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organic chemistry

Questions and Answers of Organic Chemistry

Circle the isoprene units in each of the following compounds(a)(b)(c)(d)(e)(f)
Consider a process that attempts to prepare tyrosine using a Hell‑Volhard‑Zelinski reaction:(a) Identify the necessary starting carboxylic acid.(b) When treated with Br2, the starting carboxylic
Explain why the addition of a small amount of glycerol to the polymerization mixture gives a stiffer urethane foam.
Some protecting groups can block two OH groups of a carbohydrate at the same time. One such group is shown here, protecting the 4-OH and 6-OH groups of -D-glucose.(a) What type of functional group is
Some protecting groups can block two OH groups of a carbohydrate at the same time. One such group is shown here, protecting the 4-OH and 6-OH groups of -D-glucose.(a) What type of functional group is
An important protecting group developed specifically for polyhydroxy compounds like nucleosides is the tetraisopropyldisiloxanyl group, abbreviated TIPDS, that can protect two alcohol groups in a
When the gum of the shrub Sterculia setigera is subjected to acidic hydrolysis, one of the water soluble components of the hydrolysate is found to be tagatose. The following information is known
(a) Which of the D-aldopentoses will give optically active aldaric acids on oxidation with HNO3?(b) Which of the D-aldotetroses will give optically active aldaric acids on oxidation with HNO3?(c)
An unknown reducing disaccharide is found to be unaffected by invertase enzymes. Treatment with an α-galactosidase cleaves the disaccharide to give one molecule of D-fructose and one molecule of
Which of the sugars mentioned in Problems 23-59, 23-60, and 23-61 are reducing sugars? Which ones would undergo mutarotation?
Is gentiobiose a reducing sugar? Does it mutarotate? Explain your reasoning.
Show how C3 of fructose can epimerize under basic conditions.
Many of the condensations we have studied are reversible. The reverse reactions are often given the prefix retro-, the Latin word meaning “backward.” Propose mechanisms to account for the
Show how you would accomplish the following multistep conversions. You may use any additional reagents you need.a.b.c.d. dimethyl adipate and allyl bromide
For each molecule shown below,1. indicate the most acidic hydrogens.2. draw the important resonance contributors of the anion that results from removal of the most acidic hydrogen.a.b.c.d.e.f.g.h.
Show how you would use Robinson annulations to synthesize the following compounds. Work backward, remembering that the cyclohexenone is the new ring and that the double bond of the cyclohexenone is
A chemist was called to an abandoned aspirin factory to determine the contents of a badly corroded vat. Knowing that two salvage workers had become ill from breathing the fumes, she put on her
The structures of four useful polymers are shown, together with some of their best-known products. In each case,(i) Determine the kind of polymer (polyamide, polyester, etc.).(ii) Draw the structures
In Section 21-16, we saw that Sevin® insecticide is made by the reaction of 1-naphthol with methyl isocyanate. A Union Carbide plant in Bhopal, India, once used this process to make Sevin® for use
A student has just added ammonia to hexanoic acid and has begun to heat the mixture when he is called away to the telephone. After a long telephone conversation, he returns to find that the mixture
Methyl p-nitrobenzoate has been found to undergo saponification faster than methyl benzoate.(a) Consider the mechanism of saponification, and explain the reasons for this rate enhancement.(b) Would
A student synthesized Compound 1 (below). To purify the compound, he extracted it into aqueous base and then acidified the solution to protonate the acid so that he could extract it back into ether.
