Schaum's Outline of Organic Chemistry

George Hademenos, George Hademenos

Chapter 5 STEREOCHEMISTRY - all with Video Answers

Educators

Chapter Questions

A 1.5-g sample of an enantiomer is dissolved in ethanol to make $50 \mathrm{~mL}$ of solution. Find the specific rotation at $20^{\circ} \mathrm{C}$ for sodium light $(\lambda=589.3 \mathrm{~nm}$, the $D$ line $)$, if the solution has an observed rotation of $+2.79^{\circ}$ in a 10-cm polarimeter tube.

Narayan Hari

Numerade Educator

05:58

Problem 4

A 0.5-g sample of cholesterol isolated from an atherosclerotic arterial specimen yields an observed rotation of $-0.76^{\circ}$ when dissolved in $20 \mathrm{~mL}$ of chloroform and placed in a 1-dm cell. Determine the specific rotaiton $[\alpha]$ of cholesterol for: $(a)$ the entities as defined above; $(b)$ an increase in solute from $0.5 \mathrm{~g}$ to $1.0 \mathrm{~g} ;(c)$ an increase in solvent from $20 \mathrm{~mL}$ to $40 \mathrm{~mL}$; and $(d)$ an increase in path length from $1 \mathrm{dm}$ to $2 \mathrm{dm}$.

Joshua Mangler

Numerade Educator

02:32

Problem 5

How could it be decided whether an observed dextrorotation of $+60^{\circ}$ is not actually a levorotation of $-300^{\circ}$ ?

Charles Thomas

Numerade Educator

01:31

Problem 6

Draw (a) Newman and $(b)$ Fischer projections for enantiomers of $\mathrm{CH}_3 \mathrm{CHIC}_2 \mathrm{H}_5$.

Lottie Adams

Numerade Educator

01:21

Problem 7

Determine if the configuration of the left-hand enantiomer of Fig. 5-3(b) is changed by a rotation in the plane of the paper of (i) $90^{\circ}$ and (ii) $180^{\prime}$.

Ashley High

Numerade Educator

02:32

Problem 8

Write structural formulas for the monochloroisopentanes. Place an asterisk on any chiral $\mathrm{C}$ and indicate the 4 different groups about the $\mathrm{C}^*$.

Ronald Prasad

Numerade Educator

01:26

Problem 9

Esterification of (+)-lactic acid with methyl alcohol gives (-)-methyl lactate. Has the configuration changed?
(Figure can't copy)

Raghvendra Singh

Numerade Educator

02:01

Problem 10

Structures of $\mathrm{CHClBrF}$ are written below in seven Fischer projection formulas. Relate structures (b) through $(g)$ to structure $(a)$.

Dr. Satish Ingale

Numerade Educator

01:46

Problem 11

Put the following groups in decreasing order of priority.
(Figure can't copy)

Nidhi Singhi

Numerade Educator

00:43

Problem 12

Designate as $R$ or $S$ the configuration of
(Figure can't copy)

Ankit Gupta

Numerade Educator

10:11

Problem 13

Draw and specify as $R$ and $S$ the enantiomers, if any, of all the monochloropentanes.

Grigoriy Sereda

Numerade Educator

01:01

Problem 14

D-(+)-Glyceraldehyde is oxidized to $(-)$-glyceric acid, $\mathrm{HOCH}_2 \mathrm{CH}(\mathrm{OH}) \mathrm{COOH}$. Give the D,L designation of the acid.

Narayan Hari

Numerade Educator

05:22

Problem 15

Does configuration change in the following reactions? Designate products $(\mathrm{D}, \mathrm{L})$ and $\left(R_\psi S\right)$.
(Figure can't copy)

Travis Maslanik

Numerade Educator

08:33

Problem 16

Draw three-dimensional and Fischer projections, using superscripts to show priorities, for $(a)(S)-2-$ bromopropanaldehyde, (b) (R)-3-iodo-2-chlompropanol.

Megha Ramappan

Numerade Educator

02:06

Problem 17

For the stereoisomers of 3-iodo-2-butanol, (a) assign $R$ and $S$ configurations to $\mathrm{C}^2$ and $\mathrm{C}^3$. (b) Indicate which are (i) enantiomers and (ii) diastereomers. (c) Will rotation about the $\mathrm{C}-\mathrm{C}$ bond alter the configurations?

Vasu Makani

Numerade Educator

01:53

Problem 18

Compare physical and chemical properties of $(a)$ enantiomers, $(b)$ an enantiomer and its racemic form, and $(c)$ diastereomers.

Alkendra Singh

Numerade Educator

01:22

Problem 19

How can differences in the solubilities of diastereomers be used to resolve a racemic form into individual enantiomers?

Lottie Adams

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01:02

Problem 20

(a) What two products are obtained when $\mathrm{C}^3$ of $(\mathrm{R})$-2-chlorobutane is chlorinated? (b) Are these diastereomers formed in equal amounts? (c) In terms of mechanism account for the fact that
(Figure can't copy)
is obtained when (R)- $\mathrm{ClCH}_2-{ }^{\mathrm{C}} \mathrm{H}\left(\mathrm{CH}_3\right) \mathrm{CH}_2 \mathrm{CH}_3$ is chlorinated.

