Propose a mechanism to show how acetophenone undergoes base-promoted chlorination to give trichloroacetophenone.
Propose a mechanism for the reaction of cyclohexyl methyl ketone with excess bromine in the presence of sodium hydroxide.
Predict the products of the following reactions. (a) Cyclopentyl methyl ketone + excess Cl2 + excess NaOH (b) 1-cyclopentylethanol + excess I2 + excess NaOH (c) Propiophenone + excess Br2 + excess...
Which compounds will give positive iodoform tests? (a) 1-phenylethanol (b) Pentan-2-one (c) Pentan-2-ol (d) Pentan-3-one (e) Acetone (f) Isopropyl alcohol
Propose a mechanism for the acid-catalyzed bromination of pentan-3-one.
Phosgene is the acid chloride of carbonic acid. Although phosgene was used as a war gas in World War I, it is now used as a reagent for the synthesis of many useful products. Phosgene reacts like...
Show how you would accomplish the following syntheses. Some of these conversions may require more than one step. (a) Isopentyl alcohol isopentyl acetate (banana oil) (b) 3-ethylpentanoic acid...
Grignard reagents add to carbonate esters as they add to other esters. (a) Predict the major product of the following reaction. (b) Show how you would synthesize 3-ethylpentan-3-ol using diethyl...
Show the products of the reactions of these carboxylic acids with PB3/Br2 before and after hydrolysis. (a) Pentanoic acid (b) Phenylacetic acid (c) Succinic acid (d) Oxalic acid
Propose a mechanism for the aldol condensation of cyclohexanone. Do you expect the equilibrium to favor the reactant or the product?
An unknown compound gives a mass spectrum with a weak molecular ion at m/z 113 and a prominent ion at m z 68. Its NMR and IR spectra are shown here. Determine the structure, and show how it is...
An unknown compound of molecular formula C5H9NO gives the IR and NMR spectra shown here. The broad NMR peak at δ7.55 disappears when the sample is shaken with D2O. Propose a structure,...
Which of the following proposed reactions would take place quickly under mild conditions? (a) (b) (c) (d) (e) (CHJ2CH-C-NH, + CH3OH (CHJ-CH-C-OCH, + NH, CH,CH,--C-Cl + CH3-C-OH CH,CH-_C_O_C_CH, + HCI
Propose a mechanism for the dehydration of diacetone alcohol to mesityl oxide (a) In acid (b) In base
When propionaldehyde is warmed with sodium hydroxide, one of the products is 2-methylpent- 2-enal. Propose a mechanism for this reaction.
Propose mechanisms for the following base-catalyzed condensations, with dehydration. (a) 2, 2-dimethylpropanal with acetaldehyde (b) Benzaldehyde with propionaldehyde
When acetone is treated with excess benzaldehyde in the presence of base, the crossed condensation adds two equivalents of benzaldehyde and expels two equivalents of water. Propose a structure for...
In the problem-solving feature above, methylcyclohexanone was seen to react at its unsubstituted carbon. Try to write a mechanism for the same reaction at the methyl-substituted carbon atom, and...
Predict the major products of the following base-catalyzed aldol condensations with dehydration. (a) Benzophenone (PhCOPh) + propionaldehyde (b) 2,2-dimethylpropanal + acetophenone
Give the important resonance forms for the possible enolate ions of: (a) Acetone (b) Cyclopentanone (c) Pentane-2,4-dione (d) (e) (f)
Show how octane-2,7-dione might cyclize to a cycloheptenone. Explain why ring closure to the cycloheptenone is not favored.
When cyclodecane-1,6-dione is treated with sodium carbonate, the product gives a UV spectrum similar to that of 1-acetyl-2-methylcyclopentene. Propose a structure for the product, and give a...
Show how each compound can be dissected into reagents joined by an aldol condensation, then decide whether the necessary aldol condensation is feasible. (a) (b) (c) (d) (e) CH,CH,CH-_-CH-CH-_CHO...
The following compound results from base-catalyzed aldol cyclization of a 2-substituted cyclohexanone. (a) Show the diketone that would cyclize to give this product. (b) Propose a mechanism for the...
