Questions and Answers of Organic Chemistry 6th

Treatment of (S)-(+)-5-methyl-2-cyclohexenone with lithium dimethylcuprate gives, after protonolysis, a good yield of a mixture containing mostly a dextrorotatory ketone A and a trace of an optically
In the Krebs cycle (tricarboxylic acid, or citric acid, cycle), the enzyme citrate synthase catalyzes the synthesis of citrate from oxaloacetate and acetyl-CoA as shown in Fig. P22.96. Assuming that
Ethyl vinyl ether, EtO—CH=CH2, hydrolyzes in weakly acidic water to acetaldehyde and ethanol. Under the same conditions, diethyl ether does not hydrolyze. Quantitative comparisons of the hydrolysis
The enzyme dehydroquinate synthase catalyzes reactions (1) and (3) in the sequence shown in Fig. P22.97, which is part of the pathway for the biosynthesis of aromatic amino acids such as tryptophan;
Clavulanic acid (Fig. P22.98) is an inhibitor of b-lactamase enzymes, which cause penicillin resistance.Clavulanic acid inhibits b-lactamases by first reacting with the side-chain hydroxy group of an
Arrange the following three amines in order of increasing basicity. Cl- -NH₂ Cl- -NH₂ p-chloroaniline 4-chlorocyclohexanamine -NH₂ aniline
Draw the structure of each of the following compounds.(a) N-isopropylaniline (b) Tert-butylamine(c) 3-methoxypiperidine (d) 2,2-dimethyl-3-hexanamine(e) Ethyl 2-(diethylamino)pentanoate (f)
A chemist has treated p-chloroaniline with acetic anhydride and wants to separate the amide product from any unreacted amine. Design a separation based on the basicities of the two compounds.
Outline a preparation of N-ethyl-N-methylaniline from suitable starting materials using a reductive amination sequence. -N-CH3 CH₂CH3 N-ethyl-N-methylaniline
Outline a preparation of p-nitroaniline from aniline and any other reagents.
Identify the compound that has an M + 1 ion at m/z = 136 in its CI mass spectrum, an IR absorption at 3279 cm–1, and the following NMR spectrum: δ 0.91 (1H, s), δ 1.07 (3H, t, J = 7 Hz), δ 2.60
Explain how you could distinguish between the two compounds in each of the following sets using only 13C NMR spectroscopy.(a) 2,2-dimethyl-1-propanamine and 2-methyl-2-butanamine(b)
Arrange the amines within each set in order of increasing basicity in aqueous solution, least basic first.(a) Propylamine, ammonia, dipropylamine (b) Methyl 3-aminopropanoate, sec-butylamine, (c)
Explain why the quaternary ammonium salt A can be isolated in optically active form, but the trialkylammonium salt B cannot. CH3 T PhCH,−N*CH,CH, C1- CH₂CH₂CH3 A CH3 PhCH₂ NCH₂CH3
Using their solubilities in acidic or basic solution, design a separation of p-chlorobenzoic acid, p-chloroaniline, and p-chlorotoluene from a mixture containing all three compounds.
Provide reaction mechanisms for the following equations.(a) Eq. 23.17(b) Eq. 23.18(c) Suggest a reason why the reaction in Eq. 23.18 stops after two additions, and a third doesn’t occur in high
Provide a reaction mechanism for step 1, formation of the imine, in Eq. 23.22. EtNH₂ + H3C-C-CH3 acetone -H₂O [H₂C- NEt H3C-C-CH3 an imine (not isolated) H₂, Pt 30 psi EtOH NHET H3C-CH-CH3
Why is base (NaOH or KOH) added as a second step in each of the reactions shown in Eqs. 23.23 and 23.24? Ph—C−H+H_N—C(CH3)3 benzaldehyde tert-butylamine +
Quaternization (Sec. 23.6) does not occur in the reactions shown in Eqs. 23.26 and 23.27. Explain. NH₂ + H₂C=0 NaBH3CN HOAC CH3CN/H₂O Et—NH–CH,Ph + H,C=O benzylethylamine
Suggest two syntheses of N-ethylcyclohexanamine by reductive amination.
