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1 Million+ Step-by-step solutions Q:As Problem 50 indicates, the enzymatic reactions that introduce functionalAs Problem 50 indicates, the enzymatic reactions that introduce functional groups into the steroid nucleus in nature are highly selective, unlike the laboratory chlorination described in Problem 51. However, by means of a clever adaptation of this reaction, it is possible to partly mimic nature’s selectivity in the laboratory. Two such examples are illustrated below.
Propose reasonable explanations for the results of these two reactions. Make a model of the product of the addition of Cl2 to each iodocompound (compare Problem 51) to help in analyzing each system.
Q:Consider the following compounds: Conformational analysis reveals that, though compound AConsider the following compounds:
Conformational analysis reveals that, though compound A exists in a chair conformation, compound B does not.
(a) Make a model of A. Draw chair conformations and label the substituent’s as equatorial or axial. Circle the most stable conformation.
(b) Make a model of B. Consider both transannular and gauche interactions in your analysis of its two chair forms. Discuss the steric problems of these conformations in comparison with those of A. Illustrate the key points of your discussion with Newman projections. Suggest a less satirically encumbered conformation for B.
Q:Which of the following cycloalkanes has the greatest ring strain? (a)Which of the following cycloalkanes has the greatest ring strain?
Q:The following molecule has (a) One axial chlorine and one sp1The following molecule
has (a) One axial chlorine and one sp1 carbon, (b) One axial chlorine and two sp2 carbons, (c) One equatorial chlorine and one sp2 carbon, or (d) One equatorial chlorine and two sp2 carbons.
Q:In this compound, (a) The D is equatorial (b) The methyls areIn this compound,
(a) The D is equatorial
(b) The methyls are both equatorial
(c) The CI is axial
(d) The deuterium is axial.
Q:Which of the following structures has the smallest heat ofWhich of the following structures has the smallest heat of combustion?
Q:Each part of this problem lists two objects or setsEach part of this problem lists two objects or sets of objects. As precisely as you can, describe the relation between the two sets, using the terminology of this chapter; that is, specify whether they are identical, enantiomeric, or diastereomeric.
(a) An American toy car compared with a British toy car (same color and design but steering wheels on opposite sides);
(b) Two left shoes compared with two right shoes (same color, size, and style);
(c) A pair of skates compared with two left skates (same color, size, and style);
(d) a right glove on top of a left glove (palm to palm) compared with a left glove on top of a right glove (palm to palm: same color, size, and style).
Q:For each pair of the following molecules, indicate whether itsFor each pair of the following molecules, indicate whether its members are identical, structural isomers, conformers, or stereoisomers. How would you describe the relation between conformations when they are maintained at a temperature too low to permit them to interconvert?
Q:Which of the following compounds are chiral? (a) 2-Methylheptane (b) 3-Methylheptane (c) 4-MethylWhich of the following compounds are chiral?
(g) Ethene, H2C=CH2
(h) Ethyne, HCâ¡CH2
(l) Citric acid,
(m) Ascorbic acid,
(n) p-Menthane-1,8-diol (terpin hydrate),
(o) Meperidine (demerol),
Q:Each of the following molecules has the molecular formula C5H120.Each of the following molecules has the molecular formula C5H120. Which ones are chiral?
Q:Draw either one of the enantiomers for each chiral moleculeDraw either one of the enantiomers for each chiral molecule in Problem 34 and label its stereocenter as R or S.
Q:Which of the following cyclohexane derivatives are chiral? For theWhich of the following cyclohexane derivatives are chiral? For the purpose of determining the chirality of a cyclic compound, the ring may generally be treated as if it were planar.
Q:Label every stereocenter in the molecules in Problem 36 asLabel every stereocenter in the molecules in Problem 36 as R or S.
Q:Circle each chiral molecule. Put a star (*) next toCircle each chiral molecule. Put a star (*) next to each chiral carbon and label it as R or 5.
Q:For each pair of Structures shown, indicate whether the twoFor each pair of Structures shown, indicate whether the two species are constitutional isomers, enantiomers, diastereomers of one another, or identical molecules.
Q:For identify every structural isomer containing one or more stereocenters,For identify every structural isomer containing one or more stereocenters, give the number of stereoisomers for each, and draw and fully name at least one of the stereoisomers in each case
(c) C5H10,with one ring
Q:Assign the appropriate designation of configuration (R or S) toAssign the appropriate designation of configuration (R or S) to the stereocenter in each of the following enantiomers. (Hint: Regarding cyclic structures containing stereocenters, treat the ring as if it were two separate substituents that happen to be attached to each other at the far end of the molecule – look for the first point of difference, just as you would for acyclic structures.)
