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All Textbook Solutions for Organic Chemistry
Give the ground-state electron configuration for each of the following elements: (a) Oxygen (b) Nitrogen (c) SulfurHow many electrons does each of the following elements have in its outer-most electron shell? (a) Magnesium (b) Cobalt (c) Selenium3PConvert the following representation of ethane, C2H6, into a conventional drawing that uses solid, wedged, and dashed lines to indicate tetrahedral geometry around each carbon (gray = C, ivory = H).What are likely formulas for the following substances? (a) CCl? (b) AlH? (c) CH?Cl2 (d) SiF? (e)s CH3NH?6P7PDraw a line-bond structure for propane, CH3CH2CH3. Predict the value of each bond angle, and indicate the overall shape of the molecule.Convert the following molecular model of hexane, a component of gasoline, into a line-bond structure (gray = C, ivory = H).Draw a line-bond structure for propene, CH3CH=CH2. Indicate the hybridization of the orbitals on each carbon, and predict the value of each bond angle.Draw a line-bond structure for 1, 3-butadiene, H2C==CH — CH==CH2. Indicate the hybridization of the orbitals on each carbon, and predict the value of each bond angle.Following is a molecular model of aspirin (acetylsalicylic acid). Identify the hybridization of the orbitals on each carbon atom in aspirin, and tell which atoms have lone pairs of electrons (gray = C, red = O, ivory = H).Draw a line-bond structure for propyne, CH3C≡CH. Indicate the hybridization of the orbitals on each carbon, and predict a value for each bond angle.14P15P16PThe following molecular model is a representation of para-aminobenzoic acid (PABA), the active ingredient in many sunscreens. Indicate the positions of the multiple bonds, and draw a skeletal structure (gray = C, red = O, blue = N, ivory = H).Convert each of the following molecular models into a skeletal structure, and give the formula of each. Only the connections between atoms are shown; multiple bonds are not indicated (gray = C, red = O, blue = N, ivory = H).The following model is a representation of citric acid, the key substance in the so-called citric acid cycle, by which food molecules are metabolized in the body. Only the connections between atoms are shown; multiple bonds are not indicated. Complete the structure by indicating the positions of multiple bonds and lone-pair electrons (gray = C, red = O, ivory = H).The following model is a representation of acetaminophen, a pain reliever sold in drugstores under a variety of names, including Tylenol. Identify the hybridization of each carbon atom in acetaminophen, and tell which atoms have lone pairs of electrons (gray = C, red = O, blue = N, ivory = H).The following model is a representation of aspartame, C14H18N2O5, known commercially under many names, including NutraSweet. Only the connections between atoms are shown; multiple bonds are not indicated. Complete the structure for aspartame, and indicate the positions of multiple bonds (gray = C, red = O, blue = N, ivory = H).How many valence electrons does each of the following dietary trace elements have? (a) Zinc (b) Iodine (c) Silicon (d) IronGive the ground-state electron configuration for each of the following elements: (a) Potassium (b) Arsenic (c) Aluminum (d) Germanium24AP25APDraw an electron-dot structure for acetonitrile, C2H3N, which contains a carbon-nitrogen triple bond. How many electrons does the nitrogen atom have in its outer shell? How many are bonding, and how many are nonbonding?Draw a line-bond structure for vinyl chloride, C2H3Cl, the starting material from which PVC [poly(vinyl chloride)] plastic is made.Fill in any nonbonding valence electrons that are missing from the following structures:Convert the following line-bond structures into molecular formulas:Convert the following molecular formulas into line-bond structures that are consistent with valence rules: (a) C3H8 (b) CH5N (c) C2H6O (2 possibilities) (d) C3H7Br (2 possibilities) (e) C2H4O (3 possibilities) (f) C3H9N (4 possibilities)31APOxaloacetic acid, an important intermediate in food metabolism, has the formula C4H4O5 and contains