The amino acid ( S ) -alanine has the physical characteristics listed under the structure. ( S )-alanine [ α ] = + 8.5 mp = 297 ° C a. What is the melting point of ( R ) -alanine ? b. How does the melting point of a racemic mixture of ( R ) - and ( S ) -alanine compare to the melting point of ( S ) -alanine ? c. What is the specific rotation of ( R ) -alanine , recorded under the same conditions as the reported rotation of ( S ) -alanine ? d. What is the optical rotation of a racemic mixture of ( R ) - and ( S ) -alanine ? e. Label each of the following as optically active or inactive: a solution of pure ( S ) -alanine ; an equal mixture of ( R ) - and ( S ) -alanine ; a solution that contains 75 % ( S ) - and 25 % ( R ) -alanine .

Question

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Answer 1

Textbook Question

Chapter 5, Problem 5.28P

The amino acid ( S ) -alanine has the physical characteristics listed under the structure.

Chapter 5, Problem 5.28P, Problem 5.28 The amino acid has the physical characteristics listed under the

(S)-alanine

[ α ] = + 8.5

mp = 297 ° C

a. What is the melting point of ( R ) -alanine ?

b. How does the melting point of a racemic mixture of ( R ) - and ( S ) -alanine compare to the melting point of ( S ) -alanine ?

c. What is the specific rotation of ( R ) -alanine , recorded under the same conditions as the reported rotation of ( S ) -alanine ?

d. What is the optical rotation of a racemic mixture of ( R ) - and ( S ) -alanine ?

e. Label each of the following as optically active or inactive: a solution of pure ( S ) -alanine ; an equal mixture of ( R ) - and ( S ) -alanine ; a solution that contains 75 % ( S ) - and 25 % ( R ) -alanine .

Expert Solution

Interpretation Introduction

(a)

Interpretation: The melting point of (R)-alanine is to be predicted.

Concept introduction: Enantiomers are the stereoisomers that have exactly opposite R,S notations. Diastereomers are the stereoisomers that have the opposite R,S notations for at least one stereogenic center and the same R,S notations for at least one stereogenic center. Enantiomers have identical physical properties, whereas diastereomers have different physical properties.

Answer to Problem 5.28P

The melting point of (R)-alanine is 297 °C.

Explanation of Solution

The given melting point of (S)-alanine is 297 °C. The (R)-alanine, and (S)-alanine are the enantiomers. Enantiomers are the stereoisomers that have exactly opposite R,S notations. They possess identical physical properties. Therefore, the melting point of (R)-alanine is also 297 °C.

Conclusion

The melting point of (R)-alanine is 297 °C.

Expert Solution

Interpretation Introduction

(b)

Interpretation: The melting point of a racemic mixture of (R)- and (S)-alanine is to be compared with the melting point of (S)-alanine.

Concept introduction: Enantiomers are the stereoisomers that have exactly opposite R,S notations. They possess identical physical properties. A racemic mixture is obtained when (R)-and (S) enantiomers are mixed in equal amount. Their racemic mixture possess different physical properties than parent one.

Answer to Problem 5.28P

The melting point of a racemic mixture of (R)- and (S)-alanine is different with the melting point of (S)-alanine.

Explanation of Solution

The given melting point of (S)-alanine is 297 °C. The (R)-alanine, and (S)-alanine are the enantiomers. Enantiomers are the stereoisomers that have exactly opposite R,S notations. They possess identical physical properties. A racemic mixture is obtained when (R)- and (S) enantiomers are mixed in equal amount. Their racemic mixture possess different physical properties than parent one.

Therefore, the melting point of a racemic mixture of (R)- and (S)-alanine is different with the melting point of (S)-alanine.

Conclusion

The melting point of a racemic mixture of (R)- and (S)-alanine is different with the melting point of (S)-alanine.

Expert Solution

Interpretation Introduction

(c)

Interpretation: The specific rotation of (R)-alanine is to be predicted.

Concept introduction: Enantiomers are the stereoisomers that have exactly opposite R,S notations. They possess identical physical properties. Their specific rotation values are opposite in sign but equal in magnitude, when they are recorded under same condition.

Answer to Problem 5.28P

The specific rotation of (R)-alanine is −8.5.

Explanation of Solution

The specific rotation of (S)-alanine is +8.5. The (R)-alanine, and (S)-alanine are the enantiomers. Enantiomers are the stereoisomers that have exactly opposite R,S notations. They possess identical physical properties. Their specific rotation values are opposite in sign but equal in magnitude, when they are recorded under same condition.

Thus, the specific rotation of (R)-alanine is −8.5.

Conclusion

The specific rotation of (R)-alanine is −8.5.

Expert Solution

Interpretation Introduction

(d)

Interpretation: The optical rotation of a racemic mixture of (R)- and (S)-alanine is to be calculated.

Concept introduction: Enantiomers are the stereoisomers that have exactly opposite R,S notations. They possess identical physical properties. A racemic mixture is obtained when (R)-and (S) enantiomers are mixed in equal amount.

Answer to Problem 5.28P

The optical rotation of a racemic mixture of (R)- and (S)-alanine is zero.

Explanation of Solution

The specific rotation of (S)-alanine is +8.5.

The specific rotation of (R)-alanine is −8.5.

The (R)-alanine, and (S)-alanine are the enantiomers. Enantiomers are the stereoisomers that have exactly opposite R,S notations. They possess identical physical properties. A racemic mixture is obtained when (R)- and (S) enantiomers are mixed in equal amount.

Thus, the optical rotation of a racemic mixture of (R)- and (S)-alanine is zero (−8.5+8.5=0).

Conclusion

The optical rotation of a racemic mixture of (R)- and (S)-alanine is zero.

