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chemistry
organic chemistry
Questions and Answers of
Organic Chemistry
The Pka of propene is 42, which is greater than the pka of the carbon acids listed in Table 19.1, but less than the Pka of an alkane. Explain
How could the following compounds be prepared from a carbonyl compound with no carbon-carbon double bonds?a.b.
How could the following compounds be prepared from cyclohexanone?a.b. c. d.
Explain why alkylation of an α-carbon works best if the alkyl halide used in the reaction is a primary alkyl halide and why it does not work at all if it is a tertiary alkyl halide.
How could each of the following compounds be prepared from a ketone and an alkyl halide?a.b.
Describe how the following compounds could be prepared using an enamine intermediate:a.b.
What reagents would you use to prepare the following compounds?a.b.
Show the aldol addition product that would be formed from each of the following compounds:a.b. c. d.
For each of the following compounds, indicate the aldehyde or ketone from which it would be formed by an aldol addition: a. 2-ethyl-3-hydroxyhexanal b. 4-hydroxy-4-methyl-2-pentanone c.
An aldol addition can be catalyzed by acids as well as by bases. Propose a mechanism for the acid-catalyzed aldol addition of propanal.
Give an example of a. A nitrile b. a b- a β keto b-diester
How could you prepare the following compounds using a starting material containing no more than three carbon atoms?a.b.
Give the products obtained from mixed aldol additions of the following compounds:a.b. c. d.
Describe how the following compounds could be prepared using an aldol addition in the first step of the synthesis:a.b. c.
Propose a mechanism for the following reaction:
Give the products of the following reactionsa.b.
Explain why a Claisen condensation product is not obtained from esters such as ethyl benzoate and ethyl 2-methylbutanoate.
Give the product of each of the following reactions:a.b. c. d.
Show how the following compounds could be prepared, starting with 3 cyanocyclohexanonea.b.
Write the mechanism for the base-catalyzed formation of a cyclic ester from a 1,7-diester.
If the preference for formation of a six-membered ring were not so great, what other cyclic product would be formed from the intramolecular aldol addition of a. 2,6-heptanedione? b. 2,8-nonanedione?
List the compounds in each of the following groups in order of decreasing acidity:a.b. c.
Can 2,4-pentanedione undergo an intramolecular aldol addition? If so, why? If not, why not?
What products can be obtained if the following keto aldehyde is treated with a base? Which would you expect to be the major product?
Give the product of the reaction of each of the following compounds with a base:a.b. c. d.
Propose a synthesis for each of the following compounds, using a Robinson annulations:a.b. c. d.
Which of the following compounds would be expected to decarboxylate when heated?a.b. c. d.
What alkyl bromide(s) should be used in the malonic ester synthesis of each of the following carboxylic acids? a. Propanoic acid b. 2-methylpropanoic acid c. 3-phenylpentanoic acid d.
Explain why the following carboxylic acids cannot be prepared by the malonic ester synthesis:a.b. c.
Starting with methyl propanoate, how could you prepare 4-methyl-3-heptanone?
Design a synthesis for each of the following compoundsa.b. c. d.
Only 15% of 2,4-pentanedione exists as the enol tautomer in water, but 92% exists as the enol tautomer in hexane. Explain why this is so.
Propose a mechanism for the formation of D-fructose-1,6-diphosphate from dihydroxyacetone phosphate and D-glyceraldehyde-3-phosphate, using HO- as the catalyst.
Palmitic acid (hexadecanoic acid) is a saturated 16-carbon fatty acid. How many moles of malonyl-CoA are required for the synthesis of one mole of palmitic acid?
a. If the biosynthesis of palmitic acid were carried out with CD3COSR and nondeuterated malonyl thioester, how many deuteriums would be incorporated into palmitic acid? b. If the biosynthesis of
When the enzymatic decarboxylation of acetoacetate is carried out in H218O the acetone that is formed contains 18O. What does this tell you about the mechanism of the reaction?
