The specific rotation of l-alanine in water (at 25°C) is +2.8. A chemist prepared a mixture of l-alanine and its enantiomer, and 3.50 g of the mixture was dissolved in 10.0 mL of water. This solution was then placed in a sample cell with a pathlength of 10.0 cm and the observed rotation was +0.78. Calculate the % ee of the mixture.
> Consider the following reaction: The following rate equation has been experimentally established for this process Rate = k[HO−][CH3CH2Br] An energy diagram for this process is shown on the right: a. Identify the two characteristic ar
> Predict whether each of the following carbocations will rearrange. If so, draw the expected rearrangement using curved arrows. (a) (b) (c) (d) (e) (f) (g)
> Draw the transition state for the substitution reaction that occurs between ethyl iodide and sodium acetate (CH3CO2Na).
> Draw curved arrows for each step of the following mechanism: HÖ: H HÖ: H-O: OH HÖ: sÖH :OH -O: H HÖ: H HÖ: ÖH HỘ: -H20
> Draw curved arrows for each step of the following mechanism: H :ÖH HO H H, 7 :ÖH I-o. I-z:
> Draw curved arrows for each step of the following mechanism: H@H. :0-H нӧ. TH. TH. TH. H :ÖH :ÖH HÖ но. HO OH HÖ OH H. H. TH. H
> Draw curved arrows for each step of the following mechanism: OH но. CH,SO, NO2 NO2
> For the following mechanism, identify the sequence of arrow-pushing patterns: :ÖH :ÖH OR H R H. R :ÖR R ÖR ÖR
> For the following mechanism, identify the sequence of arrow-pushing patterns: :0 :OH H R R- R R" R R R R R
> Lithium salts have been used for decades to treat mental illnesses, including depression and bipolar disorder. Although the treatment is effective, researchers are still trying to determine how lithium salts behave as mood stabilizers. a. Draw a Lewis st
> Below are two potential methods for preparing the same ether, but only one of them is successful. Identify the successful approach and explain your choice. NaOMe ONa CH3I
> For the following mechanism, identify the sequence of arrow-pushing patterns: :0: :0: :0: H-ö-H H-ö-H R R R R но. :Cl: H H
> The following two reactions will be explored in different chapters. Yet, they are very similar. Identify and compare the sequences of arrowpushing patterns for the two reactions. Reaction 1 (Chapter 19) он :OH HÖ Reaction 2 (Chapter 17) OH :CI: :OH
> For the following mechanism, identify the sequence of arrow-pushing patterns: он OH OH 0=$=0 H H so,
> For the following mechanism, identify the sequence of arrowpushing patterns: CI CI一AI CI マーる G一マーる
> Draw all constitutional isomers with the molecular formula C4H9Br, and then arrange them in order of: a. increasing reactivity toward an SN2 reaction. b. increasing reactivity toward an E2 reaction.
> Draw the transition state for each of the following SN2 reactions: Br OH NaOH + NaBr (a) (Ь) (c) NaOH OH + Naci Br SH NaSH. + NaBr (d) +
> Each of the following compounds exhibits two electrophilic centers. Identify both centers in each compound. (Hint: You will need to draw resonance structures in each case.) H. A cockroach repellant found in cucumbers Nootkatone (a) (b) Found in grape
> The following hypothetical compound cannot be prepared or isolated, because it has a very reactive nucleophilic center and a very reactive electrophilic center, and the two sites would react with each other rapidly. Identify the nucleophilic center and e
> Rank the three carbocations shown in terms of increasing stability: (a) (b)
> For each of the following reactions identify the arrow-pushing pattern that is being utilized: (a) (b) (다) он H. (d)
> Each of the following compounds can be prepared with an alkyl iodide and a suitable nucleophile. In each case, identify the alkyl iodide and the nucleophile that you would use. (a) он (b) CN (c) (d) SH
> Chlorofluorocarbons (CFCs) are gases that were once widely used as refrigerants and propellants. When it was discovered that these molecules contributed to the depletion of the ozone layer, their use was banned, but CFCs continue to be detected as contam
> Which is the better retrosynthesis for the given target molecule? Explain, and provide a one-step synthesis of the target molecule. Br or Br Target molecule
> In Chapter 3, we will explore the factors that render compounds acidic or basic. Tropolone (1) is a compound that is both fairly acidic and fairly basic. It is acidic because it is capable of losing a proton (H+) to form a relatively stable anion (2), wh
> The following compound is an amino acid derivative (Chapter 25). In solution, molecules of this compound show a tendency to “stick” together, or self-assemble, via a series of intermolecular hydrogen bonds.
