Ammonia appears in Table 1-5 both as an acid and as a conjugate base.
(a) Rank ethanol, methylamine, and acetic acid in decreasing order of acidity. (b) Rank ethanol, methylamine (pKb 3.36), and ethoxide ion (CH3CH2O-) in decreasing order of basicity. In each case,...
Amides such as acetamide are much weaker bases than amines, such as ethylamine (CH3CH2NH2). (a) Use resonance forms to show why the nonbonding electrons on the nitrogen atom of the amide are very...
(a) Draw the resonance forms for SO2 (bonded O-S-O) (b) Draw the resonance forms for ozone (bonded O-O-O) (c) Sulfur dioxide has one more resonance form than ozone. Explain why this structure is not...
Draw the important resonance forms for the following molecules and ions. (a) CO2/3- (b) NO-3 (c) NO-2 (d) H2C=CH-CH+2 (e) H2C=CH-CH-2 (f) SO2/4- (g) [CH3C(OCH3)2]+ (h) B(OH)3
Two isomers of 1,2-dichloroethene are known. One has a dipole moment of 2.4 D; the other has zero dipole moment. Draw the two isomers and explain why one has zero dipole moment. CHCl=CHCl 1,...
(a) Predict the hybridization of the oxygen atom in water, H2O. Draw a picture of its threedimensional structure, and explain why its bond angle is 104.5°. (b) The electrostatic potential maps...
Allene, CH2=C=CH2, has the structure shown below. Explain how the bonding in allene requires the two = CH2 groups at its ends to be at right angles to each other. allene
(a) There are eighteen isomeric alkanes of molecular formula C8H18. Draw and name any eight of them. (b) Draw and name the six isomeric cyclopentanes of molecular formula C7H14. These will include...
Give structures and names for: (a) The five isomers of C6H14 (b) The nine isomers of C7H16
Classify each hydrogen atom in the following compounds as primary (1), secondary (2), or tertiary (3). (a) Butane (b) Isobutene (c) 2-methylbutane (d) Cyclohexane (e) Norbornane (bicycle [2.2.1]...
(a) Write the propagation steps leading to the formation of dichloromethane (CH2Cl2) from chloromethane. (b) Explain why free-radical halogenations usually gives mixtures of products. (c) How could...
Acetylacetone (pentane-2, 4-dione) reacts with sodium hydroxide to give water and the sodium salt of a carbanion. Write a complete structural formula for the carbanion, and use resonance forms to...
Acetonitrile Is deprotonated by very strong bases? Write resonance forms to show the stabilization of the carbanion those results. CH3C N)
(a) Using bond-dissociation enthalpies from Table 4-2 (page 143), calculate the heat of reaction for each step in the free-radical bromination of methane. (b) Calculate the overall heat of reaction....
(a) Draw the reaction-energy diagram for the reverse reaction: CH3 + HCl CH4 + Cl (b) What is the activation energy for this reverse reaction? (c) What is the heat of reaction (H) for this reverse...
(a) Using the BDEs in Table 4-2 (p. 143), compute the value of Ho for each step in the iodination of methane. (b) Compute the overall value of Ho for iodination. (c) Suggest two reasons why iodine...
Make a model and draw a three-dimensional structure for each compound. Then draw the mirror image of your original structure and determine whether the mirror image is the same compound. Label each...
For each pair, give the relationship between the two compounds. Making models will be helpful. (a) (2R, 3S)-2, 3-dibromohexane and (2S, 3R)-2, 3-dibromohexane (b) (2R, 3S)-2, 3-dibromohexane and (2R,...
The specific rotation of (S)-2-iodobutane is +15.90o. (a) Draw the structure of (S)-2-iodobutane. (b) Predict the specific rotation of (R)-2-iodobutane. (c) Determine the percentage composition of a...
Which of the following pairs of compounds could be separated by recrystallization or distillation? (a) meso-tartaric acid and (±)-tartaric acid (HOOC-CHOH-CHOH-COOH) (b) (c) (d) CH,CH, O CH,CH...
A solution of 2.0 g of (+)-glyceraldehyde, HOCH2-CHOH-CHO, in 10.0 mL of water was placed in a 100-mm cell. Using the sodium D line, a rotation of +1.74o was found at 25 C. Determine the specific...
A solution of 0.50 g of (-) - epinephrine (see Figure 5-15) dissolved in 10.0 mL of dilute aqueous HCl was placed in a 20-cm polarimeter tube. Using the sodium D line, the rotation was found to be...
Show how you might use SN2 reactions to convert 1-chlorobutane into the following compounds. (a) Butan-1-ol (b) 1-fluorobutane (c) 1-iodobutane (d) CH3-(CH2)3-CN (e) (f) CH3CH2-O-(CH2)3-CH3 (g) CH3-...
