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CHEMISTRY: The Molecular Nature of Matter and Change 2016

Martin S. Silberberg, Patricia G. Amateis

Chapter 15

Organic Compounds and the Atomic Properties of Carbon

Educators


Problem 1

Give the names and formulas of two carbon compounds that are organic and two that are inorganic

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Problem 2

Explain each statement in terms of atomic properties:
(a) Carbon engages in covalent rather than ionic bonding.
(b) Carbon has four bonds in all its organic compounds.
(c) Carbon forms neither stable cations, like many metals, nor stable anions, like many nonmetals.
(d) Carbon bonds to itself more extensively than does any other element.
(e) Carbon forms stable multiple bonds.

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Problem 3

Carbon bonds to many elements other than itself.
(a) Name six elements that commonly bond to carbon in organic compounds.
(b) Which of these elements are heteroatoms?
(c) Which of these elements are more electronegative than carbon? Less electronegative?
(d) How does bonding of carbon to heteroatoms increase the number of organic compounds?

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Problem 4

Silicon lies just below carbon in Group 4A(14) and also forms four covalent bonds. Why aren’t there as many silicon compounds as carbon compounds?

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Problem 5

What is the range of oxidation states for carbon? Name a compound in which carbon has its highest oxidation state and one in which it has its lowest.

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Problem 6

Which of these bonds to carbon would you expect to be relatively reactive: $\mathrm{C}-\mathrm{H}, \mathrm{C}-\mathrm{C}, \mathrm{C}-\mathrm{I}, \mathrm{C}=\mathrm{O}, \mathrm{C}-$ Li? Explain.

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Problem 7

(a) What structural feature is associated with each type of hydrocarbon: alkane, cycloalkane, alkene, and alkyne?
(b) Give the general formula for each type.
(c) Which hydrocarbons are considered saturated?

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Problem 8

Define each type of isomer: (a) constitutional; (b) geometric; (c) optical. Which types of isomers are stereoisomers?

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Problem 9

Among alkenes, alkynes, and aromatic hydrocarbons, only alkenes exhibit cis-trans isomerism. Why don’t the others?

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Problem 10

Which objects are asymmetric (have no plane of symmetry): (a) a circular clock face; (b) a football; (c) a dime; (d) a brick; (e) a hammer; (f) a spring?

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Problem 11

Explain how a polarimeter works and what it measures.

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Problem 12

How does an aromatic hydrocarbon differ from a cycloalkane in terms of its bonding? How does this difference affect structure?

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Problem 13

Draw all possible skeletons for a 7-C compound with
(a) A 6-C chain and 1 double bond
(b) A 5-C chain and 1 double bond
(c) A 5-C ring and no double bonds

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Problem 14

Draw all possible skeletons for a 6-C compound with
(a) A 5-C chain and 2 double bonds
(b) A 5-C chain and 1 triple bond
(c) A 4-C ring and no double bonds

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Problem 15

Add the correct number of hydrogens to each of the skeletons in Problem 15.13.

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Problem 16

Add the correct number of hydrogens to each of the skeletons in Problem 15.14.

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Problem 17

Draw correct structures, by making a single change, for any that are incorrect:

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Problem 18

Draw correct structures, by making a single change, for any that are incorrect:

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Problem 19

Draw the structure or give the name of each compound:
(a) $2,3$ -dimethyloctane
(b) 1 -ethyl- 3 -methylcyclohexane

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Problem 20

Draw the structure or give the name of each compound:

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Problem 21

Each of the following names is wrong. Draw structures based on them, and correct the names:

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Problem 22

Each of the following names is wrong. Draw structures based on them, and correct the names:
$$
\begin{array}{ll}{\text { (a) } 3,3 \text { -dimethylbutane }} & {\text { (b) } 1,1,1 \text { -trimethylheptane }} \\ {\text { (c) } 1,4 \text { -diethylcyclopentane }} & {\text { (d) } 1 \text { -propylcyclohexane }}\end{array}
$$

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Problem 23

Each of the following compounds can exhibit optical activity. Circle the chiral center(s) in each:

