Questions and Answers of Organic Chemistry 6th

(a) Sketch a reaction free-energy diagram for acid-catalyzed enol formation using the mechanism in Eq. 22.17b as your guide. Assume that the second step, proton removal from the α-carbon, is
ϵ-Caprolactam is polymerized to nylon-6 when it is heated with a catalytic amount of water.Write a mechanism for the polymerization, showing clearly the role of the water. O NH E-caprolactam HO
Ordinary litmus paper turns red at pH values below about 3. Show that a 0.1 M solution of acetic acid (pKa = 4.76) will turn litmus red, and that a 0.1 M solution of phenol (pKa = 9.95) will not.
Many 1,2-diols, under the acidic conditions used for dehydration of alcohols, undergo a reaction called the pinacol rearrangement:Propose a curved-arrow mechanism for this reaction, and explain why
Calculate n in the dn notation for ferrocene, Cp2Fe.
In an effort to duplicate in the laboratory the natural processes that resemble the cyclization of 2,3-oxidosqualene, chemists in 1970 and 1980 carried out the conversions shown in Fig. P17.51. Give
One interesting use of Diels–Alder reactions is to trap very reactive alkenes that cannot be isolated and studied directly. One compound used as a diene for this purpose is diphenylisobenzofuran,
Give a complete balanced equation for the oxidation of ethanol to acetic acid by chromate ion.
Nitration of phenyl acetate (compound A) results in para substitution of the nitro group. However, nitration of dimethyl phenyl phosphate (compound B) results in meta substitution of the nitro group.
Suppose that the following curved-arrow notation and resonance structures for TPP ylid have been proposed in an attempt to demonstrate that the charges in the ylid can be neutralized by resonance.
Nicotine undergoes phase I metabolism by a reaction with CyP450 that gives a compound A. In the presence of water, compound A is converted spontaneously into compound B, with which it is in
When 1-buten-3-yne undergoes HCl addition, two compounds A and B are formed in a ratio of 2.2 : 1. Neither compound shows a C ≡ C stretching absorption in its IR spectrum. Compound B reacts with
Around 1900, Moses Gomberg, a pioneer in freeradical chemistry, prepared the triphenylmethyl radical, Ph3C?, sometimes called the trityl radical (trityl 5 triphenylmethyl).(a) Explain why the trityl
(a) Triphenylmethane [structure in part (b)] has a pKa of 31.5 and, although an alkane, it is almost as acidic as a 1-alkyne. (Most alkanes have pKa ≽ 55.) By considering the structure of its
The amount of anti-addition in the chlorination of alkenes varies with the structure of the alkene, as shown in the following table.Suggest a reason for the variation in the stereochemistry of
(a) For each of the two reactions shown in Fig. P17.58, suggest a mechanism that is consistent with all of the experimental facts given.Experimental observations:(1) Both reactions conform to the
In the late 1970s, a graduate student at a major West Coast university began synthesizing new classes of drugs and testing them on himself. After being expelled from the university, he began making
The reaction given in Fig. P17.59 occurs by a mechanism called the SN2′ mechanism, which is a bimolecular substitution that occurs by reaction of the nucleophile at an allylic carbon. In this
Consider the following mechanism for Eq. 18.19. Identify the process associated with each step. Counting electrons at each stage may help you. Pd(PPH3)4 Ph3P Ph,P Pd(PPh 3)2
Arrange the following compounds according to increasing rate of elimination with NaOEt in EtOH. What is the product in each case? Ph H C=C A Ph Br Ph H C=C B Br Ph Ph H C=C C Ph Cl H H =C D Br Ph
Within each set, rank the compounds in order of increasing rates of their SN2 reactions. Explain your reasoning.(a) Benzyl bromide, (3bromopropyl) benzene, pbromotoluene (b) 1bromocyclohexene,
Within each series, arrange the compounds according to increasing rates of their reactions by the SN1–E1 mechanism. Explain your reasoning. (b) Br -C=CH, A Cl امي
Noting the LX character of the allyl ligand in Table 18.1, sketch the allyl–metal interaction, showing both L-type and X-type bonds. Use M as a general metal. TABLE 18.1 Some Typical Ligands Used
Which of the two compounds in each of the following sets should react more rapidly in a nucleophilic aromatic substitution reaction with CH3O¯ in CH3OH? Explain your answers.
