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Questions and Answers of Organic Chemistry

The proton decoupled 13C NMR spectrum of pyridine will display how many peaks? (a) One; (b) Two; (c) Three;(d) Four; (e) Five.
This problem introduces two literature syntheses of indole derivatives, and you are asked to come up with plausible mechanisms for them. Divide your team in two, each group concentrating on one of
The sequence in the margin is a rapid synthesis of one of the heterocycles in this chapter. Draw the structure of the product, which has 1H NMR spectrum F. 'H NMR 1 H 1 H 3 H 1H. 9.2 8.5 8.4
Treatment of a 3-acylindole with LiAlH4 in (CH3CH2)2O reduces the carbonyl all the way to a CH2 group. Explain by a plausible mechanism. CR Excess LIAIH, (CH,CH,),0, A CH,R OH LIAIH, (Compare
The commercial synthesis of a useful heterocyclic derivative requires treatment of a mixture of aldopentoses (derived from corncobs, straw, etc.) with hot acid under dehydrating conditions. The
Heterocycle C, C5H6O, exhibits 1H NMR spectrum C and is converted by H2 and Raney nickel into compound D, C5H10O, with spectrum D. Identify compounds C and D. (Note: The coupling constants of the
Compound A, C8H8O, exhibits 1H NMR spectrum A. Upon treatment with concentrated aqueous HCl, it is converted almost instantaneously into a compound that exhibits spectrum B. What is compound A, and
At which position(s) do you expect 3-acetylquinoline (margin) to undergo nitration in the presence of a mixture of sulfuric and fuming nitric acids? Will this reaction be faster or slower than
Quinolines are heterocycles that are widely used in medicinal chemistry because of the diversity of biological activity — including anticancer utility — that their derivatives display. A short
Azacyclohexanes (piperidines) can be synthesized by reaction of ammonia with cross-conjugated dienones: ketones conjugated on both sides with double bonds. Propose a mechanism for the following
(a) The compound shown in the margin, with the common name 1,3-dibromo-5,5-dimethylhydantoin, is useful as a source of electrophilic bromine (Br+) for addition reactions. Give a more systematic name
The Darzens condensation is one of the older methods (1904) for the synthesis of three-membered heterocycles. It is most commonly the reaction of a 2-halo ester with a carbonyl derivative in the
Derivatives of benzimidazole possess biological activity somewhat like that of indoles and purines. Benzimidazoles are commonly prepared from benzene-1,2-diamine. Devise a short synthesis of
Starting with benzenamine (aniline) and pyridine, propose a synthesis for the antimicrobial sulfa drug sulfapyridine. -N -NHS- -NH2 Sulfapyridine
Reserpine is a naturally occurring indole alkaloid with powerful tranquilizing and antihypertensive activity. Many such compounds possess a characteristic structural feature: one nitrogen atom at a
Isoxazoles (Problem 36) have taken on increased significance as synthetic targets, because they are found in the structures of some recently discovered naturally occurring molecules that show promise
Porphyrins are polyheterocyclic constituents of hemoglobin and myoglobin, the molecules that transport molecular oxygen in living systems, of the cytochromes, which also play central roles in
Chelidonic acid, a 4-oxacyclohexanone (common name, g-pyrone), is found in a number of plants and is synthesized from acetone and diethyl ethanedioate. Formulate a mechanism for this
Melamine, or 2,4,6-triaminotriazine, is a toxic heterocyclic compound that has been implicated in the illnesses and deaths of both house pets and humans who ingested melamine-contaminated food. As
The structures of caffeine, the principal stimulant in coffee, and theobromine, its close relative in chocolate, are given in Section 25-8. Propose an efficient synthetic method to convert
Propose a synthesis of each of the following substituted heterocycles, using synthetic sequences presented in this chapter. (a)(b)(c)(d) H3C CH3 H3C CH3
Give the products expected of each of the following reactions. (a)(b)(c)(d)(e) H3C CH3 Fuming H,SO,, 270°C
Give the expected major product(s) of each of the following reactions. Explain how you chose the position of substitution in each case. (a)(b)(c)(d)(e) Cl, СООCH}
1-Hetero-2,4-cyclopentadienes can be prepared by condensation of an α-dicarbonyl compound and certain heteroatom-containing diesters. Propose a mechanism for the following pyrrole synthesis.How
Give the product of each of the following reactions. (a)(b) Ο CH,NH2 ο
Each of the heterocyclopentadienes in the margin contains more than one heteroatom. For each one, identify the orbitals occupied by all lone electron pairs on the heteroatoms and determine whether
Rank the following compounds in increasing order of basicity: water, hydroxide, pyridine, pyrrole, ammonia.
