) Two isomeric nitriles with the formula $\mathrm{C}_{4} \mathrm{H}_{7} \mathrm{~N}$
(c) Two isomeric disulfides with the formula $\mathrm{C}_{4} \mathrm{H}_{10} \mathrm{~S}_{2}$

Niamat Khuda

Numerade Educator

Problem 6

How many isomers are there with the following descriptions?
(a) Alcohols with the formula $\mathrm{C}_{3} \mathrm{H}_{8} \mathrm{O}$
(b) Bromoalkanes with the formula $\mathrm{C}_{4} \mathrm{H}_{9} \mathrm{Br}$
(c) Thioesters with the formula $\mathrm{C}_{4} \mathrm{H}_{8} \mathrm{OS}$

Niamat Khuda

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Problem 7

Draw the eight 5 -carbon alkyl groups (pentyl isomers).

Niamat Khuda

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Problem 8

Identify the carbon atoms in the following molecules as primary, secondary, tertiary, or quaternary:
(a)
(b)
(c)

Anupa Sharad Medhekar

Anupa Sharad Medhekar

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Problem 9

Identify the hydrogen atoms on the compounds shown in Problem $3-8$ as primary, secondary, or tertiary.

Anupa Sharad Medhekar

Anupa Sharad Medhekar

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Problem 10

Draw structures of alkanes that meet the following descriptions:
(a) An alkane with two tertiary carbons
(b) An alkane that contains an isopropyl group
(c) An alkane that has one quaternary and one secondary carbon

Ronald Prasad

Numerade Educator

Problem 11

Give IUPAC names for the following compounds:
(a) The three isomers of $\mathrm{C}_{5} \mathrm{H}_{12}$
(b)
(c)
(d)

Anupa Sharad Medhekar

Anupa Sharad Medhekar

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Problem 12

Draw structures corresponding to the following IUPAC names:
(a) 3,4 -Dimethylnonane
(b) 3 -Ethyl-4,4-dimethylheptane
(c) 2,2 -Dimethyl-4-propyloctane
(d) 2,2,4 -Trimethylpentane

Niamat Khuda

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Problem 13

Name the eight 5 -carbon alkyl groups you drew in Problem $3-7$.

Anupa Sharad Medhekar

Anupa Sharad Medhekar

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Problem 14

Give the IUPAC name for the following hydrocarbon, and convert the drawing into a skeletal structure.

Anupa Sharad Medhekar

Anupa Sharad Medhekar

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Problem 15

Make a graph of potential energy versus angle of bond rotation for propane, and assign values to the energy maxima.

Niamat Khuda

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Problem 16

Sight along the $\mathrm{C}_{2}-\mathrm{C} 1$ bond of 2 -methylpropane (isobutane).
(a) Draw a Newman projection of the most stable conformation.
(b) Draw a Newman projection of the least stable conformation.
(c) Make a graph of energy versus angle of rotation around the C $2-\mathrm{C} 1$ bond.
(d) Assign relative values to the maxima and minima in your graph, given that an $\mathrm{H} \leftrightarrow \mathrm{H}$ eclipsing interaction costs $4.0 \mathrm{~kJ} / \mathrm{mol}$ and an $\mathrm{H} \leftrightarrow \mathrm{CH}_{3}$ eclips-
ing interaction costs $6.0 \mathrm{~kJ} / \mathrm{mol}$.

Crystal Wang

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Problem 17

Sight along the $\mathrm{C} 2-\mathrm{C} 3$ bond of 2,3 -dimethylbutane, and draw a Newman projection of the most stable conformation.

Niamat Khuda

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Problem 18

Draw a Newman projection along the $\mathrm{C} 2-\mathrm{C} 3$ bond of the following conformation of 2,3 -dimethylbutane, and calculate a total strain energy:

Anupa Sharad Medhekar

Anupa Sharad Medhekar

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Problem 19

Identify the functional groups in the following substances, and convert each drawing into a molecular formula (red $=\mathrm{O},$ blue $=\mathrm{N}$ ).