Expert Solution

Interpretation Introduction

(e)

Interpretation: The solutions of pure (S)-alanine, an equal mixture of (R)- and (S)-alanine, 75% (S)-and 25% (R)-alanine are to be labeled as optically active or inactive.

Concept introduction: Enantiomers are the stereoisomers that have exactly opposite R,S notations. They possess identical physical properties. A racemic mixture is obtained when (R)- and (S) enantiomers are mixed in equal amount. Their racemic mixture possess different physical properties than parent one.

Answer to Problem 5.28P

The pure (S)-alanine is labeled as optically active, an equal mixture of (R)- and (S)-alanine is labeled as optically inactive, 75% (S)-and 25% (R)-alanine is labeled as optically active.

Explanation of Solution

The pure (S)-alanine is an enantiomer. Enantiomers are optically active compounds. Thus, (S)-alanine is optically active compound.

A racemic mixture is obtained when (R)- and (S) enantiomers are mixed in equal amount. Thus, an equal mixture of (R)- and (S)-alanine is optically inactive.

A 75% (S)-and 25% (R)-alanine solution is optically active. Because, in solution 25% (R)-alanine cancel only 25% (S)-alanine and still 50% of (S)-alanine is left. Therefore, 75% (S)- and 25% (R)-alanine solution is optically active.

Thus, the pure (S)-alanine is labeled as optically active, an equal mixture of (R)- and (S)-alanine is labeled as optically inactive, 75% (S)- and 25% (R)-alanine is labeled as optically active.

Conclusion

The pure (S)-alanine is labeled as optically active, an equal mixture of (R)- and (S)-alanine is labeled as optically inactive, 75% (S)- and 25% (R)-alanine is labeled as optically active.

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Students have asked these similar questions

The amino acid (S)-alanine has the physical characteristics listed under the structure. How does the melting point of a racemic mixture of (R)- and (S)-alanine compare to the melting point of (S)-alanine?

The amino acid (S)-alanine has the physical characteristics listed under the structure. What is the optical rotation of a racemic mixture of (R)- and (S)-alanine?

1. If life arose by “chemical evolution” (which is supposed to be new chemical compounds arising by random chance), what should be the proportion of each of the L- and D-enantiomers present in chiral compounds produced by random chance? How does this match with what we see in living systems? What conclusion can you make from this about the likelihood of life arising by “chemical evolution?" 2. Why does chirality make a difference when new medications are developed? What is an ethical way of addressing this concern in the development process? What is the connection with the way the body is designed?

Answer 2

Textbook Question

Chapter 5, Problem 5.28P

The amino acid ( S ) -alanine has the physical characteristics listed under the structure.

Chapter 5, Problem 5.28P, Problem 5.28 The amino acid has the physical characteristics listed under the

(S)-alanine

[ α ] = + 8.5

mp = 297 ° C

a. What is the melting point of ( R ) -alanine ?

b. How does the melting point of a racemic mixture of ( R ) - and ( S ) -alanine compare to the melting point of ( S ) -alanine ?

c. What is the specific rotation of ( R ) -alanine , recorded under the same conditions as the reported rotation of ( S ) -alanine ?

d. What is the optical rotation of a racemic mixture of ( R ) - and ( S ) -alanine ?

e. Label each of the following as optically active or inactive: a solution of pure ( S ) -alanine ; an equal mixture of ( R ) - and ( S ) -alanine ; a solution that contains 75 % ( S ) - and 25 % ( R ) -alanine .

Expert Solution

Interpretation Introduction

(a)

Interpretation: The melting point of (R)-alanine is to be predicted.

Concept introduction: Enantiomers are the stereoisomers that have exactly opposite R,S notations. Diastereomers are the stereoisomers that have the opposite R,S notations for at least one stereogenic center and the same R,S notations for at least one stereogenic center. Enantiomers have identical physical properties, whereas diastereomers have different physical properties.

Answer to Problem 5.28P

The melting point of (R)-alanine is 297 °C.

Explanation of Solution

The given melting point of (S)-alanine is 297 °C. The (R)-alanine, and (S)-alanine are the enantiomers. Enantiomers are the stereoisomers that have exactly opposite R,S notations. They possess identical physical properties. Therefore, the melting point of (R)-alanine is also 297 °C.

Conclusion

The melting point of (R)-alanine is 297 °C.

Expert Solution

Interpretation Introduction

(b)

Interpretation: The melting point of a racemic mixture of (R)- and (S)-alanine is to be compared with the melting point of (S)-alanine.

Concept introduction: Enantiomers are the stereoisomers that have exactly opposite R,S notations. They possess identical physical properties. A racemic mixture is obtained when (R)-and (S) enantiomers are mixed in equal amount. Their racemic mixture possess different physical properties than parent one.

Answer to Problem 5.28P

The melting point of a racemic mixture of (R)- and (S)-alanine is different with the melting point of (S)-alanine.

Explanation of Solution

The given melting point of (S)-alanine is 297 °C. The (R)-alanine, and (S)-alanine are the enantiomers. Enantiomers are the stereoisomers that have exactly opposite R,S notations. They possess identical physical properties. A racemic mixture is obtained when (R)- and (S) enantiomers are mixed in equal amount. Their racemic mixture possess different physical properties than parent one.

Therefore, the melting point of a racemic mixture of (R)- and (S)-alanine is different with the melting point of (S)-alanine.

Conclusion

The melting point of a racemic mixture of (R)- and (S)-alanine is different with the melting point of (S)-alanine.

Expert Solution

Interpretation Introduction

(c)

Interpretation: The specific rotation of (R)-alanine is to be predicted.

Concept introduction: Enantiomers are the stereoisomers that have exactly opposite R,S notations. They possess identical physical properties. Their specific rotation values are opposite in sign but equal in magnitude, when they are recorded under same condition.