three C=O bonds and two O-H bonds. Propose two possible structures.33APPotassium methoxide, KOCH3, contains both covalent and ionic bonds. Which do you think is which?What is the hybridization of each carbon atom in acetonitrile (Problem 1-26)?36AP37APWhat bond angles do you expect for each of the following, and what kind of hybridization do you expect for the central atom in each?Propose structures for molecules that meet the following descriptions: (a) Contains two sp2-hybridized carbons and two sp3-hybridized carbons (b) Contains only four carbons, all of which are sp2-hybridized (c) Contains two sp-hybridized carbons and two sp2-hybridized carbonsWhat kind of hybridization do you expect for each carbon atom in the following molecules?Pyridoxal phosphate, a close relative of vitamin B6, is involved in a large number of metabolic reactions. Tell the hybridization, and predict the bond angles for each nonterminal atom.42AP43APQuetiapine, marketed as Seroquel, is a heavily prescribed antipsychotic drug used in the treatment of schizophrenia and bipolar disorder. Convert the following representation into a skeletal structure, and give the molecular formula of quetiapine.Tell the number of hydrogens bonded to each carbon atom in (a) the antiinfluenza agent oseltamivir, marketed as Tamiflu, and (b) the platelet aggregation inhibitor clopidogrel, marketed as Plavix. Give the molecular formula of each.Why do you suppose no one has ever been able to make cyclopentyne as a stable molecule?Allene, H2C=C=CH2, is somewhat unusual in that it has two adjacent double bonds. Draw a picture showing the orbitals involved in the σ and Ï€ bonds of allene. Is the central carbon atom sp2- or sp-hybridized? What about the hybridization of the terminal carbons? What shape do you predict for allene?Allene (see Problem 1-47) is structurally related to carbon dioxide, CO2. Draw a picture showing the orbitals involved in the σ and Ï€ bonds of CO2, and identify the likely hybridization of carbon.Complete the electron-dot structure of caffeine, showing all lone-pair electrons, and identify the hybridization of the indicated atoms.Most stable organic species have tetravalent carbon atoms, but species with trivalent carbon atoms also exist. Carbocations are one such class of compounds. (a) How many valence electrons does the positively charged carbon atom have? (b) What hybridization do you expect this carbon atom to have? (c) What geometry is the carbocation likely to have?A carbanion is a species that contains a negatively charged, trivalent carbon. (a) What is the electronic relationship between a carbanion and a trivalent nitrogen compound such as NH3? (b) How many valence electrons does the negatively charged carbon atom have? (c) What hybridization do you expect this carbon atom to have? (d) What geometry is the carbanion likely to have?Divalent carbon species called carbenes are capable of fleeting existence. For example, methylene: CH2, is the simplest carbene. The two unshared electrons in methylene can be either paired in a single orbital or unpaired in different orbitals. Predict the type of hybridization you expect carbon to adopt in singlet (spin-paired) methylene and triplet (spin-unpaired) methylene. Draw a picture of each, and identify the valence orbitals on carbon.There are two different substances with the formula C4H10. Draw both, and tell how they differ.There are two different substances with the formula C3H6. Draw both, and tell how they differ.There are two different substances with the formula C2H6O. Draw both, and tell how they differ.56APAmong the most common over-the-counter drugs you might find in a medicine cabinet are mild pain relievers such ibuprofen (Advil, Motrin), naproxen (Aleve), and acetaminophen (Tylenol). (a) How many sp3-hybridized carbons does each molecule have? (b) How many sp2-hybridized carbons does each molecule have? (c) Can you spot any similarities in their structures?1P2PUse the electronegativity values shown in Figure 2-2 to rank the following bonds from least polar to most polar: H3C-Li, H3C-K, H3C-F, H3C-MgBr, H3C-OHLook at the following electrostatic potential map of