Calculate the oxidation state of the metal in each of the following complexes. (a) O Mn-O- permanganate (b) Pd(PPH3)4 tetrakis(triphenylphosphine) palladium (c) Cp₂Fe ferrocene
What is the oxidation state of the metal in the starting material in the following reaction? How does it change, if at all, as a result of the reaction? Is this reaction an oxidation, a reduction, or
(a) What is the electron count for the Rh complex shown in Problem 18.9c?(b) Sestamibi (trade name Cardiolite®) is a complex of 99Tc(I) (a radioactive γ-ray emitter) that is widely used for cardiac
How many CO ligands would be accommodated by Fe(0) if we assume that the resulting complex follows the 18-electron rule?
Using the 18-electron rule, explain why V(CO)6 can be easily reduced to [V(CO)6]¯.
A student has written the following ligand substitution reaction, claiming that it changes the oxidation state of the metal by one unit. What is wrong with this reasoning? CI+ Pd(PPH3)4CIPd(PPh3)3 +
Use a hybridization argument to predict the geometry of (a) The [Zn(CN)4]2– ion; (b) The neutral compound Pd(PPh3)4.
When iodobenzene and propene are subjected to the conditions of the Heck reaction, two constitutionally isomeric products are formed. What are they? Why are two products formed?
Complete the following Pd(0)-catalyzed Suzuki reactions by giving the coupling product. For parts (b) and (c), include the stereochemistry of the products. (a) 2-naphthaleneboronic acid (c)
The product of a Heck reaction is, like the starting material, an alkene. Why doesn’t a Heck reaction of the product compete with the reaction of the starting alkene?
What product is expected when cyclopentene reacts with iodobenzene in the presence of triethylamine and a Pd(0) catalyst?
Provide two different reaction sequences that could be used to synthesize 4-methoxy-3´-methylbiphenyl. Both sequences, however, should start with both p-bromoanisole and m-bromotoluene. H₂C -OCH3
Draw a curved-arrow mechanism for the last (acid-catalyzed hydrolysis) step of Eq. 18.50. MgBr OCH3 + B(OCH3)3 B(OCH3)3 MgBr OCH3 H₂0 H₂O B(OH)2 OCH3 + 3 CH3OH 2+ + Mg²+ + Br (18.50)
Show that the equilibrium mixture produced by alkene metathesis of two completely different alkenes with the following general structures contains 10 different alkenes.
Give the structure of the major product formed in each case when the reactant(s) shown undergo alkene metathesis in the presence of an appropriate ruthenium catalyst.
Suggest an alkene metathesis reaction that would yield each of the following compounds as a major product. (c) F H₂C H (-)-citronellol (oil of roses) H D OH CH₂OH (b) CO₂H
Suggest a mechanism for the oxo reaction (Eq. 18.63) involving intermediates that are consistent with the 16- and 18-electron rules. H,C=CH2 + H2 + CO ethylene HCO (CO)4 100-120
Which of the two phenols in each set is more acidic? Explain.(a) 2,5-dinitrophenol or 2,4-dinitrophenol(b) phenol or m-chlorophenol(c) OH CH 0 or OH CH=0
The following compound, unlike most phenols, is soluble in neutral aqueous solution, but insoluble in aqueous base. Explain this unusual behavior. HỌ -N(CH3)3 CI
Given the structure of phenanthrene, draw structures of(a) 9,10-phenanthroquinone (b) 1,4-phenanthroquinone phenanthrene L 5 00 لا a N 10
Outline a preparation of each of the following compounds from the indicated starting material and any other reagents.(a) p-nitroanisole from p-nitrophenol (b) 2-phenoxyethanol from phenol
(a) Using the fishhook notation, derive the important resonance structures of the vitamin C-derived radical in Eq. 18.81b.(b) In the laboratory, the radical derived from vitamin E can react with a
Consider the detailed structure of the semiquinone? QH shown in Eq. 18.79a.(a) There are two possible structures for this semiquinone; draw them both.(b) Show the resonance structures for either of
Draw the important resonance structures of the radicals formed when each of the following reacts with R?, a general free radical.(a) Vitamin E (b) BHT
Electron transport takes place in the membrane of cellular organelles called mitochondria. What is it about the structure of ubiquinone and its reduction products that ensures their localization
Give the principal organic product(s) formed in each of the following reactions. (a) o-cresol + Br₂ in CCl4 (b) m-chlorophenol (c) + HNO3, low temperature || p-bromophenol + H₂C-C-Cl AlCl3 H₂O+
(a) Give the structure of the product formed in the reaction of urushiol with K2CO3 and a large excess of methyl iodide.(b) Would this compound be likely to provoke the same allergic skin response as
Compound A is a by-product of the autoxidation of cumene, and compound B is a by-product of the acid-catalyzed conversion of cumene hydroperoxide to phenol and acetone.Draw a curved-arrow mechanism
Give the product(s) (if any) expected when p-iodotoluene or other compound indicated is subjected to each of the following conditions. (a) CH₂OH, 25 °C (b) CH3O- in CH₂OH, 25 °C (c) CH₂O,
Predict the product of the Stille reaction between ethynyltrimethylstannane, HC ≡ C—Sn(CH3)3, and phenyl triflate, PhOTf, in the presence of Pd(PPh3)4 and excess LiCl.
