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organic chemistry

Questions and Answers of Organic Chemistry

As a team, discuss the following complementary experimental results as they pertain to the mechanism of electrophilic aromatic substitution. (a) A solution of HCl and benzene is colorless and
Metal-substituted benzenes have a long history of use in medicine. Before antibiotics were discovered, phenylarsenic derivatives were the only treatment for a number of diseases. Phenylmercury
Explain the following reaction and the indicated stereochemical result mechanistically.
The 1H NMR spectrum of the most stable isomer of [14]annulene shows two signals, at δ = -0.61 (4 H) and 7.88 (10 H) ppm. Two possible structures for [14]annulene are shown here. How do they differ?
(a) The 1H NMR spectrum of [18]annulene shows two signals, at δ = 9.28 (12 H) and -2.99 (6 H) ppm. The negative chemical shift value refers to a resonance upfield (to the right) of (CH3)4Si. Explain
A characteristic reaction of fulvenes is nucleophilic addition. To which carbon in a fulvene would you expect nucleophiles to add, and why?
All the molecules shown below are examples of “fulvenes,” or methylenecyclopentadienes. (a) One of these structures is considerably more acidic than the others, with a pKa around 20.
Is cyclobutadiene dication (C4H42+) aromatic according to Hückel’s rule? Sketch its p molecular orbital diagram to illustrate.
2,3-Diphenylcyclopropenone forms an addition product with HBr that exhibits the properties of an ionic salt. Suggest a structure for this product and a reason for its existence as a stable
The energy levels of the 2-propenyl (allyl) and cyclopropenyl p systems (see margin) are compared qualitatively in the diagram below. (a) Draw the three molecular orbitals of each system, using plus
Because of cyclic delocalization, structures A and B shown here for o-dimethylbenzene (o-xylene) are simply two resonance forms of the same molecule. Can the same be said for the two
Vanillin, whose structure is shown in the margin and is the subject of the Chapter Opening, is a benzene derivative with several functional groups, each one of which displays its characteristic
Give efficient syntheses of the following compounds, beginning with benzene. (a) 1-Phenyl-1- heptanol; (b) 2-phenyl-2-butanol; (c) 1-phenyloctane.
Like haloalkanes, haloarenes are readily converted into organometallic reagents, which are sources of nucleophilic carbon. The chemical behavior of these reagents is very similar to that of
The text states that alkylated benzenes are more susceptible to electrophilic attack than is benzene itself. Draw a graph like that in Figure 15-20 to show how the energy profile of electrophilic
(a) 3-Phenylpropanoyl chloride, C6H5CH2CH2COCl, reacts with AlCl3 to give a single product with the formula C9H8O and an 1H NMR spectrum with signals at δ = 2.53 (t, J = 8 Hz, 2 H), 3.02 (t, J = 8
Benzene reacts with sulfur dichloride, SCl2, in the presence of AlCl3 to give diphenyl sulfi de, C6H5 – S – C6H5. Propose a mechanism for this process.
Propose a mechanism for the sulfonation of benzene using chlorosulfuric acid, ClSO3H (in the margin). Cl-S-OH SO,H + HCI + O=S
Hexadeuteriobenzene, C6D6, is a very useful solvent for 1H NMR spectroscopy because it dissolves a wide variety of organic compounds and, being aromatic, is very stable. Suggest a method for the
Write mechanisms for reactions (c) and (f) in Problem 48. Data from Problem 48Give the expected major product of addition of each of the following reagent mixtures to benzene. (a) Cl, + AICI, (b) T,0
Give the expected major product of addition of each of the following reagent mixtures to benzene. (a) Cl, + AICI, (b) T,0 + T,SO, (T = tritium, 'H) (с) (CH).СОН + Н.РО (d) N,O; (which tends to
Reaction review. Without consulting the Reaction Road Map on p. 721, suggest a reagent to convert benzene into each of the following compounds. C(CH3)3 NO2 „CH3 CH,CH; SO,H Br (e) (f) (h)
The species resulting from the addition of benzene to HF – SbF5 (Exercise 15-24) shows the following 13C NMR absorptions: δ = 52.2(CH2), 136.9(CH), 178.1(CH), and 186.6(CH) ppm. The signals at δ
(a) Is it possible to distinguish the three isomers of dimethoxybenzene solely on the basis of the number of peaks in their proton-decoupled 13C NMR spectra? Explain. (b) How many different
Both methylbenzene (toluene) and 1,6-heptadiyne have molecular formulas of C7H8 and molecular masses of 92. Which of the two mass spectra shown below corresponds to which compound? Explain your
Following are spectroscopic and other data for several compounds. Propose a structure for each of them. (a) Molecular formula = C6H4Br2. 1H NMR spectrum A. 13C NMR: 3 peaks. IR: v˜ = 745 (s,
Which of the following structures qualify as being aromatic, according to Hückel’s rule?