methylamine, a substance responsible for the odor of rotting fish, and tell the direction of polarization of the C-N bond:Ethylene glycol, HOCH2CH2OH, may look nonpolar when drawn, but an internal hydrogen bond results in an electric dipole moment. Explain.Make three-dimensional drawings of the following molecules, and predict whether each has a dipole moment. If you expect a dipole moment, show its direction. (a) H2C=CH2 (b) CHCl3 (c) CH2Cl2 (d) H2C=CCl2Calculate formal charges for the nonhydrogen atoms in the following molecules:Organic phosphate groups occur commonly in biological molecules. Calculate formal charges on the four O atoms in the methyl phosphate dianion.Which of the following pairs of structures represent resonance forms, and which do not? Explain.Draw the indicated number of resonance forms for each of the following species: (a) The methyl phosphate anion, CH3OPO32- (3) (b) The nitrate anion, NO3- (3) (c) The allyl cation, H2C=CH—CH2+ (2) (d) The benzoate anion (4)Nitric acid (HNO3) reacts with ammonia (NH3) to yield ammonium nitrate. Write the reaction, and identify the acid, the base, the conjugate acid product, and the conjugate base product.12PAmide ion, H2N-, is a much stronger base than hydroxide ion, HO-. Which is the stronger acid, NH3 or H2O? Explain.14P15P16PUsing curved arrows, show how the species in part (a) can act as Lewis bases in their reactions with HGl, and show how the species in part (b) can act as Lewis acids in their reaction with OH-. (a) CH3CH2OH, HN(CH3)2, P(CH3)3 (b) H3C+, B(CH3)3, MgBr218POf the two vitamins A and C, one is hydrophilic and water-soluble while the other is hydrophobic and fat-soluble. Which is which?20VCThe following model is a representation of ibuprofen, a common over- the-counter pain reliever. Indicate the positions of the multiple bonds, and draw a skeletal structure (gray = C, red = O, ivory = H).cis-l, 2-Dichloroethylene and trans-1, 2-dichloroethylene are isomers, compounds with the same formula but different chemical structures. Look at the following electrostatic potential maps, and tell whether either compound has a dipole moment.The following molecular models are representations of (a) adenine and (b) cytosine, constituents of DNA (deoxyribonucleic acid). Indicate the positions of multiple bonds and lone pairs for both, and draw skeletal structures (gray = C, red = O, blue = N, ivory = H).Predict the product(s) of the acid/base reactions below. Draw curved arrows to show the formation and breaking of bonds.Use curved arrows to draw the protonated form of each Lewis base below.26MPDouble bonds can also act like Lewis bases, sharing their electrons with Lewis acids. Use curved arrows to show how each double bond below will react with HCl and draw the resulting carbocation.28APUse the electronegativity table given in Figure 2-2 to predict which bond in each of the following pairs is more polar, and indicate the direction of bond polarity for each compound. (a) H3C-Cl or Cl-Cl (b) H3C-H or H-Cl (c) HO-CH3 or (CH3)3Si-CH3 (d) H3C-Li or Li-OHWhich of the following molecules has a dipole moment? Indicate the expected direction of each.31APPhosgene, C12C=O, has a smaller dipole moment than formaldehyde, H2C=O, even though it contains electronegative chlorine atoms in place of hydrogen. Explain.33APMethanethiol, CH3SH, has a substantial dipole moment (μ = 1.52) even though carbon and sulfur have identical electronegativities. Explain.Calculate the formal charges on the atoms shown in red.Assign formal charges to the atoms in each of the following molecules:Which of the following pairs of structures represent resonance forms?38AP1, 3-Cyclobutadiene is a rectangular molecule with two shorter double bonds and two longer single bonds. Why do the following structures not represent resonance forms?Alcohols can act either as weak acids or as weak bases, just as water can. Show the reaction of methanol, CH3OH, with a strong acid such as HCl and with a strong base such as Na+-NH2.The O-H hydrogen in acetic acid is more acidic than any of the C-H hydrogens. Explain this result using resonance structures.Draw electron-dot structures for the following