> The following compound is an intermediate in the synthesis of a gelator, which is a compound capable of self-assembling to form a gel in an organic liquid. a. Identify each functional group in the molecule. b. In Chapter 4, we will learn that single bo
> Each of 10 stereoisomeric sugar derivatives can be prepared via a multiple-step synthesis starting from either glucuronolactone 1D or its enantiomer 1L. Depending on the specific series of reactions used, the configuration at carbons 2, 3, and 5 can be s
> The natural product meloscine can be prepared via a 19-step synthesis, featuring the following allene as a key intermediate: a. Draw a Newman projection of the allene when viewed from the left side of the C=C=C unit. Note that in this case t
> Consider the structure of the following ketone: a. Does this compound exhibit rotational symmetry? b. Does this compound exhibit reflectional symmetry? c. Is the compound chiral? If so, draw its enantiomer.
> When a toluene solution of the sugar-derived compound below is cooled, the molecules self-assemble into fibrous aggregates which work in concert with the surface tension of the solvent to form a stable gel. Redraw the structure showing both nonaromatic r
> The all-trans-1,2,3,4,5,6-hexaethylcyclohexane (1) prefers the allequatorial conformation while the all-trans-1,2,3,4,5,6-hexaisopropylcyclohexane (2) possesses a severely destabilized all-equatorial conformation. a. By examining a molecular model of cy
> Draw all three staggered conformations for the following compound, viewed along the C2−C3 bond. Determine which conformation is the most stable, taking into account gauche interactions and hydrogen-bonding interactions. Provide a reason
> Triphenylmethane dyes are among the first synthetic dyes developed for commercial use. A comparison of the structures of these compounds reveals that even small differences in structure can lead to large differences in color.15 The structures of three su
> Provide a synthesis for the target molecule shown below, starting with an alkyl halide of your choice. Show your retrosynthetic analysis, and then provide a complete synthesis, showing all necessary reagents. CN
> The following questions apply to the five compounds in the previous problem. a. Which compound is meso? b. Would an equal mixture of compounds b and c be optically active? c. Would an equal mixture of compounds d and e be optically active?
> Draw bond-line structures using wedges and dashes for the following compounds: CH Et Et H- -OH H- -OH но но но -H H- FOH H- -OH H- он но (a) ČH, (b) Me (c) Me Me Me H- -CI C- -H но но- (d) Me (e) Me
> Determine whether each of the following compounds is optically active or optically inactive: CH3 он Et но H. Ме Me- .CI H- он Me (a) H Me OH H CH, (Ь) (с) CH,CH, H. HO H H- он CH,OH CH, ČH, (d) (е) (f) (9) (h) I
> For each of the following pairs of compounds, determine the relationship between the two compounds: Me Me -CI CI- HO Me -H но (а) Me (b) (с) (d) CH, CH, Et Et H- -OH но- H- OH HO но H- -OH но- -H H- он H- -он но- H- OH но FH (е) ČH, ČH, (f) Me Me
> cis-1,3-Dimethylcyclobutane has two planes of symmetry. Draw the compound and identify both planes of symmetry.
> Each of the following compounds possesses a plane of symmetry. Find the plane of symmetry in each compound. In some cases, you will need to rotate a single bond to place the molecule into a conformation where you can more readily see the plane of symmetr
> (R)-Limonene is found in many citrus fruits, including oranges and lemons: For each of the following compounds identify whether it is (R)-limonene or its enantiomer, (S)-limonene: (a) (b) (c) (d)
> When 0.075 g of penicillamine is dissolved in 10.0 mL of pyridine and placed in a sample cell 10.0 cm in length, the observed rotation at 20°C (using the D line of sodium) is −0.47°. Calculate the specific rotation of penicillamine.
> Draw the enantiomer of each compound in the previous problem.
> Determine the configuration for every chiral center in each of the following compounds: OH он он он но- -H но -H HO H но—н H- OH H- -OH HO H HO H ČH,OH CH,OH CH,OH (a) (b) (c)
> Draw a plausible mechanism for each of the following transformations он Br conc. H2SO4 HBr heat (b) OH Он conc. HSO4 HBr HO. Br (d) heat
> Determine whether each statement is true or false: a. A racemic mixture of enantiomers is optically inactive. b. A meso compound will have exactly one nonsuperimposable mirror image. c. Rotating the Fischer projection of a molecule with a single chira
> For each of the following pairs of compounds, determine the relationship between the two compounds: CI (a) (b) он OH (c) CI (d)
> For each of the following pairs of compounds, determine the relationship between the two compounds: но—н но—н CI H OH но- (a) CH,OH CH,OH (b) 'ci 'CI (c) (d)
> The specific rotation of (S)-2-butanol is +13.5. If 1.00 g of its enantiomer is dissolved in 10.0 mL of ethanol and placed in a sample cell with a length of 1.00 dm, what observed rotation do you expect?