Narayan Hari

Numerade Educator

08:02

Problem 21

Answer True or talse to each of the following statements and explain your choice. $(a)$ There are two broad classes of stereoisomers. (b) Achiral molecules cannot posscss chiral centers. (c) A reaction catalyzed by an enzyme always gives an optically active product. $(d)$ Raccmization of an enantiomer must result in the breaking of at least one bond to the chiral center. (e) An attempted resolution can distinguish a racemate from a meso compound.

Colton Wang

Numerade Educator

01:00

Problem 22

In Fig. 4-4 give the stereochemical relationship between $(a)$ the two gauche conformers; $(b)$ the anti and either ganche conformer.

Alkendra Singh

Numerade Educator

02:43

Problem 23

(a) What is the necessary and sufficient condition for the existence of enantiomers? (b) What is the necessary and sufficient condition for measurement of optical activity? (c) Are all substances with chiral atoms optically active and resolvable? $(d)$ Are enantiomers possible in molecules that do not have chiral carbon atoms? $(e)$ Can a prochiral carbon every be primary or tertiary? $(f)$ Citl conformational enantiomers cver be resolved?

Dr. Satish Ingale

Numerade Educator

01:58

Problem 24

Select the chiral atoms in each of the following compounds:
(Figure can't copy)
(a) There are eight chiral $\mathrm{C}$ 's: three $\mathrm{C}$ 's attached to a $\mathrm{CH}_3$ group, four $\mathrm{C}$ 's attached to lone $\mathrm{H}$ 's, and one $\mathrm{C}$ attached to $\mathrm{OH}$. (b) Since $\mathrm{N}$ is bonded to four different groups; it is a chiral center, as is the $\mathrm{C}$ bonded to the $\mathrm{OH}$. (c) There are no chiral atoms in this molecule. The two sides of the ring $-\mathrm{CH}_2 \mathrm{CH}_2-$ joining the C's bonded to $\mathrm{Cl}$ 's are the same. Hence, neither of the C's bonded to a $\mathrm{Cl}$ is chiral.

Raghvendra Singh

Numerade Educator

02:57

Problem 25

Draw examples of (a) a meso alkane having the molecular formula $\mathrm{C}_{\mathrm{K}} \mathrm{H}_{18}$ and $(b)$ the simplest alkane with a chiral quaternary C. Name each compound.

Niamat Khuda

Numerade Educator

01:01

Problem 26

Relative configurations of chiral atoms are sometimes established by using reactions in which there is no change in configuration because no bonds to the chiral atom are broken. Which of the following reactions can be used to establish relative configurations?

Narayan Hari

Numerade Educator

Problem 27

Account for the disappearance of optical activity observed when (R)-2-butanol is allowed to stand in aqueous $\mathrm{H}_2 \mathrm{SO}_4$ and when (S)-2-iodooctane is treated with aqueous $\mathrm{KI}$ solution.

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01:09

Problem 28

For the following compounds, draw projection formulas for all stereoisomers and point out their $R, S$ specifications, optical activity (where present), and meso compounds: (a) 1.2,3,4-tetrahydrozybutane, (b) 1-chloro2,3-dibromobutane, (c) 2,4-diiodopentane, (d) 2,3,4-tribromohexane, (e) 2,3,4-tribromopentane.

Lottie Adams

Numerade Educator

01:07

Problem 29

The specific rotation of $(R)-(-)-2$-bromooctane is -36 : What is the percentage composition of a mixture of enantiomers of 2-bromooctane whose rotation is $+18^{-}$?

Alkendra Singh

Numerade Educator

04:18

Problem 30

Predict the yieid of stereoisomeric products, and the optical activity of the mixture of products, formed from chlorination of a racemic mixture of 2-chlorobutane to give 2,3-dichlorobutane.

David Taylor

Numerade Educator

05:29

Problem 31

For the following reactions give the number of stereoisomers that are isolated, their $R, S$ configurations and their optical activities. Use Fischer projections.
(Figure can't copy)

Zubair Abdulla

Numerade Educator

21:53

Problem 32

Designate the following compounds as erythro or threo structures.
(Figure can't copy)

Tom Rutherford

Numerade Educator

00:59

Problem 33

Glyceraldehyde can be converted to lactic acid by the two routes shown below. These results reveal an ambiguity in the assignment of relative D,L configuration. Explain.
(Figure can't copy)

Grigoriy Sereda

Numerade Educator

02:08

Problem 34

Deduce the structural formula for an optically active alkene, $\mathrm{C}_6 \mathrm{H}_{12}$, which reacts with $\mathrm{H}_2$ to form an optically inactive alkane, $\mathrm{C}_6 \mathrm{H}_{14}$.

Parvati Devi

Numerade Educator