molecules, indicating any unshared electron pairs. Which of the compounds are likely to act as Lewis acids and which as Lewis bases? (a) AlBr3 (b) CH3CH2NH2 (c) BH3 (d) HF (e) CH3SCH3 (f) TiCl4Write the products of the following acid-base reactions:Rank the following substances in order of increasing acidity:Which, if any, of the substances in Problem 2-44 is a strong enough acid to react almost completely with NaOH? (The pKa of H2O is 15.74.)The ammonium ion (NH4+, pKa = 9.25) has a lower pKa than the methylammonium ion (CH3NH3+, pKa = 10.66). Which is the stronger base, ammonia (NH3) or methylamine (CH3NH2)? Explain.47AP48APCalculate Ka values from the following pka’s: (a) Acetone, pKa = 19.3 (b) Formic acid, pka = 3.75Calculate pKa values from the following Ka’s: (a) Nitromethane, Ka=5.0Ă—10-11 (b) Acrylic acid, Ka=5.6Ă—10-5What is the pH of a 0.050 M solution of formic acid, pKa=3.75?52APMaleic acid has a dipole moment, but the closely related fumaric acid, a substance involved in the citric acid cycle by which food molecules are metabolized, does not. Explain.Assume that you have two unlabeled bottles, one of which contains phenol (pka = 9.9) and one of which contains acetic acid (pka = 4.76). In light of your answer to Problem 2-52, suggest a simple way to determine what is in each bottle.Identify the acids and bases in the following reactions:Which of the following pairs represent resonance structures?Draw as many resonance structures as you can for the following species, adding appropriate formal charges to each:Carbocations, which contain a trivalent, positively charged carbon atom, react with water to give alcohols: How can you account for the fact that the following carbocation gives a mixture of two alcohols on reaction with water?We’ll see in the next chapter that organic molecules can be classified according to the functional groups they contain, where a functional group is a collection of atoms with a characteristic chemical reactivity. Use the electronegativity values given in Figure 2-2 on page 29 to predict the direction of polarization of the following functional groups.The azide functional group, which occurs in azidobenzene, contains three adjacent nitrogen atoms. One resonance structure for azidobenzene is shown. Draw three additional resonance structures, and assign appropriate formal charges to the atoms in all four.Phenol, C6H5OH, is a stronger acid than methanol, CH3OH, even though both contain an Q-H bond. Draw the structures of the anions resulting from loss of H+ from phenol and methanol, and use resonance structures to explain the difference in acidity.Thiamin diphosphate (TPP), a derivative of vitamin B1 required for glucose metabolism, is a weak acid that can be deprotonated by a base. Assign formal charges to the appropriate atoms in both TPP and its deprotonation product.Determine if each compound or ion below has a dipole moment.64AP65APDraw the conjugate base for each compound below (the acidic hydrogen in each case is marked with an *).1, 1, 1-Trichloroethanol is an acid more than 1000 times stronger than ethanol, even though both have a conjugate base where the negative charge is on an oxygen. Provide an explanation for this observation.1P2PIdentify the functional groups in the following model of arecoline, a veterinary drug used to control worms in animals. Convert the drawing into a line-bond structure and a molecular formula (red=O, blue=N).Draw structures of the five isomers of C6H14.Propose structures that meet the following descriptions: (a) Two isomeric esters with the formula C5H10O2 (b) Two isomeric nitriles with the formula C4H7N (c) Two isomeric disulfides with the formula C4H10S26PDraw the eight 5-carbon alkyl groups (pentyl isomers).Identify the carbon atoms in the following molecules as primary, secondary, tertiary, or quaternary:9P10PGive IUPAC names for the following compounds:12PName the eight 5-carbon alkyl groups you drew in Problem 3-7.Give the IUPAC name for the following hydrocarbon, and convert the drawing into a skeletal structure.Make a graph of potential energy versus angle of bond rotation for propane, and assign values to the energy