Ethoxide is used as the base in the condensation of ethyl acetate to avoid some unwanted side reactions. Show what side reactions would occur if the following bases were used. (a) Sodium methoxide...
Esters with only one hydrogen generally give poor yields in the Claisen condensation. Propose a mechanism for the Claisen condensation of ethyl isobutyrate, and explain why a poor yield is obtained.
Propose a mechanism for the self-condensation of methyl 3-phenylpropionate catalyzed by sodium methoxide.
Propose mechanisms for the two Dieckmann condensations just shown.
Predict the products of self-condensation of the following esters. (a) Methyl propanoate + NaOCH3 (b) Ethyl phenylacetate + NaOCH2CH3 (c) (d) CH-C-OCH + NaOCH COOEt +NaOEt
Show what esters would undergo Claisen condensation to give the following b-keto esters. (a) (b) (c) CH,CHCH,-C" - CH,CH,-CH-C-OCH,CH, Ph-CH,-C" O Ph CHCOCH CH(CH32
Some (but not all) of the following keto esters can be formed by Dieckmann condensations. Determine which ones are possible, and draw the starting diesters. (a) (b) (c) (d) C-OCH,CH
Propose a mechanism for the crossed Claisen condensation between ethyl acetate and ethyl benzoate.
Show how crossed Claisen condensations could be used to prepare the following esters. (a) (b) (c) (d) Ph C-CH-C OCH,CH CH CH-C-OCH3 C-C-oCH Eto C CH-C OCH,CH Ph CH,CH,CH,
Predict the major products of the following crossed Claisen condensations. (a) (b) (c) NaOCH + Ph-C OCH NaOCH,CH CH,CH C CH CH,CHO C 0CH2CH NaOCH2CH
The base-catalyzed reaction of an aldehyde (having no hydrogens) with an anhydride is called the Perkin condensation. Propose a mechanism for the following example of the Perkin condensation. (Sodium...
Propose a mechanism for the acid-catalyzed reaction of cyclohexanone with pyrrolidine.
Without looking back, propose a mechanism for the hydrolysis of this iminium salt to the alkylated ketone. The first step is attack by water, followed by loss of a proton to give a carbinolamine....
Give the expected products of the following acid-catalyzed reactions. (a) Acetophenone + methylamine (b) Acetophenone + dimethylamine (c) Cyclohexanone + aniline (d) Cyclohexanone + piperidine
Show how you would accomplish each conversion using an enamine synthesis with pyrrolidine as the secondary amine. (a) Cyclopentanone 2-allylcyclopentanone (b) Pentan-3-one...
Draw the mirror images of glucose and fructose. Are glucose and fructose chiral? Do you expect them to be optically active?
Talose is the C4 epimer of mannose. Draw the chair conformation of D-talopyranose.
(a) Figure 23-2 shows that the degradation of D-glucose gives D-arabinose, an aldopentose. Arabinose is most stable in its furanose form. Draw D-arabinofuranose. (b) Ribose, the C2 epimer of...
The carbonyl group in D-galactose may be isomerized from C1 to C2 by brief treatment with dilute base (by the enediol rearrangement, Section 23-8). The product is the C4 epimer of fructose. Draw the...
Draw the following monosaccharides, using chair conformations for the pyranoses and Haworth projections for the furanoses. (a) -D-mannopyranose (C2 epimer of glucose) (b) -D-galactopyranose (C4...
Propose a mechanism for the base-catalyzed epimerization of erythrose to a mixture of erythrose and threose.
Show how another enediol rearrangement can move the carbonyl group from C2 in fructose to C3.
When D-glucose is reduced with sodium borohydride, optically active glucitol results. When optically active D-galactose is reduced, however, the product is optically inactive. Explain this loss of...
(a) How many asymmetric carbon atoms are there in an aldotetrose? Draw all the aldotetrose stereoisomers. (b) How many asymmetric carbons are there in a ketotetrose? Draw all the ketotetrose...