For each structure, 1. Draw all the stereoisomers. 2. Label each structure as chiral or achiral. 3. Give the relationships between the stereoisomers (enantiomers, diastereomers). (a) (b) (c) CHO OH...
Free-radical bromination of the following compound introduces bromine primarily at the benzylic position next to the aromatic ring. If the reaction stops at the monobromination stage, two...
3, 4-Dimethylpent-1-ene has the formula When pure (R)-3, 4-dimethylpent-1-ene is treated with hydrogen over a platinum catalyst, the product is (S)-2, 3-dimethylpentane. (a) Draw the equation for...
For each pair, predict the stronger nucleophile in the SN2 reaction (using an alcohol as the solvent). Explain your prediction. (a) CH3CH2)3N or (CH3CH2)2NH (b) (CH3)2O or (CH3)2S (c) NH3 or PH3 (d)...
Give the structures of the following compounds. (a) Methylene iodide (b) Carbon tetrabromide (c) 3-bromo-2-methylpentane (d) Iodoform (e) 2-bromo-3-ethyl-2-methylhexane (f) Isobutyl bromide (g)...
Propose an SN1 mechanism for the solvolysis of 3-bromo-2,3-dimethylpentane in ethanol.
A graduate student was studying enzymatic reductions of cyclohexan ones when she encountered some interesting chemistry. When she used an enzyme and NADPH to reduce the following ketone, she was...
For each compound, determine whether the molecule has an internal mirror plane of symmetry. If it does, draw the mirror plane on a three-dimensional drawing of the molecule. If the molecule does not...
Star (*) each asymmetric carbon atom in the following examples, and determine whether it has the (R) or (S) configuration. (a) (b) (c) (d) (e) (f) (g) (h) (i) CH H CH,CH, H,C CH,CH, H H CH CCH, CI H...
Classify each reaction as a substitution, elimination, or neither. Identify the leaving group in each reaction, and the nucleophile in substitutions. (a) (b) (c) Na OCH OCH NaBr H,SO +HHso, Br KI +...
Give the structures of the products expected from the indicated mechanisms in the preceding examples.
Predict the products and mechanisms of the following reactions. When more than one product or mechanism is possible, explain which are most likely. (a) 1-bromohexane + sodium ethoxide in ethanol (b)...
Draw the structures of the following compounds. (a) sec-butyl chloride (b) Isobutyl bromide (c) 1,2-dibromo-3-methylpentane (d) 2,2,2-trichloroethanol (e) trans-1-chloro-2-methylcyclohexane (f)...
Chlorocyclohexane reacts with sodium cyanide (NaCN) in ethanol to give cyanocyclohexane. The rate of formation of cyanocyclohexane increases when a small amount of sodium iodide is added to the...
A solution of pure (S)-2-iodobutane ([a] = + 15.90( in acetone is allowed to react with radioactive iodide, 131I , until 1.0% of the iodobutane contains radioactive iodine. The specific rotation of...
Give a mechanism to explain the two products formed in the following reaction. CH Br CH, H CH CCH NBS, hv CH3 Br CC 3-methylbut-1-ene not rearranged rearranged
Because the SN1 reaction goes through a flat carbocation, we might expect an optically active starting material to give a completely racemized product. In most cases, however, SN1 reactions actually...
Allylic halides have the structure (a) Show how the first-order ionization of an allylic halide leads to a resonance-stabilized cation. (b) Draw the resonance structures of the allylic cations formed...
(a) Two stereoisomers of a bromodecalin are shown. Although the difference between these stereoisomers may seem trivial, one isomer undergoes elimination with KOH much faster than the other. Predict...
Draw five more compounds of formula C4H6NOCl.
Explain the dramatic difference in rotational energy barriers of the following three alkenes. 259 kJ/mol 179 kJ/mol 66 kJ/mol COOCH3 Ph Ph (HChN COOCH3
Predict the major products of the following reactions, and propose mechanisms to support your predictions. (a) pent-1-ene + HCl (b) 2-methylpropene + HC (c) 1-methylcyclohexene + HI (d)...
Propose mechanisms for the following reactions. Additional products may be formed, but your mechanism only needs to explain the products shown. (a) (Hydride shift) (b) (c) H-S04. 140C CH3 CH CH CH3...
Propose mechanisms for the following reactions. (a) (b) (c) (d) DEH H PO heat CH,OH CH2 CH3 H,SO4 heat H2SO4 heat OH H,SOA heat
Predict the major products of the following reactions. (a) propene + BH3 THF (b) the product from part (a) + H2O2/OH- (c) 2-methylpent-2-ene + BH3 THF (d) the product from part (c) + H2O2 /OH- (e)...