Anupa Sharad Medhekar

Anupa Sharad Medhekar

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Problem 20

Give IUPAC names for the following alkanes, and convert each drawing into a skeletal structure.

Crystal Wang

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Problem 21

Give IUPAC names for the following alkanes, and convert each drawing into a skeletal structure.

Crystal Wang

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Problem 21

Draw a Newman projection along the $\mathrm{C}_{2}-\mathrm{C} 3$ bond of the following conformation of 2 -butanol.

Anupa Sharad Medhekar

Anupa Sharad Medhekar

Numerade Educator

Problem 22

Locate and identify the functional groups in the following molecules.
(a)
(b)
(c)
(d)
(e)
(f)

Crystal Wang

Numerade Educator

Problem 23

Propose structures that meet the following descriptions:
(a) A ketone with five carbons
(b) A four-carbon amide
(c) A five-carbon ester
(d) An aromatic aldehyde
(e) A keto ester
(f) An amino alcohol

Niamat Khuda

Numerade Educator

Problem 24

Propose structures for the following:
(a) A ketone, $\mathrm{C}_{4} \mathrm{H}_{8} \mathrm{O}$
(b) A nitrile, $\mathrm{C}_{5} \mathrm{H}_{9} \mathrm{~N}$
(c) A dialdehyde, $\mathrm{C}_{4} \mathrm{H}_{6} \mathrm{O}_{2}$
(d) A bromoalkene, $\mathrm{C}_{6} \mathrm{H}_{11} \mathrm{Br}$
(e) An alkane, $\mathrm{C}_{6} \mathrm{H}_{14}$
[f) A cyclic saturated hydrocarbon, $\mathrm{C}_{6} \mathrm{H}_{12}$
(g) A diene (dialkene), $\mathrm{C}_{5} \mathrm{H}_{8}$ ( h) $\mathrm{A}$ keto alkene, $\mathrm{C}_{5} \mathrm{H}_{8} \mathrm{O}$

Niamat Khuda

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Problem 25

Predict the hybridization of the carbon atom in each of the following functional groups:
(a) Ketone
(b) Nitrile (c) Carboxylic acid

Niamat Khuda

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Problem 26

Draw the structures of the following molecules:
(a) Biacetyl, $\mathrm{C}_{4} \mathrm{H}_{6} \mathrm{O}_{2},$ a substance with the aroma of butter; it contains no rings or carbon-carbon multiple bonds.
(b) Ethylenimine, $\mathrm{C}_{2} \mathrm{H}_{5} \mathrm{~N}, \mathrm{a}$ substance used in the synthesis of melamine polymers; it contains no multiple bonds.
(c) Glycerol, $\mathrm{C}_{3} \mathrm{H}_{8} \mathrm{O}_{3},$ a substance isolated from fat and used in cosmetics; it has an - OH group on each carbon.

Niamat Khuda

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Problem 27

Draw structures that meet the following descriptions (there are many possibilities):
(a) Three isomers with the formula $\mathrm{C}_{8} \mathrm{H}_{18}$
(b) Two isomers with the formula $\mathrm{C}_{4} \mathrm{H}_{8} \mathrm{O}_{2}$

Niamat Khuda

Numerade Educator

Problem 28

Draw structures of the nine isomers of $\mathrm{C}_{7} \mathrm{H}_{16}$

Hailey Tomashek

Hailey Tomashek

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Problem 29

In each of the following sets, which structures represent the same compound and which represent different compounds?
(a)
(b)
(c)

Anupa Sharad Medhekar

Anupa Sharad Medhekar

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Problem 30

There are seven constitutional isomers with the formula $\mathrm{C}_{4} \mathrm{H}_{10} \mathrm{O}$. Draw
as many as you can.