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Problem 24

Each of the following compounds can exhibit optical activity. Circle the chiral center(s) in each:

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Problem 25

Draw structures from the following names, and determine which compounds are optically active
(a) 3 -bromohexane
(b) 3 -chloro- 3 -methylpentane
(c) $1,2$ -dibromo-2-methylbutane

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Problem 26

Draw structures from the following names, and determine which compounds are optically active:
(a) $1,3$ -dichloropentane
(b) 3 -chloro-2,2, 5 -trimethylhexane
(c) 1 -bromo- 1 -chlorobutane

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Problem 27

Which of the following structures exhibit geometric isomerism? Draw and name the two isomers in each case:

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Problem 28

Which of the following structures exhibit geometric isomerism? Draw and name the two isomers in each case:

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Problem 29

Which compounds exhibit geometric isomerism? Draw and name the two isomers in each case:
$$
\begin{array}{ll}{\text { (a) propene }} & {\text { (b) } 3 \text { -hexene }} \\ {\text { (c) } 1,1 \text { -dichloroethene }} & {\text { (d) } 1,2 \text { -dichloroethene }}\end{array}
$$

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Problem 30

Which compounds exhibit geometric isomerism? Draw and name the two isomers in each case:
$$
\begin{array}{ll}{\text { (a) } 1 \text { -pentene }} & {\text { (b) } 2 \text { -pentene }} \\ {\text { (c) } 1 \text { -chloropropene }} & {\text { (d) } 2 \text { -chloropropene }}\end{array}
$$

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Problem 31

Draw and name all the constitutional isomers of dichlorobenzene.

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Problem 32

Draw and name all the constitutional isomers of trimethylbenzene.

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Problem 33

Butylated hydroxytoluene (BHT) is a common preservative added to cereals and other dry foods. Its systematic name is 1 -hydroxy-2,6-di-tert-buty-4-methylbenzene (where "tert-butyl" is $1,1$ -dimethylethyl). Draw the structure of BHT.

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Problem 34

There are two compounds with the name 2-methyl-3- hexene, but only one with the name 2-methyl-2-hexene. Explain with structures.

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Problem 35

Any tetrahedral atom with four different groups attached can be a chiral center. Which of these species is optically active?
$$
\begin{array}{ll}{\text { (a) CHCIBrF }} & {\text { (b) } \mathrm{NBrCl}_{2} \mathrm{H}^{+}} \\ {\text { (c) PFClBrI^+ }} & {\text { (d) SeFClBrH }}\end{array}
$$

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Problem 36

Breaking the $\mathrm{C}=\mathrm{C} \pi$ bond in the molecule retinal in the eye requires approximately 250 $\mathrm{kJ} / \mathrm{mol}$ of energy. Find the longest wavelength (in $\mathrm{nm} )$ of visible light that has the energy to break the \pi bond.

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Problem 37

In terms of numbers of reactant and product substances, which organic reaction type corresponds to (a) a combination reaction, (b) a decomposition reaction, (c) a displacement reaction?

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Problem 38

The same type of bond is broken in an addition reaction and formed in an elimination reaction. Name the type.

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Problem 39

Can a redox reaction also be an addition, elimination, or substitution reaction? Explain with examples.

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Problem 40

Determine the type of each of the following reactions:

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Problem 41

Determine the type of each of the following reactions:

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Problem 42

Write equations for the following: (a) an addition reaction between $\mathrm{H}_{2} \mathrm{O}$ and 3 -hexene $\left(\mathrm{H}^{+} \text { is a catalyst); (b) an elimina- }\right.$ tion reaction between 2 -bromopropane and hot potassium ethoxide,$\mathrm{CH}_{3}-\mathrm{CH}_{2}-\mathrm{OK}(\mathrm{KBr} \text { and ethanol are also products }) ;(\mathrm{c}) \mathrm{a}$ light-induced substitution reaction between $\mathrm{Cl}_{2}$ and ethane to form $1,1$ -dichloroethane.

