Tell precisely how you would use the proton NMR spectra to distinguish between the following pairs of compounds. (a) 1-bromopropane and 2-bromopropane (b) (c) (d) CH3-CH-t-CH 3 (CH3)2C -_CH3 and CHCH...
For each compound shown below, (1) Sketch the 13C NMR spectrum (totally decoupled, with a singlet for each type of carbon), showing approximate chemical shifts. (2) Show the multiplicity expected for...
A major university was designated as a national nuclear magnetic resonance center by the National Science Foundation. Several large superconducting instruments were being installed when a government...
Draw the integral trace expected for the NMR spectrum of tert-butyl acetoacetate, shown in Figure 13-17. CH3 C-O-CCH3 3 0 6 10 (ppm)
(a) Draw all six isomers of formula C4H8 (including stereoisomers). (b) For each structure, show how many types of H would appear in the proton NMR spectrum. (c) For each structure, show how many...
When 2-chloro-2-methylbutane is treated with a variety of strong bases, the products always seem to contain two isomers (A and B) of formula C5H10. When sodium hydroxide is used as the base, isomer A...
A compound was isolated as a minor constituent in an extract from garden cress. Its spectra are shown here. (1) Look at each spectrum individually, and list the structural characteristics you can...
The three isomers of dimethylbenzene are commonly named ortho-xylene, meta-xylene, and para-xylene. These three isomers are difficult to distinguish using proton NMR, but they are instantly...
Show how you would distinguish among the following three isomers: (a) Using infrared spectroscopy and no other information. (b) Using proton NMR spectroscopy and no other information. (c) Using 13C...
Rank the given solvents in decreasing order of their ability to dissolve each compound. (a) NaOAc (b) (c) naphthalene OH 2-naphthol
Aluminum trichloride (AICI3) dissolves in ether with the evolution of a large amount of heat. (In fact, this reaction can become rather violent if it gets too warm.) Show the structure of the...
Different types of protons and carbons in alkanes tend to absorb at similar chemical shifts, making structure determination difficult. Explain how the 13C NMR spectrum, including the DEPT technique,...
For each pair of compounds, describe which instrumental technique (IR, MS, proton NMR, carbon NMR) you could use to distinguish for certain which of the two compounds was in a sample. Describe what...
Hexamethylbenzene undergoes free-radical chlorination to give one monochlorinated product (C12H17Cl) and four dichlorinated products (C12H16Cl2). These products are easily separated by GC-MS, but the...
Determine the ratios of the peak areas in the following spectra. Then use this information, together with the chemical shifts, to pair up the compounds with their spectra. Assign the peaks in each...
Write structural formulas for the following compounds. (a) Ethyl isopropyl ether (b) di-n-butyl ether (c) 2-ethoxyoctane (d) divinyl ether (e) allyl methyl ether (f) cyclohexene oxide (g) cis-2,...
Addition of 1-bromobut-2-ene to magnesium metal in dry ether results in formation of a Grignard reagent. Addition of water to this Grignard reagent gives a mixture of but-1-ene and but-2-ene (cis and...
Draw the NMR spectra you expect for the following compounds. (a) (b) (c) (d) C(CH33 CH3O CH3 - Cl C-OCH CH - CH3
(a) Show that the [4 + 4] cycloaddition of two butadiene molecules to give cycloocta-1,5-diene is thermally forbidden but photochemically allowed. (b) There is a different, thermally allowed...
A solution was prepared using 0.0010 g of an unknown steroid (of molecular weight around 255) in 100 mL of ethanol. Some of this solution was placed in a 1-cm cell, and the UV spectrum was measured....
Anions of hydrocarbons are rare, and dianions of hydrocarbons are extremely rare. The following hydrocarbon reacts with two equivalents of butyllithium to form a dianion of formula [C8H6]2-. Propose...
(a) Sketch the pi molecular orbitals of hexa-1, 3, 5-triene (Figure 15-25). (b) Show the electronic configuration of the ground state of hexa-1, 3, 5-triene. (c) Show what product would result from...
A student was studying terpene synthesis, and she wanted to make the compound shown here. First she converted 3-bromo-6-methylcyclohexene to alcohol A. She heated alcohol A with sulfuric acid and...
p-Xylene undergoes nitration much faster than benzene. Use resonance forms of the sigma complex to explain this accelerated rate.
Propose a mechanism for the bromination of ethylbenzene shown above.
(a) Use the polygon rule to draw an energy diagram (as in Figures 16-5 and 16-7) for the MOs of a planar cyclooctatetraenyl system. In Figure 16.5 In Figure 16.7 (b) Fill in the eight pi electrons...