Answer to Problem 5.28P

The specific rotation of (R)-alanine is −8.5.

Explanation of Solution

The specific rotation of (S)-alanine is +8.5. The (R)-alanine, and (S)-alanine are the enantiomers. Enantiomers are the stereoisomers that have exactly opposite R,S notations. They possess identical physical properties. Their specific rotation values are opposite in sign but equal in magnitude, when they are recorded under same condition.

Thus, the specific rotation of (R)-alanine is −8.5.

Conclusion

The specific rotation of (R)-alanine is −8.5.

Expert Solution

Interpretation Introduction

(d)

Interpretation: The optical rotation of a racemic mixture of (R)- and (S)-alanine is to be calculated.

Concept introduction: Enantiomers are the stereoisomers that have exactly opposite R,S notations. They possess identical physical properties. A racemic mixture is obtained when (R)-and (S) enantiomers are mixed in equal amount.

Answer to Problem 5.28P

The optical rotation of a racemic mixture of (R)- and (S)-alanine is zero.

Explanation of Solution

The specific rotation of (S)-alanine is +8.5.

The specific rotation of (R)-alanine is −8.5.

The (R)-alanine, and (S)-alanine are the enantiomers. Enantiomers are the stereoisomers that have exactly opposite R,S notations. They possess identical physical properties. A racemic mixture is obtained when (R)- and (S) enantiomers are mixed in equal amount.

Thus, the optical rotation of a racemic mixture of (R)- and (S)-alanine is zero (−8.5+8.5=0).

Conclusion

The optical rotation of a racemic mixture of (R)- and (S)-alanine is zero.

Expert Solution

Interpretation Introduction

(e)

Interpretation: The solutions of pure (S)-alanine, an equal mixture of (R)- and (S)-alanine, 75% (S)-and 25% (R)-alanine are to be labeled as optically active or inactive.

Concept introduction: Enantiomers are the stereoisomers that have exactly opposite R,S notations. They possess identical physical properties. A racemic mixture is obtained when (R)- and (S) enantiomers are mixed in equal amount. Their racemic mixture possess different physical properties than parent one.

Answer to Problem 5.28P

The pure (S)-alanine is labeled as optically active, an equal mixture of (R)- and (S)-alanine is labeled as optically inactive, 75% (S)-and 25% (R)-alanine is labeled as optically active.

Explanation of Solution

The pure (S)-alanine is an enantiomer. Enantiomers are optically active compounds. Thus, (S)-alanine is optically active compound.

A racemic mixture is obtained when (R)- and (S) enantiomers are mixed in equal amount. Thus, an equal mixture of (R)- and (S)-alanine is optically inactive.

A 75% (S)-and 25% (R)-alanine solution is optically active. Because, in solution 25% (R)-alanine cancel only 25% (S)-alanine and still 50% of (S)-alanine is left. Therefore, 75% (S)- and 25% (R)-alanine solution is optically active.

Thus, the pure (S)-alanine is labeled as optically active, an equal mixture of (R)- and (S)-alanine is labeled as optically inactive, 75% (S)- and 25% (R)-alanine is labeled as optically active.

Conclusion

The pure (S)-alanine is labeled as optically active, an equal mixture of (R)- and (S)-alanine is labeled as optically inactive, 75% (S)- and 25% (R)-alanine is labeled as optically active.

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Answer 3

Textbook Question

Chapter 5, Problem 5.28P

The amino acid ( S ) -alanine has the physical characteristics listed under the structure.

Chapter 5, Problem 5.28P, Problem 5.28 The amino acid has the physical characteristics listed under the

(S)-alanine

[ α ] = + 8.5

mp = 297 ° C

a. What is the melting point of ( R ) -alanine ?

b. How does the melting point of a racemic mixture of ( R ) - and ( S ) -alanine compare to the melting point of ( S ) -alanine ?

c. What is the specific rotation of ( R ) -alanine , recorded under the same conditions as the reported rotation of ( S ) -alanine ?

d. What is the optical rotation of a racemic mixture of ( R ) - and ( S ) -alanine ?

e. Label each of the following as optically active or inactive: a solution of pure ( S ) -alanine ; an equal mixture of ( R ) - and ( S ) -alanine ; a solution that contains 75 % ( S ) - and 25 % ( R ) -alanine .

Expert Solution

Interpretation Introduction

(a)

Interpretation: The melting point of (R)-alanine is to be predicted.

Concept introduction: Enantiomers are the stereoisomers that have exactly opposite R,S notations. Diastereomers are the stereoisomers that have the opposite R,S notations for at least one stereogenic center and the same R,S notations for at least one stereogenic center. Enantiomers have identical physical properties, whereas diastereomers have different physical properties.

Answer to Problem 5.28P

The melting point of (R)-alanine is 297 °C.

Explanation of Solution

The given melting point of (S)-alanine is 297 °C. The (R)-alanine, and (S)-alanine are the enantiomers. Enantiomers are the stereoisomers that have exactly opposite R,S notations. They possess identical physical properties. Therefore, the melting point of (R)-alanine is also 297 °C.

Conclusion

The melting point of (R)-alanine is 297 °C.

Expert Solution

Interpretation Introduction

(b)

Interpretation: The melting point of a racemic mixture of (R)- and (S)-alanine is to be compared with the melting point of (S)-alanine.

Concept introduction: Enantiomers are the stereoisomers that have exactly opposite R,S notations. They possess identical physical properties. A racemic mixture is obtained when (R)-and (S) enantiomers are mixed in equal amount. Their racemic mixture possess different physical properties than parent one.

Answer to Problem 5.28P

The melting point of a racemic mixture of (R)- and (S)-alanine is different with the melting point of (S)-alanine.