Niamat Khuda

Numerade Educator

Problem 31

Draw as many compounds as you can that fit the following descriptions:
(a) Alcohols with formula $\mathrm{C}_{4} \mathrm{H}_{10} \mathrm{O}$
(b) Amines with formula $\mathrm{C}_{5} \mathrm{H}_{13} \mathrm{~N}$
(c) Ketones with formula $\mathrm{C}_{5} \mathrm{H}_{10} \mathrm{O}$
(d) Aldehydes with formula $\mathrm{C}_{5} \mathrm{H}_{10} \mathrm{O}$
(e) Esters with formula $\mathrm{C}_{4} \mathrm{H}_{8} \mathrm{O}_{2}$
(f) Ethers with formula $\mathrm{C}_{4} \mathrm{H}_{10} \mathrm{O}$

Travis Maslanik

Travis Maslanik

Numerade Educator

Problem 32

Draw compounds that contain the following:
(a) A primary alcohol
(b) A tertiary nitrile
(c) A secondary thiol
(d) Both primary and secondary alcohols
(e) An isopropyl group
(f) A quaternary carbon

Niamat Khuda

Numerade Educator

Problem 33

Draw and name all monobromo derivatives of pentane, $\mathrm{C}_{5} \mathrm{H}_{11} \mathrm{Br}$.

Niamat Khuda

Numerade Educator

Problem 34

Draw and name all monochloro derivatives of 2,5 -dimethylhexane, $\mathrm{C}_{8} \mathrm{H}_{17} \mathrm{Cl}$

Niamat Khuda

Numerade Educator

Problem 35

Draw structures for the following:
(a) 2 -Methylheptane
(b) 4-Ethyl-2,2-dimethylhexane
(c) 4-Ethyl-3,4-dimethyloctane
(d) 2,4,4 -Trimethylheptane
(e) 3,3 -Diethyl-2,5-dimethylnonane
(f) 4-Isopropyl-3-methylheptane

Niamat Khuda

Numerade Educator

Problem 36

Draw a compound that:
(a) Has only primary and tertiary carbons
(b) Has no secondary or tertiary carbons
(c) Has four secondary carbons

Niamat Khuda

Numerade Educator

Problem 37

Draw a compound that:
(a) Has nine primary hydrogens
(b) Has only primary hydrogens

Niamat Khuda

Numerade Educator

Problem 38

Give IUPAC names for the following compounds:
(a)
(b)
(c)
(d)
(e)

Crystal Wang

Numerade Educator

Problem 39

Name the five isomers of $\mathrm{C}_{6} \mathrm{H}_{14}$.

Niamat Khuda

Numerade Educator

Problem 40

Explain why each of the following names is incorrect:
(a) 2,2 -Dimethyl-6-ethylheptane
(c) 3 -Ethyl-4,4-dimethylhexane
(d) 5,5,6 -Trimethyloctane
(e) 2 -Isopropyl-4-methylheptane

Crystal Wang

Numerade Educator

Problem 41

Propose structures and give IUPAC names for the following:
(a) A diethyldimethylhexane
(b) $A$ (3-methylbutyl)-substituted alkane

Niamat Khuda

Numerade Educator

Problem 42

Consider 2 -methylbutane (isopentane). Sighting along the $\mathrm{C}_{2}-\mathrm{C} 3$ bond:
(a) Draw a Newman projection of the most stable conformation.
(b) Draw a Newman projection of the least stable conformation.
(c) If a $\mathrm{CH}_{3} \leftrightarrow \mathrm{CH}_{3}$ eclipsing interaction costs $11 \mathrm{~kJ} / \mathrm{mol}$ ( $2.5 \mathrm{kcal} / \mathrm{mol}$ )
and $\mathrm{a} \mathrm{CH}_{3} \leftrightarrow \mathrm{CH}_{3}$ gauche interaction costs $3.8 \mathrm{~kJ} / \mathrm{mol}(0.9 \mathrm{kcal} / \mathrm{mol})$
make a quantitative plot of energy versus rotation about the $\mathrm{C} 2-\mathrm{C} 3 \mathrm{bond}$

Crystal Wang

Numerade Educator

Problem 43

What are the relative energies of the three possible staggered conformations around the C2-C3 bond in 2,3 -dimethylbutane? (See Prob$\operatorname{lem} 3-42 .)$

Crystal Wang

Numerade Educator

Problem 44

Construct a qualitative potential-energy diagram for rotation about the C- C bond of 1,2 -dibromoethane. Which conformation would you expect to be most stable? Label the anti and gauche conformations of 1,2 -dibromoethane.

