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chemistry
organic chemistry

Questions and Answers of Organic Chemistry

Among the ways in which 1, 4-dioxane may be prepared are the methods expressed in the equations shown:
Deduce the identity of the missing compounds in the following reaction sequences. Show stereochemistry in parts (b) through (d).
Cineole is the chief component of eucalyptus oil; it has the molecular formula C10H18O and contains no double or triple bonds. It reacts with hydrochloric acid to give the dichloride shown:
The p-toluenesulfonate shown undergoes an intramolecular Williamson reaction on treatment with base to give spirocyclic ether. Demonstrate your understanding of the terminology used in the preceding
All the following questions pertain to 1H NMR spectra of isomeric ethers having the molecular formula C5H12O. (a) Which one has only singlets in its 1H NMR spectrum? (b) Along with other signals,
The 1H NMR spectrum of compound A (C8H8O) consists of two singlets of equal area at δ 5.1 (sharp) and 7.2 ppm (broad). On treatment with excess hydrogen bromide, compound A is converted to a
The 1H NMR spectrum of a compound (C10H13BrO) is shown in Figure 16.10. The compound gives benzyl bromide, along with a second compound C3H6Br2, when heated with HBr. What is the first compound?
A compound is a cyclic ether of molecular formula C9H10O. Its 13C NMR spectrum is shown in Figure 16.11. Oxidation of the compound with sodium dichromate and sulfuric acid gave 1, 2-
Which of the isomeric C4H10O alcohols can be prepared by hydrogenation of aldehydes? Which can be prepared by hydrogenation of ketones? Which cannot be prepared by hydrogenation of a carbonyl
Sodium borodeuteride (NaBD4) and lithium aluminum deuteride (LiAlD4) are convenient reagents for introducing deuterium, the mass 2 isotope of hydrogen, into organic compounds. Write the structure of
Give the structure of an ester that will yield a mixture containing equimolar amounts of 1-propanol and 2-propanol on reduction with lithium aluminum hydride
Each of the following alcohols has been prepared by reaction of a Grignard reagent with ethylene oxide. Select the appropriate Grignardreagent in each case.
Write equations showing how 3-methyl-1,5-pentanediol could be prepared from a dicarboxylic acid or a diester.
Give the structures, including stereochemistry, for the diols obtained by hydroxylation of cis-2-butene and trans-2-butene.
On the basis of the mechanism for the acid-catalyzed formation of diethyl ether from ethanol in Figure 15.2, write a stepwise mechanism for the formation of oxane from 1,5-pentanediol (see the
Write the structure of the ester formed in each of the following reactions:
A similar conclusion may be drawn by considering the reactions of the cis and Tran isomers of 4-tert-butylcyclohexanol with acetic anhydride. On the basis of the information just presented, predict
Alfred Nobel’s fortune was based on his 1866 discovery that nitroglycerin, which is far too shock-sensitive to be transported or used safely, can be stabilized by adsorption onto a substance called
Predict the principal organic product of each of the following reactions: Discuss.
The mechanism of enzymatic oxidation has been studied by isotopic labeling with the aid of deuterated derivatives of ethanol. Specify the number of deuterium atoms that you would expect to find
Predict the products formed on oxidation of each of the following with periodic acid: (a) HOCH2CH2OH
Outline a synthesis of 1-hexanethiol from 1-hexanol.
The main components of a skunk’s scent fluid are 3-methyl-1-butanethiol and cis- and trans-2-butene-1-thiol. Write structural formulas for each of these compounds.
Three of the most intense peaks in the mass spectrum of 2-methyl-2-butanol appear at m/z 59, 70, and 73. Explain the origin of these peaks.