Explanation of Solution

The given melting point of (S)-alanine is 297 °C. The (R)-alanine, and (S)-alanine are the enantiomers. Enantiomers are the stereoisomers that have exactly opposite R,S notations. They possess identical physical properties. A racemic mixture is obtained when (R)- and (S) enantiomers are mixed in equal amount. Their racemic mixture possess different physical properties than parent one.

Therefore, the melting point of a racemic mixture of (R)- and (S)-alanine is different with the melting point of (S)-alanine.

Conclusion

The melting point of a racemic mixture of (R)- and (S)-alanine is different with the melting point of (S)-alanine.

Expert Solution

Interpretation Introduction

(c)

Interpretation: The specific rotation of (R)-alanine is to be predicted.

Concept introduction: Enantiomers are the stereoisomers that have exactly opposite R,S notations. They possess identical physical properties. Their specific rotation values are opposite in sign but equal in magnitude, when they are recorded under same condition.

Answer to Problem 5.28P

The specific rotation of (R)-alanine is −8.5.

Explanation of Solution

The specific rotation of (S)-alanine is +8.5. The (R)-alanine, and (S)-alanine are the enantiomers. Enantiomers are the stereoisomers that have exactly opposite R,S notations. They possess identical physical properties. Their specific rotation values are opposite in sign but equal in magnitude, when they are recorded under same condition.

Thus, the specific rotation of (R)-alanine is −8.5.

Conclusion

The specific rotation of (R)-alanine is −8.5.

Expert Solution

Interpretation Introduction

(d)

Interpretation: The optical rotation of a racemic mixture of (R)- and (S)-alanine is to be calculated.

Concept introduction: Enantiomers are the stereoisomers that have exactly opposite R,S notations. They possess identical physical properties. A racemic mixture is obtained when (R)-and (S) enantiomers are mixed in equal amount.

Answer to Problem 5.28P

The optical rotation of a racemic mixture of (R)- and (S)-alanine is zero.

Explanation of Solution

The specific rotation of (S)-alanine is +8.5.

The specific rotation of (R)-alanine is −8.5.

The (R)-alanine, and (S)-alanine are the enantiomers. Enantiomers are the stereoisomers that have exactly opposite R,S notations. They possess identical physical properties. A racemic mixture is obtained when (R)- and (S) enantiomers are mixed in equal amount.

Thus, the optical rotation of a racemic mixture of (R)- and (S)-alanine is zero (−8.5+8.5=0).

Conclusion

The optical rotation of a racemic mixture of (R)- and (S)-alanine is zero.

Expert Solution

Interpretation Introduction

(e)

Interpretation: The solutions of pure (S)-alanine, an equal mixture of (R)- and (S)-alanine, 75% (S)-and 25% (R)-alanine are to be labeled as optically active or inactive.

Concept introduction: Enantiomers are the stereoisomers that have exactly opposite R,S notations. They possess identical physical properties. A racemic mixture is obtained when (R)- and (S) enantiomers are mixed in equal amount. Their racemic mixture possess different physical properties than parent one.

Answer to Problem 5.28P

The pure (S)-alanine is labeled as optically active, an equal mixture of (R)- and (S)-alanine is labeled as optically inactive, 75% (S)-and 25% (R)-alanine is labeled as optically active.

Explanation of Solution

The pure (S)-alanine is an enantiomer. Enantiomers are optically active compounds. Thus, (S)-alanine is optically active compound.

A racemic mixture is obtained when (R)- and (S) enantiomers are mixed in equal amount. Thus, an equal mixture of (R)- and (S)-alanine is optically inactive.

A 75% (S)-and 25% (R)-alanine solution is optically active. Because, in solution 25% (R)-alanine cancel only 25% (S)-alanine and still 50% of (S)-alanine is left. Therefore, 75% (S)- and 25% (R)-alanine solution is optically active.

Thus, the pure (S)-alanine is labeled as optically active, an equal mixture of (R)- and (S)-alanine is labeled as optically inactive, 75% (S)- and 25% (R)-alanine is labeled as optically active.

Conclusion

The pure (S)-alanine is labeled as optically active, an equal mixture of (R)- and (S)-alanine is labeled as optically inactive, 75% (S)- and 25% (R)-alanine is labeled as optically active.

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Answer 4

Textbook Question

Chapter 5, Problem 5.28P

The amino acid ( S ) -alanine has the physical characteristics listed under the structure.

Chapter 5, Problem 5.28P, Problem 5.28 The amino acid has the physical characteristics listed under the

(S)-alanine

[ α ] = + 8.5

mp = 297 ° C

a. What is the melting point of ( R ) -alanine ?

b. How does the melting point of a racemic mixture of ( R ) - and ( S ) -alanine compare to the melting point of ( S ) -alanine ?

c. What is the specific rotation of ( R ) -alanine , recorded under the same conditions as the reported rotation of ( S ) -alanine ?

d. What is the optical rotation of a racemic mixture of ( R ) - and ( S ) -alanine ?

e. Label each of the following as optically active or inactive: a solution of pure ( S ) -alanine ; an equal mixture of ( R ) - and ( S ) -alanine ; a solution that contains 75 % ( S ) - and 25 % ( R ) -alanine .

Expert Solution

Interpretation Introduction

(a)

Interpretation: The melting point of (R)-alanine is to be predicted.

Concept introduction: Enantiomers are the stereoisomers that have exactly opposite R,S notations. Diastereomers are the stereoisomers that have the opposite R,S notations for at least one stereogenic center and the same R,S notations for at least one stereogenic center. Enantiomers have identical physical properties, whereas diastereomers have different physical properties.

Answer to Problem 5.28P

The melting point of (R)-alanine is 297 °C.