maxima.Sight along the C2-C1 bond of 2-methylpropane (isobutane). (a) Draw a Newman projection of the most stable conformation. (b) Draw a Newman projection of the least stable conformation. (c) Make a graph of energy versus angle of rotation around the C2-C1 bond. (d) Assign relative values to the maxima and minima in your graph, given that an HH eclipsing interaction costs 4.0 kJ/mol and an HCH3 eclipsing interaction costs 6.0 kJ/mol.Sight along the C2-C3 bond of 2,3-dimethylbutane, and draw a Newman projection of the most stable conformation.Draw a Newman projection along the C2-C3 bond of the following conformation of 2,3-dimethylbutane, and calculate a total strain energy:19VC20VCDraw a Newman projection along the C2-C3 bond of the following conformation of 2-butanol.22AP23APPropose structures for the following: (a) A ketone, C4H8O (b) A nitrile, C5H9N (c) A dialdehyde, C4H6O2 (d) A bromoalkene, C6H11Br (e) An alkane, C6H14 (f) A cyclic saturated hydrocarbon, C6H12 (g) A diene (dialkene), C5H8 (h) A keto alkene, C5H8O25APDraw the structures of the following molecules: (a) Biacetyl, C4H6O2, a substance with the aroma of butter; it contains no rings or carbon-carbon multiple bonds. (b) Ethylenimine, C2H5N, a substance used in the synthesis of melamine polymers; it contains no multiple bonds. (c) Glycerol, C3H8O3, a substance isolated from fat and used in cosmetics; it has an -OH group on each carbon.Draw structures that meet the following descriptions (there are many possibilities): (a) Three isomers with the formula C8H18 (b) Two isomers with the formula C4H8O228APIn each of the following sets, which structures represent the same compound and which represent different compounds?There are seven constitutional isomers with the formula C4H10O. Draw as many as you can.31APDraw compounds that contain the following: (a) A primary alcohol (b) A tertiary nitrile (c) A secondary thiol (d) Both primary and secondary alcohols (e) An isopropyl group (f) A quaternary carbon33APDraw and name all monochloro derivatives of 2,5-dimethylhexane, C8H17Cl.Draw structures for the following: (a) 2-Methylheptane (b) 4-Ethyl-2,2-dimethylhexane (c) 4-Ethyl-3,4-dimethyloctane (d) 2,4,4-Trimethylheptane (e) 3,3-Diethyl-2,5-dimethylnonane (f) 4-Isopropyl-3-methylheptane36APDraw a compound that: (a) Has nine primary hydrogens (b) Has only primary hydrogensGive IUPAC names for the following compounds:Name the five isomers of C6H14.Explain why each of the following names is incorrect: (a) 2,2-Dimethyl-6-ethylheptane (b) 4-Ethyl-5,5-dimethylpentane (c) 3-Ethyl-4,4-dimethylhexane (d) 5,5,6-Trimethyloctane (e) 2-Isopropyl-4-methylheptane41APConsider 2-methylbutane (isopentane). Sighting along the C2-C3 bond: (a) Draw a Newman projection of the most stable conformation. (b) Draw a Newman projection of the least stable conformation. (c) If a CH3CH3 eclipsing interaction costs 11 kJ/mol (2.5 kcal/mol) and a CH3CH3 gauche interaction costs 3.8 kJ/mol (0.9 kcal/mol), make a quantitative plot of energy versus rotation about the C2-C3 bond.What are the relative energies of the three possible staggered conformations around the C2-C3 bond in 2,3-dimethylbutane? (See Problem 3-42.)Construct a qualitative potential-energy diagram for rotation about the C-C bond of 1,2-dibromoethane. Which conformation would you expect to be most stable? Label the anti and gauche conformations of 1,2-dibromoethane.45APDraw the most stable conformation of pentane, using wedges and dashes to represent bonds coming out of the paper and going behind the paper, respectively.Draw the most stable conformation of 1,4-dichlorobutane, using wedges and dashes to represent bonds coming out of the paper and going behind the paper, respectively.48AP49APFormaldehyde, H2C=O, is known to all biologists because of its usefulness as a tissue preservative. When pure, formaldehyde trimerizes to give trioxane, C3H6O3, which, surprisingly enough, has no carbonyl groups. Only one monobromo derivative (C3H5BrO3) of trioxane is possible. Propose a structure for trioxane.51APIncreased substitution around a bond leads to increased strain. Take the four substituted butanes listed below, for