Write chemical equations, showing all necessary reagents, for the preparation of 1-butanol by each of the following methods: (a) Hydroboration–oxidation of an alkene (b) Use of a Grignard
Write chemical equations, showing all necessary reagents, for the preparation of 2-butanol by each of the following methods: (a) Hydroboration–oxidation of an alkene (b) Use of a Grignard
Write chemical equations, showing all necessary reagents, for the preparation of tert-butyl alcohol by: (a) Reaction of a Grignard reagent with a ketone (b) Reaction of a Grignard reagent with an
Which of the isomeric C5H12O alcohols can be prepared by lithium aluminum hydride reduction of? (a) An aldehyde (c) A carboxylic acid (b) A ketone (d) An ester of the type RCOCH3
Evaluate the feasibility of the route
Sorbitol is a sweetener often substituted for cane sugar, since it is better tolerated by diabetics. It is also an intermediate in the commercial synthesis of vitamin C. Sorbitol is prepared by
Write equations showing how 1-phenylethanol (C6H5CHCH3) could be prepared from each of the following starting materials: (a) Bromobenzene (d) Acetophenone (b) Benzaldehyde (e) Benzene (c)
Write equations showing how 2-phenylethanol (C6H5CH2CH2OH) could be prepared from each of the following starting materials: (a) Bromobenzene (b) Styrene (c) 2-Phenylethanal (C6H5CH2CHO) (d)
Outline practical syntheses of each of the following compounds from alcohols containing no more than four carbon atoms and any necessary organic or inorganic reagents. In many cases the desired
Outline practical syntheses of each of the following compounds from benzene, alcohols, and any necessary organic or inorganic reagents: (a) 1-Chloro-2-phenylethane
Show how each of the following compounds can be synthesized from cyclopentanol and any necessary organic or inorganic reagents. In many cases the desired compound can be made from one prepared in an
Write the structure of the principal organic product formed in the reaction of 1-propanol with each of the following reagents: (a) Sulfuric acid (catalytic amount), heat at 140°C (b) Sulfuric acid
Each of the following reactions has been reported in the chemical literature. Predict the product in each case, showing stereochemistry where appropriate.
On heating 1, 2, 4-butanetriol in the presence of an acid catalyst, cyclic ether of molecular formula C4H8O2 was obtained in 81–88% yield. Suggest a reasonable structure for this product.
Give the Cahn–Ingold–Prelog R and S descriptors for the diol(s) formed from cis-2-pentene and trans-2-pentene on treatment with the osmium tetraoxide/tert-butyl hydroperoxide reagent.
Suggest reaction sequences and reagents suitable for carrying out each of the following conversions. Two synthetic operations are required in each case.
The fungus responsible for Dutch elm disease is spread by European bark beetles when they burrow into the tree. Other beetles congregate at the site, attracted by the scent of a mixture of chemicals,
Show by a series of equations how you could prepare 3-methylpentane from ethanol and any necessary inorganic reagents.
(a) The cis isomer of 3-hexen-1-ol (CH3CH2CH═CHCH2CH2OH) has the characteristic odor of green leaves and grass. Suggest a synthesis for this compound from acetylene and any necessary organic or
R. B. Woodward was one of the leading organic chemists of the middle part of the twentieth century. Known primarily for his achievements in the synthesis of complex natural products, he was awarded
Complete the following series of equations by writing structural formulas for compounds A through I:
When 2-phenyl-2-butanol is allowed to stand in ethanol containing a few drops of sulfuric acid, the following ether is formed:
Suggest a chemical test that would permit you to distinguish between the two glycerol monobenzyl ethers shown.
Choose the correct enantiomer of 2-butanol that would permit you to prepare (R)-2-butanethiol by way of a p-toluenesulfonate ester
The amino acid cysteine has the structure shown:
A diol (C8H18O2) does not react with periodic acid. Its 1H NMR spectrum contains three singlets at δ 1.2 (12 protons), 1.6 (4 protons), and 2.0 ppm (2 protons). What is the structure of this
Identify compound A (C8H10O) on the basis of its 1H NMR spectrum (Figure 15.6). The broad peak at δ 2.1 ppm disappears when D2O is added.
