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Calculate the specific rotations of the following samples taken at 25 °C using the sodium D line. (a)  1.00 g of sample is dissolved in 20.0 mL of ethanol. Then 5.00 mL of this solution is placed in a 20.0-cm polarimeter tube. The observed rotation is 1.25° counterclockwise. (b)  0.050 g of sample is dissolved in 2.0 mL of ethanol, and this solution is placed in a 2.0-cm polarimeter tube. The observed rotation is clockwise 0.043°.

Calculate the specific rotations of the following samples taken at 25 °C using the sodium D line. (a)  1.00 g of sample is dissolved in 20.0 mL of ethanol. Then 5.00 mL of this solution is placed in a 20.0-cm polarimeter tube. The observed rotation is 1.25° counterclockwise. (b)  0.050 g of sample is dissolved in 2.0 mL of ethanol, and this solution is placed in a 2.0-cm polarimeter tube. The observed rotation is clockwise 0.043°.

Chemistry
Chemistry
10th Edition
ISBN:9781305957404
Author:Steven S. Zumdahl, Susan A. Zumdahl, Donald J. DeCoste
Publisher:Steven S. Zumdahl, Susan A. Zumdahl, Donald J. DeCoste
Chapter1: Chemical Foundations
Section: Chapter Questions
Problem 1RQ: Define and explain the differences between the following terms. a. law and theory b. theory and...
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stereochemistry question:

  1. Calculate the specific rotations of the following samples taken at 25 °C using the sodium D line.

    1. (a)  1.00 g of sample is dissolved in 20.0 mL of ethanol. Then 5.00 mL of this solution is placed in a 20.0-cm polarimeter

      tube. The observed rotation is 1.25° counterclockwise.

    2. (b)  0.050 g of sample is dissolved in 2.0 mL of ethanol, and this solution is placed in a 2.0-cm polarimeter tube. The

      observed rotation is clockwise 0.043°.