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Problem 43

Write equations for the following: (a) a substitution reaction between 2 -bromopropane and $\mathrm{KI} ;(\mathrm{b})$ an addition reaction between cyclohexene and $\mathrm{Cl}_{2} ;(\mathrm{c})$ an addition reaction between 2 -propanone and $\mathrm{H}_{2}$ (Ni metal is a catalyst).

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Problem 44

Based on the number of bonds and the nature of the bonded atoms, state whether each of the following changes is an oxidation or a reduction:
$$
\begin{array}{l}{\text { (a) }=\mathrm{CH}_{2} \text { becomes }-\mathrm{CH}_{2}-\mathrm{OH}} \\ {\text { (b) }=\mathrm{CH}-\text { becomes }-\mathrm{CH}_{2}-} \\ {\text { (c) } \equiv \mathrm{C}-\text { becomes }-\mathrm{CH}_{2}-}\end{array}
$$

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Problem 45

Based on the number of bonds and the nature of the bonded atoms, state whether each of the following changes is an oxidation or a reduction:
$$
\begin{array}{l}{\text { (a) }-\mathrm{C}-\mathrm{OH} \text { becomes }-\mathrm{C}=\mathrm{O}} \\ {\text { (b) }-\mathrm{CH}_{2}-\mathrm{OH} \text { becomes }=\mathrm{CH}_{2}} \\ {\text { (c) }-\mathrm{C}-\mathrm{c}-\text { becomes }-\mathrm{C}-\mathrm{O}-}\end{array}
$$

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Problem 46

Is the organic reactant oxidized, reduced, or neither in each of the following reactions?
$$
2 \text { -hexene } \frac{\mathrm{KMnO}_{4}}{\text { cold } \mathrm{OH}^{-}} 2,3
$$
$$
\frac{\Delta}{\text { catalyst }} \text { benzene }+3 \mathrm{H}_{2}
$$

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Problem 47

Is the organic reactant oxidized, reduced, or neither in each of the following reactions?
$$
\begin{array}{l}{\text { (a) } 1 \text { -butyne }+\mathrm{H}_{2} \stackrel{\mathrm{Pt}}{\longrightarrow} 1 \text { -butene }} \\ {\text { (b) toluene } \frac{\mathrm{KMnO}_{4}}{\mathrm{H}_{3} \mathrm{O}^{7}, \Delta} \text { benzoic acid }}\end{array}
$$

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Problem 48

Phenylethylamine is a natural substance that is structurally similar to amphetamine. It is found in sources as diverse as almond oil and human urine, where it occurs at elevated concentrations as a result of stress and certain forms of schizophrenia. One method of synthesizing the compound for pharmacological and psychiatric studies involves two steps:

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Problem 49

Compounds with nearly identical molar masses often have very different physical properties. Choose the compound with the higher value for each of the following properties, and explain your choice
(a) Solubility in water: chloroethane or methylethylamine
(b) Melting point: diethyl ether or 1-butanol
(c)Boiling point: trimethylamine or propylamine

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Problem 50

Fill in each blank with a general formula for the type of compound formed:

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Problem 51

Of the three major types of organic reactions, which do not occur readily with benzene? Why?

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Problem 52

Why does the $\mathrm{C}=\mathrm{O}$ group react differently from the $\mathrm{C}=\mathrm{C}$ group? Show an example of the difference.

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Problem 53

Many substitution reactions are initiated by electrostatic attraction between reactants. Show where this attraction arises in the formation of an amide from an amine and an ester

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Problem 54

Although both carboxylic acids and alcohols contain an - OH group, one is acidic in water and the other is not. Explain.

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Problem 55

What reaction type is common to the formation of esters and acid anhydrides? What is the other product?

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Problem 56

Both alcohols and carboxylic acids undergo substitution, but the processes are very different. Explain.

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Problem 57

Name the type of organic compound from each description of the functional group: (a) polar group that has only single bonds and does not include O or N; (b) group that is polar and has a triple bond; (c) group that has single and double bonds and is acidic in water; (d) group that has a double bond and must be at the end of a C chain

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Problem 58

Name the type of organic compound from each description of the functional group: (a) N-containing group with single and double bonds; (b) group that is not polar and has a double bond; (c) polar group that has a double bond and cannot be at the end of a C chain; (d) group that has only single bonds and is basic in water.