> Predict the value for the specific rotation of the following compound. Explain your answer. он HO.
> You are given a solution containing a pair of enantiomers (A and B). Careful measurements show that the solution contains 98% A and 2% B. What is the ee of this solution?
> Identify the configuration of each chiral center in the following compounds: CI Et OH NH, Me (b) (c) HO H F Et (d) CI (e) Me H- OH Cl HO H (f) Me (g)
> Draw the enantiomer for each of the following compounds: OH (а) (b) (с) H- -OH он он ÇI OH H -OH но (d) ČH, (е) Me Me
> Identify the number of stereoisomers expected for each of the following: Me он CI он Me (а) OH (b) Он (с) (d) (е) Но OH (f)
> Predict the major product for each of the following reactions. OH он ? ? HBr conc. H2SO4 heat (a) (b)
> For each of the following pairs of compounds, determine the relationship between the two compounds: Br (a) (b) Br (c) (d) он он (e) (f) (g) он он (h)
> Carbon is not the only element that can function as a chiral center. In Problem 5.6 we saw an example in which a phosphorus atom is a chiral center. In such a case, the lone pair is always assigned the fourth priority. Using this information, assign the
> Assign the configuration of the chiral center in the following compound:
> Paclitaxel (marketed under the trade name Taxol) is found in the bark of the Pacific yew tree, Taxus brevifolia, and is used in the treatment of cancer: a. Draw the enantiomer of paclitaxel. b. How many chiral centers does this compound possess? он
> Atropine, extracted from the plant Atropa belladonna, has been used in the treatment of bradycardia (low heart rate) and cardiac arrest. Draw the enantiomer of atropine: CH -OH
> Atorvastatin is sold under the trade name Lipitor and is used for lowering cholesterol. Annual global sales of this compound exceed $13 billion. Assign a configuration to each chiral center in atorvastatin: он он но. F
> Bogorol A is a natural product with the potential to fight antibiotic-resistant bacteria. Shown below is an intermediate that was used in a synthesis of bogorol A. Assign the configuration of the alkene unit as either E or Z. R. N. OMe Intermediate i
> For each of the following alkenes, assign the configuration of the double bond as either E or Z: (a) (b) CI (c) (d)
> Determine whether each of the following allenes is chiral or achiral: H3C H3C CC=C CH, *CH3 C=C=c "CH,CH3 C=C=C CH3 (a) H (b) (c) (d) CH3
> Protease inhibitors are a class of anti-viral drugs that have had success in treating HIV/AIDS. The following molecules were synthesized as potential HIV protease inhibitors. Compound 1 was found to be an effective protease inhibitor, while compound 2 wa
> Predict the major and minor products for each of the following reactions. OTs NaOE OTs ? ? NaOH (a) (b) LOTS OTs ? NaH ? NASH (c) (d) CH3 1) TSCI, py 2 BUOK ? 1) TsCI, py 2) NaOE! ? HO, (e) (f)
> Identify the configuration of the chiral center in each of the following compounds: OH CH,OH CH;OH H- (а) -NH2 но но -H Br- CH,OH (b) CH3 (с) ČH,CH, (d) CH3
> A racemic mixture with the constitution shown below was isolated from the Maytenus apurimacensis plant that is used in South American folk medicine. In an effort to find another source of these compounds, all of the stereoisomers with this constitution h
> Draw all possible stereoisomers for each of the following compounds. Each possible stereoisomer should be drawn only once: он OH но OH (a) (b) (c) (d) (е)
> Each of the following molecules has one plane of symmetry. Find the plane of symmetry in each case: (Hint: A plane of symmetry can slice atoms in half.) Me (a) Mе Br (b) HO он Me (с) Me (d) (е) (f) CI
> In the previous problem, one object has three planes of symmetry. Identify that object.
> For each of the following objects determine whether or not it possesses a plane of symmetry: (a) (b) (c) (d) (e) (f)
> In the field of chemical research, one area of interest is the study of how variations in structure, including stereochemical variations, affect the biological activity of natural products. (−)-Lariciresinol, shown on the right, is a na
> Identify whether each of the following pairs of compounds are enantiomers or diastereomers: (a) (Ь) он он он он (c) CI (d) (е)
> Synthetic chemists often employ enzymes to conduct asymmetric syntheses that favor the production of one enantiomer over another. Baker’s yeast was used to convert the diketone shown into alcohol 1, with an ee of 84%. The specific rotat
> The specific rotation of vitamin B7 in water (at 22°C) is +92. A chemist prepared a mixture of vitamin B7 and its enantiomer, and this mixture had a specific rotation of +85. Calculate the % ee of this mixture.