Explanation of Solution

The given melting point of (S)-alanine is 297 °C. The (R)-alanine, and (S)-alanine are the enantiomers. Enantiomers are the stereoisomers that have exactly opposite R,S notations. They possess identical physical properties. Therefore, the melting point of (R)-alanine is also 297 °C.

Conclusion

The melting point of (R)-alanine is 297 °C.

Expert Solution

Interpretation Introduction

(b)

Interpretation: The melting point of a racemic mixture of (R)- and (S)-alanine is to be compared with the melting point of (S)-alanine.

Concept introduction: Enantiomers are the stereoisomers that have exactly opposite R,S notations. They possess identical physical properties. A racemic mixture is obtained when (R)-and (S) enantiomers are mixed in equal amount. Their racemic mixture possess different physical properties than parent one.

Answer to Problem 5.28P

The melting point of a racemic mixture of (R)- and (S)-alanine is different with the melting point of (S)-alanine.

Explanation of Solution

The given melting point of (S)-alanine is 297 °C. The (R)-alanine, and (S)-alanine are the enantiomers. Enantiomers are the stereoisomers that have exactly opposite R,S notations. They possess identical physical properties. A racemic mixture is obtained when (R)- and (S) enantiomers are mixed in equal amount. Their racemic mixture possess different physical properties than parent one.

Therefore, the melting point of a racemic mixture of (R)- and (S)-alanine is different with the melting point of (S)-alanine.

Conclusion

The melting point of a racemic mixture of (R)- and (S)-alanine is different with the melting point of (S)-alanine.

Expert Solution

Interpretation Introduction

(c)

Interpretation: The specific rotation of (R)-alanine is to be predicted.

Concept introduction: Enantiomers are the stereoisomers that have exactly opposite R,S notations. They possess identical physical properties. Their specific rotation values are opposite in sign but equal in magnitude, when they are recorded under same condition.

Answer to Problem 5.28P

The specific rotation of (R)-alanine is −8.5.

Explanation of Solution

The specific rotation of (S)-alanine is +8.5. The (R)-alanine, and (S)-alanine are the enantiomers. Enantiomers are the stereoisomers that have exactly opposite R,S notations. They possess identical physical properties. Their specific rotation values are opposite in sign but equal in magnitude, when they are recorded under same condition.

Thus, the specific rotation of (R)-alanine is −8.5.

Conclusion

The specific rotation of (R)-alanine is −8.5.

Expert Solution

Interpretation Introduction

(d)

Interpretation: The optical rotation of a racemic mixture of (R)- and (S)-alanine is to be calculated.

Concept introduction: Enantiomers are the stereoisomers that have exactly opposite R,S notations. They possess identical physical properties. A racemic mixture is obtained when (R)-and (S) enantiomers are mixed in equal amount.

Answer to Problem 5.28P

The optical rotation of a racemic mixture of (R)- and (S)-alanine is zero.

Explanation of Solution

The specific rotation of (S)-alanine is +8.5.

The specific rotation of (R)-alanine is −8.5.

The (R)-alanine, and (S)-alanine are the enantiomers. Enantiomers are the stereoisomers that have exactly opposite R,S notations. They possess identical physical properties. A racemic mixture is obtained when (R)- and (S) enantiomers are mixed in equal amount.

Thus, the optical rotation of a racemic mixture of (R)- and (S)-alanine is zero (−8.5+8.5=0).

Conclusion

The optical rotation of a racemic mixture of (R)- and (S)-alanine is zero.

Expert Solution

Interpretation Introduction

(e)

Interpretation: The solutions of pure (S)-alanine, an equal mixture of (R)- and (S)-alanine, 75% (S)-and 25% (R)-alanine are to be labeled as optically active or inactive.

Concept introduction: Enantiomers are the stereoisomers that have exactly opposite R,S notations. They possess identical physical properties. A racemic mixture is obtained when (R)- and (S) enantiomers are mixed in equal amount. Their racemic mixture possess different physical properties than parent one.

Answer to Problem 5.28P

The pure (S)-alanine is labeled as optically active, an equal mixture of (R)- and (S)-alanine is labeled as optically inactive, 75% (S)-and 25% (R)-alanine is labeled as optically active.

Explanation of Solution

The pure (S)-alanine is an enantiomer. Enantiomers are optically active compounds. Thus, (S)-alanine is optically active compound.

A racemic mixture is obtained when (R)- and (S) enantiomers are mixed in equal amount. Thus, an equal mixture of (R)- and (S)-alanine is optically inactive.

A 75% (S)-and 25% (R)-alanine solution is optically active. Because, in solution 25% (R)-alanine cancel only 25% (S)-alanine and still 50% of (S)-alanine is left. Therefore, 75% (S)- and 25% (R)-alanine solution is optically active.

Thus, the pure (S)-alanine is labeled as optically active, an equal mixture of (R)- and (S)-alanine is labeled as optically inactive, 75% (S)- and 25% (R)-alanine is labeled as optically active.

Conclusion

The pure (S)-alanine is labeled as optically active, an equal mixture of (R)- and (S)-alanine is labeled as optically inactive, 75% (S)- and 25% (R)-alanine is labeled as optically active.

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Answer 5

Textbook Question

Answer 6

Textbook Question

Answer 7

Expert Solution

Interpretation Introduction

(a)

Interpretation: The melting point of (R)-alanine is to be predicted.

Concept introduction: Enantiomers are the stereoisomers that have exactly opposite R,S notations. Diastereomers are the stereoisomers that have the opposite R,S notations for at least one stereogenic center and the same R,S notations for at least one stereogenic center. Enantiomers have identical physical properties, whereas diastereomers have different physical properties.

Answer to Problem 5.28P

The melting point of (R)-alanine is 297 °C.