example. For each compound, sight along the C2-C3 bond and draw Newman projections of the most stable and least stable conformations. Use the data in Table 3-5 to assign strain-energy values to each conformation. Which of the eight conformations is most strained? Which is least strained? (a) 2-Methylbutane (b) 2,2-Dimethylbutane (c) 2,3-Dimethylbutane (d) 2,2,3-Trimethylbutane53APIn the next chapter we'll look at cycloalkanes—saturated cyclic hydrocarbons—and we’ll see that the molecules generally adopt puckered, nonplanar conformations. Cyclohexane, for instance, has a puckered shape like a lounge chair rather than a flat shape. Why?We’ll see in the next chapter that there are two isomeric substances, both named 1,2-dimethylcyclohexane. Explain.Give IUPAC names for the following cycloalkanes:Draw structures corresponding to the following IUPAC names: (a) 1, 1-Dimethylcyclooctane (b) 3-Cyclobutylhexane (c) 1, 2-Dichlorocyclopentane (d) l, 3-Dibromo-5-methylcyclohexaneName the following cycloalkane:4PDraw the structures of the following molecules: (a) trans-l-Bromo-3-methylcyclohexane (b) cis-1, 2-Dimethylcyclobutane (c) trans-1 -tert-Butyl-2-ethylcyclohexaneProstaglandin F2α, a hormone that causes uterine contraction during childbirth, has the following structure. Are the two hydroxyl groups (-OH) on the cyclopentane ring cis or trans to each other? What about the two carbon chains attached to the ring?Name the following substances, including the cis- or trans- prefix (red-brown=Br):Each H↔H eclipsing interaction in ethane costs about 4.0 kJ/mol. How many such interactions are percent in cyclopropane? What fraction of the overall 115 kJ/mol (27.5 kcal/mol) strain energy of cyclopropane is due to torsional strain.cis-1, 2-Dimethylcyclopropane has more strain than trans-l, 2-dimethylcyclo propane. How can you account for this difference? Which of the two com pounds is more stable?10PTwo conformations of cis-l, 3-dimethylcyclobutane are shown. What is the difference between them, and which do you think is likely to be more stable?Draw two different chair conformations of cyclohexanol (hydroxycyclohexane), showing all hydrogen atoms. Identify each position as axial or equatorial.Draw two differant chair conformations of trans-1, 4-dimethylcyc1ohexane, and label all positions as axial or equatorial.14PWhat is the energy difference between the axial and equatorial conformations of cyclohexanol (hydroxycyclohexane)?16PLook at Figure 4-12 on page 105, and estimate the percentages of axial and equatorial conformations present at equilibrium in bromocyclohexane.Draw the more stable chair conformation of the following molecules, and estimate the amount of strain in each: (a) trans-1-Chloro-3-methy1cyclohexane (b) cis-1 - Ethy1-2-methylcyc1ohexane (c) cis-l-Bromo-4-ethylcyclohexane (d) cis-1-terf-BUty1-4-ethyIcyclohexaneIdentify each substituent in the following compound as axial or equatorial, and tell whether the conformation shown is the more stable or less stable chair form (green = Cl):Which isomer is more stable, cis-decalin or trans-decalin? Explain.Look at the following structure of the female hormone estrone, and tell whether each of the indicated ring-fusions is cis or trans.22VCName the following compound, identify each substituent as axial or equatorial, and tell whether the conformation shown is the more stable or less stable chair form (green=Cl):A trisubstituted cyclohexane with three substituents-red, green, and blue-undergoes a ring-flip to its alternate chair conformation. Identify each substituent as axial or equatorial, and show the positions occupied by the three substituents in the ring-flipped form.The following cyclohexane derivative has three substituents-red, green, and blue. Identify each substituent as axial or equatorial, and identify each pair of relationships (red-blue, red-green, and blue- green) as cis or trans.26VCDraw the five cycloalkanes with the formula C5H10.Draw two constitutional isomers of cis-1, 2-dibromocyclopentane.29APTell whether the following pairs of compounds are identical, constitutional isomers, stereoisomers, or unrelated. (a) cis-1, 3-Dibromocyclohexane