Chapter 4 — Exercises
Thirty-five problems. Mix of drawing and naming. ∗ = worked solution in appendix.
Section A — Functional-group recognition
4.1∗ (routine) For each compound, list every functional group present: (a) ibuprofen (b) aspirin (c) acetaminophen (d) morphine (see Case Study 1 of Ch 2) (e) glucose (an aldohexose with a CHO and five OH groups)
4.2 (routine) Identify whether each alcohol is primary, secondary, or tertiary: (a) methanol (b) 2-methyl-2-propanol (t-butanol) (c) 2-butanol (d) cyclohexanol (e) 1-phenylethanol
4.3 (routine) Classify each amine as primary, secondary, or tertiary: (a) methylamine ($CH_3NH_2$) (b) diethylamine (c) trimethylamine (d) N,N-dimethylformamide (careful — an amide, not an amine)
4.4 (moderate) For each compound, state the highest-priority functional group: (a) 3-oxobutanoic acid (b) 2-aminoethanol (c) ethyl acetate (d) 3-hydroxybenzaldehyde (e) glycine
Section B — Naming simple compounds
4.5∗ (routine) Give the IUPAC name of each: (a) $CH_3CH_2CH_2CH_2CH_3$ (b) $(CH_3)_2CHCH_2CH_3$ (c) $CH_3CH_2CH(OH)CH_3$ (d) $CH_3CH=CHCH_3$ (cis) (e) $CH_3C \equiv CCH_3$ (f) $CH_3CH_2CHO$ (g) $CH_3COCH_3$ (h) $CH_3CH_2COOH$
4.6 (moderate) Draw the structure from each IUPAC name: (a) 2-methylbutane (b) 3-hexyne (c) cyclopentanol (d) butan-2-one (e) ethyl propanoate (f) N-methylbutanamide
4.7∗ (moderate) Give the IUPAC name: (a) $CH_3CH(CH_3)CH_2CH_2OH$ (b) $(CH_3)_3CCOOH$ (c) $CH_3CH(Br)CH_2CH_3$ (d) $CH_3CH_2COCH_2CH_3$ (e) $CH_3CH_2CH_2CN$
4.8 (moderate) Draw: (a) 3-chloro-2-methylpentan-1-ol (b) 4-hydroxybutanoic acid (GHB — the so-called "date-rape drug") (c) (E)-3-methyl-2-pentenoic acid (d) 2,2-dimethylpropan-1-ol (neopentyl alcohol)
Section C — Nomenclature with multiple groups
4.9∗ (moderate) Name each compound: (a) $HOCH_2CH_2COOH$ (b) $CH_3COCH_2COOH$ (c) $H_2NCH_2COOH$ (glycine) (d) $CH_3CH(NH_2)COOH$ (alanine)
4.10 (challenge) Draw β-alanine (3-aminopropanoic acid) and contrast its structure with α-alanine (2-aminopropanoic acid). The α form is one of the twenty standard amino acids; the β form is a metabolite but not a protein amino acid. Comment on how the position of the amine group affects the chemistry.
4.11 (moderate) Name each: (a) $CH_3CH(OH)CH(OH)CH_3$ (butane-2,3-diol; a metabolite) (b) $CH_3C(=O)CH_2CH_2C(=O)CH_3$ (hexane-2,5-dione — a diketone) (c) $HO-C_6H_4-OH$ (p-hydroquinone)
Section D — Nomenclature of aromatic compounds
4.12 (routine) Give the IUPAC or common name: (a) $C_6H_5-CH_3$ (toluene) (b) $C_6H_5-NH_2$ (aniline) (c) $C_6H_5-OH$ (phenol) (d) $C_6H_5-COOH$ (benzoic acid) (e) $O_2N-C_6H_4-OH$ at para (p-nitrophenol)
4.13 (moderate) Draw 3,5-dinitrobenzoic acid and 2,4,6-trinitrophenol (picric acid).
4.14 (challenge) Using the substituent priority rules, name the aromatic ring of acetaminophen as a substituted phenol. Confirm the IUPAC name given in the chapter: N-(4-hydroxyphenyl)acetamide. Why is the amide group (not the phenol) named as the parent (i.e., with the -amide suffix)?
Section E — Naming the anchor examples
4.15∗ (moderate) Confirm that the IUPAC name of aspirin is 2-(acetyloxy)benzoic acid: (a) Identify the parent compound (benzoic acid — why this and not phenol?). (b) Identify the substituent (acetyloxy — what does it mean?). (c) Verify the locant (why 2, not 3 or 4?).
4.16 (challenge) Ibuprofen has the IUPAC name (2RS)-2-[4-(2-methylpropyl)phenyl]propanoic acid. Break this name apart: (a) What is the parent chain? (b) What is the substituent on the phenyl ring? (c) What does 2RS mean? (d) Draw the structure from the name.