Propose reasonable mechanisms for the following transformations. (a)(b)(c) 1. SnCl, (a Lewis acid), CH,CI, 2. H', Н.О ČH,OH
The penicillins are a class of antibiotics containing two heterocyclic rings that interfere with the construction of cell walls by bacteria (Chemical Highlight 20-2). The interference results from
Give the expected product of each of the following reaction sequences. (a)(b)(c) H 1. LIAIH,, (CH,CH,),O 2. H., Н.О H
Identify by name (either IUPAC or common) as many of the heterocyclic rings contained in the structures shown in Table 25-1 as you can. Top Ten U.S. Prescription Drugs (Ranked by 2007 Sales) by
Identify by name (either IUPAC or common) as many of the heterocyclic rings contained in the structures shown in Table 25-1 as you can. Top Ten U.S. Prescription Drugs (Ranked by 2007 Sales) by
Name or draw the following compounds. (a) cis-2,3-Diphenyloxacyclopropane; (b) 3-azacyclobutanone; (c) 1,3-oxathiacyclopentane; (d)
One of the statements below is correct about the sugar shown. Which one? (a) It is a nonreducing sugar. (b) It forms an osazone. (c) It exists in two anomeric forms. (d) It
The methyl glycoside of mannose is made by treating the sugar with (a) AlBr3, CH3Br; (b) Dilute aqueous CH3OH; (c) CH3OCH3 and LiAlH4; (d) CH3OH, HCl; (e) Oxacyclopropane,
The methyl glycoside of mannose is made by treating the sugar with (a) AlBr3, CH3Br; (b) Dilute aqueous CH3OH; (c) CH3OCH3 and LiAlH4; (d) CH3OH, HCl; (e) oxacyclopropane,
Which one of the following statements is true about the oxacyclohexane conformer of the sugar β-D-(1)-glucopyranose? (a) One OH group is axial, but all remaining substituents are
What kind of sugar is the compound shown in the margin? (a) An aldopentose; (b) A ketopentose; (c) An aldohexose; (d) A ketohexose СНО H- OH CH,OH OH НОСН-СНCHCH-CH
Most natural sugars have a stereocenter that is identical to that in (R)-2,3-dihydroxypropanal, shown as a Fischer projection in the margin. What is the (very popular) common name for this
This problem is meant to encourage you to think as a team about how you might establish the structure of a simple disaccharide, with some additional information at your disposal. Consider d-lactose
Vitamin C is present almost universally in the plant and animal kingdoms. (According to Linus Pauling, mountain goats biosynthesize from 12 to 14 g of it per day.) Animals produce it from D-glucose
Vitamin C is present almost universally in the plant and animal kingdoms. (According to Linus Pauling, mountain goats biosynthesize from 12 to 14 g of it per day.) Animals produce it from D-glucose
Fischer’s solution to the problem of sugar structures was actually much more difficult to achieve experimentally than implies. For one thing, the only sugars that he could readily obtain from
Write or draw the missing reagents and structures (a) through (g). What is the common name of (g)? The preceding sequence (called the Weerman degradation) achieves the same end as what procedure
(a) A mixture of (R)-2,3-dihydroxypropanal (D-glyceraldehyde) and 1,3-dihydroxyacetone that is treated with aqueous NaOH rapidly yields a mixture of three sugars: D-fructose, D-sorbose, and racemic
Glucose reacts with ammonia in the presence of a trace of acid to give predominantly β-D- glucopyranosylamine. Propose a reasonable mechanism for this transformation. Why is only the hydroxy group
The disaccharide at the terminus of the oligosaccharide attached to the surface of type B red blood cells is an α-D-galactopyranosyl-β-D-galactopyranose. The linkage is an acetal from C1 of the
Identify and, using the information in Sections 24-1 and 24-11, provide names for the carbohydrates that are contained in the structure of stevioside.
Trehalose, sophorose, and turanose are disaccharides. Trehalose is found in the cocoons of some insects, sophorose turns up in a few bean varieties, and turanose is an ingredient in low-grade honey
Is α-lactose capable of mutarotation? Write an equation to illustrate your answer.