and trans-1, 4-dibromocyclohexane (b) 2, 3-Dimethylhexane and 2, 3, 3-trimethy1pentane31AP32APDraw 1, 3, 5-trimethylcyclohexane using a hexagon to represent the ring. How many cis-trans stereoisomers are possible?Hydrocortisone, a naturally occurring hormone produced in the adrenal glands, is often used to treat inflammation, severe allergies, and numerous other conditions. Is the indicated -OH group axial or equatorial?A 1, 2-cis disubstituted cyclohexane, such as cis-1, 2-dichlorocyclohexane, must have one group axial and one group equatorial. Explain.A 1, 2-trans disubstituted cyclohexane must have either both groups axial or both groups equatorial. Explain.37APWhich is more stable, a 1, 4-trans disubstituted cyclohexane or its cis isomer?cis-1, 2-Dimethylcyclobutane is less stable than its trans isomer, but cis-l, 3-dimethylcyclobutane is more stable than its trans isomer. Draw the most stable conformations of both, and explain.From the data in Figure 4-12 and Table 4-1, estimate the percentages of molecules that have their substituents in an axial orientation for the following compounds: (a) Isopropylcyclohexane (b) Fluorocyclohexane (c) Cyclohexanecarbonitrile, C6H11CN41APDraw the two chair conformations of cis-l-chloro-2-methylcyclohexane. Which is more stable, and by how much?Draw the two chair conformations of trans-l-chloro-2-methylcyclohexane. Which is more stable?Galactose, a sugar related to glucose, contains a six-membered ring in which all the substituents except the -OH group, indicated below in red, are equatorial. Draw galactose in its more stable chair conformation.There are four cis-trans isomers of menthol (Problem 4-45), including the one shown. Draw the other three.There are four cis-trans isomers of menthol (Problem 4-45), including the one shown. Draw the other three.The diaxial conformation of cis-1, 3-dimethylcyclohexane is approximately 23 kJ/mol (5.4 kcal/mol) less stable than the diequatorial conformation. Draw the two possible chair conformations, and suggest a reason for the large energy difference.Approximately how much steric strain does the 1,3-diaxial interaction between the two methyl groups introduce into the diaxial conformation of cis-1, 3-dimethylcyclohexane? [See Problem 4-47.]In light of your answer to Problem 4-43, draw the two chair conformations of 1, 1, 3-trimethylcyclohexane and estimate the amount of strain energy in each. Which conformation is favored?50AP51APUsing molecular models as well as structural drawings, explain why trans-decalin is rigid and cannot ring-flip whereas cis-decalin can easily ring-flip.trans-Decalin is more stable than its cis isomer, but cis-bicyclo[4.1.0]-heptane is more stable than its trans isomer. Explain.As mentioned in Problem 3-53, the statin drugs, such as simvastatin (Zocor), pravastatin (Pravachol), and atorvastatin (Lipitor) are the most widely prescribed drugs in the world. (a) Are the two indicated bonds on simvastatin cis or trans? (b) What are the cis/trans relationships among the three indicated bonds on pravastatin? (c) Why cant the three indicated bonds on atorvastatin be identified as cis or trans?myo-Inositol, one of the isomers of 1,2,3,4,5,6-hexahydroxycyclohexane, acts as a growth factor in both animals and microorganisms. Draw the most stable chair conformation of myo-inositol.How many cis–trans stereoisomers of myo-inositol (Problem 4-55) are there? Draw the structure of the most stable isomer.The German chemist J. Bredt proposed in 1935 that bicycloalkenes such as 1-norbornene, which have a double bond to the bridgehead carbon, are too strained to exist. Explain. (Making a molecular model will be helpful.)Tell whether each of the following substituents on a steroid is axial or equatorial. (A substituent that is up is on the top face of the molecule as drawn, and a substituent that is down is on the bottom face.) (a) Substituent up at C3 (b) Substituent down at C7 (c) Substituent down at C1159AP60APKetones react with alcohols to yield products called acetals. Why does the all-cis isomer of 4-tert-butyl-1,3-cyclohexanediol react readily with acetone and an acid catalyst to form an acetal, but other