Identify each of the following (C4H10O) isomers on the basis of their 13C NMR spectra: (a) δ 31.2 ppm: CH3 (c) δ 18.9 ppm: CH3, area 2 δ 68.9 ppm: C δ 30.8 ppm: CH, area
A compound C3H7ClO2 exhibited three peaks in its 13C NMR spectrum at δ 46.8 (CH2), δ 63.5 (CH2), and δ 72.0 ppm (CH). What is the structure of this compound?
A compound C6H14O has the 13C NMR spectrum shown in Figure 15.7. Its mass spectrum has a prominent peak at m/z 31. Suggest a reasonable structure for this compound.
What fatty acids are produced on hydrolysis of 2-oleyl-1, 3- distearylglycerol? What other triacylglycerol gives the same fatty acids and in the same proportions as 2-oleyl-1, 3-distearylglycerol?
Using HSCoA and HS─ACP as abbreviations for coenzyme A and acyl carrier protein, respectively, write a structural formula for the tetrahedral intermediate in the preceding reaction.
By analogy to the intermediates given in steps 1–4 of Figure 26.3, write the sequence of acyl groups that are attached to the acyl carrier protein in the conversion of
What is the absolute configuration (R or S) of L-glycerol 3- phosphate? What must be the absolute configuration of the naturally occurring phosphatidic acids biosynthesized from it?
Spermaceti is a wax obtained from the sperm whale. It contains, among other materials, an ester known as cetyl palmitate, which is used as an emollient in a number of soaps and cosmetics. The
Arachidonic acid is the biosynthetic precursor to PGE2. The structures of PGE1 (see Figure 26.5) and PGE2 are identical except that PGE2 has one more double bond than PGE1. Suggest a reasonable
Locate the isoprene units in each of the monoterpenes, sesquiterpenes, and diterpenes shown in Figure 26.6. (In some cases there are two equally correct arrangements.)
Identify the isoprene units in ß-carotene (see Figure 26.6). Which carbons are joined by a tail-to-tail link between isoprene units?
Write a sequence of reactions that describes the formation of geranylgeraniol from farnesyl pyrophosphate.
The structure of the bicyclic monoterpene borneol is shown in Figure 26.7. Isoborneol, a stereoisomer of borneol, can be prepared in the laboratory by a two-step sequence. In the first step, borneol
How many carbon atoms of citronellal would be radioactively labeled if the acetic acid used in the experiment were enriched with 14C at C-1 instead of at C-2? Identify these carbon atoms.
The biosynthesis of cholesterol as outlined in Figure 26.10 is admittedly quite complicated. It will aid your understanding of the process if you consider the following questions: (a) Which carbon
The biosynthetic pathway shown in Figure 26.10 was developed with the aid of isotopic labeling experiments. Which carbon atoms of cholesterol would you expect to be labeled when acetate enriched with
Suggest a reasonable structure for vitamin D2.
Suggest a reasonable structure for vitamin D2. Discuss.
Identify the carbon atoms expected to be labeled with 14C when each of the following substances is biosynthesized from acetate enriched with 14C in its methyl group:
The biosynthetic pathway to prostaglandins leads also to a class of physiologically potent substances known as prostacyclins. Which carbon atoms of the prostacyclin shown here would you expect to be
Identify the isoprene units in each of the following naturally occurring substances: (a) Ascaridole, a naturally occurring peroxide present in chenopodium oil:
Cubitene is a diterpene present in the defense secretion of a species of African termite. What unusual feature characterizes the joining of isoprene units in cubitene?
Pyrethrins are a group of naturally occurring insecticidal substances found in the flowers of various plants of the chrysanthemum family. The following is the structure of a typical pyrethrin,
Cerebrosides are found in the brain and in the myelin sheath of nerve tissue. The structure of the cerebroside phrenosine is
Each of the following reactions has been reported in the chemical literature and proceeds in good yield. What are the principal organic products of each reaction? In some of the exercises more than
Describe an efficient synthesis of each of the following compounds from octadecanoic (stearic) acid using any necessary organic or inorganic reagents: (a) Octadecane (e) 1-Heptadecanamine (b)
A synthesis of triacylglycerols has been described that begins with the substance shown.