Niamat Khuda

Numerade Educator

Problem 45

Which conformation of 1,2 -dibromoethane (Problem $3-44$ ) would you expect to have the largest dipole moment? The observed dipole moment of 1,2 -dibromoethane is $\mu=1.0 \mathrm{D} .$ What does this tell you about the actual conformation of the molecule?

Anupa Sharad Medhekar

Anupa Sharad Medhekar

Numerade Educator

Problem 46

Draw the most stable conformation of pentane, using wedges and dashes to represent bonds coming out of the paper and going behind the paper, respectively.

Niamat Khuda

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Problem 47

Draw the most stable conformation of 1,4 -dichlorobutane, using wedges and dashes to represent bonds coming out of the paper and going behind the paper, respectively.

Niamat Khuda

Numerade Educator

Problem 48

For each of the following compounds, draw an isomer that has the same functional groups.
(a)
(b)
(c)
(d)
(e)
(f)

Anupa Sharad Medhekar

Anupa Sharad Medhekar

Numerade Educator

Problem 49

Malic acid, $\mathrm{C}_{4} \mathrm{H}_{6} \mathrm{O}_{5}$, has been isolated from apples. Because this compound reacts with 2 molar equivalents of base, it is a dicarboxylic acid.
(a) Draw at least five possible structures.
(b) If malic acid is a secondary alcohol, what is its structure?

Niamat Khuda

Numerade Educator

Problem 50

Formaldehyde, $\mathrm{H}_{2} \mathrm{C}=\mathrm{O},$ is known to all biologists because of its usefulness as a tissue preservative. When pure, formaldehyde trimerizes to give trioxane, $\mathrm{C}_{3} \mathrm{H}_{6} \mathrm{O}_{3},$ which, surprisingly enough, has no carbonyl groups. Only one monobromo derivative $\left(\mathrm{C}_{3} \mathrm{H}_{5} \mathrm{Br} \mathrm{O}_{3}\right)$ of trioxane is possible. Propose a structure for trioxane.

Niamat Khuda

Numerade Educator

Problem 51

The barrier to rotation about the $\mathrm{C}-\mathrm{C}$ bond in bromoethane is $15 \mathrm{~kJ} / \mathrm{mol}$ $(3.6 \mathrm{kcal} / \mathrm{mol})$
(a) What energy value can you assign to an $\mathrm{H} \leftrightarrow \mathrm{Br}$ eclipsing interaction?
(b) Construct a quantitative diagram of potential energy versus bond rotation for bromoethane.

Niamat Khuda

Numerade Educator

Problem 52

Increased substitution around a bond leads to increased strain. Take the four substituted butanes listed below, for example. For each compound, sight along the C2-C3 bond and draw Newman projections of the most stable and least stable conformations. Use the data in Table $3-5$ to assign strain-energy values to each conformation. Which of the eight conformations is most strained? Which is least strained?
(a) 2 -Methylbutane
(b) 2,2 -Dimethylbutane
(c) 2,3 -Dimethylbutane
(d) 2,2,3 -Trimethylbutane

Crystal Wang

Numerade Educator

Problem 53

The cholesterol-lowering agents called statins, such as simvastatin (Zocor) and pravastatin (Pravachol), are among the most widely prescribed drugs in the world, with annual sales estimated at approximately $\$ 25$ billion. Identify the functional groups in both, and tell how the two substances differ.

Crystal Wang

Numerade Educator

Problem 54

In the next chapter we'll look at cycloalkanes-saturated cyclic hydrocarbons - and we'll see that the molecules generally adopt puckered, nonplanar conformations. Cyclohexane, for instance, has a puckered shape like a lounge chair rather than a flat shape. Why?

Crystal Wang

Numerade Educator

Problem 55

We'll see in the next chapter that there are two isomeric substances, both named 1,2 -dimethylcyclohexane. Explain.

Crystal Wang

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