stereoisomers do not react? In formulating your answer, draw the more stable chair conformations of all four stereoisomers and the product acetal for each one.Alcohols undergo an oxidation reaction to yield carbonyl compounds on treatment with CrO3. For example, 2-tert-butylcyclohexanol gives 2-tert-butylcyclohexanone. If axial OH groups are generally more reactive than their equatorial isomers, which do you think reacts faster, the cis isomer of 2-tert-butylcyclohexanol or the trans isomer? Explain.1P2P3P4PIs cocaine (Worked Example 5-2) dextrorotatory or levorotatory?6P7P8P9PAssign R or S configuration to the chirality center in each of the following molecules:Draw a tetrahedral representation of (S)-2-pentanol (2-hydroxypentane).12POne of the following molecules (a)–(d) is d-erythrose 4-phosphate, an intermediate in the Calvin photosynthetic cycle by which plants incorporate CO2 into carbohydrates. If d-erythrose 4-phosphate has R stereochemistry at both chirality centers, which of the structures is it? Which of the remaining three structures is the enantiomer of d-erythrose 4-phosphate, and which are diastereomers?14PAssign R or S configuration to each chirality center in the following molecular model of the amino acid isoleucine (blue = N):16PWhich of the following have a meso form? (Recall that the -ol suffix refers to an alcohol, ROH.) (a) 2, 3-Butanediol (b) 2, 3-Pentanediol (c) 2, 4-PentanediolDoes the following structure represent a meso compound? If so, indicate the symmetry plane.19P20P21P22P23PThe lactic acid that builds up in tired muscles is formed from pyruvate. If the reaction occurs with addition of hydrogen to the Re face of pyruvate, what is the stereochemistry of the product?The aconitase-catalyzed addition of water to cis-aconitate in the citric acid cycle occurs with the following stereochemistry. Does the addition of the OH group occur on the Re or Si face of the substrate? What about the addition of the H? Do the H and OH groups add from the same side of the double bond or from opposite sides?Which of the following structures are identical? (Green = Cl.)27VC28VCAssign R or S configuration to each chirality center in pseudoephedrine, an over-the-counter decongestant found in cold remedies (blue = N).30VC31APWhich of the following compounds are chiral? Draw them, and label the chirality centers. (a) 2, 4-Dimethylheptane (b) 5-Ethyl-3, 3-dimethylheptane (c) cis-1, 4-Dichlorocyclohexane33APEight alcohols have the formula C5H12O. Draw them. Which are chiral?Draw compounds that fit the following descriptions: (a) A chiral alcohol with four carbons (b) A chiral carboxylic acid with the formula C5H10O2 (c) A compound with two chirality centers (d) A chiral aldehyde with the formula C3H5BrO36AP37AP38APWhat is the stereochemical configuration of the enantiomer of (2S, 4R)-2, 4-octanediol? (A diol is a compound with two —OH groups.)40AP41AP42AP43APAssign R or S configuration to each chirality center in the following molecules:Assign R or S configuration to each chirality center in the following biological molecules:46APAssign R or S configuration to each chirality center in the following molecules:Assign R or S configurations to the chirality centers in ascorbic acid (vitamin C).Assign R or S stereochemistry to the chirality centers in the following Newman projections:50APDraw examples of the following: (a) A meso compound with the formula C8H18 (b) A meso compound with the formula C9H20 (c) A compound with two chirality centers, one R and the other52AP53AP54APOn reaction with hydrogen gas by a platinum catalyst, ribose (Problem 5-54) is converted into ribitol. Is ribitol optically active or inactive? Explain.56AP57APOne of the steps in fat metabolism is the hydration of crotonate to yield 3-hydroxybutyrate. This reaction occurs by addition of —OH to the Si face at C3, followed by protonation at C2, also from the Si face. Draw the product of the reaction, showing the stereochemistry of each step.The dehydration of citrate to yield cis-aconitate, a step in the citric acid cycle, involves the pro-R “arm’’ of citrate rather than the pro-S arm. Which of the following two products is formed?