Explanation of Solution

The given melting point of (S)-alanine is 297 °C. The (R)-alanine, and (S)-alanine are the enantiomers. Enantiomers are the stereoisomers that have exactly opposite R,S notations. They possess identical physical properties. Therefore, the melting point of (R)-alanine is also 297 °C.

Conclusion

The melting point of (R)-alanine is 297 °C.

Expert Solution

Interpretation Introduction

(b)

Interpretation: The melting point of a racemic mixture of (R)- and (S)-alanine is to be compared with the melting point of (S)-alanine.

Concept introduction: Enantiomers are the stereoisomers that have exactly opposite R,S notations. They possess identical physical properties. A racemic mixture is obtained when (R)-and (S) enantiomers are mixed in equal amount. Their racemic mixture possess different physical properties than parent one.

Answer to Problem 5.28P

The melting point of a racemic mixture of (R)- and (S)-alanine is different with the melting point of (S)-alanine.

Explanation of Solution

The given melting point of (S)-alanine is 297 °C. The (R)-alanine, and (S)-alanine are the enantiomers. Enantiomers are the stereoisomers that have exactly opposite R,S notations. They possess identical physical properties. A racemic mixture is obtained when (R)- and (S) enantiomers are mixed in equal amount. Their racemic mixture possess different physical properties than parent one.

Therefore, the melting point of a racemic mixture of (R)- and (S)-alanine is different with the melting point of (S)-alanine.

Conclusion

The melting point of a racemic mixture of (R)- and (S)-alanine is different with the melting point of (S)-alanine.

Expert Solution

Interpretation Introduction

(c)

Interpretation: The specific rotation of (R)-alanine is to be predicted.

Concept introduction: Enantiomers are the stereoisomers that have exactly opposite R,S notations. They possess identical physical properties. Their specific rotation values are opposite in sign but equal in magnitude, when they are recorded under same condition.

Answer to Problem 5.28P

The specific rotation of (R)-alanine is −8.5.

Explanation of Solution

The specific rotation of (S)-alanine is +8.5. The (R)-alanine, and (S)-alanine are the enantiomers. Enantiomers are the stereoisomers that have exactly opposite R,S notations. They possess identical physical properties. Their specific rotation values are opposite in sign but equal in magnitude, when they are recorded under same condition.

Thus, the specific rotation of (R)-alanine is −8.5.

Conclusion

The specific rotation of (R)-alanine is −8.5.

Expert Solution

Interpretation Introduction

(d)

Interpretation: The optical rotation of a racemic mixture of (R)- and (S)-alanine is to be calculated.

Concept introduction: Enantiomers are the stereoisomers that have exactly opposite R,S notations. They possess identical physical properties. A racemic mixture is obtained when (R)-and (S) enantiomers are mixed in equal amount.

Answer to Problem 5.28P

The optical rotation of a racemic mixture of (R)- and (S)-alanine is zero.

Explanation of Solution

The specific rotation of (S)-alanine is +8.5.

The specific rotation of (R)-alanine is −8.5.

The (R)-alanine, and (S)-alanine are the enantiomers. Enantiomers are the stereoisomers that have exactly opposite R,S notations. They possess identical physical properties. A racemic mixture is obtained when (R)- and (S) enantiomers are mixed in equal amount.

Thus, the optical rotation of a racemic mixture of (R)- and (S)-alanine is zero (−8.5+8.5=0).

Conclusion

The optical rotation of a racemic mixture of (R)- and (S)-alanine is zero.

Expert Solution

Interpretation Introduction

(e)

Interpretation: The solutions of pure (S)-alanine, an equal mixture of (R)- and (S)-alanine, 75% (S)-and 25% (R)-alanine are to be labeled as optically active or inactive.

Concept introduction: Enantiomers are the stereoisomers that have exactly opposite R,S notations. They possess identical physical properties. A racemic mixture is obtained when (R)- and (S) enantiomers are mixed in equal amount. Their racemic mixture possess different physical properties than parent one.

Answer to Problem 5.28P

The pure (S)-alanine is labeled as optically active, an equal mixture of (R)- and (S)-alanine is labeled as optically inactive, 75% (S)-and 25% (R)-alanine is labeled as optically active.

Explanation of Solution

The pure (S)-alanine is an enantiomer. Enantiomers are optically active compounds. Thus, (S)-alanine is optically active compound.

A racemic mixture is obtained when (R)- and (S) enantiomers are mixed in equal amount. Thus, an equal mixture of (R)- and (S)-alanine is optically inactive.

A 75% (S)-and 25% (R)-alanine solution is optically active. Because, in solution 25% (R)-alanine cancel only 25% (S)-alanine and still 50% of (S)-alanine is left. Therefore, 75% (S)- and 25% (R)-alanine solution is optically active.

Thus, the pure (S)-alanine is labeled as optically active, an equal mixture of (R)- and (S)-alanine is labeled as optically inactive, 75% (S)- and 25% (R)-alanine is labeled as optically active.

Conclusion

The pure (S)-alanine is labeled as optically active, an equal mixture of (R)- and (S)-alanine is labeled as optically inactive, 75% (S)- and 25% (R)-alanine is labeled as optically active.

Answer 8

Expert Solution

Interpretation Introduction

(a)

Interpretation: The melting point of (R)-alanine is to be predicted.

Concept introduction: Enantiomers are the stereoisomers that have exactly opposite R,S notations. Diastereomers are the stereoisomers that have the opposite R,S notations for at least one stereogenic center and the same R,S notations for at least one stereogenic center. Enantiomers have identical physical properties, whereas diastereomers have different physical properties.

Answer to Problem 5.28P

The melting point of (R)-alanine is 297 °C.