Give the major product formed when each of the following amines is treated exhaustively with methyl iodide and then heated with Ag2O. Explain your reasoning. (a) NH₂ CH3 (b) N. C Ph
Provide a reaction mechanism for the reaction shown in Eq. 23.36. NH₂ 5- + 3 Br₂ Br NH₂ Br Br + 3HBr (23.36)
Outline a preparation of sulfanilamide, a sulfa drug, from aniline and any other reagents. H₂N- 0=5 O -S—NH, sulfanilamide
Outline a preparation of each of the following compounds from aniline and any other reagents.(a) 2,4-dinitroaniline(b) Sulfathiazole, a sulfa drug H₂N- -NH- sulfathiazole H₂N- 2-aminothiazole
As shown in the following equation, when (R)-1-deuterio-1-butanamine is diazotized with nitrous acid in water, the alcohol product formed has the S configuration (D = 2H).(a) Give the stereochemical
(a) Write a Lewis structure for HNO2 in Eq. 23.50.(b) Write a mechanism for the reaction shown in Eq. 23.50. Me,NH + HNO, + H₂O Me₂N N,N-dimethylnitrosamine (89-90% yield) (23.50)
Design a synthesis of methyl orange (Eq. 23.49) using aniline as the only aromatic starting material. -N=N- methyl orange (yellow) an azo dye -NMe₂ H3O+ NH–N protonated methyl orange (red) pka =
(a) Which one of the following three amines can be prepared by either the Gabriel synthesis or the Staudinger reaction: 2,2-dimethyl-1-propanamine, 3-methyl-1-pentanamine, or N-butylaniline?(b)
Outline a synthesis of each of the following compounds from the indicated starting material and any other reagents. (a) N-(sec-butyl)-N-ethylaniline from chlorobenzene (b) (CH3)3C from
Outline syntheses of the following compounds from the indicated starting materials.(a) P-iodoanisole from phenol and any other reagents(b) M-bromoiodobenzene from nitrobenzene
(a) Could tert-butylamine be prepared by the Gabriel synthesis? If so, write out the synthesis. If not, explain why.(b) Propose a synthesis of tert-butylamine by another route.
Write a curved-arrow mechanism for each of the following reactions.(a) Ethyl isocyanate (CH3CH2—N=C=O) with ethanol to yield ethyl N-ethylcarba mate (b) Ethyl isocyanate with ethylamine to yield
When hexanamide is subjected to the conditions of the Hofmann rearrangement, pentanamine (A) is obtained as expected. However, a significant by-product is N,N′-dipen tyl urea (B). Explain the
What product is formed when 2-methylpropanamide is subjected to the conditions of the Hofmann rearrangement (a) In ethanol solvent? (b) In aqueous NaOH?
Illustrate the Brønsted basicity of (a) Morphine and (b) Mescaline (Fig. 23.4) by giving the structures of their conjugate acids.
Give the principal organic product(s) expected when p-chloroaniline or other compound indicated reacts with each of the following reagents.(a) Dilute HBr(b) CH3CH2MgBr in ether(c) NaNO2, HCl, 0°C(d)
On the package insert for the drug labetalol, used in the control of blood pressure and hypertension, is given the following structure:(a) Labetalol is claimed to be a salt. Explain by giving a more
Explain how you would distinguish the compounds within each set by a simple chemical test with readily observable results, such as solubility in acid or base, evolution of a gas, and so forth.(a)
(a) When anthranilic acid is treated with NaNO2 in aqueous HCl solution, and the resulting solution is treated with N,N-dimethylaniline, a dye called methyl red is formed. Give the structure of
Design a separation of a mixture containing the following four compounds into its pure components. Describe exactly what you would do and what you would expect to observe.nitrobenzene, aniline,
Amanda Amine, an organic chemistry student, has proposed the reactions given in Fig. P23.55. Indicate in each case why the reaction would not succeed as written. (a) (b) (d) -NH₂
Outline a sequence of reactions that would bring about the conversion of aniline into each of the following compounds.(a) Benzylamine(b) Benzyl alcohol(c) 2-phenylethanamine(d)
Give an explanation for each of the following facts.(a) The barrier to internal rotation about the N-phenyl bond in N-methyl-p-nitroaniline is considerably higher (42–46 kJ mol–1, or 10–11 kcal
Imagine that you have been given a sample of racemic 2-phenylbutanoic acid. Outline steps that would allow you to obtain pure samples of each of the following compounds from this starting material
Complete the reactions given in Fig. P23.65 by giving the structure(s) of the major product(s). Explain how you arrived at your answers. (a) NH3 + HNO₂ (d) (f) (h) Cl CI Cl -OH + HCl +
Outline a synthesis for each of the following compounds from the indicated starting materials and any other reagents. The starting material for the compounds in parts (a) through (e) is pentanoic
Offer an explanation for each of the following observations, including the structure of each product and the role of the quaternary ammonium salt.(a) When sodium benzenethiolate, Na+ PhS–, is mixed
A compound A (C22H27NO) is insoluble in acid and base but reacts with concentrated aqueous HCl and heat to give a clear aqueous solution from which, on cooling, benzoic acid precipitates. When the
In the NMR spectrum of a concentrated (4.5 M) aqueous solution of methylamine, the methyl group appears as a quartet when the solution pH = 1. At intermediate pH, the methyl group appears as a broad
Aniline has a UV spectrum with peaks at λmax 5 230 nm (ϵ = 8600) and 280 nm (ϵ = 1430). In the presence of dilute HCl, the spectrum of aniline changes dramatically: λmax 5 203 (ϵ = 7500) and 254
Imagine that you have samples of the following four isomeric amines, but you don’t know which is which. Explain how you could use proton NMR to distinguish among them.
