Chapter 24

From examination of the molecular models i-v, choose the substance that \((\mathbf{a})\) can be hydrolyzed to form a solution containing glucose, \((\mathbf{b})\) is capable of forming a zwitterion, (c) is one of the four bases present in DNA, (d) reacts with an acid to form an ester, \((\mathbf{e})\) is a lipid. [Sections \(24.6-24.10]\)

Indicate whether each statement is true or false. (a) All carbon atoms in propene are \(s p^{2}\) hybridized. (b) Acetone is another name for propanone. (c) The phenyl group contains six \(s p^{2}\) -hybridized carbons. (d) A hydrocarbon containing only \(s p^{3}\) carbons must be an alkane.

Indicate whether each statement is true or false. (a) Ethane has a higher molar mass than ethene. (b) For molecules of the same homologous family, the higher the molecular mass, the higher the boiling point. (c) The local geometry around the alkene group is T-shaped. (d) Butene has two structural isomers.

Predict the ideal values for the bond angles about each carbon atom in the following molecule. Indicate the hybridization of orbitals for each carbon. $$ \mathrm{CH}_{2} \mathrm{CHCOOCH}_{3} $$

True or false: The weaker a single bond in a molecule, the greater the chance it will be the site of a reaction (compared to stronger single bonds in the molecule).

Indicate whether each statement is true or false. (a) Alkanes do not contain any carbon-carbon multiple bonds. (b) Cyclobutane contains a four-membered ring. (c) Alkenes contain carbon-carbon triple bonds. (d) Alkynes contain carbon-carbon double bonds. (e) Pentane is a saturated hydrocarbon but 1 -pentene is an unsaturated hydrocarbon. (f) Cyclohexane is an aromatic hydrocarbon. (g) The methyl group contains one less hydrogen atom than methane.

What structural features help us identify a compound as (a) an alkane, \((\mathbf{b})\) a cycloalkane, \((\mathbf{c})\) an alkene, \((\mathbf{d})\) an alkyne, (e) a saturated hydrocarbon, (f) an aromatic hydrocarbon?

Give the name or condensed structural formula, as appropriate: a. (b) 2,2 -dimethylpentane (c) 4 -ethyl-1,1-dimethylcyclohexane (d) \(\left(\mathrm{CH}_{3}\right)_{2} \mathrm{CHCH}_{2} \mathrm{CH}_{2} \mathrm{C}\left(\mathrm{CH}_{3}\right)_{3}\) (e) \(\mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{CH}\left(\mathrm{C}_{2} \mathrm{H}_{5}\right) \mathrm{CH}_{2} \mathrm{CH}_{2} \mathrm{CH}_{2} \mathrm{CH}_{3}\)

Give the name or condensed structural formula, as appropriate: (a) 3-phenylpentane (b) 2,3-dimethylhexane (c) 3,3-dimethyloctane (d) \(\mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{CH}\left(\mathrm{CH}_{3}\right) \mathrm{CH}_{2} \mathrm{CH}\left(\mathrm{CH}_{3}\right)_{2}\) e.

What is the octane number of a mixture that is \(35 \%\) heptane and \(65 \%\) isooctane?

Describe two ways in which the octane number of a gasoline consisting of alkanes can be increased.

(a) Can \(\mathrm{C}_{6} \mathrm{H}_{12}\) be a saturated hydrocarbon? (b) Are all molecules containing a benzene ring unsaturated?

(a) Is the compound \(\mathrm{CBr}_{3} \mathrm{CH}=\mathrm{CHCH}_{3}\) saturated or unsaturated? Explain. (b) What is wrong with the formula \(\mathrm{CH}_{2}=\mathrm{CH}_{2} \mathrm{CH}_{2} \mathrm{CH}_{3} ?\)

Give the molecular formula of a hydrocarbon containing five carbon atoms that is (a) an alkane, \((\mathbf{b})\) a cycloalkane, (c) an alkene,(d) an alkyne.

Give the molecular formula of a hydrocarbon containing six carbon atoms that is (a) a cyclic alkane, (b) a cyclic alkene, \((\mathbf{c})\) a linear alkyne, \((\mathbf{d})\) an aromatic hydrocarbon.

Enediynes are a class of compounds that include some antibiotic drugs. Draw the structure of an "enediyne" fragment that contains six carbons in a row.

Give the general formula for any cyclic alkene, that is, a cyclic hydrocarbon with one double bond.