Biphenyl is two benzene rings joined by a single bond. The site of substitution for a biphenyl is determined by (1) which phenyl ring is more activated (or less deactivated), and (2) which position...
A student added 3-phenylpropanoic acid (PhCH2CH2COOH) to a molten salt consisting of a 1:1 mixture of NaCl and AlCl3 maintained at 170 °C. After 5 minutes, he poured the molten mixture into water...
Phenol reacts with three equivalents of bromine in CCl4 (in the dark) to give a product of formula C6H3OBr3. When this product is added to bromine water, a yellow solid of molecular formula...
Agent Orange contains (2, 4, 5-trichlorophenoxy) acetic acid, called 2, 4, 5-T. This compound is synthesized by the partial reaction of 1, 2, 4, 5-etrachlorobenzene with sodium hydroxide, followed by...
Predict the products of the following reactions: (a) (b) (c) (d) (e) (f) CI )LiAIH (2)H30 CI LiAIHO--Bu) (1) DIBALH OCH (2) H20 (I) excess CH2Mgl CI ) Ho (1) DIBAL-H (-78C) (2) H,0
Trimethylphosphine is a stronger nucleophile than triphenylphosphine, but it is rarely used to make ylides. Why is trimethylphosphine unsuitable for making most phosphorus ylides?
Like other strong nucleophiles, triphenylphosphine attacks and opens epoxides. The initial product (a betaine) quickly cyclizes to an oxaphosphetane that collapses to an alkene and triphenylphosphine...
Propose mechanisms for (a) The acid-catalyzed hydration of chloral to form chloral hydrate. (b) The base-catalyzed hydration of acetone to form acetone hydrate.
Show how you would accomplish the following synthetic conversions. You may use any additional reagents and solvents you need. (a) (b) (c) (d) Ph-CHO OH PhCHOPhCHC CCH2CH3
Sodium triacetoxyborohydride, NaBH(OAc)3 is a mild reducing agent that reduces aldehydes much more quickly than ketones. It can be used to reduce aldehydes in the presence of ketones, such as in the...
Show how you would accomplish the following syntheses. (a) Cyanohydrins acetorphenone cyanohydrin (b) Cyclopentanecarbaldehyde 2-cyclopentyl-2-hydroxyacetic acid (c) hexan-1-ol 2-hydroxyheptanoic...
Give the structures of the carbonyl compound and the amine used to form the following imines. (a) (b) (c) (d) (e) (f) NH N=CHCH, N CH
Propose a mechanism for the hydrolysis of benzaldehyde methyl imine just shown.
2, 4-Dinitrophenylhydrazine is frequently used for making derivatives of ketones and aldehydes because the products (2, 4-dinitrophenylhydrazones, called 2, 4-DNP derivatives) are even more likely...
Propose a mechanism for the acid-catalyzed reaction of benzaldehyde with methanol to give benzaldehyde dimethyl acetal.
Propose a mechanism for the acid-catalyzed hydrolysis of cyclohexanone dimethyl acetal.
In the mechanism for acetal hydrolysis shown, the ring oxygen atom was protonated first, the ring was cleaved, and then the methoxy group was lost. The mechanism could also be written to show the...
Propose a mechanism for both parts of the Wolff-Kishner reduction of cyclohexanone: the formation of the hydrazone, then the base-catalyzed reduction with evolution of nitrogen gas.
Predict the products of the following reactions. (a) (b) (c) (d) Ht Ph-C-Ph +PhNHNH,
Show what amines and carbonyl compounds combine to give the following derivatives. (a) (b) (c) (d) (e) (f) Ph-CH=N-NH-C-NH, NOH N NHPh HNN : O
Predict the products formed when cyclohexanone reacts with the following reagents. (a) CH3NH2. H+ (b) Excess CH3OH. H+ (c) Hydroxylamine and weak acid (d) Ethylene glycol and p-toluenesulfonic acid...
An unknown compound gives a molecular ion of m / z70 in the mass spectrum. It reacts with semicarbazide hydrochloride to give a crystalline derivative, but it gives a negative Tollens test. The NMR...
Show how you would accomplish the following synthetic conversions efficiently and in good yield. You may use any necessary additional reagents and solvents. (a) (b) (c) (d) (e) (f) (g) (h) - , CH,Br...
Solving the following road-map problem depends on determining the structure of A, the key intermediate. Give structures for compounds A through K. hept-1-yne SOCI CH3CuLi (2) (CHj,S (2) Ho HCN (2)...