  2. refer to the question below
2-37 Rank the following species in order of increasing acidity. Explain your reasons for ordering them as you do. HF NH3 H,SO4 CH3OH CH;COOH H,O* H,0 2-38 Rank the following species in order of increasing basicity. Explain your reasons for ordering them as you do. NH3 CH30 H2O CH3CO0" NaOH NH, HSO, 2-39 The Ka of phenylacetic acid is 5.2 × 10°, and the pK, of propionic acid is 4.87. CH, —С—оН CH, —СH, —С-ОН phenylacetic acid, K = 5.2 x 10-s propionic acid, pK, = 4.87 (a) Calculate the pKa of phenylacetic acid and the Ka of propionic acid. (b) Which of these is the stronger acid? Calculate how much stronger an acid it is. (c) Predict whether the following equilibrium will favor the reactants or the products. CH,COO + CH,CH,COOH -CH,COOH + CH,CH,COO- *2-40 The following compound can become protonated on any of the three nitrogen atoms. One of these nitrogens is much more basic than the others, however. (a) Draw the important resonance forms of the products of protonation on each of the three nitrogen atoms. (b) Determine which nitrogen atom is the most basic. NH CH, —NH—С `NH, 2-41 The following compounds are listed in increasing order of acidity. In each case, the most acidic proton is shown in red. OH CH, NH H H. W, pKa = 25 X, pKa = 23 Y, pKa = 8.8 Z, pKa = 4.2 (a) Show the structure of the conjugate base of each acid, including any resonance forms. (b) Explain why X is a stronger acid than W. (c) Explain why Y is a stronger acid than X. (d) Explain why Z is a stronger acid than Y. Predict the products of the following acid-base reactions. (а) H-SO4 2-42 CH;COO (b) СH;CООН (CH3)3N: (c) С—ОН + FHO- (d) Но—С— ОН + 2-ОН (1) (CH.),NH (h) NH,CH,COOH + (е) Н,О + NH, OH (g) HCООН CH30 2 -ОН 2-43 Consider the following proposed Brønsted-Lowry acid-base reactions. In each case, draw the products of a transfer of the most acidic proton on the acid to the most basic site on the base. Use Appendix 4 to find or estimate the pKa values for the acids and the pKp values for the bases. Then determine which side of the reaction is favored, either reactants or products. СООН (а) (b) O,N O,N
Transcribed Image Text:2-37 Rank the following species in order of increasing acidity. Explain your reasons for ordering them as you do. HF NH3 H,SO4 CH3OH CH;COOH H,O* H,0 2-38 Rank the following species in order of increasing basicity. Explain your reasons for ordering them as you do. NH3 CH30 H2O CH3CO0" NaOH NH, HSO, 2-39 The Ka of phenylacetic acid is 5.2 × 10°, and the pK, of propionic acid is 4.87. CH, —С—оН CH, —СH, —С-ОН phenylacetic acid, K = 5.2 x 10-s propionic acid, pK, = 4.87 (a) Calculate the pKa of phenylacetic acid and the Ka of propionic acid. (b) Which of these is the stronger acid? Calculate how much stronger an acid it is. (c) Predict whether the following equilibrium will favor the reactants or the products. CH,COO + CH,CH,COOH -CH,COOH + CH,CH,COO- *2-40 The following compound can become protonated on any of the three nitrogen atoms. One of these nitrogens is much more basic than the others, however. (a) Draw the important resonance forms of the products of protonation on each of the three nitrogen atoms. (b) Determine which nitrogen atom is the most basic. NH CH, —NH—С `NH, 2-41 The following compounds are listed in increasing order of acidity. In each case, the most acidic proton is shown in red. OH CH, NH H H. W, pKa = 25 X, pKa = 23 Y, pKa = 8.8 Z, pKa = 4.2 (a) Show the structure of the conjugate base of each acid, including any resonance forms. (b) Explain why X is a stronger acid than W. (c) Explain why Y is a stronger acid than X. (d) Explain why Z is a stronger acid than Y. Predict the products of the following acid-base reactions. (а) H-SO4 2-42 CH;COO (b) СH;CООН (CH3)3N: (c) С—ОН + FHO- (d) Но—С— ОН + 2-ОН (1) (CH.),NH (h) NH,CH,COOH + (е) Н,О + NH, OH (g) HCООН CH30 2 -ОН 2-43 Consider the following proposed Brønsted-Lowry acid-base reactions. In each case, draw the products of a transfer of the most acidic proton on the acid to the most basic site on the base. Use Appendix 4 to find or estimate the pKa values for the acids and the pKp values for the bases. Then determine which side of the reaction is favored, either reactants or products. СООН (а) (b) O,N O,N
154 CHAPTER 3 Structure and Stereochemistry of Alkanes In each pair of compounds, which compound has the higher boiling point? Explain your reasoning. (a) octane or 2,2,3-trimethylpentane 3-42 (b) nonane or 2-methylheptane (c) 2,2,5-trimethylhexane or nonane 3-43 There are eight different five-carbon alkyl groups. (a) Draw them. (c) In each case, label the degree of substitution (primary, secondary, or tertiary) of the head carbon atom bonded to the (b) Give them systematic names. main chain. 3-44 Use a Newman projection about the indicated bond to draw the most stable conformer for each compound. (a) 3-methylpentane about the C2-C3 bond (a) Draw the two chair conformations of cis-1,3-dimethylcyclohexane, and label all the positions as axial or equatorial. (b) Label the higher-energy conformation and the lower-energy conformation. (c) The energy difference in these two conformations has been measured to be about 23 kJ (5.4 kcal) per mole. How (b) 3,3-dimethylhexane about the C3-C4 bond 3-45 much of this energy difference is due to the torsional energy of gauche relationships? (d) How much energy is due to the additional steric strain of the 1,3-diaxial interaction? 