Draw a curved-arrow mechanism for each of the rearrangement reactions given in Fig. P23.74. (a) PhCH,C-NH–O–C–Ph (b) Z N-Br+ KOH H₂N-C-CH₂CH₂-C-N3 Figure
(a) Propose a structure for an amine A (C4H9N), which liberates a gas when treated with NaNO2 and HCl. The 13C NMR spectrum of A is as follows, with attached protons in parentheses: δ 14(2), δ
Provide a curved-arrow mechanism for the example of the Bayliss –Hilman reaction shown in Fig. P23.75. Be sure that the role of the triethylamine catalyst is clearly indicated. H₂C=CH-C-OEt +
A chemist, Mada Meens, treated ammonia with pentanal in the presence of hydrogen gas and a catalyst in the expectation of obtaining 1-pentanamine by reductive amination.In addition to 1-pentanamine,
Around 1912, Swiss chemist Richard Willstätter (who subsequently was awarded the 1915 Nobel Prize in Chemistry) treated diamine A with methyl iodide and then with Ag2O and heat, whereupon a
Explain the transformations shown in Fig. P23.78 by showing relevant intermediates, providing analogies to known reactions, and, where appropriate, giving curved-arrow mechanisms. (a) (c) +
Explain the fact that the amines shown in Fig. P23.79, despite their similarities in structure, have considerably different basicities. conjugate-acid pka: Figure P23.79 N A 5.20 of A C 10.95 B 7.79
Amide A, δ-valerolactam, is a typical amide with a conjugate-acid pKa of 0.8. The two cyclic tertiary amines B and C also have typical conjugate-acid pKa values. In contrast, the conjugate-acid pKa
The Staudinger ligation is a method that has found increasing use in the growing field of chemical biology for labeling biomolecules, such as proteins, with fluorescent probes. Proteins possessing an
The rates of the reactions in Eqs. 10.71a–b are increased when the thiol is ionized by a base such as sodium ethoxide.Suggest a mechanism for Eq. 10.71a that is consistent with this observation,
Outline a synthesis of each of the following compounds from the indicated starting material. Begin each synthesis with a retrosynthetic analysis. (a) 2-methyl-3-pentanol from
The primary alcohol 2-methoxyethanol, CH3O—CH2CH2—OH, can be oxidized to the corresponding carboxylic acid with aqueous nitric acid (HNO3).The by-product of the oxidation is nitric oxide, NO. How
(a) Suppose 2,2-dimethyloxirane reacts with water that has been enriched with the oxygen isotope 18O. Indicate how the hydrolysis product would differ under acidic and basic conditions.(b) Show how
Complete the following reactions by giving the structures of the alcohol products. In part (b), show the stereochemistry of the product as well. (a) (b) bromocyclopentane 2Ph—Li +
(a) From what Grignard reagent can 3-methyl-1-pentanol be prepared by reaction with ethylene oxide, then aqueous acid?(b) From what epoxide and what higher-order cuprate reagent can
What organic product is formed (including its stereochemistry) when each of the following alkenes is treated with NMMO in the presence of H2O and a catalytic amount of OsO4?(a)
Tell whether each of the following compounds can be prepared by the reaction of a Grignard reagent with ethylene oxide. If so, show the reaction; if not, explain why and give a different synthesis
Phosphoric acid, H3PO4, has the following structure.(a) Draw the structure of trimethyl phosphate.(b) Draw the structure of the monoethyl ester of phosphoric acid. 0 HO-P-OН OH
Draw both the complete structure and the abbreviated structure, and give another name for each of the following compounds.(a) Isopropyl methanesulfonate (b) Methyl p-toluenesulfonate (c) Phenyl
An important class of substitution reactions that you will study in Chapter 21 is called nucleophilic acyl substitution. Substitution reactions of this type occur at the carbon of a carbonyl (C = O)
Considering the organic compound, classify each of the following transformations, some of which may be unfamiliar, as an oxidation, a reduction, or neither. For those that are oxidations or
Give the structure of two secondary alcohols that could be converted by HBr/H2SO4 into the corresponding alkyl bromide without rearrangement.
For each of the following balanced oxidation–reduction reactions, indicate which compound(s) are oxidized and which are reduced. Pd/C (a) H₂C=CH₂ + H₂ (b) CH3CH₂Br + Li+ AlH4 (c)
Contrast the products expected when 2-methyl-3-pentanol is treated with (a) HBr/H2SO4 or (b) Ph3PBr2. Explain.