4.17 (challenge) Thalidomide's IUPAC name is 2-(2,6-dioxopiperidin-3-yl)-1H-isoindole-1,3(2H)-dione. This is intentionally complicated. Identify: (a) The parent heterocyclic ring (isoindole). (b) The -dione suffix (meaning two ketone-like carbonyls). (c) The 1H and 2H designations (which positions of the ring bear protons).
You are not expected to name thalidomide from scratch — this is a look at how IUPAC handles complex heterocycles.
Section F — Functional group interconversion preview
4.18 (moderate) Fill in the missing functional group: (a) Alcohol + carboxylic acid → ? (b) Ester + water (strong acid) → ? + ? (c) Nitrile + hot water → ? + ? (d) Amide + hot water (acid) → ? + ?
4.19 (moderate) The oxidation state of carbon changes when functional groups change. Rank the following in order of increasing oxidation at the central carbon: alkane — alcohol — aldehyde — carboxylic acid — $CO_2$.
4.20 (challenge) Several drugs contain a "bioisostere" — a replacement functional group that has similar electronic properties but different metabolism. Research what bioisostere is commonly used to replace a carboxylic acid, and why.
Section G — Application to synthesis preview
4.21 (challenge) Acetaminophen is synthesized industrially from p-nitrophenol: (a) Reduction of the nitro group gives what functional group? (b) Reaction of that functional group with acetic anhydride gives an N-acylated product. What is the product? (c) Name the product and confirm it is acetaminophen.
4.22 (challenge) Aspirin is synthesized from salicylic acid by acetylation of the phenol: (a) Which of salicylic acid's OH groups is acetylated to form aspirin? (b) Why is acetic anhydride used rather than acetic acid itself? (c) Write the byproduct of the reaction.
Section H — Biology-side vocabulary
4.23 (routine) Each of the 20 standard amino acids has one or more characteristic functional groups in its side chain. Match: (a) Serine — ? (b) Aspartate — ? (c) Lysine — ? (d) Cysteine — ? (e) Phenylalanine — ?
4.24 (moderate) The three-letter and one-letter abbreviations of the twenty standard amino acids. Memorize at least the ten most common (Gly, Ala, Val, Leu, Ile, Ser, Thr, Asp, Glu, Lys). Appendix A lists all twenty.
4.25 (challenge) A dipeptide is formed when two amino acids link via an amide bond. Draw the dipeptide Gly-Ala (glycine + alanine, in that order). Identify the amide bond and the free amine and free carboxylic acid.
Section I — Drawing practice
4.26 (routine) Draw: (a) 3,4-dimethylhexane (b) 2-bromo-3-methylbutanoic acid (c) 4-aminobutan-2-ol (d) cyclohexyl acetate
4.27 (moderate) Draw a structural isomer of each compound that has a different functional group (e.g., an ester vs. a carboxylic acid): (a) Ethanol (molecular formula $C_2H_6O$) (b) Acetone (molecular formula $C_3H_6O$)
Section J — Cumulative challenges
4.28 (challenge) A compound has molecular formula $C_3H_6O_2$ and is known to have a $pK_a$ of about 5. What is its most likely structure? (Multiple structures satisfy the formula; $pK_a$ narrows it down.)
4.29 (challenge) A compound has molecular formula $C_2H_4O$. Draw two constitutional isomers and identify the functional group in each. Compare their expected $pK_a$ values.
4.30 (challenge) The molecule $(CH_3)_2N-C(=O)-H$ is dimethylformamide (DMF), a common polar aprotic solvent. Identify the functional groups and discuss why it is a poor Brønsted acid despite containing a $C-H$.
Section K — Problems requiring searches
4.31 (challenge) Look up the IUPAC name of atorvastatin (Lipitor). Identify every functional group in it. How many chiral centers does it have?
4.32 (challenge) Look up the structure of caffeine. Identify the heterocyclic rings and the functional groups.
4.33 (challenge) Look up the structure of testosterone (the steroid hormone). Identify every functional group in it and count the chiral centers.
Section L — Preview problems
4.34 (challenge) The functional group "vinyl" refers to $CH_2=CH-$. The functional group "allyl" refers to $CH_2=CHCH_2-$. Draw vinyl chloride and allyl chloride and note the structural difference. Chapter 15 will explain why they are different in reactivity.
4.35 (challenge) A common synthetic strategy is functional group interconversion (FGI) — converting one group to another without changing the carbon skeleton. Given a starting material $RCH_2OH$, list three different products you could make by FGI (without looking anything up; reason from what you know).
Preview of Chapter 5
Chapter 5 returns to real chemistry — alkane conformations (why does ethane have a rotation barrier?) and the thermodynamics and kinetics of chemical reactions. You will use alkane nomenclature from Chapter 4 constantly.