The reaction given in Fig. P18.74 occurs readily at 95°C (X = halogen). The relative rates of the reaction for the various halogens are 290 (X = F), 1.4 (X = Cl), and 1.0 (X = Br). When a nitro
Give the structure for each of the following compounds.(a) Isobutryaldehyde (b) Valerophenone(c) O-bromoacetophenone (d) G-chlorobutyraldehyde(e) 3-hydroxy-2-butanone (f)
Outline a synthesis of tricarballylic acid from diethyl fumarate and any other reagents. EtO₂C C=C H H CO₂Et diethyl fumarate HOC–CH–CH,—COH CH,—CO,H tricarballylic acid
Suggest a sequence of reactions for carrying out each of the following conversions.(a) Benzoic acid to Ph3C—OH (triphenylmethanol)(b) Butyric acid to 3-methyl-3-hexanol(c) Isobutyronitrile to
Bearing in mind the hydrolysis reaction discussed in Problem 22.94, predict the final product of the reaction sequence shown in Fig. P22.95. CH3OCH₂Cl + Ph3P Figure P22.95 Bu-Li H3O+, H₂O,
Outline a synthesis of p-dipropylaminoacetophenone from chlorobenzene.
(+)-Coniine is the toxic component of the poison hemlock, the plant believed to have killed Socrates. Coniine has the molecular formula C8H17N. When coniine is exhaustively methylated, and the
A compound has IR absorptions at 3400–3500 cm–1 and the following NMR spectrum: δ 2.07 (6H, s), δ 2.16 (3H, s), δ 3.19 (broad, exchanges with D2O), δ 6.63 (2H, s). To which one of the
Determine whether the following carbohydrate derivative, shown in Fischer projection, has the D or L configuration. HOCH₂- Н- но- OH -Н -ОН -Н CO₂H
When 1,5-dibromopentane reacts with ammonia, among several products isolated is a water- soluble compound A that rapidly gives a precipitate of AgBr with acidic AgNO3 solution. Compound A is
Draw at least two Fischer projections for each of the following molecules. S S R HOC–CH–CH CH–CH,OH I T T OH OH OH (b) (S)-2-butanol
Indicate whether the structures in each of the following pairs are enantiomers, diastereomers, or identical molecules.
Convert the Fischer projection of β-d-glucopyranose into a Haworth projection, a line-and-wedge structure, and a chair conformation. (A Haworth projection is defined below.)
Outline a sequence of reactions by which d-glucose can be converted into methyl 2,3,4,6-tetra-O-acetyld-glucopyranoside. ACO ACOCH₂ ACO- OCH 3 OAC methyl 2,3,4,6-tetra-O-acetyl-D-glucopyranoside
Name each of the following aldoses. In part (a), work back to the Fischer projection and consult Fig. 24.3. In part (b), decide which carbons have configurations different from those of glucose, and
Which of the following are Fischer projections of a meso compound?
Which pair of the following aldoses are epimers and which pair are enantiomers?
Provide reaction mechanisms for the following equations.(a) Eq. 24.12a (b) Eq. 24.12b H3C-CH-CH2CH2CH2-CH=0 T OH H3C-CH-CH2CH2-CH=0 T OH HO HO Н H 0 CH3 CH3 (24.12a) (24.12b)
Consider the β-D-pyranose forms of glucose and talose (Fig. 24.3). Suggest one reason why talose contains a smaller fraction of β-pyranose form than glucose. Н- Н- H Н CH=0 -OH
Draw a Fischer projection, a Haworth projection, and a line-and wedge structure for each of the following compounds. For the pyranoses, draw the two possible chain conformations.(a)
Using the curved-arrow notation, fill in the details for acid-catalyzed mutarotation of glucopyranose shown in Eq. 24.19. Begin by protonating the ring oxygen.
