Chapter 22

In what ways do DNA and RNA differ structurally?

Which base pairs with (a) \(\mathrm{A}\) in DNA, (b) \(A\) in \(\mathrm{RNA},\) and (c) C in DNA or RNA?

The process of transcription begins with which nucleic acid and ends with which one?

The process of translation begins with which nucleic acid? What is the end result of translation?

Write the structures of the products that form when ethylene reacts with each of the following substances by an addition reaction. (Assume that needed catalysts or other conditions are provided.) (a) \(\mathrm{H}_{2}\) (c) \(\mathrm{Br}_{2}\) (e) \(\operatorname{HBr}(g)\) (b) \(\mathrm{Cl}_{2}\) (d) \(\mathrm{HCl}(g)\) (f) \(\mathrm{H}_{2} \mathrm{O}\) (in acid)

The isopropyl cation is more stable than the propyl cation, so the former forms almost exclusively when propene undergoes addition reactions with protondonating species. On the basis of this fact, predict the final products of the reaction of propene with each of the following reagents: (a) hydrogen chloride (b) hydrogen iodide (c) water in the presence of an acid catalyst

If one mole of benzene were to add one mole of \(\mathrm{Br}_{2}\), what would form? What forms, instead, when \(\mathrm{Br}_{2}\), benzene, and a \(\mathrm{FeBr}_{3}\) catalyst are heated together? (Write the structures.)

Predict the products of the reaction of benzene and nitric acid with a sulfuric acid catalyst.

Write condensed structures and the IUPAC names for all of the saturated alcohols with three or fewer carbon atoms per molecule.

Write the condensed structures and the IUPAC names for all of the possible alcohols with the general formula \(\mathrm{C}_{4} \mathrm{H}_{10} \mathrm{O}\).

Write the condensed structures of all of the possible ethers with the general formula \(\mathrm{C}_{4} \mathrm{H}_{10} \mathrm{O}\). Following the pattern for the common names of ethers given in the chapter, what are the likely common names of these ethers?

Write the structures of the isomeric alcohols of the formula \(\mathrm{C}_{4} \mathrm{H}_{10} \mathrm{O}\) that could be oxidized to aldehydes. Write the structure of the isomer that could be oxidized to a ketone.

When ethanol is heated in the presence of an acid catalyst, ethene and water form; an elimination reaction occurs. When butan-2-ol is heated under similar conditions, two alkenes form (although not in equal quantities). Write the structures and IUPAC names of these two alkenes.

Write the structures of the products that form in each of the following situations. If no reaction occurs, write "no reaction." (a) \(\mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{CO}_{2}^{-}+\mathrm{HCl}(a q) \longrightarrow\) (b) \(\mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{CO}_{2} \mathrm{CH}_{3}+\mathrm{H}_{2} \mathrm{O} \stackrel{\text { heat }}{\longrightarrow}\) (c) \(\mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{CH}_{2} \mathrm{CO}_{2} \mathrm{H}+\mathrm{NaOH}(a q) \longrightarrow\)

Write the structures of the products that form in each of the following situations. If no reaction occurs, write "no reaction." (a) \(\mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{CO}_{2} \mathrm{H}+\mathrm{NH}_{3} \stackrel{\text { heat }}{\longrightarrow}\) (b) \(\mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{CH}_{2} \mathrm{CONH}_{2}+\mathrm{H}_{2} \mathrm{O} \stackrel{\text { heat }}{\longrightarrow}\) (c) \(\mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{CO}_{2} \mathrm{CH}_{3}+\mathrm{NaOH}(a q) \stackrel{\text { heat }}{\longrightarrow}\)

Write the structure of a triacylglycerol that could be made from palmitic acid, oleic acid, and linoleic acid.

What parts of glycerophospholipid molecules provide hydrophobic sites? Which provide hydrophilic sites?

In general terms, describe the structure of the membrane of an animal cell. What kinds of molecules are present? How are they arranged? What forces keep the membrane intact? What functions are served by the protein components?

What is the structure of the tripeptide that could be hydrolyzed to give three molecules of alanine?

What are the structures of the two dipeptides that could be hydrolyzed to give glycine and phenylalanine?

The \(\mathrm{H}_{2} \mathrm{SO}_{4}\) -catalyzed addition of water to 2 -methylpropene could give two isomeric alcohols. (a) Write their condensed structures. (b) Actually, only one forms. It is not possible to oxidize this alcohol to an aldehyde or to a ketone having four carbons. Which alcohol, therefore, is the product? (c) Write the structures of the two possible carbocations. (d) One of the two carbocations of part \((\mathrm{c})\) is more stable than the other. Which one is it, and how can you tell?

Suggest a reason why trimethylamine, \(\left(\mathrm{CH}_{3}\right)_{3} \mathrm{~N},\) has a lower boiling point (BP \(3{ }^{\circ} \mathrm{C}\) ) than dimethylamine, \(\left(\mathrm{CH}_{3}\right)_{2} \mathrm{NH}\) (BP \(8^{\circ} \mathrm{C}\) ), despite having a larger number of atoms.

How many tripeptides can be made from three different amino acids? If the three are glycine (Gly), alanine (Ala), and phenylalanine (Phe), what are the structures of the possible tripeptides. (Hint: Gly-Ala-Phe is one structure.)

Why doesn't PVC have chlorines on adjacent atoms?

When \(0.2081 \mathrm{~g}\) of an organic acid was dissolved in \(50.00 \mathrm{~mL}\) of \(0.1016 \mathrm{M} \mathrm{NaOH}\), it took \(23.78 \mathrm{~mL}\) of \(0.1182 \mathrm{M} \mathrm{HCl}\) to neutralize the \(\mathrm{NaOH}\) that was not used up by the sample of the organic acid. Calculate the formula mass from the data given. Is the answer necessarily the molecular mass of the organic acid? Explain.

The compound \(\mathrm{CH}_{2} \mathrm{Cl}_{2}\) only exists as one isomer. Why does this support the statement that the \(\mathrm{H}\) and \(\mathrm{Cl}\) atoms in the compound are arranged tetrahedrally around the carbon rather than in a square planar structure?

The \(\alpha\) -carbon atom in an amino acid is a chiral center (except for glycine). Of the two possible enantiomers of these optically active substances, only one is produced naturally. What does this suggest about the mechanism whereby amino acids are synthesized in living creatures?

Use resonance structures to explain why urea, \(\left(\mathrm{NH}_{2}\right)_{2}\) \(\mathrm{C}=\mathrm{O},\) is not basic like typical amines. Without using resonance structures, use electronegativities to explain the same fact.

In general terms, what attractive forces are at work that determine the final shape of a polypeptide strand?