Chapter 10

What are some major end uses for recycled PET and HDPE polymers?

State one major difference between proteins and synthetic polyamides.

How are amide linkages and peptide linkages similar? How are they different?

Which biological molecules have monomer units that are not all alike, as in synthetic copolymers?

Which biological molecules have monomer units that are all alike, as in synthetic polymers?

Draw the structural formula of alanylglycylphenylalanine.

Draw the structural formula of leucylmethionylalanylserine

Explain the difference between (a) monosaccharides and disaccharides, and (b) disaccharides and polysaccharides.

What is the chief function of glycogen in animal tissue?

What polysaccharides yield only D-glucose upon complete hydrolysis?

(a) How do amylose and amylopectin differ? (b) How are they similar? (c) Are amylose and glycogen similar?

(a) Explain why humans can use glycogen but not cellulose for energy. (b) Why can cows digest cellulose?

The total mass of carbon in living systems on Earth is estimated to be \(7.5 \times 10^{17} \mathrm{~g} ;\) the total mass of carbon in all forms on Earth is estimated as \(7.5 \times 10^{22} \mathrm{~g} .\) Calculate the concentration of organic carbon as a fraction of total carbon. Express your answer as percent and in parts per million (ppm).

In his 1989 essay "The End of Nature," William McKibben states that "... a clean burning automobile engine will emit \(5.5 \mathrm{lb}\) of carbon in the form of carbon dioxide for every gallon of gasoline it consumes." Assume that the gasoline is \(\mathrm{C}_{8} \mathrm{H}_{18}\) and its density is \(0.703 \mathrm{~g} / \mathrm{mL}\) (a) Write a balanced equation for the complete combustion of gasoline. (b) Is McKibben's assertion correct? Support your answer with calculations.

Explain why ethanol, \(\mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{OH},\) is soluble in water in all proportions, but decanol, \(\mathrm{CH}_{3}\left(\mathrm{CH}_{2}\right)_{9} \mathrm{OH},\) is almost insoluble in water.

Nitrile rubber (Buna \(\mathrm{N}\) ) is a copolymer of two parts 1,3 -butadiene to one part acrylonitrile. Draw the repeating unit of this polymer.

Write the condensed structural formula for 3 -ethyl5-methyl-3-hexanol. Is this a primary, secondary, or tertiary alcohol?

Assume that a car burns pure octane, $$ \mathrm{C}_{8} \mathrm{H}_{18}\left(d=0.703 \mathrm{~g} / \mathrm{cm}^{3}\right) $$ (a) Write the balanced equation for burning octane in air, forming \(\mathrm{CO}_{2}\) and \(\mathrm{H}_{2} \mathrm{O}\). (b) If the car has a fuel efficiency of 32 miles per gallon of octane, what volume of \(\mathrm{CO}_{2}\) at \(25^{\circ} \mathrm{C}\) and \(1.0 \mathrm{~atm}\) is generated when the car goes on a 10.0 -mile trip? (The volume of \(1 \mathrm{~mol} \mathrm{CO}_{2}(\mathrm{~g})\) at \(25^{\circ} \mathrm{C}\) and \(1 \mathrm{~atm}\) is \(\left.24.5 \mathrm{~L} .\right)\)

Polytetrafluoroethylene (Teflon) is made by first treating HF with chloroform, then cracking the resultant difluorochloromethane. $$ \begin{array}{c} \mathrm{CHCl}_{3}+2 \mathrm{HF} \longrightarrow \mathrm{CHClF}_{2}+2 \mathrm{HCl} \\ 2 \mathrm{CHClF}_{2} \frac{\text { high }}{T} \mathrm{~F}_{2} \mathrm{C}=\mathrm{CF}_{2}+2 \mathrm{HCl} \\ \mathrm{F}_{2} \mathrm{C}=\mathrm{CF}_{2} \stackrel{\text { peroxide catalyst }}{\longrightarrow} \text { Teflon } \end{array} $$ You want to make \(1.0 \mathrm{~kg}\) Teflon. Calculate the mass of chloroform and HF required to make the starting material, \(\mathrm{CHClF}_{2}\). (Although it is not realistic, assume that each reaction step proceeds to a \(100 \%\) yield.)

A \(1.685-\mathrm{g}\) sample of a hydrocarbon is burned completely to form \(5.287 \mathrm{~g}\) carbon dioxide and \(2.164 \mathrm{~g}\) water. (a) Determine the empirical formula of the hydrocarbon. (b) Identify whether it is an alkane or an alkene. (c) Write a plausible Lewis structure for it.

Suppose \(2.511 \mathrm{~g}\) of a hydrocarbon is burned completely to form \(7.720 \mathrm{~g}\) carbon dioxide and \(3.612 \mathrm{~g}\) water. (a) Determine the empirical formula of the hydrocarbon. (b) Identify whether it is an alkane or an alkene. (c) Write a plausible Lewis structure for it.

Draw a structural formula for each of three possible repeating units of poly(vinyl chloride).

Two different compounds each have the formula \(\mathrm{C}_{2} \mathrm{H}_{4} \mathrm{O}_{2}\). Each contains a \(\mathrm{C}=\mathrm{O}\) group. Write the Lewis structure of each compound and identify the functional group or functional groups in each one

Glycolic acid, \(\mathrm{HOCH}_{2} \mathrm{COOH},\) and lactic acid form a copolymer used as absorbable stitches in surgery. Use structural formulas to write a chemical equation showing the formation of four units of the copolymer.