How many moles of permanganate are required to oxidize one mole of toluene to benzoic acid? (Use H2O and protons to balance the equation.) Ph-CH3 + MnO toluene permanganate Ph-CO₂H + MnO₂ benzoic
Write a curved-arrow mechanism for the following oxidation of 2-heptanol, which proceeds in 82% yield. OH 2-heptanol + Ph3C+ BFT a relatively stable carbocation 2-heptanone + HBF4 + Ph3CH
How many electrons are involved in the oxidation of 1-propanethiol to each of the following compounds. (See Fig. 10.3 for detailed Lewis structures.)(a) 1-propanesulfonic acid, CH3CH2CH2SO3H (b)
How many chemically nonequivalent sets of hydrogens are in each of the following structures? (a) CH3CH₂ (c) H C=C CI Cl Cl H CH₂CH3 (d) (b) CH3O-CH₂-CH ỌCH₂CH3 Br T CH3CH₂O-CH-CH3 CI
(a) How many electrons are involved in the oxidation of triphenylphosphine (Ph3P;) to triphenylphosphine oxide (Ph3P = O)? Show your reasoning.(b) Draw a resonance structure for triphenylphosphine
The following triester is a powerful explosive, but is also a medication for angina pectoris (chest pain). From what inorganic acid and what alcohol is it derived? ONO₂ T CH₂- ONO₂ ONO₂ L
Give the product expected, if any, when 1-butanol (or other compound indicated) reacts with each of the following reagents.(a) Concentrated aqueous HBr, H2SO4 catalyst, heat (b) Cold aqueous
Arrange the compounds or ions within each set in order of increasing acidity (decreasing pKa) in solution. Explain your reasoning. (a) propyl alcohol, isopropyl alcohol, tert-butyl
When tert-butyl alcohol is treated with H218O (water containing the heavy oxygen isotope 18O) in the presence of a small amount of acid, and the tert-butyl alcohol is re-isolated, it is found to
Outline a synthesis for the conversion of enantiomerically pure (R)-CH3CH2CHD—OH into each of the following isotopically labeled compounds. Assume that Na18OH or H218O is available as needed.(a)
(a) When the rate of oxidation of isopropyl alcohol to acetone is compared with the rate of oxidation of a deuterated derivative, a primary isotope effect (Sec. 9.5D) is observed (see part (a) of
Chemist Stench Thiall, intending to prepare the disulfide A, has mixed one mole each of 1-butanethiol and 2-octanethiol with I2 and base. Stench is surprised at the low yield of the desired compound
A police officer, Lawin Order, has detained a driver, Bobbin Weaver, after observing erratic driving behavior. Administering a breathalyzer test, Officer Order collects 52.5 mL of expired air from
The Swern oxidation, shown in Fig. P10.61, is a very mild two-step procedure for the oxidation of primary and secondary alcohols.(a) How many electrons are involved in this oxidation? Explain.(b)
In a laboratory are found two different compounds: A (melting point 24.7°C) and B (melting point 21°C). Both compounds have the same molecular formula (C7H14O), and both can be resolved into
When the hydration of fumarate is catalyzed by the enzyme fumarase in D2O, only (2S,3R)-3-deuteriomalate is formed as the product. (Each—CO–2 group is the conjugate base of a carboxylic acid
Monoamine oxidase (MAO) is an enzyme that catalyzes the oxidation of certain biologically important amines. One form of the enzyme catalyzes the following oxidation of serotonin, an important
Primary alcohols, when treated with H2SO4, do not dehydrate to alkenes under the usual conditions. However, they do undergo another type of “dehydration” to form ethers if heated strongly in the
The reactions shown in Fig. P10.67 all involve conversion of the alcohol oxygen into a good leaving group, followed by the reaction of the resulting compound with a nucleophile provided by the
Buster Bluelip, a student repeating organic chemistry for the fifth time, has observed that alcohols can be converted into alkyl bromides by treatment with concentrated HBr. He has proposed that, by
The trichloromethyl anion, –:CCl3, which is the conjugatebase anion of chloroform (HCCl3), is stabilized not only by the polar effect of the chlorines but also by resonance:Show the orbital overlap
(a) Describe the π bond for the double bond in Ph3P=CH2; that is, what orbitals are involved on carbon and phosphorus?(b) Draw a resonance structure for the compound in part (a) that maintains the
Outline a Williamson ether synthesis for tert-butyl methyl ether. CH3 H3C-C-0-CH3 I CH3 tert-butyl methyl ether
Arrange the ions in the following list in order of increasing acidity, and explain your reasoning. | Н A H3C B CH3 H3C C H С Н D
Predict the major product in each case that would be obtained when the following epoxide reacts with water under (a) Basic conditions; (b) Acidic conditions. (CH3)3C- CH₂

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