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Problem 59

Circle and name the functional group(s) in each molecule:

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Problem 60

Circle and name the functional group(s) in each molecule:

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Problem 61

Draw all alcohols with the formula $\mathrm{C}_{5} \mathrm{H}_{12} \mathrm{O}$

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Problem 62

Draw all aldehydes and ketones with the formula $\mathrm{C}_{5} \mathrm{H}_{10} \mathrm{O}$ .

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Problem 63

Draw all amines with the formula $\mathrm{C}_{4} \mathrm{H}_{11} \mathrm{N}$ .

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Problem 64

Draw all carboxylic acids with the formula $\mathrm{C}_{5} \mathrm{H}_{10} \mathrm{O}_{2}$

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Problem 65

Draw the product resulting from mild oxidation of (a) 2-butanol; (b) 2-methylpropanal; (c) cyclopentanol

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Problem 66

Draw the alcohol you’d oxidize to produce (a) 2-methylpropanal; (b) 2-pentanone; (c) 3-methylbutanoic acid.

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Problem 67

Draw the organic product formed when the following compounds undergo a substitution reaction: (a) acetic acid and methylamine; (b) butanoic acid and 2-propanol; (c) formic acid and 2-methyl-1-propanol.

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Problem 68

Draw the organic product formed when the following compounds undergo a substitution reaction: (a) acetic acid and 1-hexanol; (b) propanoic acid and dimethylamine; (c) ethanoic acid and diethylamine.

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Problem 69

Draw condensed formulas for the carboxylic acid and alcohol that form the following esters:

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Problem 70

Draw condensed formulas for the carboxylic acid and amine that form the following amides:

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Problem 71

Fill in the expected organic substances:

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Problem 72

Fill in the expected organic substances:

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Problem 73

Supply the missing organic and/or inorganic substances:

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Problem 74

Supply the missing organic and/or inorganic substances:

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Problem 75

(a) Draw the four isomers of $\mathrm{C}_{5} \mathrm{H}_{12} \mathrm{O}$ that can be oxidized to an aldehyde. (b) Draw the three isomers of $\mathrm{C}_{5} \mathrm{H}_{12} \mathrm{O}$ that can be
oxidized to a ketone. (c) Draw the isomers of $\mathrm{C}_{5} \mathrm{H}_{12} \mathrm{O}$ that cannot be easily oxidized to an aldehyde or ketone. (d) Name any isomer that is an alcohol.

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Problem 76

Ethyl formate $\left(\mathrm{HC}-\mathrm{O}-\mathrm{CH}_{2}-\mathrm{CH}_{3}\right)$ is added to foods to give them the flavor of rum. How would you synthesize ethyl nformate from ethanol, methanol, and any inorganic reagents?

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Problem 77

Name the reaction processes that lead to the two types of synthetic polymers

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Problem 78

Which functional group occurs in the monomers of addition polymers? How are these polymers different from one another?

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Problem 79

What is a free radical? How is it involved in polymer formation?

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Problem 80

Which intermolecular force is primarily responsible for the different types of polyethylene? Explain

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Problem 81

Which of the two types of synthetic polymer is more similar chemically to biopolymers? Explain.

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Problem 82

Which functional groups react to form nylons? Polyesters?

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Problem 83

Draw an abbreviated structure for the following polymers, with brackets around the repeat unit:
(a) Poly(vinyl chloride) (PVC) from
(b) Polypropylene from

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Problem 84

Draw an abbreviated structure for the following polymers, with brackets around the repeat unit:
(a) Teflon from
(b) Polystyrene from

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Problem 85

Polyethylene terephthalate (PET) is used to make synthetic fibers, such as Dacron, thin films, such as Mylar, and bottles for carbonated beverages. PET is produced from ethylene glycol and either of two
monomers, depending on whether the reaction proceeds by dehydration-condensation or by displacement. Write equations for the two syntheses. (Hint: The displacement. Wreversed by adding methanol to PET at high $T$ and $P .$ .