3-46 Draw the two chair conformations of each compound, and label the substituents as axial and equatorial. In each case, determine which conformation is more stable. (a) cis-l-ethyl-2-isopropylcyclohexane (c) cis-1-ethyl-3-methylcyclohexane (e) cis-1-ethyl-4-methylcyclohexane Using what you know about the conformational energetics of substituted cyclohexanes, predict which of the two decalin isomers is more stable. Explain your reasoning. (b) trans-1-ethyl-2-isopropylcyclohexane (d) trans-1-ethyl-3-methylcyclohexane (f) trans-1-ethyl-4-methylcyclohexane 3-47 3-48 Convert each Newman projection to the equivalent line-angle formula, and assign the IUPAC name. (a) (b) (c) (d) (e) H. CH,CH3 Br C(CH3)3 CH,CH3 CI H. H. „CH3 H. CH3 H. Br. H H H H `CH3 CH(CH3)2 H H. Cl CH3 CH3 CH3 CH,CH3 H CH,CH3 CHCH3 (f) (g) (h) (i) (j) CH(CH3)2 Br. CH3 F Br H. CH3 H. F Cl H. CH3 H H F F H Br Br H F CH(CH3)2 H CH2CH3 CH,CH3 CH;CH3 *3-49 Draw Newman projections along the C3-C4 bond to show the most stable and least stable conformations of 3-ethyl-2,4,4-trimethylheptane. *3-50 Conformational studies on ethane-1,2-diol (HOCH, C-C bond to be the gauche conformation, which is 9.6 kJ/mol (2.3 kcal/mol) more stable than the anti conformation. CH,OH) have shown the most stable conformation about the central Draw Newman projections of these conformers, and explain this curious result. 3-51 The most stable form of the common sugar glucose contains a -membered ring in the chair conformation with all the substituents equatorial. Draw this most stable conformation of glucose. Но. CH,OH Но HO, ОН glucose 3-52 This is a Newman projection of a substituted cyclohexane. (a) Draw the equivalent chair form. (b) Draw the equivalent structure using wedge and dash notation on a cyclohexane hexagon. (c) Give the IUPAC name. Br H H H CH3 H H
Transcribed Image Text:154 CHAPTER 3 Structure and Stereochemistry of Alkanes In each pair of compounds, which compound has the higher boiling point? Explain your reasoning. (a) octane or 2,2,3-trimethylpentane 3-42 (b) nonane or 2-methylheptane (c) 2,2,5-trimethylhexane or nonane 3-43 There are eight different five-carbon alkyl groups. (a) Draw them. (c) In each case, label the degree of substitution (primary, secondary, or tertiary) of the head carbon atom bonded to the (b) Give them systematic names. main chain. 3-44 Use a Newman projection about the indicated bond to draw the most stable conformer for each compound. (a) 3-methylpentane about the C2-C3 bond (a) Draw the two chair conformations of cis-1,3-dimethylcyclohexane, and label all the positions as axial or equatorial. (b) Label the higher-energy conformation and the lower-energy conformation. (c) The energy difference in these two conformations has been measured to be about 23 kJ (5.4 kcal) per mole. How (b) 3,3-dimethylhexane about the C3-C4 bond 3-45 much of this energy difference is due to the torsional energy of gauche relationships? (d) How much energy is due to the additional steric strain of the 1,3-diaxial interaction? 3-46 Draw the two chair conformations of each compound, and label the substituents as axial and equatorial. In each case, determine which conformation is more stable. (a) cis-l-ethyl-2-isopropylcyclohexane (c) cis-1-ethyl-3-methylcyclohexane (e) cis-1-ethyl-4-methylcyclohexane Using what you know about the conformational energetics of substituted cyclohexanes, predict which of the two decalin isomers is more stable. Explain your reasoning. (b) trans-1-ethyl-2-isopropylcyclohexane (d) trans-1-ethyl-3-methylcyclohexane (f) trans-1-ethyl-4-methylcyclohexane 3-47 3-48 Convert each Newman projection to the equivalent line-angle formula, and assign the IUPAC name. (a) (b) (c) (d) (e) H. CH,CH3 Br C(CH3)3 CH,CH3 CI H. H. „CH3 H. CH3 H. Br. H H H H `CH3 CH(CH3)2 H H. Cl CH3 CH3 CH3 CH,CH3 H CH,CH3 CHCH3 (f) (g) (h) (i) (j) CH(CH3)2 Br. CH3 F Br H. CH3 H. F Cl H. CH3 H H F F H Br Br H F CH(CH3)2 H CH2CH3 CH,CH3 CH;CH3 *3-49 Draw Newman projections along the C3-C4 bond to show the most stable and least stable conformations of 3-ethyl-2,4,4-trimethylheptane. *3-50 Conformational studies on ethane-1,2-diol (HOCH, C-C bond to be the gauche conformation, which is 9.6 kJ/mol (2.3 kcal/mol) more stable than the anti conformation. CH,OH) have shown the most stable conformation about the central Draw Newman projections of these conformers, and explain this curious result. 3-51 The most stable form of the common sugar glucose contains a -membered ring in the chair conformation with all the substituents equatorial. Draw this most stable conformation of glucose. Но. CH,OH Но HO, ОН glucose 3-52 This is a Newman projection of a substituted cyclohexane. (a) Draw the equivalent chair form. (b) Draw the equivalent structure using wedge and dash notation on a cyclohexane hexagon. (c) Give the IUPAC name. Br H H H CH3 H H
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