Write a structure for each of the following: a. Ethyl acctoacclae b. Cx.nwthylmalonic acid c. A fi.keto ester d. The enol lautomer of cyclopentanone e. The carboxylic acid obtained from the maloic
Give the products of the following rcaciioiis: a. Dicthyl hcpanedioaac: (I) sodium ethosidc: (2) IICI b. Pcnloic acid + Pbr3 + Br2. followed by hydrolysis c. Acetom + ethyl acelale: (I) sodium
The chemical shifts of nitromethane, dinitromethane, and trinitromethane are at δ 6.10 δ 4.33, δ 7.52 Match each chemical shift with the compound. Explain how chemical shift correlates with pKa.
a. Explain why a racemic mixture of 2-methyl-1-phenyl-1-butanone is formed when (R)-2-methyl-1-phenyl-1-butanone is dissolved in an acidic or basic aqueous solution. b. Give an example of another
Identify A-L. (Hint: A shows three singlets in its spectrum with integral ratios and gives a positive iodoform test; see Section 19.4)
Show how the following compounds could be prepared from cyclohexanone
Draw the enol tautomers for each of the following compounds. For those compounds that have more than one enol tautomer, indicate which is more stable.a.b. c. d. e. f.
A carbonyl compound rearranges to a more stable conjugated compound in the presence of either acid or base.a. Propose a mechanism for the base-catalyzed rearrangement.b. Propose a mechanism for the
There are other condensation reactions similar to the aldol and Claisen condensations:a. The Perkin condensation is the condensation of an aromatic aldehyde and acetic anhydride. Give the product
The Reformatsky reaction is an addition reaction in which an organozinc reagent is used instead of a Grignard reagent to attack the carbonyl group of an aldehyde or a ketone. Because the organozinc
The ketone whose 1H NMR spectrum is shown here was obtained as the product of an acetoacetic ester synthesis. What alkyl halide was used in the synthesis?
Indicate how the following compounds could be synthesized from cyclohexanone and any other necessary reagents:a.b. c. d. e. f.
Compound A with molecular formula C6H10 has two peaks in its spectrum, both of which are singlets (with ratio). Compound A reacts with an acidic aqueous solution containing mercuric sulfate to form
Indicate how each of the following compounds could be synthesized from the given starting material and any other necessary reagents:a.b. c. d. e. f.
Bupropion hydrochloride is an antidepressant marketed under the trade name Wellbutrin®. Propose a synthesis of bupropion hydrochloride, starting with benzene.
What reagents would be required to carry out the following transformations?
Give the products of the following reactions:a.b.
a. Show how the amino acid alanine can be synthesized from propanoic acid.b. Show how the amino acid glycine can be synthesized from phthalimide and diethyl 2 bromomalonate.
Cindy Synthon tried to prepare the following compounds using aldol condensations. Which of these compounds was she successful in synthesizing? Explain why the other syntheses were not
Explain why the following bromoketone forms different bicyclic compounds under different reaction conditions:
Explain why the product obtained in the following reactions depends on the number of equivalents of base used in the reaction:
A Mannich reaction puts angroup on the of a carbon acid. Propose a mechanism for the reaction
What carbonyl compounds are required to prepare a compound with molecular formula C10H10Owhose spectrum is shown?
Ninhydrin reacts with an amino acid to form a purple-colored compound. Propose a mechanism to account for the formation of the colored compound.
A carboxylic acid is formed when an α haloketone reacts with hydroxide ion. This reaction is called a Favorskii reaction. Propose a mechanism for the following Favorskii reaction.
Give the products of the following reactions. (Hint: See Problem 67.)a.b.
An carbonyl compound can be prepared by a reaction known as a selenenylation-oxidation reaction. A selenoxide is formed as an intermediate. Propose a mechanism for the reaction.
Why do only methyl ketones undergo the haloform reaction?
a. What carboxylic acid would be formed if the malonic ester synthesis were carried out with one equivalent of malonic ester, one equivalent of 1,5-dibromopentane, and two equivalents of base? b.
A Cannizzaro reaction is the reaction of an aldehyde that has no α-hydrogens with concentrated aqueous sodium hydroxide. In this reaction, half the aldehyde is converted to a carboxylic
Propose a reasonable mechanism for each of the following reactions:a.b.
The following reaction is known as the benzoin condensation. The reaction will not take place if sodium hydroxide is used instead of sodium cyanide. Propose a mechanism for the reaction.