(a) When (Z)-3-methylhex-3-ene undergoes hydroboration-oxidation, two isomeric products are formed. Give their structures, and label each asymmetric carbon atom as (R) or (S). What is the...
(a) When HBr adds across the double bond of 1,2-dimethylcyclopentene, the product is a mixture of the cis and trans isomers. Show why this addition is not stereospecific. (b) When...
(a) When 1 mol of buta-1,3-diene reacts with 1 mol of HBr, both 3-bromobut-1-ene and 1-bromobut-2-ene are formed. Propose a mechanism to account for this mixture of products. (b) When...
Give the systematic (IUPAC) names of the following alkenes. (a) (b) (c) (d) (e) (f) (g) (h) (i) (j) CH2 CHCH2CH(CH3)2 CH3(CH2)3-C-CH2CH3 CH2 CH CHCH2 CH CH2 CH2=C=CH-CH-CH2 " CH3 CH3
Propose a mechanism for the triolefin process using a metal alkylidene as the catalyst. CH IM CHCH CH - - - CH3 propylene but-2-ene (cis + trans) ethylene
Show how you might use olefin metathesis to assemble the following alkenes from smaller units: (a) (b)
Propose a mechanism for the following reaction. H2SO IM
A routine addition of HBr across the double bond of a vinylcyclopentane gave a small amount of an unexpected rearranged product. Propose a mechanism for the formation of this product, and explain why...
An unknown compound decolorizes bromine in carbon tetrachloride, and it undergoes catalytic reduction to give decalin. When treated with warm, concentrated potassium permanganate, this compound gives...
(a) Propose a mechanism for the following reaction. (b) Give the structure of the product that results when this intermediate is reduced by sodium borohydride. CH CH Hg(OAc), CH CH2OH CH,-C-CH-CH...
(a) The following cyclization has been observed in the oxymercuration-demercuration of this unsaturated alcohol. Propose a mechanism for this reaction. (b) Predict the product of formula C2H13Brofrom...
An inexperienced graduate student treated dec-5-ene with borane in THF, placed the flask in a refrigerator, and left for a party. When he returned from the party, he discovered that the refrigerator...
Write structural formulas for the following compounds (includes both old- and new-style names). (a) 2-octyne (b) ethylisopentylacetylene (c) ethynylbenzene (d) cyclohexylacetylene (e)...
Using cyclooctyne as your starting material, show how you would synthesize the following compounds. (Once you have shown how to synthesize a compound, you may use it as the starting material in any...
Predict the products of the following acid-base reactions, or indicate if no significant reaction would take place. (a) H---C = C----H + NaNH2 (b) H---C= C---H + CH3Li (c) H--C = C--H + NaOCH3 (d)...
Show how you would synthesize each compound, beginning with acetylene and any necessary additional reagents. (a) prop-2-yn-1-ol (propargyl alcohol) H----C === C--- CH2OH (b) (c) (d) hept-2-yn-4-ol OH...
Predict the products of the following reactions. (a) sec-butylmagnesium iodide + D2 O (b) n-butyllithium + CH3CH2OH (c) isobutylmagnesium bromide + but-1-yne cyclohexyllithium Li acetic acid + DO D20...
Give a systematic (IUPAC) name for each alcohol. Classify each as primary, secondary, or tertiary. (a) (b) (c) (d) (e) (f) (g) Br_CHCH3 OH Cl OH Br OH CI CH2OH
(a) Show how ethanol and cyclohexanol may be used to synthesize cyclohexyl ethyl ether (tosylation followed by the Williamson ether synthesis). (b) Why can't we synthesize this product simply by...
Give the structure of the principal product(s) when each of the following alcohols reacts with (1) Na2Cr2O7/H2SO4, (2) PCC, (3) DMP, (4) NaOCl. (a) Octan-1-ol (b) Octan-3-ol (c) 4-hydroxydecanal (d)...
Predict the products you expect when the following starting material undergoes oxidation with an excess of each of the reagents shown below. (a) Chromic acid (b) PCC (Pyridinium Chlorochromate) (c)...
Show how you would accomplish the following transformations. You may use any additional reagents you need. (a) (b) (c) (d) (e) (f) CH,CH,CH3 OH (racemic) SO3H CH,-C-CH-CH,--C-OCH-CH,...
Suggest the most appropriate method for each of the following laboratory syntheses. In each case, suggest both a chromium reagent and a chromium-free reagent. (a) butan -1-o1 butanal, CH3CH2CH2CHO...
A nitro group( - NO2) effectively stabilizes a negative charge on an adjacent carbon atom through resonance: Two of the following nitrophenols are much more acidic than phenol itself. The third...
Unknown Q is determined to have a molecular formula of C6H12O. Q is not optically active, and passing it through a chiral column does not separate it into enantiomers. Q does not react with Br2, nor...