The backbone of a DNA molecule is a polymer of alternating sugar (deoxyribose) and phosphoric acid units held together by a phosphate ester bond. Draw a segment of the polymer consisting of at least two sugar and two phosphate units. Circle the phosphate ester bonds.

Draw the structure of a molecule that could undergo a condensation reaction with itself to form a polyester. Draw a segment of the polymer consisting of at least five monomer units.

It has been asserted that the photosynthesis of the trees in a forest the size of Australia would be needed to compensate for the additional \(\mathrm{CO}_{2}\) put into the atmosphere each year from burning fossil fuels. Identify the data that would be required to check whether this assertion is valid.

Towels made from polyester fibers are less water absorbent than towels made from cotton. Explain this difference on a molecular basis.

Locate the grid for Question \(115 .\) Each of its nine lettered boxes contains an item that can be used to fill in the blanks that follow. Items may be used more than once and there may be more than one correct item for a blank. Place the letter(s) of the correct selection(s) on the appropriate line. (a) A triglyceride (b) Final oxidation product of a primary alcohol (c) Condensation polymerization monomer (d) Segment of an addition polymer molecule (e) Initial oxidation product of a primary alcohol (f) Contains an amide bond (g) Addition polymerization monomer

Consider the compound \(\mathrm{C}_{3} \mathrm{H}_{7} \mathrm{NO}\) in which there is no nitrogen-to-oxygen bond and there is an ethyl group. (a) Write a Lewis structure for the compound. (b) Draw two resonance structures for this molecule. (c) Use VSEPR theory to predict the geometry around each carbon atom and the nitrogen atom in each resonance structure. (d) Experimental evidence indicates that the nitrogen atom is triangular planar with bond angles close to \(120^{\circ} .\) Which prediction in part (c) is correct? (e) Describe the hybridization of the nitrogen atom.

A hydrocarbon is \(90.0 \%\) carbon and \(10.0 \%\) hydrogen by mass; its molar mass is \(40.1 \mathrm{~g} / \mathrm{mol}\). The hydrocarbon reacts with bromine by an addition reaction. It also undergoes hydrogenation with a nickel catalyst; \(1.58 \mathrm{~g}\) of the hydrocarbon reacts with \(1.77 \mathrm{~L} \mathrm{H}_{2}\) (measured at STP). (a) From these data, derive the molecular formula of the hydrocarbon. (b) Write the structural formulas of two possible isomers. (c) For one of the isomers, use Lewis structures to write a balanced chemical equation for: (i) the bromination reaction; and (ii) the hydrogenation reaction.

In the laboratory, a student was given three bottles labeled \(\mathrm{X}, \mathrm{Y},\) and \(\mathrm{Z}\). One of the bottles contained acetic acid, the second acetaldehyde, and the third ethanol. The student ran a series of experiments to determine the contents of each bottle. Substance \(\mathrm{X}\) reacted with substance \(\mathrm{Y}\) to form an ester under certain conditions and substance Y formed an acidic solution when dissolved in water. (a) Identify which compound is in which bottle, and write the Lewis structure for each compound. (b) Using structural formulas, write a chemical equation for the ester formation reaction and for the ionization of the acid. (c) The student confirmed the identifications by treating each compound with a strong oxidizing agent and found that compound \(\mathrm{X}\) required roughly twice the amount of oxidizing agent as compound \(Z\). Explain why this was the case.

Consider these data: \begin{tabular}{lcc} \hline & & Enthalpy of \\ Hydrocarbon & Formula & Combustion (kJ/mol) \\ \hline Butane & \(\mathrm{C}_{4} \mathrm{H}_{10}\) & 2853.9 \\ Pentane & \(\mathrm{C}_{5} \mathrm{H}_{12}\) & 3505.8 \\ Hexane & \(\mathrm{C}_{6} \mathrm{H}_{14}\) & 4159.5 \\ Heptane & \(\mathrm{C}_{7} \mathrm{H}_{16}\) & \\ Octane & \(\mathrm{C}_{8} \mathrm{H}_{18}\) & 4812.8 \\ \hline \end{tabular} Graph these data with enthalpy of combustion on the \(y\) -axis and number of carbon atoms on the \(x\) -axis. (a) Use the graph to estimate the enthalpy of combustion of propane, \(\mathrm{C}_{3} \mathrm{H}_{8},\) nonane, \(\mathrm{C}_{9} \mathrm{H}_{20},\) and hexadecane, \(\mathrm{C}_{16} \mathrm{H}_{34}\) (b) Use bond enthalpies to explain why the graph has a positive slope.

Explain why an amino acid has a higher boiling point than an amine with the same number of electrons.

Silicones are Si-containing polymers used in waterproof caulking. They do not contain carbon-to-carbon bonds. (a) Silly Putty is a polymer made from the monomer dimethylsilanol, \(\left(\mathrm{CH}_{3}\right)_{2} \mathrm{Si}(\mathrm{OH})_{2}\). Write the structure of four units of this polymer. (b) Identify the type of polymerization that occurs.

Polyacetylene is an electrically conducting polymer of acetylene, \(\mathrm{HC} \equiv \mathrm{CH}\). Now used in batteries, the polymer was discovered accidentally in 1970 when far too much catalyst was used in an experimental attempt to polymerize acetylene into synthetic rubber. Write a plausible Lewis structure for a portion of a polyacetylene molecule.