From the specific rotations shown in Eq. 24.18, calculate the percentages of α- and β-D- glucopyranose present at equilibrium.Compare your answer to the data given in Table 24.1. TABLE 24.1
Using the curved-arrow notation, fill in the details for base-catalyzed mutarotation of glucopyranose. Begin by removing a proton from the hydroxy group at carbon-1.
Draw a conformational representation of(a) β-D-allopyranose (b) α-D-idofuranose
(a) Assuming the presence of acids (AH) and bases (A¯) as needed, give a curved-arrow mechanism for the isomerization of isopentenyl pyrophosphate into dimethylallyl pyrophosphate.(b) In some
Consider the hydrolysis of geranyl pyrophosphate to geraniol shown in Eq. 17.46.(a) What isotopically substituted derivative of geranyl pyrophosphate could be used to establish the assertion that
(a) Geranyl pyrophosphate is methylated by S-adenosylmethionine (SAM; Sec. 11.7B) in the reaction shown in Fig. P17.41, which is catalyzed by the enzyme geranyl pyrophosphate C-methyl transferase.
One of the compounds responsible for the odor of moist soil is geosmin, which is produced by streptomycetes in soil from farnesyl pyrophosphate, as shown in Fig. P17.43. Compounds A and B are
Account for each of the following facts with an explanation.(a) 1,3-Cyclopentadiene is a considerably stronger carbon acid than 1,4-pentadiene, even though the acidic hydrogens in both cases are
Complete the reactions given in Fig. P17.45 by proposing structures for the major organic products. (a) H₂C=CH-CH=CH-CH₂MgBr + D₂O (b) + H₂CH₂ H₂C=CH-CH=CH-CH₂MgBr + H₂C-CH₂ (c)
Propose a curved-arrow mechanism for the reaction given in Fig. P17.48, and give at least two structural reasons why the equilibrium lies to the right. CH - CH=CH Figure
Consider the relative rates of the two solvolysis reactions in acetic acid solvent shown in Fig. P17.50.(a) Suggest a reason that compound A undergoes solvolysis much faster than compound B.(b)
Propose a curved-arrow mechanism for each of the reactions given in Fig. P17.46. (b) CH3(CH₂)3 C=C-CH₂-Br + Mg (e) Ph-C=C-CH₂CH₂OH CH3 (c) 1-penten-4-yne + Na+ :C=CH; then allyl bromide +
Specify the relationship(s) of the compounds in each of the following sets. Choose among the following terms: identical compounds, epimers, anomers, enantiomers, diastereomers, constitutional
Into what other aldose and 2-ketose would each of the following aldoses be transformed on treatment with base? Give the structure and name of the aldose, and the structure of the 2-ketose.(a)
(a) Name the following glycoside.(b) Into what products will this glycoside be hydrolyzed in aqueous acid? HO CH₂OH ОН -О онтн ОН H - -NO2
Draw structures for(a) Methyl β-D-fructofuranoside (b) Isopropyl α-D-galactopyranoside
Using Table 24.2 to assist you, draw a Fischer projection for the structure of (a) Galac turonic acid, the uronic acid derived from galactose; (b) Ribitol, the alditol derived from ribose. TABLE
Explain why acetals hydrolyze more rapidly than ordinary ethers.
Outline a sequence of reactions that will bring about each of the following conversions.(a) D-galactopyranose to ethyl 2,3,4,6-tetra-O-methyl-d-galactopyranoside(b) D-glucopyranose to
An aldohexose A is either d-idose or d-gulose (see Fig. 24.3). It is found that a different aldohexose, L-(2)-glucose, gives the same aldaric acid as A. What is the identity of A?
Give the product formed when each of the following alcohols is oxidized by dilute HNO3. HO CH₂OH (b) HOCH₂CH₂CH₂CH₂OH
Give Fischer projections for the aldaric acids derived from both D-glucose and L- gulose. What is the relationship between these structures?
Assuming the D configuration, identify A and B. an aldopentose A Kiliani-Fischer synthesis an aldohexose B (one of two formed) dilute HNO3 dilute HNO3 an aldaric acid, optically inactive an aldaric
Draw a Fischer projection for the aldaric acid, and a structure of the 1,4-lactone, derived from the oxidation of (a) D-galactose;(b) D-mannose.
Explain why the methyl α-D-pyranosides of all D-aldohexoses give, in addition to formic acid, the same compound when oxidized by periodate.

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