The isoprenoid compound shown is a scent marker present in the urine of the red fox. Suggest a reasonable synthesis for this substance from 3-methyl-3-buten-1-ol and any necessary organic or
Sabinene is a monoterpene found in the oil of citrus fruits and plants. It has been synthesized from 6-methyl-2, 5-heptanedione by the sequence that follows. Suggest reagents suitable for carrying
Isoprene has sometimes been used as a starting material in the laboratory synthesis of terpenes. In one such synthesis, the first step is the electrophilic addition of 2 moles of hydrogen bromide to
The ionones are fragrant substances present in the scent of iris and are used in perfume. A mixture of a- and ß-ionone can be prepared by treatment of pseudoionone with sulfuric acid.
ß, Ύ-Unsaturated steroidal ketones represented by the partial structure shown here are readily converted in acid to their a, ß-unsaturated isomers. Write a stepwise mechanism for this reaction.
Consider all the isomers of C7H7Cl containing a benzene ring and write the structure of the one that has the weakest carbon–chlorine bond as measured by its bond dissociation energy.
Write the structure of the expected product from the reaction of 1-chloro-2, 4-dinitrobenzene with each of the following reagents: (a) CH3CH2ONa (b) C6H5CH2SNa (c) NH3 (d) CH3NH2
Write the most stable resonance structure for the cyclohexadienyl anion formed by reaction of methoxide ion with o-fluoronitrobenzene.
Reaction of 1, 2, 3-tribromo-5-nitrobenzene with sodium ethoxide in ethanol gave a single product, C8H7Br2NO3, in quantitative yield. Suggest a reasonable structure for this compound.
Write equations describing the addition–elimination mechanism for the reaction of hexafluorobenzene with sodium methoxide, clearly showing the structure of the rate-determining intermediate.
Offer an explanation for the observation that 4-chloropyridine is more reactive toward nucleophiles than 3-chloropyridine.
2-Bromo-1, 3-dimethylbenzene is inert to nucleophilic aromatic substitution on treatment with sodium amide in liquid ammonia. It is recovered unchanged even after extended contact with the reagent.
Two isomeric phenols are obtained in comparable amounts on hydrolysis of p-iodotoluene with 1 M sodium hydroxide at 300°C. Suggest reasonable structures for these two products.
Give the structure of the cycloaddition product formed when benzyne is generated in the presence of furan. (See Section 11.21, if necessary, to remind yourself of the structure of furan)
Write a structural formula for each of the following: (a) m-Chlorotoluene (f) 1-Chloro-1-phenylethane (b) 2, 6-Dibromoanisole (g) p-Bromobenzyl chloride (c) p-Fluorostyrene (h)
Identify the major organic product of each of the following reactions. If two regioisomers are formed in appreciable amounts, show them both.
Potassium tert-butoxide reacts with halobenzenes on heating in dimethyl sulfoxide to give tert-butyl phenyl ether. (a) o-Fluorotoluene yields tert-butyl o-methylphenyl ether almost exclusively
Predict the products formed when each of the following isotopically substituted derivatives of chlorobenzene is treated with sodium amide in liquid ammonia. Estimate as quantitatively as possible the
Choose the compound in each of the following pairs that reacts faster with sodium methoxide in methanol at 50°C: (a) Chlorobenzene or o-chloronitrobenzene (b) o-Chloronitrobenzene or
In each of the following reactions, an amine or a lithium amide derivative reacts with an aryl halide. Give the structure of the expected product, and specify the mechanism by which it is formed.
Piperidine, the amine reactant in parts (b) and (c) of the preceding problem, reacts with 1-bromonaphthalene on heating at 230°C to give a single product, compound A (C15H17N), as a
1,2,3,4,5-Pentafluoro-6-nitrobenzene reacts readily with sodium methoxide in methanol at room temperature to yield two major products, each having the molecular formula C7H3F4NO3. Suggest reasonable

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