Complete hydrogenation of 1,3,5,7-cyclooctatetraene is exothermic by -101 kcal mol-1. Hydrogenation of cyclooctene proceeds with ΔH° = 223 kcal mol-1. Are these data consistent with the description
The 1H NMR spectrum of naphthalene shows two multiplets (Figure 15-16). The upfield absorption (δ = 7.49 ppm) is due to the hydrogens at C2, C3, C6, and C7, and the downfield multiplet (δ = 7.86
The complete combustion of benzene is exothermic by approximately -789 kcal mol-1. What would this value be if benzene lacked aromatic stabilization?
Draw the structure of each of the following compounds. If the name itself is incorrect, give a correct systematic alternative. (a) o-Chlorobenzaldehyde; (b)
Give a proper IUPAC name for each of the following commonly named substances. CH3 OH OH CH3 LOCH3 (a) (b) (c) H;C HO, ČH3 ČH-(CH,),CH3 CH,CH=CH, Durene Hexylresorcinol Eugenol
Name each of the following compounds by using the IUPAC system and, if possible, a reasonable common alternative. (The order of functional group precedence is – COOH >. – CHO > – OH>
Which common analytical method will most clearly and rapidly distinguish A from B? (a) IR spectroscopy; (b) UV spectroscopy; (c) combustion analysis; (d) visible spectroscopy CH3
When cyclopentadiene is treated with tetracyanoethene, a new product results. Its most likely structure is CN CN CN (а) Н—С—С- CN CN (b) ČN ČN CN CN CN H,C-C-CN (с) H2C-C-CN (d) CN
Arrange the following three chlorides in decreasing order of SN1 reactivity. (a) A > B > C; (b) B > C > A; (c) B > A > C; (d) C > B > A. CH;CH,CH2CI H2C=CHCHCH3
How many nodes are present in the LUMO (lowest unoccupied molecular orbital) of 1,3- butadiene? (a) Zero; (b) one; (c) two; (d) three; (e) four
As a team, consider the following historic preparation of a tris(1,1-dimethylethyl) derivative of Dewar benzene, B, by the photochemical isomerisation of 1,2,4-tris(1,1-dimethylethyl)benzene by van
Diels-Alder cycloaddition of 1,3-butadiene with the cyclic dienophile shown in the margin takes place at only one of the two carbon – carbon double bonds in the latter to give a single product.
The ratio of 1,2- to 1,4-addition of Br2 to 1,3-butadiene is temperature dependent. Identify the kinetic and thermodynamic products, and explain your choices.
Farnesol is a molecule that makes flowers smell good (lilacs, for instance). Treatment with hot concentrated H2SO4 converts farnesol fi rst into bisabolene and finally into cadinene, a compound of
In a published synthetic procedure, acetone is treated with ethenyl (vinyl) magnesium bromide, and the reaction mixture is then neutralized with strong aqueous acid. The product exhibits the 1H NMR
The ultraviolet spectrum of a 2×10-4 M solution of 3-penten-2-one exhibits a π→π* absorption at 224 nm with A = 1.95 and an n→π* band at 314 nm with A = 0.008. Calculate the molar
Ethanol, methanol, and cyclohexane are commonly used solvents for UV spectroscopy because they do not absorb radiation of wavelength longer than 200 nm. Why not?