Explanation of Solution

The given melting point of (S)-alanine is 297 °C. The (R)-alanine, and (S)-alanine are the enantiomers. Enantiomers are the stereoisomers that have exactly opposite R,S notations. They possess identical physical properties. Therefore, the melting point of (R)-alanine is also 297 °C.

Conclusion

The melting point of (R)-alanine is 297 °C.

Answer 9

Expert Solution

Answer 10

Expert Solution

Answer 11

Expert Solution

Answer 12

Interpretation Introduction

(a)

Interpretation: The melting point of (R)-alanine is to be predicted.

Concept introduction: Enantiomers are the stereoisomers that have exactly opposite R,S notations. Diastereomers are the stereoisomers that have the opposite R,S notations for at least one stereogenic center and the same R,S notations for at least one stereogenic center. Enantiomers have identical physical properties, whereas diastereomers have different physical properties.

Answer 13

Answer to Problem 5.28P

The melting point of (R)-alanine is 297 °C.

Answer 14

Explanation of Solution

The given melting point of (S)-alanine is 297 °C. The (R)-alanine, and (S)-alanine are the enantiomers. Enantiomers are the stereoisomers that have exactly opposite R,S notations. They possess identical physical properties. Therefore, the melting point of (R)-alanine is also 297 °C.

Answer 15

Conclusion

The melting point of (R)-alanine is 297 °C.

Answer 16

Expert Solution

Interpretation Introduction

(b)

Interpretation: The melting point of a racemic mixture of (R)- and (S)-alanine is to be compared with the melting point of (S)-alanine.

Concept introduction: Enantiomers are the stereoisomers that have exactly opposite R,S notations. They possess identical physical properties. A racemic mixture is obtained when (R)-and (S) enantiomers are mixed in equal amount. Their racemic mixture possess different physical properties than parent one.

Answer to Problem 5.28P

The melting point of a racemic mixture of (R)- and (S)-alanine is different with the melting point of (S)-alanine.

Explanation of Solution

The given melting point of (S)-alanine is 297 °C. The (R)-alanine, and (S)-alanine are the enantiomers. Enantiomers are the stereoisomers that have exactly opposite R,S notations. They possess identical physical properties. A racemic mixture is obtained when (R)- and (S) enantiomers are mixed in equal amount. Their racemic mixture possess different physical properties than parent one.

Therefore, the melting point of a racemic mixture of (R)- and (S)-alanine is different with the melting point of (S)-alanine.

Conclusion

The melting point of a racemic mixture of (R)- and (S)-alanine is different with the melting point of (S)-alanine.

Answer 17

Expert Solution

Answer 18

Expert Solution

Answer 19

Expert Solution

Answer 20

Interpretation Introduction

(b)

Interpretation: The melting point of a racemic mixture of (R)- and (S)-alanine is to be compared with the melting point of (S)-alanine.

Concept introduction: Enantiomers are the stereoisomers that have exactly opposite R,S notations. They possess identical physical properties. A racemic mixture is obtained when (R)-and (S) enantiomers are mixed in equal amount. Their racemic mixture possess different physical properties than parent one.

Answer 21

Answer to Problem 5.28P

The melting point of a racemic mixture of (R)- and (S)-alanine is different with the melting point of (S)-alanine.

Answer 22

Explanation of Solution

The given melting point of (S)-alanine is 297 °C. The (R)-alanine, and (S)-alanine are the enantiomers. Enantiomers are the stereoisomers that have exactly opposite R,S notations. They possess identical physical properties. A racemic mixture is obtained when (R)- and (S) enantiomers are mixed in equal amount. Their racemic mixture possess different physical properties than parent one.

Therefore, the melting point of a racemic mixture of (R)- and (S)-alanine is different with the melting point of (S)-alanine.

Answer 23

Conclusion

The melting point of a racemic mixture of (R)- and (S)-alanine is different with the melting point of (S)-alanine.

Answer 24

Expert Solution

Interpretation Introduction

(c)

Interpretation: The specific rotation of (R)-alanine is to be predicted.

Concept introduction: Enantiomers are the stereoisomers that have exactly opposite R,S notations. They possess identical physical properties. Their specific rotation values are opposite in sign but equal in magnitude, when they are recorded under same condition.

Answer to Problem 5.28P

The specific rotation of (R)-alanine is −8.5.

Explanation of Solution

The specific rotation of (S)-alanine is +8.5. The (R)-alanine, and (S)-alanine are the enantiomers. Enantiomers are the stereoisomers that have exactly opposite R,S notations. They possess identical physical properties. Their specific rotation values are opposite in sign but equal in magnitude, when they are recorded under same condition.

Thus, the specific rotation of (R)-alanine is −8.5.

Conclusion

The specific rotation of (R)-alanine is −8.5.

Answer 25

Expert Solution

Answer 26

Expert Solution

Answer 27

Expert Solution

Answer 28

Interpretation Introduction

(c)

Interpretation: The specific rotation of (R)-alanine is to be predicted.

Concept introduction: Enantiomers are the stereoisomers that have exactly opposite R,S notations. They possess identical physical properties. Their specific rotation values are opposite in sign but equal in magnitude, when they are recorded under same condition.

Answer 29

Answer to Problem 5.28P

The specific rotation of (R)-alanine is −8.5.

Answer 30

Explanation of Solution

The specific rotation of (S)-alanine is +8.5. The (R)-alanine, and (S)-alanine are the enantiomers. Enantiomers are the stereoisomers that have exactly opposite R,S notations. They possess identical physical properties. Their specific rotation values are opposite in sign but equal in magnitude, when they are recorded under same condition.

Thus, the specific rotation of (R)-alanine is −8.5.

Answer 31

Conclusion

The specific rotation of (R)-alanine is −8.5.

Answer 32

Expert Solution

Interpretation Introduction

(d)

Interpretation: The optical rotation of a racemic mixture of (R)- and (S)-alanine is to be calculated.