Classify each of the following sugars and sugar derivatives as either reducing or nonreducing. (a) D-Glyceraldehyde; (b) D-arabinose; (c) β-D-arabinopyranose 3,4-acetone
(a) Write a detailed mechanism for the isomerization of β-D-fructofuranose from the hydrolysis of sucrose into an equilibrium mixture of the β-pyranose and β-furanose forms. (b) Although
Illustrate the results of chain elongation of D-talose through a cyanohydrin. How many products are formed? Draw them. After treatment with warm HNO3, does the product(s) give optically active or
In each of the following groups of three d aldoses, identify the two that give the same product upon Ruff degradation. (a) Galactose, gulose, talose; (b) Glucose, gulose, idose; (c)
Is it possible for two different diastereomeric aldoses to give the same product upon KilianiFischer chain elongation? Why or why not?
D -Sedoheptulose is a sugar intermediate in a metabolic cycle (the pentose oxidation cycle) that ultimately converts glucose into 2,3-dihydroxypropanal (glyceraldehyde) plus three equivalents of CO2.
Of the four aldopentoses, two form diacetals readily when treated with excess acidic acetone, but the other two form only monoacetals. Explain.
(a) Explain why the oxygen at C1 of an aldopyranose can be methylated so much more easily than the other oxygens in the molecule. (b) Explain why the methyl ether unit at C1 of a fully
Which of the following glucoses and glucose derivatives are capable of undergoing mutarotation? (a) α-D-Glucopyranose; (b) methyl α-D-glucopyranoside; (c) methyl
(a) Which of the aldopentoses (Figure 24-1) would give optically active alditols upon reduction with NaBH4? (b) Using d-fructose, illustrate the results of NaBH4 reduction of a ketose. Is the
Draw the Fischer projection of an aldohexose that will give the same osazone as (a) D-(-)-idose (b) L-(+)-altrose.
Write the expected products of the reaction of each of the following sugars with (i) Br2, H2O; (ii) HNO3, H2O, 60°C; (iii) NaBH4, CH3OH; and (iv) excess C6H5NHNH2, CH3CH2OH,
What are the products (and their ratios) of periodic acid cleavage of each of the following substances: (a) 1,3-dihydroxyacetone; (b) rhamnose (Problem 34); (c) glucitol. Problem
Ketoses show positive Fehling’s and Tollens’s tests not only by oxidation to α-dicarbonyl compounds, but through a second process: Ketoses isomerize to aldoses in the presence of base. The
Draw the most stable pyranose conformation of each of the following sugars. (a) α-D-Arabinose; (b) β-D-galactose; (c) β-D-mannose; (d) α-D-idose.
Are any of the sugars in Problem 38 incapable of mutarotation? Explain your answer. Problem 38(a) (-)-Threose; (b) (-)-allose; (c) (-)-ribulose; (d) (+)-sorbose; (e)
For each of the following sugars, draw all reasonable cyclic structures, using either Haworth or conformational formulas; indicate which structures are pyranoses and which are furanoses; and label a
Redraw each of the following sugars in open-chain form as a Fischer projection, and find its common name. (a)(b)(c)(d) Н Он Н ОН OHC CH2OH н ОН НО н
Identify the following sugars, which are represented by unconventionally drawn Fischer projections. (It will be necessary to convert these projections into more conventional representations without
Draw open-chain (Fischer-projection) structures for L-(+)-ribose and L-(-)-glucose (see Exercise 24-2). What are their systematic names? Exercise 24-2Give a systematic name for (a) D-(-)-ribose
To which classes of sugars do the following monosaccharides belong? Which are d and which are L? CH,OH СНО H- OH НО H. СНО H- OH Но- H- H- -OH HO H OH (а) НОСН OH (b) Но— H-
The designations d and l as applied to sugars refer to the configuration of the highest-numbered stereocenter. If the configuration of the highest numbered stereocenter of d-ribose (Figure 24-1) is
A compound with m.p. = -22°C has a parent peak in its mass spectrum at m/z = 113. The 1H NMR spectrum shows absorptions at δ = 1.2 (t, 3 H), 3.5 (s, 2 H), and 4.2 (q, 2 H). The IR spectrum exhibits
When acid A (margin) is heated to 230°C, CO2 and H2O are evolved and a new compound is formed. Which one?(a)(b) HO2CCH2CH2CH2CH3 (c)(d) CH3CH2CH(CO2H)2 (e) CO,H HO,C(CH2),CH CO,H А
The reaction of ethyl butanoate with sodium ethoxide in CH3CH2OH gives (a)(b)(c)(d) ОН CH;CH,CH,CHCHCO,CH,CH3 ČH,CH3
Two of the following four compounds are more acidic than CH3OH (i.e., two of these have Ka greater than methanol). Which ones? (a) A and B; (b) B and C; (c) C and D; (d) D and
Two of the following four compounds are more acidic than CH3OH (i.e., two of these have Ka greater than methanol). Which ones? (a) A and B; (b) B and C; (c) C and D; (d) D and
Split your team in two, each group to analyze one of the following reaction sequences by a mechanism (13C 5 carbon-13 isotope).