What is the longest-wavelength electronic transition in each of the following species? Use molecular-orbital designations such as n → π*, π1→π2, in your answer. (Prepare a molecular-orbital
The carbocation derived from geranyl pyrophosphate is the biosynthetic precursor of not only camphor, but also limonene (Problem 68) and a-pinene (Chapter 4, Problem 46). Formulate mechanisms for the
The structure of the terpene limonene is shown in the margin. Identify the two 2-methyl-1,3-butadiene (isoprene) units in limonene. (a) Treatment of isoprene with catalytic amounts of acid leads to a
Give abbreviated structures of each of the following compounds: (a) (E)-1,4-poly-2-methyl-1,3- butadiene [(E)-1,4-polyisoprene]; (b) 1,2-poly-2-methyl-1,3-butadiene
Explain the following reaction sequence. 1. Pd(OCCH,), R,P, K.CO, COCH,CH; Br 2. H,C=CH-COCH.CH,
Which of the reactions shown below will occur under the influence of heat? Light? (a) (b) (c) H H
Formulate the expected product of each of the following reactions. H;CO. H,C CH3 hv hv (а) (b) (с) (d) D CH3 H H;C H. CH;Ó
Bicyclic diene A reacts readily with appropriate alkenes by the Diels-Alder reaction, whereas diene B is totally unreactive. Explain. A B
Dimethyl azodicarboxylate (see margin) takes part in the Diels-Alder reaction as a dienophile. Write the structure of the product of cycloaddition of this molecule with each of the following
Propose an efficient synthesis of the cyclohexenol in the margin, beginning exclusively with acyclic starting materials and employing sound retrosynthetic analysis strategy. OH
Give the product(s) of each of the following reactions. (a) 3-Chloro-1-propene (allyl chloride) + NaOCH3 (b) cis-2-Butene + NBS, peroxide (ROOR) (c) 3-Bromo-1-cyclopentene +
The haloconduritols are members of a class of compounds called glycosidase inhibitors. These substances possess an array of intriguing biological activity, from antidiabetic and antifungal to
Propose a synthesis of each of the following molecules by Diels-Alder reactions. CH3 COCH3 H;C (b) CN (а) (с) СОСH CH3 Ö CN
Give the structures of all possible products of the acid-catalyzed dehydration of vitamin A. OH HO НО Br Bromoconduritol A В
Dienes may be prepared by elimination reactions of substituted allylic compounds. For example, Propose detailed mechanisms for each of these 2-methyl-1,3-butadiene (isoprene) syntheses. CH3 CH3
Sketch the molecular orbitals for the pentadienyl system in order of ascending energy (see Figures 14-2 and 14-7). Indicate how many electrons are present, and in which orbitals, for (a) the radical;
Arrange the following carbocations in order of decreasing stability. Draw all possible resonance forms for each of them. (a) CH2=CH–CH2 (b) СH— СH (c) CH3CH2 (d) CH,
Give the products expected from reaction of deuterium iodide (DI) with (a) 1,3-cycloheptadiene; (b) trans-1,3-pentadiene; (c) 2-methyl-1,3-pentadiene. In what way does the observable result of
Write a detailed step-by-step mechanism to show how each of the products arises from the reactions in Problem 51,. Data From Problem 51What are the products of reaction of
What are the products of reaction of 2-methyl-1,3-pentadiene with each of the reagents in Problem 49? Data From Problem 49What products would you expect from the electrophilic addition of each of the
Give the products of the reaction of trans-1,3-pentadiene with each of the reagents in Problem 49. Data From Problem 49What products would you expect from the electrophilic addition of each of the
What products would you expect from the electrophilic addition of each of the following reagents to 1,3-cycloheptadiene? (a) HI; (b) Br2 in H2O; (c) IN3; (d) H2SO4 in CH3CH2OH.
Compare the addition of H1 to 1,3-pentadiene and 1,4-pentadiene (see Problem 46). Draw the structures of the products. Draw a qualitative reaction profile showing both dienes and both proton addition
Electrophilic additions to conjugated dienes at low reaction temperatures give kinetic product ratios. Furthermore, these kinetic mixtures may change to mixtures with thermodynamic product ratios
Compare the allylic bromination reactions of 1,3-pentadiene and 1,4-pentadiene. Which should be faster? Which is more energetically favorable? How do the product mixtures compare? NBS, ROOR,
Give a systematic name to each of the following molecules. Br. (а) (b) (d) (с) Br
Starting with cyclohexene, propose a reasonable synthesis of the cyclohexene derivative shown in the margin. OH
The following reaction sequence gives rise to two isomeric products. What are they? Explain the mechanism of their formation. OH 1. Mg 2. D.O `CH3
Write a detailed step-by-step mechanism to show how each of the products arises from the reaction in Problem 41, part (a). Data From Problem 41, part (a) H;C I (а) H