Orsellinic acid, a common constituent of lichens, is synthesized from the condensation of acetyl thioester and malonyl thioester. If a lichen were grown on a medium containing acetate that was
A compound known as Hagemann's ester can be prepared by treating a mixture of formaldehyde and ethyl acetoacetate first with base and then with acid and heat. Write the structure for the product of
Amobarbital is a sedative marketed under the trade name Amytal®. Propose a synthesis of amobarbital, using diethyl malonate and urea as two of the starting materials.
Propose a reasonable mechanism for each of the following reactions:a.b.
Tyramine is an alkaloid found in mistletoe, ripe cheese, and putrefied animal tissue. Dopamine is a neurotransmitter involved in the regulation of the central nervous system.a. Gwe two ways to
Show how estrone, a steroid hormone, can be prepared from the given starting materials. (Hint: Start with a Robinson annulation.)
A ketone undergoes acid-catalyzed bromination, acid-catalyzed chlorination, and acid-catalyzed deuterium exchange at the α-carbon, all at about the same rate. What does this tell you about the
a. Ketoprofen, like ibuprofen, is an anti-inflammatory analgesic. How could ketoprofen be synthesized from the given starting material?b. Ketoprofen and ibuprofen both have a propanoic acid
How would you prepare the following compounds from the given starting materials?a.b. c. d.
Indicate whether each of the following reactions is an oxidation reaction, a reduction reaction, or neither:a.b. c. d. e. f.
How could butanone be prepared from butane?
Give the products of the following reactions:a.b. c. d. e. f.
What alkene would you treat with a peroxyacid in order to obtain each of the following epoxides?a.b. c. d.
Give the major product of the reaction of each of the following compounds with one equivalent of a peroxyacid. Indicate the configuration of the product.a.b. c. d.
Show how the following target molecules could be synthesized from propene: a. 1-methoxy-2-propanol b. 2-butanol c. 2-butanone
Explain why an epoxide is a relatively stable product, whereas a bromonium ion is a reactive intermediate.
What is the product of the reaction of methylmagnesium bromide with either of the enantiomerically pure epoxides that can be prepared from (E)-3-methyl-2-pentene by the preceding method? Assign R or
Is the addition of Br2 to an alkene such as trans-2-pentene a stereoselective reaction? Is it a stereospecific reaction? Is it an enantioselective reaction?
Give the products that would be formed from the reaction of each of the following alkenes with OsO4, followed by aqueous H2O2a.b.
What stereoisomers would be formed from the reaction of each of the following alkenes with OsO4 followed by H2O2? a. trans-2-butene b. cis-2-butene c. cis-2-pentene d. trans-2-pentene
Give the products of the following reactions:a.b. c. d. e. f. g. h.
An alkene is treated with OsO4 followed by H2O2. When the resulting diol is treated with HIO4, the only product obtained is an unsubstituted cyclic ketone with molecular formula C6H10O. What is the
Which of each pair of diols is cleaved more rapidly by periodic acid?a.b.
Give an example of an alkene that will form the same ozonolysis products, regardless of whether the ozonide is worked up under reducing conditions (Zn, H2O) or oxidizing conditions (H2O2).
Give the products that you would expect to obtain when the following compounds are treated with ozone, followed by work-up witha. Zn, H2O:b. H2O21.2. CH2¡CHCH2CH2CH2CH3 3. 4. 5.
a. What alkene would give only acetone as a product of ozonolysis? b. What alkenes would give only butanal as a product of ozonolysis?
The following products were obtained from ozonolysis of a diene followed by work-up under reducing conditions. Give the structure of the diene.
Describe how the following compound could be prepared, using the given starting materials (perform a retrosynthetic analysis to help you arrive at your answer):
a. How could you synthesize the following compound from starting materials containing no more than four carbons? (A 1,6-diketone can be synthesized by oxidative cleavage of a 1,2 disubstituted
What is the structure of the alkyne that gives each of the following sets of products upon ozonolysis followed by hydrolysis?a.b.
Explain why terminal alkynes cannot be reduced by Na in liquid NH3.
Add the necessary reagents over the reaction arrows.a.b.
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