Q:Mark the stereocenters in each of the chiral molecules inMark the stereocenters in each of the chiral molecules in Problem 33. Draw any single stereoisomer of each of these molecules, and assign the appropriate designation (R or 5) to each stereocenter.
Q:The two enantiomers of carvone [systematic name: 2-methyl-5-(l-methylethenyl)-2-cyclohexenone; ChemiThe two enantiomers of carvone [systematic name: 2-methyl-5-(l-methylethenyl)-2-cyclohexenone; Chemical Highlight 5-1] are drawn in the margin. Which is R and which is S?
Q:Draw structural representations of each of the following molecules. BeDraw structural representations of each of the following molecules. Be sure that your structure clearly shows the configuration at the stereocenter. (Hint: You may find it useful to first draw the enantiomer whose configuration is easiest for you to determine and then, if necessary, modify your structure to fit the one requested in the problem.)
Q:Draw structural representations of each of the following molecules. BeDraw structural representations of each of the following molecules. Be sure that your structure clearly shows the configuration at each stereocenter.
(f) (1R,2R,3S)-1,2- dichloro-3-ethylcyclohexane.
Q:Draw and name all possible stereoisomers of (CH3)2CHCHBrCHClCH3.Draw and name all possible stereoisomers of (CH3)2CHCHBrCHClCH3.
Q:For each of the following questions, assume that all measurementsFor each of the following questions, assume that all measurements are made in 10-cm polarimeter sample containers, (a) A 10-mL solution of 0.4 g of optically active 2-butanol in water displays an optical rotation of -0.56°. What is its specific rotation? (b) The specific rotation of sucrose (common sugar) is +66.4. What would be the observed optical rotation of such a solution containing 3 g of sucrose? (c) A solution of pure (S)-2-bromobutane in ethanol is found to have an observed a = 57.3°. If [a] for (S)-2-bromobutane is 23.1. what is the concentration of the solution?
Q:Natural epinephrine, [a]D25oC = -50, is used medicinally. Its enantiomerNatural epinephrine, [a]D25oC = -50, is used medicinally. Its enantiomer is medically worthless and is. in fact, toxic. You, a pharmacist, are given a solution said to contain 1 g of epinephrine in 20 mL of liquid, but the optical purity is not specified. You place it in a polarimeter (10-cm tube) and get a reading of -2.5°. What is the optical purity of the sample? Is it safe to use medicinally?
Q:Sodium hydrogen (S)-glutamate [(S)-monosodium glutamate], [a]D25oC = +24, is theSodium hydrogen (S)-glutamate [(S)-monosodium glutamate], [a]D25oC = +24, is the active flavor enhancer known as MSG. The condensed formula of MSG is shown in the margin, (a) Draw the structure of the S enantiomer of MSG. (b) If a commercial sample of MSG were found to have a [a]D25oC = +8. what would be its optical purity?”What would be the percentages of the S and R enantiomers in the mixture? (c) Answer the same questions for a sample with [a]D25oC = +16.
Q:The molecule in the margin is menthol, with the stereochemistryThe molecule in the margin is menthol, with the stereochemistry omitted, (a) Identify all stereocenters in menthol, (b) How many stereoisomers exist for the menthol structure? (c) Draw all the stereoisomers of menthol, and identify all pairs of enantiomers.
Q:Natural (-)-menthol, the essential oil primarily responsible for the flavorNatural (-)-menthol, the essential oil primarily responsible for the flavor and aroma of peppermint, is the 1R,2S,5R -stereoisomer. (a) Identify (-)-menthol from the structures you drew for Problem 50, part (b). (b) Another of the naturally occurring diastereomers of menthol is ( + )-isomenthol, the 15,2/?,5/?-stereoisomer. Identify (+)-isomenthol among your structures, (c) A third is (+)-neomenthol, the lS,25,5R-compound. Find (+)-neomenthol among your structures, (d) Based on your understanding of the conformations of substituted cyclohexanes (Section 4-4), what is the stability order (from most stable to least) for the three diastereomers. menthol, isomenthol, and neomenthol?
Q:Of the stereoisomers described in the two problems above, (-)-mentholOf the stereoisomers described in the two problems above, (-)-menthol ([a]D = -51) and ( +)-neomenthol ([a]D = +21) are the major constituents in mentha oil, their main natural source. The menthol-neomenthol mixture in a natural sample of mentha oil exhibits [a]D = -33. What are the percentages of menthol and neomenthol in this oil?
Q:For each of the following pairs of structures, indicate whetherFor each of the following pairs of structures, indicate whether the two compounds are identical or enantiomers of each other.
Q:Determine the R or S designation for each stereocenter inDetermine the R or S designation for each stereocenter in the structures in problem 53.