Write the condensed structural formulas for two alkenes and one alkyne that all have the molecular formula \(\mathrm{C}_{6} \mathrm{H}_{10}\).

Draw all the possible noncyclic structural isomers of \(\mathrm{C}_{5} \mathrm{H}_{10}\) Name each compound.

Name or write the condensed structural formula for the following compounds: (a) cis-2-pentene (b) 1,6-dichloro-3-hexyne (c) \(\mathrm{BrC} \equiv \mathrm{CBr}\) (d) 1,3 -Benzenediol (e) \(\mathrm{CH}_{2}=\mathrm{CH}_{2} \mathrm{CH}\left(\mathrm{CH}_{3}\right) \mathrm{CH}=\mathrm{CH}_{2}\)

Name or write the condensed structural formula for the following compounds: (a) para-dibromobenzene (b) \(\mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{C} \equiv \mathrm{CC}\left(\mathrm{CH}_{3}\right)_{3}\) (c) trans-2-butene (d) cycloheptene (e) methylcyclopentane

Indicate whether each statement is true or false. (a) The three isomers of dimethylbenzene are \(o\) -dimethylbenzene, \(m\) -dimethylbenzene, and \(p\) -dimethylbenzene. (b) Alkenes with at least three carbon atoms differing in the position of the \(\mathrm{C}=\mathrm{C}\) double bond are called geometric isomers. \((\mathbf{c})\) Substituted benzenes can form cis and trans isomers.

Draw all structural and geometric isomers of butene and name them.

Indicate whether each of the following molecules is capable of geometrical isomerism. For those that are, draw the structures: (a) 2 -methylpropene, (b) 1,3-diiodobenzene, (c) 1,2-dichloropent-1-ene, (d) 3-methyl-1-butyne.

(a) True or false: Alkenes undergo addition reactions and aromatic hydrocarbons undergo substitution reactions. (b) Using condensed structural formulas, write the balanced equation for the reaction of 2 -pentene with \(\mathrm{Br}_{2}\) and name the resulting compound. Is this an addition or a substitution reaction? (c) Write a balanced chemical equation for the reaction of \(\mathrm{Cl}_{2}\) with benzene to make paradichlorobenzene in the presence of \(\mathrm{FeCl}_{3}\) as a catalyst. Is this an addition or a substitution reaction?

Using condensed structural formulas, write a balanced chemical equation for each of the following reactions: (a) hydrogenation of cyclohexene, \((\mathbf{b})\) addition of \(\mathrm{H}_{2} \mathrm{O}\) to trans-2-pentene using \(\mathrm{H}_{2} \mathrm{SO}_{4}\) as a catalyst (two products), (c) reaction of 2 -chloropropane with benzene in the presence of \(\mathrm{AlCl}_{3}\)

(a) One test for the presence of an alkene is to add a small amount of bromine, which is a red-brown liquid, and look for the disappearance of the red-brown color. This test does not work for detecting the presence of an aromatic hydrocarbon. Explain. (b) Write a series of reactions leading to para-bromoethylbenzene, beginning with benzene and using other reagents as needed. What isomeric side products might also be formed?

Describe the intermediate that is thought to form in the addition of a hydrogen halide to an alkene, using cyclohexene as the alkene in your description.

The molar heat of combustion of gaseous cyclopropane is $-2089 \mathrm{~kJ} / \mathrm{mol} ;\( that for gaseous cyclopentane is \)-3317 \mathrm{~kJ} / \mathrm{mol}\(. Calculate the heat of combustion per \)\mathrm{CH}_{2}$ group in the two cases, and account for the difference.

The heat of combustion of decahydronaphthalene \(\left(\mathrm{C}_{10} \mathrm{H}_{18}\right)\) is \(-6286 \mathrm{~kJ} / \mathrm{mol}\). The heat of combustion of naphthalene \(\left(\mathrm{C}_{10} \mathrm{H}_{8}\right)\) is \(-5157 \mathrm{~kJ} / \mathrm{mol}\). (In both cases \(\mathrm{CO}_{2}(g)\) and \(\mathrm{H}_{2} \mathrm{O}(l)\) are the products.) Using these data and data in Appendix \(\mathrm{C}\), calculate the heat of hydrogenation and the resonance energy of naphthalene.

Draw the molecular structure for \((\mathbf{a})\) a carboxylic acid that is an isomer of ethyl ethanoate, \((\mathbf{b})\) an alcohol that is an isomer of dimethylether.