Predict the products of the following reactions. (a) CH3CH2CH2CH2C'N + CH3CH2MgBr, then H3O+ (b) CH3CH2CH2CH2C'N + DIBAL-H, then H3O+ (c) Benzyl bromide + sodium cyanide (d) Product of (c) +...
Show how the following transformations may be accomplished in good yield. You may use any additional reagents that are needed. (a) Bromobenzene propiophenone (b) CH3CH2CN heptan-3-one (c) Benzoic...
Show how you would accomplish the following syntheses efficiently and in good yield. You may use any necessary reagents. (a) acetaldehyde lactic acid, CH3CH(OH)COOH (b) (c) (d) (e) (f) (g) CHPh CHO...
Show how you would synthesize the following derivatives from appropriate carbonyl compounds. (a) (b) (c) (d) (e) (f) CH,O OCH,
(a) Show how fragmentation occurs to give the base peak at m/z 58 in the mass spectrum of ethyl propyl amine (N-ethylpropan-1- amine), shown below. (b) Show how a similar cleavage in the ethyl group...
(a) Propose a mechanism for the reaction of 2-bromopyridine with sodium amide to give 2-aminopyridine. (b) When 3-bromopyridine is used in this reaction, stronger reaction conditions are required and...
Addition of one equivalent of ammonia to 1-bromoheptane gives a mixture of heptan-1-amine, some dialkylamine, some trialkylamine, and even some tetraalkylammonium bromide. (a) Give a mechanism to...
Show how you would accomplish the following synthetic conversions by adding an organolithium reagent to an acid. (a) (b) (c) Pentanoic acid heptan-3-one (d) Phenylacetic acid...
Draw the structures of the following carboxylic acids. (a) - methylbutyric acid (b) 2-bromobutanoic acid (c) 4-aminopentanoic acid (d) cis-4-phenylbut-2-enoic acid (e)...
Show how Fischer esterification might be used to form the following esters. In each case, suggest a method for driving the reaction to completion. (a) Methyl salicylate (b) Methyl formate (bp 32 C)...
Show how the following ketones might be synthesized from the indicated acids, using any necessary reagents. (a) Propiophenone from propionic acid (two ways, using alkylation of the acid and using...
Most of the Fischer esterification mechanism is identical with the mechanism of acetal formation. The difference is in the final step, where a carbocation loses a proton to give the ester. Write...
The mechanism of the Fischer esterification was controversial until 1938, when Irving Roberts and Harold Urey of Columbia University used isotopic labeling to follow the alcohol oxygen atom through...
Show how you would use an acid chloride as an intermediate to synthesize (a) N-phenylbenzamide (PhCONHPh) from benzoic acid and aniline. (b) Phenyl propionate (CH3CH2COOPh) from propionic acid and...
Draw the structures of the following compounds. (a) Ethanoic acid (b) Terephthalic acid (c) Magnesium formate (d) Malonic acid (e) Dichloroacetic acid (f) Salicylic acid (g) Zinc undecanoate...
Name the following carboxylic acids (when possible, give both a common name and a systematic name). (a) (b) (c) (d) (e) (f) CH3 CH2CH, COOH COOH NO NO. COOH COOH HO Cl COOH COOH
What do the following pKa values tell you about the electron-withdrawing abilities of nitro, cyano, chloro, and hydroxyl groups? CH COOH CH,COOH CH COOH CHACOOH CHACOOH NO, 1.68 CN 2.46 CI 2.86 3.83...
Given the structure of ascorbic acid (vitamin C): (a) Is ascorbic acid a carboxylic acid? (b) Compare the acid strength of ascorbic acid (pKa = 4.71) with acetic acid. (c) Predict which proton in...
Suppose you have just synthesized heptanoic acid from heptan-1-ol. The product is contaminated by sodium dichromate, sulfuric acid, heptan-1-ol, and possibly heptanal. Explain how you would use...
Phenols are less acidic than carboxylic acids, with values of pKa around 10. Phenols are deprotonated by (and therefore soluble in) solutions of sodium hydroxide but not by solutions of sodium...
Oxidation of a primary alcohol to an aldehyde usually gives some over-oxidation to the carboxylic acid. Assume you have used PCC to oxidize pentan-1-ol to pentanal. (a) Show how you would use...
The IR spectrum of trans-oct-2-enoic acid is shown. Point out the spectral characteristics that allow you to tell that this is a carboxylic acid, and show which features lead you to conclude that the...
Draw all four resonance forms of the fragment at m/z 73 in the mass spectrum of pentanoic acid.
(a) Explain why we speak of acidic hydrolysis of an ester as acid-catalyzed, but of basic hydrolysis as base-promoted. (b) Soap manufacturers always use base to hydrolyze fats, and never acid....