Q:The compound pictured in the margin is a sugar calledThe compound pictured in the margin is a sugar called (-)arabinose. Its specific rotation is -105. (a) Draw the enanfiomer of (-)-arabinose. (b) Does (-)-arabinose have any other enantiomers? (c) Draw a diastereorner of (-)-arahinose. d) Does (-)-arahinose have any other diastereomers? (e) If possible predict the specific rotation o1 the sructure that you drew for (a). (f) If possible predict the specific rotation of the structure that you drew for (C). (g) Does (-)-arabinose have any optically inactive diastereomers? If it does, draw one.
Q:Write the complete IUPAC name of the following enantiomer (DoWrite the complete IUPAC name of the following enantiomer (Do not forget stereochemical designations).
Reaction of this compound with 1 mol of Cl2 in the presence of light produces several isomers of the formula C5H9CI3. For each part of this problem, give the following information: How many stereoisomers are formed? If more than one is formed, are they generated in equal or unequal amounts? Designate every stereocenter in each stereoisomer as R or 5.
(a) Chlorination at C3
(b) Chlorination at C4
(c) Chlorination at C5
Q:Monochlorination of methylcyclopentane can result in several products. Give theMonochlorination of methylcyclopentane can result in several products. Give the same information as that requested in Problem 56 for the monochlorination of methylcyclopentane at Cl, C2, and C3.
Q:Draw all possible products of the chlorination of (S)-2-bromo-l,l-dimethylcyclobutane. SpecifyDraw all possible products of the chlorination of (S)-2-bromo-l,l-dimethylcyclobutane. Specify whether they are chiral or achiral, whether they are formed in equal or unequal amounts, and which are optically active when formed.
Q:Illustrate how to resolve racemic 1-phenylethanamine (shown in the margin),Illustrate how to resolve racemic 1-phenylethanamine (shown in the margin), using the method of reversible conversion into diastereomers.
Q:Draw a flowchart that diagrams a method for the resolutionDraw a flowchart that diagrams a method for the resolution of racemic 2-hydroxypropanoic acid (lactic acid, Table 5-1), using (5)-1-phenylethanamine.
Q:How many different stereoisomeric products are formed in the monobrominationHow many different stereoisomeric products are formed in the monobromination of (a) racemic l,2-dimethylcyclohexane and (b) pure (R,R)-1,2-dimethylcyclohexane? (c) For your answers to (a) and (b), indicate whether you expect equal or unequal amounts of the various products to be formed. Indicate to what extent products can be separated on the basis of having different physical properties (e.g., solubility, boiling point).
Q:Make a model of cis-1,2-dimethylcyclohexane in its most stable conformation.Make a model of cis-1,2-dimethylcyclohexane in its most stable conformation. If the molecule were rigidly locked into this conformation, would it be chiral? (Test your answer by making a model of the mirror image and checking for superimposability.)
Flip the ring of the model. What is the stereoisomeric relation between the original conformation and the conformation after flipping the ring? How do the results that you have obtained in this problem relate to your answer to Problem 36(a).
Q:Morphinane is the parent substance of the broad class ofMorphinane is the parent substance of the broad class of chiral molecules known as the morphine alkaloids. Interestingly, the (+) and (-) enantiomers of the compounds in this family have rather different physiological properties. The (-) compounds, such as morphine, are “narcotic analgesics” (painkillers), whereas the (+) compounds are “antitussives” (ingredients in cough syrup). Dextro-methorphan is one of the simplest and most common of the latter.
(a) Locate and identify all the stereocenters in dextromethorphan.
(b) Draw the enantiomer of dextromethorphan.
(c) As best you can (it is not easy), assign R and S configurations to all the stereocenters in dextromethorphan.
Q:We will learn in Chapter 18 that hydrogens on theWe will learn in Chapter 18 that hydrogens on the carbon atom adjacent to the carbonyl functional group (C=0) are acidic. The compound (S)-3-methyl-2-pentanone, loses its optical activity when it is dissolved in a solution containing a catalytic amount of base. Explain.
Q:The enzymatic introduction of a functional group into a biologicallyThe enzymatic introduction of a functional group into a biologically important molecule is not only specific with regard to the location at which the reaction occurs in the molecule (see Chapter 4, Problem 50), but also usually specific in the stereochemistry obtained. The biosynthesis of epinephrine first requires that a hydroxy group be introduced specifically to produce (-)-norepinephrine from the achiral substrate dopamine. (The completion of the synthesis of epinephrine will be presented in Problem 71 of Chapter 9.) Only the (-) enantiomer is functional in the appropriate physiological manner, so the synthesis must be highly stereoselective.
(a) Is the configuration of (-) norepinephrine R or S?
(b) In the absence of an enzyme, would the transition states of a radical oxidation leading to (-)- and (+)-norepinephrine be of equal or unequal energy? What term describes the relation between these transition states
(c) In your own words, describe how the enzyme must affect the energy of these transition states to favor production of the (-) enantiomer. Does the enzyme have to be chiral or can it be achiral?