(a) Give the empirical formula and structural formula for a cyclic ether containing four carbon atoms in the ring. (b) Write the structural formula for a straight-chain compound that is a structural isomer of your answer to part (a).

The IUPAC name for a carboxylic acid is based on the name of the hydrocarbon with the same number of carbon atoms. The ending -oic is appended, as in ethanoic acid, which is the IUPAC name for acetic acid. Draw the structure of the following acids: (a) methanoic acid, \((\mathbf{b})\) pentanoic acid, \((\mathbf{c}) 2\) -chloro-3-methyldecanoic acid.

Aldehydes and ketones can be named in a systematic way by counting the number of carbon atoms (including the carbonyl carbon) that they contain. The name of the aldehyde or ketone is based on the hydrocarbon with the same number of carbon atoms. The ending -al for aldehyde or-one for ketone is added as appropriate. Draw the structural formulas for the following aldehydes or ketones: (a) 3-ethyl-2-pentanone, (b) 2,2 -diethylbutanal, (c) pentanal, (d) 1-bromo-3-heptanone.

Draw the condensed structure of the compounds formed by condensation reactions between (a) benzoic acid and ethanol, (b) ethanoic acid and methylamine, (c) acetic acid and phenol. Name the compound in each case.

Draw the condensed structures of the compounds formed from (a) butanoic acid and methanol, (b) benzoic acid and 2 -propanol, \((\mathbf{c})\) propanoic acid and dimethylamine. Name the compound in each case.

Write a balanced chemical equation using condensed structural formulas for the saponification (base hydrolysis) of (a) methyl propionate, \((\mathbf{b})\) phenyl acetate.

Write a balanced chemical equation using condensed structural formulas for \((\mathbf{a})\) the formation of butyl propionate from the appropriate acid and alcohol, \((\mathbf{b})\) the saponification (base hydrolysis) of methyl benzoate.

Pure acetic acid is a viscous liquid, with high melting and boiling points \(\left(16.7^{\circ} \mathrm{C}\right.\) and \(\left.118^{\circ} \mathrm{C}\right)\) compared to compounds of similar molecular weight. Suggest an explanation.

Acetic anhydride is formed from two acetic acid molecules, in a condensation reaction that involves the removal of a molecule of water. Write the chemical equation for this process, and show the structure of acetic anhydride.

Write the condensed structural formula for each of the following compounds: (a) 2 -pentanol, (b) 1,2-propanediol, (c) ethyl acetate, (d) diphenyl ketone, (e) methyl ethyl ether.

Write the condensed structural formula for each of the following compounds: (a) 2-ethyl-1-hexanol, (b) methyl phenyl ketone, \((\mathbf{c})\) para- bromobenzoic acid, (d) butyl ethyl ether, \((\mathbf{e}) N, N\) -dimethylbenzamide.

How many chiral carbons are in 4 -bromo- 2 -chloro-2butanol? \((\mathbf{a}) 0,(\mathbf{b}) 1,(\mathbf{c}) 2,(\mathbf{d}) 3,(\mathbf{e}) 4\) or more.

Is 2-butanol chiral?

(a) Draw the chemical structure of a generic amino acid, using \(\mathrm{R}\) for the side chain. (b) When amino acids react to form proteins, do they do so via substitution, addition, or condensation reactions? (c) Draw the bond that links amino acids together in proteins. What is this called?

Indicate whether each statement is true or false. (a) Tryptophan is an aromatic amino acid. (b) Lysine is positively charged at pH 7. (c) Asparagine has two amide bonds. (d) Isoleucine and leucine are enantiomers. (e) Valine is probably more water-soluble than arginine.

Draw the two possible heterodimeric dipeptides formed by condensation reactions between glycine and alanine.

Write a chemical equation for the formation of threonylaspartic acid from the constituent amino acids, assuming that the reaction is made possible by enzymatic catalysis.

Indicate whether each statement is true or false. (a) The sequence of amino acids in a protein, from the amine end to the acid end, is called the primary structure of the protein. (b) Alpha helix and beta sheet structures are examples of quaternary protein structure. \((\mathbf{c})\) It is impossible for more than one protein to bind to another and make a higher order structure.

Indicate whether each statement is true or false: (a) In the alpha helical structure of proteins, ion-dipole and dipole-dipole interactions occur between the carbonyl groups of the protein backbone and polar side chains of the protein. (b) Only hydrogen bonding is involved in forming the tertiary structure of a protein.