The relative acidities of carboxylic acids (and, by inference, the stabilities of their carboxylate ions) have been used to compare the electron-donating and electron-withdrawing properties of
(A true story) The manager of an organic chemistry stockroom prepared unknowns for a “Ketones and Aldehydes” experiment by placing two drops of the liquid unknowns in test tubes and storing the
(A true story) The manager of an organic chemistry stockroom prepared unknowns for a “Ketones and Aldehydes” experiment by placing two drops of the liquid unknowns in test tubes and storing the
Two of the methods for converting alkyl halides to carboxylic acids are covered in Sections 20-8B and 20-8C. One is formation of a Grignard reagent followed by addition of carbon dioxide and then
The IR, NMR, and mass spectra are provided for an organic compound.(a) Consider each spectrum individually, and tell what characteristics of the molecule are apparent from that spectrum.(b) Propose a
The IR, NMR, and mass spectra are provided for an organic compound.(a) Consider each spectrum individually, and tell what characteristics of the molecule are apparent from that spectrum.(b) Propose a
(a) Hydrogen peroxide (HOOH) has a pKa of 11.6, making it roughly 10,000 times as strong an acid as water (pKa = 15.7). Explain why H2O2 is a stronger acid than H2O.(b) In contrast to part (a),
In the presence of a trace of acid, acid forms a cyclic ester (lactone).HO-CH2CH2CH2CH2-COOHδ-hydroxyvaleric acid(a) Give the structure of the lactone, called δ-valerolactone.(b) Propose a
The following NMR spectra correspond to compounds of formulas (A) C9H10O2, (B) C4H6O2, and (C) respectively. Propose structures, and show how they are consistent with the observed absorptions. A
Show how you would accomplish the following multistep syntheses. You may use any additional reagents and solvents you need.a. PhCH2CH2OH → PhCH2CH2COOHb.c.d.e.f. CH3 CH2 СООН
When pure (S)-lactic acid is esterified by racemic butan-2-ol, the product is 2-butyl lactate, with the following structure:(a) Draw three-dimensional structures of the two stereoisomers formed,
Predict the products and propose mechanisms for the following reactions.a.b.c.d. H+ OCH,CH3 excess H,0
Show how you would accomplish the following syntheses efficiently (you may use any necessary reagents).(a) Trans-l-bromobut-2-ene → trans-pent-3-enoic acid (two ways)(b) Hex-3-ene →, propanoic
Propose mechanisms for the nucleophilic acyl substitutions to form ethyl benzoate and N-methylacetamide as shown on the previous page.
Show how you might synthesize the following tertiary amine three different ways, each using a different secondary amine and adding the final substituent by(a) Reductive amination (3 ways).(b)
A compound of formula C11H16N2 gives the IR 1H NMR, and 13C NMR spectra shown. The proton NMR peak at δ2.0 disappears on shaking with D2O Propose a structure for this compound, and show how your
An unknown compound shows a weak molecular ion at m/z87 in the mass spectrum, and the only large peak is at m/z30. The IR spectrum follows. The NMR spectrum shows only three singlets: one of area 9
Propose mechanisms for the following reactions.a.b.c.d.e.f. CH,OH, H* CH;O OCH3 Ph-C-H Ph—С—Н
For each compound,1. Name the functional group.2. Show what compound(s) result from complete hydrolysis.a.b.c.d.e.f.g.h. CH,0 OCH; CH;CH,CH,-C-CH;
The following road-map problem centers on the structure and properties of A, a key intermediate in these reactions. Give structures for compounds A through J. NaBH4 не (1) J I (2) Н,о+ H+ G warm
The proton NMR spectrum of a compound of formula C10H12O follows. This compound reacts with an acidic solution of 2,4-dinitrophenylhydrazine to give a crystalline derivative, but it gives a negative
A compound of formula C6H10O2 shows only two absorptions in the proton NMR: a singlet at 2.67 ppm and a singlet at 2.15 ppm. These absorptions have areas in the ratio 2:3. The IR spectrum shows a
Sketch the expected proton NMR spectrum of 3,3-dimethylbutanal.
Acetals can serve as protecting groups for 1,2-diols, as well as for aldehydes and ketones. When the acetal is formed from acetone plus the diol, the acetal is called an acetonide. Show the
Rank the following carbonyl compounds in order of increasing equilibrium constant for hydration: CH,COCH,CI CICH,CHO CH,0 CH3COCH3 CH3CHO
Predict the major products of the following reactions.a.b.c.d.e.f.g.h.i.j. PHNHNH2 H+
Name the following ketones and aldehydes. When possible, give both a common name and an IUPAC name.a. CH3CO(CH2)4CH3b. CH3(CH2)2CO(CH2)2CH3c. CH3(CH2)5CHOd. PhCOPhe. CH3CH2CH2CHOf. CH3COCH3g.
Draw structures of the following derivatives.(a) The 2,4-dinitrophenylhydrazone of benzaldehyde (b) The semicarbazone of cyclobutanone(c) Cyclopropanone oxime (d) The ethylene acetal of
Draw structures of the following derivatives.(a) the 2,4-dinitrophenylhydrazone of benzaldehyde (b) the semicarbazone of cyclobutanone(c) cyclopropanone oxime (d) the ethylene acetal of
Propose mechanisms for the three imine-forming reactions just shown.