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Problem 86

Write a balanced equation for the reaction of dihydroxydimethylsilane (right) to form the condensation polymer known as Silly Putty.

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Problem 87

Which type of polymer is formed from each of the following monomers: (a) amino acids; (b) alkenes; (c) simple sugars; (d) mononucleotides?

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Problem 88

What is the key structural difference between fibrous and globular proteins? How is it related, in general, to the proteins’ amino acid composition?

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Problem 89

Protein shape, function, and amino acid sequence are interrelated. Which determines which?

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Problem 90

What linkage joins the monomers in each strand of DNA?

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Problem 91

What is base pairing? How does it pertain to DNA structure?

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Problem 92

RNA base sequence, protein amino acid sequence, and DNA base sequence are interrelated. Which determines which in the process of protein synthesis?

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Problem 93

Draw the R group of (a) alanine; (b) histidine; (c) methionine.

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Problem 94

Draw the R group of (a) glycine; (b) isoleucine; (c) tyrosine.

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Problem 95

Draw the structure of each of the following tripeptides:
(a) Aspartic acid-histidine-tryptophan
(b) Glycine-cysteine-tyrosine with the charges that exist in cell fluid

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Problem 96

Draw the structure of each of the following tripeptides:
(a) Lysine-phenylalanine-threonine
(b) Alanine-leucine-valine with the charges that exist in cell fluid

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Problem 97

Write the sequence of the complementary DNA strand that pairs with each of the following DNA base sequences:
(a) TTAGCC
(b) AGACAT

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Problem 98

Write the sequence of the complementary DNA strand that pairs with each of the following DNA base sequences:
(a) GGTTAC
(b) CCCGAA

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Problem 99

Write the base sequence of the DNA template from which this RNA sequence was derived: UGUUACGGA. How many amino acids are coded for in this sequence?

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Problem 100

Write the base sequence of the DNA template from which this RNA sequence was derived: GUAUCAAUGAACUUG. How many amino acids are coded for in this sequence?

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Problem 101

Protein shapes are maintained by a variety of forces that arise from interactions between the amino-acid R groups. Name the amino acid that possesses each R group and the force that could arise in each of the following interactions:

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Problem 102

Amino acids have an average molar mass of 100 $\mathrm{g} / \mathrm{mol}$ . How many bases on a single strand of DNA are needed to code for a protein with a molar mass of $5 \times 10^{5} \mathrm{g} / \mathrm{mol} ?$

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Problem 103

Ethers (general formula $\mathrm{R}-\mathrm{O}-\mathrm{R}^{\prime}$ ) have many important uses. Until recently, methyl tert-butyl ether (MTBE, below) was used as an octane booster and fuel additive for gasoline. It increases the oxygen content of the fuel, which reduces CO emissions. MTBE is synthesized by the catalyzed reaction of 2 -methylpropene with methanol.
(a) Write a balanced equation for the synthesis of MTBE. (Hint: Alcohols add to alkenes similarly to the way water does.)
(b) If the government required that auto fuel mixtures contain 2.7\% oxygen by mass to reduce CO emissions, how many grams of MTBE would have to be added to each $100 .$ g of gasoline?
(c) How many liters of MTBE would be in each liter of fuel mixture? (The density of both gasoline and MTBE is 0.740 $\mathrm{g} / \mathrm{mL.}$ )
(d) How many liters of air $\left(21 \% \mathrm{O}_{2} \text { by volume) are needed at } 24^{\circ} \mathrm{C}\right.$ and 1.00 $\mathrm{atm}$ to fully combust 1.00 $\mathrm{L}$ of MTBE?

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Problem 104

An alcohol is oxidized to a carboxylic acid, and 0.2003 g of the acid is titrated with 45.25 $\mathrm{mL}$ of 0.03811 $\mathrm{M} \mathrm{NaOH}$ . (a) What is the molar mass of the acid? (b) What are the molar mass and molecular formula of the alcohol?