Emil Fischer synthesized L-gulose, an unusual aldohexose that reduces to give D-glucitol. Suggest a structure for this L sugar, and show how L-gulose gives the same alditol as D-glucose.
Draw and name the products of bromine water oxidation of (a) D-mannose (b) D-galactose (c) D-fructose
Draw and name the products of nitric acid oxidation of (a) D-mannose (b) D-galactose
Two sugars, A and B, are known to be glucose and galactose, but it is not certain which one is which. On treatment with nitric acid, A gives an optically inactive aldaric acid, while B gives an...
Draw the structures of the compounds named in Problem 23-24 parts (a), (c), and (d). Allose is the C3 epimer of glucose, and ribose is the C2 epimer of arabinose.
The mechanism of glycoside formation is the same as the second part of the mechanism for acetal formation. Propose a mechanism for the formation of methyl -D-glucopyranoside.
Show the products that result from hydrolysis of amygdalin in dilute acid. Can you suggest why amygdalin might be toxic to tumor (and possibly other) cells?
Propose a mechanism for methylation of any one of the hydroxyl groups of methyl -D-glucopyranoside, using NaOH and dimethyl sulfate.
Draw the expected product of the reaction of the following sugars with excess methyl iodide and silver oxide. (a) -D-fructofuranose (b) -D-galactopyranose
Predict the products formed when the following sugars react with excess acetic anhydride and pyridine. (a) -D-glucopyranose (b) -D-ribofuranose
Show that Ruff degradation of D-mannose gives the same aldopentose (D-arabinose) as does D-glucose.
D-Lyxose is formed by Ruff degradation of galactose. Give the structure of D-lyxose. Ruff degradation of D-lyxose gives D-threose. Give the structure of D-threose.
D-Altrose is an aldohexose. Ruff degradation of D-altrose gives the same aldopentose as does degradation of D-allose, the C3 epimer of glucose. Give the structure of D-altrose.
Ruff degradation of D-arabinose gives D-erythrose. The Kiliani-Fischer synthesis converts D-erythrose to a mixture of D-arabinose and D-ribose. Draw out these reactions, and give the structure of...
The Wohl degradation, an alternative to the Ruff degradation, is nearly the reverse of the Kiliani-Fischer synthesis. The aldose carbonyl group is converted to the oxime, which is dehydrated by...
In 1891, Emil Fischer determined the structures of glucose and the seven other D-aldohexoses using only simple chemical reactions and clever reasoning about stereochemistry and symmetry. He received...
Draw and name the enantiomers of the sugars shown in Figure 23-2. Give the relative configuration (D or L) and the sign of the rotation in each case.
(a) Draw the reaction of methyl -D-fructofuranoside with periodic acid, and predict the products. (b) Draw the structure of a hypothetical methyl -D-fructopyranoside, and predict the products from...
Draw the structures of the individual mutarotating and anomers of maltose.
Give an equation to show the reduction of Tollens reagent by maltose.
Does lactose mutarotate? Is it a reducing sugar? Explain. Draw the two anomeric forms of lactose.
Trehalose is a nonreducing disaccharide (C12H22O11) isolated from the poisonous mushroom Amanita muscaria. Treatment with an -glucosidase converts trehalose to two molecules of glucose, but no...
Cellulose is converted to cellulose acetate by treatment with acetic anhydride and pyridine. Cellulose acetate is soluble in common organic solvents, and it is easily dissolved and spun into fibers....
Raffinose is a trisaccharide (C18H32O16) isolated from cottonseed meal. Raffinose does not reduce Tollens reagent, and it does not mutarotate. Complete hydrolysis of raffinose gives D-glucose,...
Cytosine, uracil, and guanine have tautomeric forms with aromatic hydroxyl groups. Draw these tautomeric forms.
Which configuration (R or S) does the bottom asymmetric carbon have for the D series of sugars? Which configuration for the L series?
(a) An aliphatic aminoglycoside is relatively stable to base, but it is quickly hydrolyzed by dilute acid. Propose a mechanism for the acid-catalyzed hydrolysis. (b) Ribonucleosides are not so easily...