Propose a synthesis of ketone C, which was central in attempts to synthesize several antitumor agents. Start with aldehyde A, lactone B, and anything else you need. СНО H,C H2C A B C
Using methods reverse polarization, propose a simple synthesis of each of the following molecules. (a)(b)(c) НО О CH2=CHCHCCH2C,H5
A short construction of the steroid skeleton (part of a total synthesis of the hormone estrone) is shown here. Formulate mechanisms for each of the steps. 6. CH, O: KOH, CH,OH, A CH;0 CH, CH3
Some of the most important building blocks for synthesis are very simple molecules. Although cyclopentanone and cyclohexanone are readily available commercially, an understanding of how they can be
The following ketones cannot be synthesized by the acetoacetic ester method (why?), but they can be prepared by a modified version of it. The modification includes the preparation (by Claisen
β-Dicarbonyl compounds condense with aldehydes and ketones that do not undergo self-aldol reaction. The products are α,β-unsaturated dicarbonyl compounds, and the process goes by the colorful name
The nootkatones are bicyclic ketones responsible for the flavor and aroma of grapefruits. Nootkatones also repel termites and are used commercially to protect wood structures from termite
Write chemical equations to illustrate all primary reaction steps that can occur between a base such as ethoxide ion and a carbonyl compound such as acetaldehyde. Explain why the carbonyl carbon is
(a) On the basis of the following data, identify unknowns A, found in fresh cream prior to churning, and B, possessor of the characteristic yellow color and buttery odor of butter. (b) What kind
Give the products of the following reactions. (a)(b)What are the results of reaction of the substance formed in (b) with each aldehyde in Problem 41, followed by hydrolysis in the presence of
Give the products of reaction of the following aldehydes with catalytic N-dodecylthiazolium bromide. (a) (CH3)2CHCHO; (b) C6H5CHO; (c) cyclohexanecarbaldehyde; (d) C6H5CH2CHO.
Using the methods described in this chapter, design a multistep synthesis of each of the following molecules, making use of the indicated building blocks as the sources of all the carbon atoms in
Based on the mechanism presented for the Pd-catalyzed reaction of a halobenzene with hydroxide ion, write out a reasonable mechanism for the Pd-catalyzed reaction of Problem 38(a). Problem
Give the likely products of each of the following reactions. All are carried out in the pre sence of a Pd catalyst, a ligand for the metal such as a phosphine, and heat. (a)(b) Br +
Write out, in full detail, the mechanism of the Michael addition of malonic ester to 3-buten-2-one in the presence of ethoxide ion. Be sure to indicate all steps that are reversible. Does the overall
Based on your answer to Problem 35, predict whether or not water should catalyze the decarboxylation of each of the following compounds. For each case in which your answer is yes, draw the transition
Carbonic acid, H2CO3, is commonly assumed to be an unstable compound that easily decomposes into a molecule of water and a molecule of carbon dioxide: H2CO3 → H2O + CO2↑. Indeed, the evidence of
Use the Michael Addition methods , with other reactions if necessary, to synthesize each of the following compounds. In each case, your starting materials should include one aldehyde or ketone and
Devise a synthesis for each of the following four compounds by using the malonic ester synthesis. (a)(b)(c)(d) HO
Devise a preparation of each of the following ketones by using the acetoacetic ester synthesis. (a)(b)(c)(d) OCH,CH3
Do you think that propanedial, shown in the margin, can be easily prepared by a simple Claisen condensation? Why or why not? HÖCH,CH Propanedial
Suggest a synthesis of each of the following β-dicarbonyl compounds by Claisen or Dieckmann condensations.(a)(b)(c)(d)(e)(f)(g) оо -CH,CCHCOCH,CH3

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