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Problem 105

Some of the most useful compounds for organic synthesis are Grignard reagents (general formula $\mathrm{R}-\mathrm{MgX},$ where $\mathrm{X}$ is a halogen), which are made by combining an alkyl halide, $\mathrm{R}-\mathrm{X}$ , halogen), which are made by combining an alkyl halide, R-X,
with Mg. They are used to change the carbon skeleton of a starting carbonyl compound in a reaction similar to that with R-Li:
(a) What is the product, after a final step with water, of the reaction between ethanal and the Grignard reagent of bromobenzene?
(b) What is the product, after a final step with water, of the reaction between 2-butanone and the Grignard reagent of 2-bromopropane?
(c) There are often two (or more) combinations of Grignard reagent and carbonyl compound that will give the same product. Choose another pair of reactants to give the product in (a).
(d) What carbonyl compound must react with a Grignard reagent to yield a product with the ±OH group at the end of the carbon chain? (e) What Grignard reagent and carbonyl compound would you use to prepare 2-methyl-2-butanol?

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Problem 106

Starting with the given organic reactant and any necessary inorganic reagents, explain how you would perform each of the following syntheses:

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Problem 107

Compound A, composed of $\mathrm{C}, \mathrm{H},$ and $\mathrm{O},$ is heated in a $1.00-\mathrm{L}$ flask to $160 .^{\circ} \mathrm{C}$ until all of the A has vaporized and dis- placed the air. The flask is then cooled, and 2.48 $\mathrm{g}$ of A remains. When 0.500 $\mathrm{g}$ of A burns in $\mathrm{O}_{2}, 0.409 \mathrm{g}$ of $\mathrm{H}_{2} \mathrm{O}$ and 1.00 $\mathrm{g}$ of $\mathrm{CO}_{2}$ are produced. Compound A is not acidic, but it can be oxidized to $260^{\circ} \mathrm{C},$ it gives off water and forms $\mathrm{C},$ whose solution in $\mathrm{CDCl}_{3}$ (where $D$ is deuterium, $^{2} H )$ has one peak in its $^{T} H-N M R$ spectrum. (a) What are the structures of $\mathrm{A}, \mathrm{B},$ and $\mathrm{C} ?$ (b) Compound A is a controlled substance because it is metabolized to the weakly acidic "date rape" drug $\mathrm{GHB}$ , $\mathrm{C}_{4} \mathrm{H}_{8} \mathrm{O}_{3} .$ What are the structure and name of GHB?

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Problem 108

Cadaverine (1,5-diaminopentane) and putrescine (1,4- diaminobutane) are two compounds that are formed by bacterial action and are responsible for the odor of rotting flesh. Draw their structures. Suggest a series of reactions to synthesize putrescine from 1,2-dibromoethane and any inorganic reagents.

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Problem 109

Pyrethrins, such as jasmolin II (facing page), are a group of natural compounds synthesized by flowers of the genus Chrysanthemum (known as pyrethrum flowers) to act as insecticides.
(a) Circle and name the functional groups in jasmolin II.
(b) What is the hybridization of the numbered carbons?
(c) Which, if any, of the numbered carbons are chiral centers?

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Problem 110

Compound $A$ is branched and optically active and contains $\mathrm{C}, \mathrm{H},$ and $\mathrm{O}$ (a) $\mathrm{A} 0.500-\mathrm{g}$ sample burns in excess $\mathrm{O}_{2}$ to yield 1.25 $\mathrm{g}$ of $\mathrm{CO}_{2}$ and 0.613 $\mathrm{g}$ of $\mathrm{H}_{2} \mathrm{O}$ . Determine the empirical formula. (b) When 0.225 $\mathrm{g}$ of compound A vaporizes at 755 torr
and $97^{\circ} \mathrm{C}$ , the vapor occupies 78.0 $\mathrm{mL}$ . Determine the molecular formula. (c) Careful oxidation of the compound yields a ketone. Name and draw compound A, and circle the chiral center.

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Problem 111

Ibuprofen is one of the most common anti-inflammatory drugs. (a) Identify the functional group(s) and chiral center(s) in ibuprofen. (b) Write a four-step synthesis of a racemic mixture of ibuprofen from 4-isobutylbenzaldehyde, using inorganic reactants and one organometallic reactant (see Problem 15.105).