Propose a mechanism for each cyanohydrin synthesis just shown.
An unknown compound gives the following mass, IR, and NMR spectra. Propose a structure, and show how it is consistent with the spectra. Show the fragmentations that give the prominent peaks at m>z
A student found an old bottle labeled “thymol” on the stockroom shelf. After noticing a pleasant odor, she obtained the following mass, IR, and NMR spectra. The NMR peak at δ 4.8 disappears on
Consider the following compound, which has been synthesized and characterized:(a) Assuming this molecule is entirely conjugated, do you expect it to be aromatic, antiaromatic, or nonaromatic?(b) Why
The ribonucleosides that make up ribonucleic acid (RNA) are composed of D-ribose (a sugar) and four heterocyclic “bases.” The general structure of a ribonucleoside is The four heterocyclic
Draw and name all the methyl, dimethyl, and trimethylbenzenes.
In a strongly acidic solution, cyclohexa-1,4-diene tautomerizes to cyclohexa-1,3-diene. Propose a mechanism for this rearrangement, and explain why it is energetically favorable.
Show how you would convert 3-bromocyclohexanol to the following diol. You may use any additional reagents you need. CH3 HO. Br HO. (several steps) CH,CH3
Glycerol (propane-1,2,3-triol) is a viscous syrup with molecular weight 92 g/mol, boiling point 290 °C, and density 1.24 g/mL. Transforming the three hydroxyl groups into their trimethylsilyl ethers
Tetramethyloxirane is too hindered to undergo nucleophilic substitution by the hindered alkoxide, potassium tert butoxide. Instead, the product is the allylic alcohol shown. Propose a mechanism to
A new graduate student was studying the insecticidal properties of a series of polycyclic epoxides. He epoxidized alkene A using two different methods. First he used MCPBA, which gave an excellent
A compound of molecular formula C8H8O gives the IR and NMR spectra shown here. Propose a structure, and show how it is consistent with the observed absorptions. wavelength (um) 5,5 6. 8 9 10 2.5 100
An acid-catalyzed reaction was carried out using methyl cellosolve (2-methoxyethanol) as the solvent. When the 2-methoxyethanol was redistilled, a higher-boiling fraction (bp 162 °C) was also
Propylene oxide is a chiral molecule. Hydrolysis of propylene oxide gives propylene glycol, another chiral molecule.(a) Draw the enantiomers of propylene oxide.(b) Propose a mechanism for the
Under the right conditions, the following acid-catalyzed double cyclization proceeds in remarkably good yields. Propose a mechanism. Does this reaction resemble a biological process you have seen?
(a) When ethylene oxide is treated with anhydrous HBr gas, the major product is 1,2-dibromoethane. When ethylene oxide is treated with concentrated aqueous HBr, the major product is ethylene glycol.
There are two different ways of making 2-ethoxyoctane from octan-2-ol using the Williamson ether synthesis. When pure 1-2-octan-2-ol of specific rotation -8.24° is treated with sodium metal and then
Show how you would synthesize the following ethers in good yield from the indicated starting materials and any additional reagents needed.(a) cyclopentyl n-propyl ether from cyclopentanol and
(Another true story.) An organic lab student carried out the reaction of methylmagnesium iodide with acetone followed by hydrolysis. During the distillation to isolate the product, she forgot to mark
Give the structures of intermediates A through H in the following synthesis of trans-1-cyclohexyl-2-methoxycyclohexane. concd. HBr В C (gas) + D heat product Mg, (1) Hg(OAc),. CH,OH (2) NaBH, ether
Show how you would convert hex-1-ene to each of the following compounds. You may use any additional reagents and solvents you need.(a) 2-methoxyhexane (b) 1-methoxyhexane (c)
The following reaction resembles the acid-catalyzed cyclization of squalene oxide. Propose a mechanism for this reaction. CH,OH H,0 CH3 ОН
(a) Predict the values of m/z and the structures of the most abundant fragments you would observe in the mass spectrum of di-n-propyl ether.(b) Give logical fragmentations to account for the
(a) Show how you would synthesize the pure (R) enantiomer of 2-butyl methyl sulfide starting with pure (R) butan-2-ol and any reagents you need.(b) Show how you would synthesize the pure (S)