Concept introduction: Enantiomers are the stereoisomers that have exactly opposite R,S notations. They possess identical physical properties. A racemic mixture is obtained when (R)-and (S) enantiomers are mixed in equal amount.

Answer to Problem 5.28P

The optical rotation of a racemic mixture of (R)- and (S)-alanine is zero.

Explanation of Solution

The specific rotation of (S)-alanine is +8.5.

The specific rotation of (R)-alanine is −8.5.

The (R)-alanine, and (S)-alanine are the enantiomers. Enantiomers are the stereoisomers that have exactly opposite R,S notations. They possess identical physical properties. A racemic mixture is obtained when (R)- and (S) enantiomers are mixed in equal amount.

Thus, the optical rotation of a racemic mixture of (R)- and (S)-alanine is zero (−8.5+8.5=0).

Conclusion

The optical rotation of a racemic mixture of (R)- and (S)-alanine is zero.

Answer 33

Expert Solution

Answer 34

Expert Solution

Answer 35

Expert Solution

Answer 36

Interpretation Introduction

(d)

Interpretation: The optical rotation of a racemic mixture of (R)- and (S)-alanine is to be calculated.

Concept introduction: Enantiomers are the stereoisomers that have exactly opposite R,S notations. They possess identical physical properties. A racemic mixture is obtained when (R)-and (S) enantiomers are mixed in equal amount.

Answer 37

Answer to Problem 5.28P

The optical rotation of a racemic mixture of (R)- and (S)-alanine is zero.

Answer 38

Explanation of Solution

The specific rotation of (S)-alanine is +8.5.

The specific rotation of (R)-alanine is −8.5.

The (R)-alanine, and (S)-alanine are the enantiomers. Enantiomers are the stereoisomers that have exactly opposite R,S notations. They possess identical physical properties. A racemic mixture is obtained when (R)- and (S) enantiomers are mixed in equal amount.

Thus, the optical rotation of a racemic mixture of (R)- and (S)-alanine is zero (−8.5+8.5=0).

Answer 39

Conclusion

The optical rotation of a racemic mixture of (R)- and (S)-alanine is zero.

Answer 40

Expert Solution

Interpretation Introduction

(e)

Interpretation: The solutions of pure (S)-alanine, an equal mixture of (R)- and (S)-alanine, 75% (S)-and 25% (R)-alanine are to be labeled as optically active or inactive.

Concept introduction: Enantiomers are the stereoisomers that have exactly opposite R,S notations. They possess identical physical properties. A racemic mixture is obtained when (R)- and (S) enantiomers are mixed in equal amount. Their racemic mixture possess different physical properties than parent one.

Answer to Problem 5.28P

The pure (S)-alanine is labeled as optically active, an equal mixture of (R)- and (S)-alanine is labeled as optically inactive, 75% (S)-and 25% (R)-alanine is labeled as optically active.

Explanation of Solution

The pure (S)-alanine is an enantiomer. Enantiomers are optically active compounds. Thus, (S)-alanine is optically active compound.

A racemic mixture is obtained when (R)- and (S) enantiomers are mixed in equal amount. Thus, an equal mixture of (R)- and (S)-alanine is optically inactive.

A 75% (S)-and 25% (R)-alanine solution is optically active. Because, in solution 25% (R)-alanine cancel only 25% (S)-alanine and still 50% of (S)-alanine is left. Therefore, 75% (S)- and 25% (R)-alanine solution is optically active.

Thus, the pure (S)-alanine is labeled as optically active, an equal mixture of (R)- and (S)-alanine is labeled as optically inactive, 75% (S)- and 25% (R)-alanine is labeled as optically active.

Conclusion

The pure (S)-alanine is labeled as optically active, an equal mixture of (R)- and (S)-alanine is labeled as optically inactive, 75% (S)- and 25% (R)-alanine is labeled as optically active.

Answer 41

Expert Solution

Answer 42

Expert Solution

Answer 43

Expert Solution

Answer 44

Interpretation Introduction

(e)

Interpretation: The solutions of pure (S)-alanine, an equal mixture of (R)- and (S)-alanine, 75% (S)-and 25% (R)-alanine are to be labeled as optically active or inactive.

Concept introduction: Enantiomers are the stereoisomers that have exactly opposite R,S notations. They possess identical physical properties. A racemic mixture is obtained when (R)- and (S) enantiomers are mixed in equal amount. Their racemic mixture possess different physical properties than parent one.

Answer 45

Answer to Problem 5.28P

The pure (S)-alanine is labeled as optically active, an equal mixture of (R)- and (S)-alanine is labeled as optically inactive, 75% (S)-and 25% (R)-alanine is labeled as optically active.

Answer 46

Explanation of Solution

The pure (S)-alanine is an enantiomer. Enantiomers are optically active compounds. Thus, (S)-alanine is optically active compound.

A racemic mixture is obtained when (R)- and (S) enantiomers are mixed in equal amount. Thus, an equal mixture of (R)- and (S)-alanine is optically inactive.

A 75% (S)-and 25% (R)-alanine solution is optically active. Because, in solution 25% (R)-alanine cancel only 25% (S)-alanine and still 50% of (S)-alanine is left. Therefore, 75% (S)- and 25% (R)-alanine solution is optically active.

Thus, the pure (S)-alanine is labeled as optically active, an equal mixture of (R)- and (S)-alanine is labeled as optically inactive, 75% (S)- and 25% (R)-alanine is labeled as optically active.

Answer 47

Conclusion

The pure (S)-alanine is labeled as optically active, an equal mixture of (R)- and (S)-alanine is labeled as optically inactive, 75% (S)- and 25% (R)-alanine is labeled as optically active.