All of the rings of the four heterocyclic bases are aromatic. This is more apparent when the polar resonance forms of the amide groups are drawn, as is done for thymine at the right. Redraw the...
Use Figure 23-3 (the D family of aldoses) to name the following aldoses. (a) The C2 epimer of D-arabinose (b) The C3 epimer of D-mannose (c) The C3 epimer of D-threose (d) The enantiomer of...
Draw Fischer projections for the enantiomers of threo-hexane-1, 2, 3-triol. HOCH2 - CH(OH) - CH(OH) - CH2CH2CH3
After a series of Kiliani-Fischer syntheses on (+)-glyceraldehyde, an unknown sugar is isolated from the reaction mixture. The following experimental information is obtained: (1) Molecular formula...
The bronchodilator ephedrine is erythro-2-(methylamino)-1-phenylpropan-1-ol. The decongestant pseudoephedrine is threo-2-(methylamino)-1-phenylpropan-1-ol. (a) Draw the four stereoisomers of...
(a) Draw D-allose, the C3 epimer of glucose. (b) Draw D-talose, the C2 epimer of D-galactose. (c) Draw D-idose, the C3 epimer of D-talose. Now compare your answers with Figure 23-3. (d) Draw the C4...
Draw the Haworth projection for the cyclic structure of D-mannose by laying down the Fischer projection.
Show how the Gabriel-malonic ester synthesis could be used to make (a) Valine (b) Phenylalanine (c) Glutamic acid (d) Leucine
Give equations for the formation and hydrogenolysis of glutamine benzyl ester.
Give equations for the formation and hydrogenolysis of N-benzyloxycarbonyl methionine.
Use resonance forms to show delocalization of the negative charge in the Ruhemann's purple anion.
Most naturally occurring amino acids have chirality centers (the asymmetric carbon atoms) that are named (S) by the Cahn-Ingold-Prelog convention (Section 5-3). The common naturally occurring form of...
Show how you would synthesize Ala-Val-Phe-Gly-Leu starting with Z-Ala-Val-Phe.
Show how you would synthesize Leu-Gly-Ala-Val-Phe starting with Boc-Ala-Val-Phe- P.
Show how you would use the Strecker synthesis to make tryptophan. What stereochemistry would you expect in your synthetic product?
Aspartame (Nutrasweet) is a remarkably sweet-tasting dipeptide ester. Complete hydrolysis of aspartame gives phenyl alanine, aspartic acid, and methanol. Mild incubation with carboxypeptidase has no...
Although tryptophan contains a heterocyclic amine, it is considered a neutral amino acid. Explain why the indole nitrogen of tryptophan is more weakly basic than one of the imidazole nitrogens of...
A molecular weight determination has shown that an unknown peptide is a pentapeptide, and an amino acid analysis shows that it contains the following residues: one Gly, two Ala, one Met, one Phe....
Draw each molecule in a stable chair conformation, and tell whether each red group is axial or equatorial. (a) (b) (c) (d) CH CH3 CH CH3 l1 C H,C H HIH OH H androsterone H.C H,C H HOH HO...
A triglyceride can be optically active if it contains two or more different fatty acids. (a) Draw the structure of an optically active triglyceride containing one equivalent of myristic acid and two...
The structure of limonene appears in Problem 25-13. Predict the products formed when limonene reacts with the following reagents. In problem 25.13 (a) Excess HBr (b) Excess HBr, peroxides (c) Excess...
The following five compounds are found in Vicks Vapo-Rub®. (a) Which are terpenes? Circle the isoprene units of the terpenes. (b) Do you expect Vicks Vapo-Rub to be optically active? Explain.
(a) Nomex, a strong fire-resistant fabric, is a polyamide made from meta-phthalic acid and meta-diaminobenzene. Draw the structure of Nomex. (b) Kevlar, made from terephthalic acid (para-phthalic...
(a) Propose a mechanism for the reaction of bisphenol A with phosgene. (b) Diethyl carbonate serves as a less-toxic alternative to phosgene for making Lexan. Propose a mechanism for the...
Write an equation for the reaction of sodium atoms (Na) with chlorine atoms (Cl).