Give the major product(s) of each of the following reactions. (a)(b)(c)(d)(e)(f) H;C I HO H
How would you expect the SN2 reactivities of simple saturated primary, secondary, and tertiary chloroalkanes to compare with the SN2 reactivities of the compounds in Problem 39? Make the same
Rank the following six molecules in approximate order of decreasing SN1 reactivity and decreasing SN2 reactivity. (а) (b) CI (d) CI (f)
Rank the following six molecules in approximate order of decreasing SN1 reactivity and decreasing SN2 reactivity. (а) (b) CI (d) CI (f)
Rank primary, secondary, tertiary, and (primary) allylic chlorides in approximate order of (a) decreasing SN1 reactivity; (b) decreasing SN2 reactivity
Formulate detailed mechanisms for the reactions in Problem 5 (a, c, e, f ). Data From Problem 5 OH Conc. HBr H,O Br CH,CH,OH (b) -CH3 (c) `CH=CH, CH3 CH3 OH CH,NO, A CH,COH KSCH, DMSO (d) (e)
Give the major product(s) of each of the following reactions. OH Conc. HBr H.O Br CH,CH,OH (a) (b) -CH3 (c) CH=CH, CI CH3 CH3 O- CH,COH KSCH,, DMSO CH,NO,, A (d) (e) (f) Cl- CH,I CH,I
Rank primary, secondary, tertiary, and allylic radicals in order of decreasing stability. Do the same for the corresponding carbocations. Do the results indicate something about the relative ability
Illustrate by means of appropriate structures (including all relevant resonance forms) the initial species formed by (a) breaking the weakest C – H bond in 1-butene; (b) treating
For each species in Problem 32, indicate the resonance form that is the major contributor to the resonance hybrid. Explain your choices. Data From Problem 32 CH3 (а) (b) (с) (d)
Name each of the compounds below, using the IUPAC system of nomenclature. 28. Name each of the compounds below, using the IUPAC system of nomenclature. CI OH (a) (b) HO. (c) (d) 3 (e) (f)
Draw all resonance forms and a representation of the appropriate resonance hybrid for each of the following species. CH3 (а) (b) (с) (d) (е)
From the choices shown below, pick the one that best describes the structure of compound A. Br Br Br. (2 equivalents) H:(2 equivalents), Raney Ni CH;C-CCH,OH A 1-butanol (A primary alcohol; %C
From the choices shown below, pick the one that best describes the structure of compound A. Br Br Br. (2 equivalents) H:(2 equivalents), Raney Ni CH;C-CCH,OH A 1-butanol (A primary alcohol; %C
From the choices shown below, pick the one that best describes the structure of compound A. Br Br Br. (2 equivalents) H:(2 equivalents), Raney Ni CH;C-CCH,OH A 1-butanol (A primary alcohol; %C
From the choices shown below, pick the one that best describes the structure of compound A. CH3 H,PO,. pH 2, 270°C, 100 atm A (a) HOCH,CH(CH),OH (b) HOCH,CHCH,OH CH3 (c) HC=CCHCH,OH (d)
When cyclooctyne is treated with dilute, aqueous sulfuric acid and HgSO4, a new compound results. It is best represented as (а) (b) (с) OH OH (d)
A nucleophile made by deprotonation of propyne is (a) :CH,CH;; (b) :HC=CH;; (c) :C=CH; (d) :C=CCH; (e) :HC=CHCH3.
The compound whose structure is H – C ≡ C(CH2)3Cl is best named (IUPAC)(a) 4-chloro-1-pentyne; (b) 5-chloropent-1-yne; (c) 4-pentyne-1-chloroyne; (d) 1-chloropent-4-yne.
Your team is studying the problem of an intramolecular ring closure of enediyne systems important in the total synthesis of dynemicin A, which exhibits potent antitumor activity. One research
A synthesis of the sesquiterpene farnesol requires the conversion of a dichloro compound into an alkynol, as shown below. Suggest a way of achieving this transformation. CI. CI -C=C-CH;OH
Formulate a plausible mechanism for the hydration of ethyne in the presence of mercuric chloride. ΙΗ ΝMR 3 H IH 1H 1 H (CH3)4Si 6.0 5.5 5.0 4.5 4.0 3.5 3.0 2.5 2.0 1.5 1.0 0.5 0.0 300-MHz 'H
An unknown molecule displays 1H NMR and IR spectra D (next page). Reaction with H2 in the presence of the Lindlar catalyst gives a compound that, after ozonolysis and treatment with Zn in aqueous
Synthesis of the sesquiterpene bergamotene proceeds from the alcohol shown here. Suggest a sequence to complete the synthesis. HOH,C CH3 CH3 Bergamotene
The synthesis of chamaecynone, the essential oil of the Benihi tree, requires the conversion of a chloroalcohol into an alkynyl ketone. Propose a synthetic strategy to accomplish this task.
Propose two different syntheses of linalool, a terpene found in cinnamon, sassafras, and orange flower oils. Start with the eight-carbon ketone shown here and use ethyne as your source of the
Propose a reasonable structure for calcium carbide, CaC2, on the basis of its chemical reactivity (Section 13-10). What might be a more systematic name for it?Section 13-10Ethyne chemistry underwent

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