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Problem 112

Which features of retinal make it so useful as a photon absorber in the visual systems of organisms?

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Problem 113

The polypeptide chain in proteins does not exhibit free rotation because of the partial double-bond character of the peptide bond. Explain this fact with resonance structures.

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Problem 114

Other nonmetals form compounds that are structurally analogous to those of carbon, but these inorganic compounds are usually more reactive. Predict any missing products and write balanced equations for each reaction: (a) the decomposition and chlorination of diborane to boron trichloride; (b) the combustion of pentaborane $\left(\mathrm{B}_{5} \mathrm{H}_{9}\right)$ in $\mathrm{O}_{2} ;(\mathrm{c})$ the hydrolysis of trisilane $\left(\mathrm{Si}_{3} \mathrm{H}_{8}\right)$
to silica $\left(\mathrm{SiO}_{2}\right)$ and $\mathrm{H}_{2} ;(\mathrm{d})$ the complete halogenation of disilane with $\mathrm{Cl}_{2} ;(\mathrm{e})$ the thermal decomposition of $\mathrm{H}_{2} \mathrm{S}_{5}$ to hydrogen sulfide and sulfur molecules; (f) the hydrolysis of $\mathrm{PCl}_{5} .$

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Problem 115

In addition to their use in water treatment, ion-exchange resins are used to extract Au, Ag, and Pt ions from solution. One of the most common resins consists of a polymer with a benzene-containing backbone to which sulfonic acid groups $\left(-\mathrm{SO}_{3} \mathrm{H}\right)$ have been added. (a) What monomer can be used to prepare the polymer backbone? (b) This polymer typically contains $4-16 \%$ crosslinking. Draw the structure of the benzene- containing monomer used to crosslink the polymer.

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Problem 116

Complete hydrolysis of a 100.00-g sample of a peptide gave the following amounts of individual amino acids (molar masses, in g/mol, appear in parentheses):
$$
\begin{array}{ll}{3.00 \mathrm{g} \text { of glycine }(75.07)} & {0.90 \mathrm{g} \text { of alanine }(89.10)} \\ {3.70 \mathrm{g} \text { of valine }(117.15)} & {6.90 \mathrm{g} \text { of proline }(115.13)} \\ {7.30 \mathrm{g} \text { of serine }(105.10)} & {86.00 \mathrm{g} \text { of arginine }(174.21)}\end{array}
$$
(a) Why does the total mass of amino acids exceed the mass of peptide? (b) What are the relative numbers of amino acids in the peptide? (c) What is the minimum molar mass of the peptide?

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Problem 117

2- Butanone is reduced by hydride ion donors, such as sodium borohydride $\left(\mathrm{NaBH}_{4}\right),$ to the alcohol 2 -butanol. Even though the alcohol has a chiral center, the product isolated from the redox reaction is not optically active. Explain.

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Problem 118

Wastewater from a cheese factory has the following composition: 8.0 $\mathrm{g} / \mathrm{L}$ protein $\left(\mathrm{C}_{16} \mathrm{H}_{24} \mathrm{O}_{5} \mathrm{N}_{4}\right) ; 12 \mathrm{g} / \mathrm{L}$ carbohydrate $\left(\mathrm{CH}_{2} \mathrm{O}\right) ;$ and 2.0 $\mathrm{g} / \mathrm{L}$ fat $\left(\mathrm{C}_{8} \mathrm{H}_{16} \mathrm{O}\right) .$ What is the total organic carbon $(\mathrm{TOC})$ of the wastewater in $\mathrm{g}$ of $\mathrm{C} \mathrm{L} ?$

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Problem 119

Structures $A, B,$ and $C$ show the three common forms of vitamin A. (a) Match each structure with the correct vitamin A compound: retinal (an aldehyde), retinol (an alcohol), and retinoic acid (a carboxylic acid). (b) Retinal, the molecule responsible for the chemistry of vision, can be converted to retinol or to retinoic acid. Identify each of these reactions as a reduction or an oxidation. (c) Structure $D$ is that of beta-carotene, found in carrots. Suggest a reason for the importance of beta-carotene in the vision process.

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