> An unknown compound with the molecular formula C6H13Cl is treated with sodium ethoxide to produce 2,3-dimethyl-2-butene as the major product. Identify the structure of the unknown compound.
> A common method for confirming the proposed structure and stereochemistry of a natural product is to synthesize the proposed structure and then compare its properties with those of the natural product. This technique was used to verify the structure of c
> The specific rotation of ephedrine in ethanol (at 20°C) is −6.3. A chemist prepared a mixture of ephedrine and its enantiomer, and this mixture had a specific rotation of −6.0. Calculate the % ee of this mixture.
> The specific rotation of l-dopa in water (at 15°C) is −39.5. A chemist prepared a mixture of l-dopa and its enantiomer, and this mixture had a specific rotation of −37. Calculate the % ee of this mixture.
> Levetiracetam is used for the treatment of seizures in patients with epilepsy. For patients who have a hard time swallowing the needed pills twice daily, relief is in sight now that the FDA has granted approval for the use of rapidly dissolving, porous t
> When 1.30 g of menthol is dissolved in 5.00 mL of ether and placed in a sample cell 10.0 cm in length, the observed rotation at 20°C (using the D line of sodium) is +0.57°. Calculate the specific rotation of menthol.
> When 0.095 g of cholesterol is dissolved in 1.00 mL of ether and placed in a sample cell 10.0 cm in length, the observed rotation at 20°C (using the D line of sodium) is −2.99°. Calculate the specific rotation of cholesterol.
> When 0.575 g of monosodium glutamate (MSG) is dissolved in 10.0 mL of water and placed in a sample cell 10.0 cm in length, the observed rotation at 20°C (using the D line of sodium) is +1.47°. Calculate the specific rotation of MSG.
> In Chapter 24, we will see that amino acids (like the ones shown below) can be linked together to give short chains, called peptides, or longer chains (≈50–2000 amino acids linked together) called proteins. High-protei
> Each of the following compounds possesses carbon atoms that are chiral centers. Locate each of these chiral centers and identify the configuration of each one: он H Br .H он (a) (b) CI Br Ephedrine A bronchodilator and decongestant obtained from the
> Ixabepilone is a cytotoxic compound approved by the FDA in 2007 for the treatment of advanced breast cancer. Bristol-Myers Squibb is marketing this drug under the trade name Ixempra. Draw the enantiomer of this compound: OH .N. H OH Ixabepilone
> Draw the enantiomer of each of the following compounds: он но 'N HO HO OH Albuterol (sold under the trade name Ventolin) Propranolol A beta blocker used in the treatment of hypertension Oxybutynin (c) Used to treat urinary and bladder disorders A bro
> Compound A and compound B are constitutional isomers with the molecular formula C4H9Cl. Treatment of compound A with sodium methoxide gives trans-2-butene as the major product, while treatment of compound B with sodium methoxide gives a different disubst
> Do you expect the following compound to be chiral? Explain your answer (consider whether this compound is superimposable on its mirror image).
> Draw all constitutional isomers with the molecular formula C4H9Br and identify the isomer(s) that possess chiral centers.
> Identify all chiral centers in each of the following compounds: OH Но но. но OH Ascorbic acid (a) (vitamin C) (b) Vitamin Da OH но OH Mestranol Fexofenadine OH (c) An oral contraceptive (d) A nonsedating antihistamine
> Compound X and compound Y are constitutional isomers with the molecular formula C5H10. Compound X possesses a carbon-carbon double bond in the trans configuration, while compound Y possesses a carbon-carbon double bond that is not stereoisomeric: a. Ide
> Identify the number of stereoisomers that are possible for a compound with the following constitution: H2C=CHCH2CH2CH2CH=CH2.
> In the following compound, identify each C=C unit as cis, trans, or not stereoisomeric.
> The pKa of the most acidic CH2 group in each of the following compounds was measured in DMSO as solvent. Given the data above, determine which of the following two compounds (5 or 6) is more acidic by comparing the stability of the corresponding conjuga
> Crude extracts from the ginkgo tree, Ginkgo biloba, have been used for centuries to alleviate symptoms associated with asthma. There are four principal components of Ginkgo extracts, called ginkgolide A B, D, and M. During E. J. Corey’s
> Phakellin (3), a natural product isolated from marine organisms, has been studied for its potential use as an antibiotic agent. During studies aimed at developing a strategy for the synthesis of phakellin and its derivatives, compound 1 was investigated
> Aspernomine, a natural product isolated from the fungus Aspergillus nomius, was found to be an antiinsectan (it protects against predation by insects). a. Two of the six-membered rings are represented in chair conformations. Is the connection between th