Account for the peaks at m/z 87, 111, and 126 in the mass spectrum of 2,6-dimethylheptan-4-ol. 100 OH 80 2,6-dimethylheptan-4-o1 E 40 83 111 126 20 10 20- 30 40 50 60mm 80 m90ml00 110T20 130T 140...
Alcohols combine with ketones and aldehydes to form interesting derivatives, which we will discuss in Chapter 18. The following reactions show the hydrolysis of two such derivatives. Propose...
Draw a splitting tree, similar to Figures 13-32 and 13-33, for proton Hc in styrene. What is the chemical shift of proton Hc?
The NMR spectrum of cinnamaldehyde follows. (a) Determine the chemical shifts of Ha, Hb and Hc. The absorption of one of these protons is difficult to see; look carefully at the integrals. (b)...
Consider the proton NMR spectrum of the following ketone. (a) Predict the approximate chemical shift of each type of proton. (b) Predict the number of NMR peaks for each type of proton. (c) Raw a...
Use the imaginary replacement technique to show that protons Hc and Hd in cyclobutanol are diastereotopic.
If the imaginary replacement of either of two protons forms enantiomers, then those protons are said to be enantiotopic. The NMR is not a chiral probe, and it cannot distinguish between enantiotopic...
Predict the theoretical number of different NMR signals produced by each compound, and give approximate chemical shifts. Point out any diastereotopic relationships. (a) 2-bromobutane (b)...
Spectra are given for three compounds. Each compound has one or more of the following functional groups: alcohol, amine, ketone, aldehyde, and carboxylic acid. Determine the functional group(s) in...
Propose mechanisms to show the interchange of protons between ethanol molecules under (a) Acid catalysis (b) Base catalysis
Predict the chemical shifts of the protons in the following compounds. (a) (b) (c) (d) (e) (f) HC(CH3)3 CH CH CH3 , - CH,CCCH OH CH,CH,-C-OH CH3 CHC-CH Br
Draw the NMR spectrum expected from ethanol that has been shaken with a drop of D2O.
Propose chemical structures consistent with the following NMR spectra and molecular formulas. In spectrum (a) Explain why the peaks around δ 1.65 and δ 3.75 are not clean...
Draw the expected NMR spectrum of methyl propionate, and point out how it differs from the spectrum of ethyl acetate. CH--0-C-CH,--CH, methyl propionate
Give the spectral assignments for the protons in isobutyl alcohol (Solved Problem 13-4). For example, Ha is a singlet, area = 1, at 2.4
Five proton NMR spectra are given here, together with molecular formulas. In each case, propose a structure that is consistent with the spectrum. (a) C4Hg02 Offset: 24 ppm 0 4 10 (ppm) 50Hz (b)...
Draw the expected broadband-decoupled 13C NMR spectra of the following compounds. Use Figure 13-41 (page 603) to estimate the chemical shifts. (a) (b) (c) (d) C CH H,C CH C-H C-C
Repeat Problem 13-25, sketching the off-resonance-decoupled 13C spectra of the compounds. Problem 13-25 Draw the expected broadband-decoupled 13C NMR spectra of the following compounds. Use Figure...
The standard 13C NMR spectrum of phenyl propanoate is shown here. Predict the appearance of the DEPT-90 and DEPT-135 spectra. 13C NMR 0-C-CH2CH3 pheny! propanoate 200 180 160140 10 100 80 40 20 0 8...
Sets of spectra are given for two compounds. For each set, (1) Look at each spectrum individually, and list the structural characteristics you can determine from that spectrum. (2) Look at the set of...
The following proton NMR spectrum is of a compound of molecular formula C3H8O. (a) Propose a structure for this compound. (b) Assign peaks to show which protons give rise to which signals in the...
A laboratory student was converting cyclohexanol to cyclohexyl bromide by using one equivalent of sodium bromide in a large excess of concentrated sulfuric acid. The major product she recovered was...
Predict the multiplicity (the number of peaks as a result of splitting) and the chemical shift for each shaded proton in the following compounds. (a) (b) (c) (d) (e) (f) CH3 CH3-C H-C H 3 CH CH3 CH 3
Using a 60-MHz spectrometer, a chemist observes the following absorption: doublet, J = 7 Hz, at 4.00 (a) What would the chemical shift ()be in the 300-MHz spectrum? (b) What would the splitting...
A compound (C10H12O2) whose spectrum is shown here was isolated from a reaction mixture containing 2-phenylethanol and acetic acid. (a) Propose a structure for this compound. (b) Assign peaks to show...
Sketch your predictions of the proton NMR spectra of the following compounds. (a) CH3-O-CH2CH3 (b) (c) Cl-CH2-CH2-CH2-Cl (d) (e) (f) NH2 NH2 CH CH-O NO2 CH,