Q:Studies have shown that one stereoisomeric certain types of neurodegenerativeStudies have shown that one stereoisomeric certain types of neurodegenerative disorders, system, as illustrated in structure B, and that form of compound A is an effective agent against Recognize that structure A contains a decalin-type the nitrogen can be treated just like a carbon.
(a) Use your model kits to analyze the ring juncture. Make models of the cis as well as the trans ring juncture of structure B. You should have four different models. Identify the stereochemical relation between them as diastereomeric or enantiomeric. Draw the isomers and assign the R or S configuration to the stereocenters at the ring fusion.
(b) Although the trans ring juncture is the energetically more favorable one, the compound with cis ring juncture is the stereoisomer of structure A that shows biological activity. Make models of structure A that have the cis ring juncture exclusively. Set the stereochemistry of C3 as shown in structure A and vary the center at C6 in relation to that at C3. Again, there are four different models. Draw them and convince yourselves that none of them are enantiomers by assigning the R or S configuration to all four of the stereocenters in each of the compounds.
(c) The stereoisomer of compound A that shows the greatest biological activity has a cis ring fusion with substituents at C3 and C6 that are both equatorial. Which of the stereoisomers that you drew encompasses these constraints? Identify it by recording the absolute configuration at C3, C4a, C6, and C8a.
Q:Which compound will not exhibit optical activity? (Note that theseWhich compound will not exhibit optical activity? (Note that these are all Fischer projections.)
Q:The enantiomer of (a) Is (b) Can exist only at low temperatures (c)The enantiomer of
(b) Can exist only at low temperatures
(c) Is nonisomeric
(d) Is incapable of existence
Q:The molecule that is of the R configuration according toThe molecule that is of the R configuration according to the Cahn-Ingold-Prelog convention is (remember these are Fischer projections):
Q:Which compound is not a meso compound? (a) (b) (c) (d) (e)Which compound is not a meso compound?
Q:Name the following molecules according to the IUPAC system.Name the following molecules according to the IUPAC system.
Q:Draw structures for each of the following molecules: (a) 3-ethyl-2-iodopentane: (b)Draw structures for each of the following molecules:
(b) 3-bromo-1.1 -dichlorobutane;
(c) Cis- l-(bromomethyl)-2-(2-chloroethyl(cyclobutane:
Q:Draw and name all possible structural isomers having the formulaDraw and name all possible structural isomers having the formula C3H6BrCl.
Q:Draw and name all structurally isomeric compounds having the formulaDraw and name all structurally isomeric compounds having the formula C5H11Br.
Q:For each structural isomer in Problems 33 and 34, identifyFor each structural isomer in Problems 33 and 34, identify all stereocenters and give the total number of stereoisomers that can exist for the structure.
Q:For each reaction in Table 6-3, identify the nucleophile, itsFor each reaction in Table 6-3, identify the nucleophile, its nucleophilic atom (draw its Lewis structure first), the electrophilic atom in the substrate, and the leaving group.
Q:A second Lewis structure can be drawn for one ofA second Lewis structure can be drawn for one of the nucleophiles in Problem 36. (a) Identify it and draw its alternate structure (which is simply a second resonance form), (b) Is there a second nucleophilic atom in the nucleophile? If so, rewrite the reaction of Problem 36. Using the new nucleophilic atom, and write a correct Lewis structure for the product.
Q:For each reaction shown here, identify the nucleophile, its atom,For each reaction shown here, identify the nucleophile, its atom, the eletrophilic atom in the substate molecule, and the leaving groups. Write the organic product of the reaction.
Q:For each reaction presented in Problem 38, write out theFor each reaction presented in Problem 38, write out the mechanism using the curved-arrow notation.
(a) CH3I + NaNH2 â
Q:A solution containing 0.1 M CH3C1 and 0.1 M KSCNA solution containing 0.1 M CH3C1 and 0.1 M KSCN in DMF reacts to give CH3SCN and KC1 with an initial rate of 2 × 10-8 mol L-1 s-1.
(a) What is the rate constant for this reaction?
(b) Calculate the initial reaction rate for each of the following sets of reactant concentrations:
(i) [CH3C1] = 0.2 M. [KSCN] = 0.1 M.
(ii) [CH, C1] = 0.2 M, [KSCN] = 0.3 M.
(iii) [CH3CI] = 0.4 M. [KSCN] = 0.4 M.
Q:Write the product of each of the following bimolecular substitutions.Write the product of each of the following bimolecular substitutions. The solvent is indicated above the reaction arrow.
Q:Determine the R/S designations for both starting materials and productsDetermine the R/S designations for both starting materials and products in the following SN2 reactions. Which of the products are optically active?