(A true story.) An inexperienced graduate student moved into a laboratory and began work. He needed some diethyl ether for a reaction, so he opened an old, rusty 1-gallon can marked “ethyl ether”
Predict the products of the following reactions.(a) Sec-butyl isopropyl ether + concd. HBr, heat(b) 2-ethoxy-2-methylpentane + concd. HBr, heat(c) Di-n-butyl ether + hot concd. NaOH(d) Di-n-butyl
Give IUPAC names for the following compounds.a. CH3OCH(CH3)CH2OHb. phOCH2CH3c. d.e.f.g.h.i. OCH3
Give common names for the following compounds.a. (CH3)2CHOCH(CH3)CH2CH3b. (CH3)3COCH2CH(CH3)2c. phOCH2CH3d. ClCH2OCH2CH2CH3e.f.g.h.i.j. H. OH OCH3 H
The ultimate test of fluency in MS and IR is whether you can determine a moderately complex structure from just the MS and the IR, with no additional information. The IR and MS of a compound are
Three common lab experiments are shown. In each case, describe how the IR spectrum of the product would differ from that of the reactant. Give approximate frequencies for distinctive peaks in the IR
(Another true story.) A student who was checking into her lab desk found an unlabeled sample from a previous student. She was asked to identify the sample. She did an IR spectrum and declared, “It
A laboratory student added 1-bromobutane to a flask containing dry ether and magnesium turnings. An exothermic reaction resulted, and the ether boiled vigorously for several minutes. Then she added
Three IR spectra are shown, corresponding to three of the following compounds. For each spectrum, determine the structure and explain how the peaks in the spectrum correspond to the structure you
Chapter 9 covered a synthesis of alkynes by a double dehydrohalogenation of dihalides. A student tried to convert trans-2,5-dimethylhex-3-ene to 2,5-dimethylhex-3-yne by adding bromine across the
An unknown, foul-smelling hydrocarbon gives the mass spectrum and infrared spectrum shown.(a) Use the mass spectrum to propose a molecular formula. How many elements of unsaturation are there?(b) Use
The mass spectrum of n-octane shows a prominent molecular ion peak (m z 114). There is also a large peak at m/z 57, but it is not the base peak. The mass spectrum of 3,4-dimethylhexane shows a
A (C-D) (carbon–deuterium) bond is electronically much like a C-H bond, and it has a similar stiffness, measured by the spring constant, k. The deuterium atom has twice the mass (m) of a hydrogen
(A true story.) While organizing the undergraduate stockroom, a new chemistry professor found a half-gallon jug containing a cloudy liquid (bp 100–105 °C), marked only “STUDENT PREP.” She ran
A common lab experiment is the dehydration of cyclohexanol to cyclohexene.(a) Explain how you could tell from the IR spectrum whether your product was pure cyclohexene, pure cyclohexanol, or a
Give logical fragmentation reactions to account for the following ions observed in these mass spectra.(a) N-octane: 114, 85, 71, 57(b) Methylcyclohexane: 98, 83(c) 2-methylpent-2-ene: 84, 69(d)
Authentic skunk spray has become valuable for use in scent-masking products. Show how you would synthesize the two major components of skunk spray (3-methylbutane-1-thiol and but-2-ene-1-thiol) from
Propose a mechanism for the reaction of pent-1-yne with HBr in the presence of peroxides. Show why anti-Markovnikov orientation results.
Cyclohexene is dissolved in a solution of lithium chloride in chloroform. To this solution is added one equivalent of bromine. The material isolated from this reaction contains primarily a mixture of
When cyclohexanol is dehydrated to cyclohexene, a gummy green substance forms on the bottom of the flask. Suggest what this residue might be, and propose a mechanism for its formation (as far as the
Label each structure as Z, E, or neither.a.b.c.d. H,C CH, C=C H CI
Draw the enantiomer, if any, for each structure.a.b.c.d.e.f.g.h. CH3 Br H C
Give the stereochemical relationships between each pair of structures. Examples are same compound, structural isomers, enantiomers, diastereomers. Which pairs could you (theoretically) separate by
Convert the following Fischer projections to perspective formulas.(a)(b)(c)(d) СООН H,N- H- CH;

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