Propose a mechanism for the base-promoted hydrolysis of g-butyrolactone:
Draw the important resonance contributors for both resonance-stabilized cations (in brackets) in the mechanism for acid-catalyzed hydrolysis of an amide.
Suppose we have some optically pure (R)-2-butyl acetate that has been "labeled" with the heavy 18O isotope at one oxygen atom as shown. (a) Draw a mechanism for the hydrolysis of this compound under...
What characteristics of the methyl benzoate spectrum rule out an aldehyde or carboxylic acid functional group giving the absorption at 1723 cm-1?
The equilibrium for hydrolysis of amides, under both acidic and basic conditions, favors the products. Use your mechanisms for the hydrolysis of N,N-dimethylacetamide to show which steps are...
The mechanism for acidic hydrolysis of a nitrile resembles the basic hydrolysis, except that the nitrile is first protonated, activating it toward attack by a weak nucleophile (water). Under acidic...
(a) In which step(s) of the hydride reduction of an ester does the compound undergo reduction? (b) Propose a mechanism for the reduction of octanoyl chloride by lithium aluminum hydride.
Give the expected products of lithium aluminum hydride reduction of the following compounds (followed by hydrolysis). (a) Butyronitrile (b) N-cyclohexylacetamide (c) ε-carprolactam (d)...
Draw a mechanism for the acidic hydrolysis of the magnesium salt shown above to acetophenone.
Draw a mechanism for the reaction of propanoyl chloride with 2 moles of phenylmagnesium bromide.
Draw a mechanism for the acylation of anisole by propionyl chloride. Recall that Friedel-Crafts acylation involves an acylium ion as the electrophile in electrophilic aromatic substitution.
Show how Friedel-Crafts acylation might be used to synthesize the following compounds. (a) Acetophenone (b) Benzophenone (c) N-butylbenzene
(a) Give the products expected when acetic formic anhydride reacts with (i) aniline and (ii) benzyl alcohol. (b) Propose mechanisms for these reactions.
Show how you would use anhydrides to synthesize the following compounds. In each case, explain why an anhydride might be preferable to an acid chloride. (a) N-octyl formate (b) N-octyl acetate (c)...
Show how you would synthesize each compound, starting with an ester containing no more than eight carbon atoms. Any other necessary reagents may be used. (a) Ph3C¬OH (b) (PhCH2)2CHOH (c)...
Show how you would accomplish the following synthetic transformations. You may use any necessary reagents. (a) N-ethylbenzamide benzylethylamine (b) Ethyl benzoate N-ethylbenzamide (c) Pyrrolidine ...
Show how you would accomplish the following syntheses using amides as intermediates. You may use any necessary reagents. (a) Benzoic acid benzyldimethylamine (b) Pyrrolidine N-ethylpyrrolidine (c)...
Show how you would convert the following starting materials to the indicated nitriles: (a) Phe(nylacetic acid phenylacetonitrile (b) Phenylacetic acid 3-phenylpropionitrile (c) P-chloronitrobenzene...
Show how each transformation may be accomplished by using a nitrile as an intermediate. You may use any necessary reagents. (a) Hexan-1-ol heptan-1-amine (b) Cyclohexanecarboxamide cyclohexyl ethyl...
The IR spectra shown next may include a carboxylic acid, an ester, an amide, a nitrile, an acid chloride, or an acid anhydride. Determine the functional group suggested by each spectrum, and list the...
For each heterocyclic compound, (i) Explain what type of acid derivative is present. (ii) Show what compounds would result from complete hydrolysis. (iii) Are any of the rings aromatic? Explain. (a)...
Two widely used pain relievers are aspirin and acetaminophen. Show how you would synthesize these drugs from phenol. 0-C-CH3 NH C CH COOH HO aspirin acetaminophen
One mole of acetyl chloride is added to a liter of triethylamine, resulting in a vigorous exothermic reaction. Once the reaction mixture has cooled, 1 mole of ethanol is added. Another vigorous...
Show how you would synthesize the following esters from appropriate acyl chlorides and alcohols. (a) Ethyl propionate (b) Phenyl 3-methylhexanoate (c) Benzyl benzoate (d) Cyclopropyl...
Show how you would use appropriate acyl chlorides and amines to synthesize the following amides. (a) N,N-dimethylacetamide (b) Acetanilide (PhNHCOCH3) (c) Cyclohexanecarboxamide (d) O-C
For each set of IR and NMR spectra, determine the structure of the unknown compound. Explain how your proposed structure fits the spectra. (a) C3H5NO (b) C5H8O2 200 180 160 140 120 100 80 40 20 S0Hz...