Stereochemistry at Tetrahedral Centers

Assign R or S configurations to each chirality center in the following molecules:

Draw tetrahedral representations of the following molecules: S-2-chlorobutane

$$\begin{gathered} \mathbf{\left(}\mathbf{R}\mathbf{\right)}\mathbf{\text{ - 3 - Chloro - 1 - pentene}} \\ \mathbf{[}{\mathbf{H}}_{\mathbf{2}}\mathbf{C}\mathbf{=}\mathbf{CHCH}\mathbf{\left(}\mathbf{Cl}\mathbf{\right)}{\mathbf{CH}}_{\mathbf{2}}{\mathbf{CH}}_{\mathbf{3}}\mathbf{]} \end{gathered}$$

Question: Which of the following objects are chiral?

(a) Soda can 

(b) Screwdriver 

(c) Screw 

(d) Shoe

Question: Which of the following molecules are chiral? Identify the chirality center(s) in each.

(a)

Coniine

(poison hemlock)

(b)

Menthol

(flavoring agent)

(c)

Dextromethorphan

(cough suppressant)

Question: Alanine, an amino acid found in proteins, is chiral. Draw the two enantiomers of alanine using the standard convention of solid, wedged, and dashed lines.

Question: Identify the chirality centers in the following molecules (green 5 Cl, yellow-green 5 F):

Question: Is cocaine (Worked Example 5-2) dextrorotatory or levorotatory?

A 1.50 g sample of coniine, the toxic extract of poison hemlock, was dissolved in 10.0 mL of ethanol and placed in a sample cell with a 5.00 cm pathlength. The observed rotation at the sodium D line was 11.21°. Calculate ${\mathbf{\left[}\mathbf{\alpha }\mathbf{\right]}}_{\mathbf{D}}$ for coniine.

Question: Which member in each of the following sets ranks higher?  

$$\begin{gathered} \mathbf{a}\mathbf{)}\mathbf{ }\mathbf{-}\mathbf{H}\mathbf{ }\mathbf{or}\mathbf{ }\mathbf{-}\mathbf{Br} \\ \mathbf{b}\mathbf{)}\mathbf{ }\mathbf{-}\mathbf{CI}\mathbf{ }\mathbf{or}\mathbf{ }\mathbf{-}\mathbf{Br} \\ \mathbf{c}\mathbf{)}\mathbf{ }\mathbf{-}{\mathbf{CH}}_{\mathbf{3}}\mathbf{ }\mathbf{or}\mathbf{ }\mathbf{-}{\mathbf{CH}}_{\mathbf{2}}{\mathbf{CH}}_{\mathbf{3}} \\ \mathbf{d}\mathbf{)}\mathbf{ }\mathbf{-}{\mathbf{NH}}_{\mathbf{2}}\mathbf{ }\mathbf{or}\mathbf{ }\mathbf{-}\mathbf{OH} \\ \mathbf{e}\mathbf{)}\mathbf{ }\mathbf{-}{\mathbf{CH}}_{\mathbf{2}}\mathbf{OH}\mathbf{ }\mathbf{or}\mathbf{ }\mathbf{-}{\mathbf{CH}}_{\mathbf{2}} \\ \mathbf{f}\mathbf{)}\mathbf{ }\mathbf{-}{\mathbf{CH}}_{\mathbf{2}}\mathbf{OH}\mathbf{ }\mathbf{or}\mathbf{ }\mathbf{-}\mathbf{CH}\mathbf{=}\mathbf{O} \end{gathered}$$

Cis-1,2-Dimethylcyclohexane is optically inactive even though it has two chirality centers. Explain.

Identify the indicated faces in the following molecules as Re or Si:

Erythronolide B is the biological precursor of erythromycin, a broadspectrumantibiotic. How many chirality centers does erythronolide B have? Identify them.

Draw both cis- and trans-1,3-dimethyl cyclohexane in their more stable chair conformations. 

(a) How many stereoisomers are there of cis-1,3-dimethyl cyclohexane, and how many of trans-1,3-dimethyl cyclohexane? 

(b) Are any of the structures chiral? 

(c) What are the stereochemical relationships among the various stereoisomers of 1,3-dimethyl cyclohexane?

Draw both cis- and trans-1,4-dimethylcyclohexane in their more stable chair conformations. 

(a) How many stereoisomers are there of cis-1,4-dimethylcyclohexane, and how many of trans-1,4-dimethylcyclohexane? 

(b) Are any of the structures chiral? 

(c) What are the stereochemical relationships among the various stereoisomers of 1,4-dimethylcyclohexane?

How many stereoisomers of 2,4-dibromo-3-chloropentane are there? Draw them, and indicate which are optically active.

(S)-1-Chloro-2-methylbutane undergoes light-induced reaction with ${\mathrm{Cl}}_2$to yield a mixture of products, among which are 1,4-dichloro-2-methylbutane and 1,2-dichloro-2-methylbutane.

1. Write the reaction, showing the correct stereochemistry of the reactant.
2. One of the two products is optically active, but the other is optically inactive. Which is which?

Xylose is a common sugar found in many types of wood, including maple and cherry. Because it is much less prone to cause tooth decay than sucrose, xylose has been used in candy and chewing gum. Assign R or S configurations to the chirality centers in xylose.

Assign R or S stereochemistry to the chirality centers in the following

Newman projections:

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?

The first step in the metabolism of glycerol, formed by digestion of fats, is phosphorylation of the pro-R   $\mathbf{-}{\mathbf{CH}}_{\mathbf{2}}\mathbf{OH}$  group by reaction with adenosine triphosphate (ATP) to give the corresponding glycerol phosphate plus adenosine diphosphate (ADP). Show the stereochemistry of the product.

Assign R or S configurations to the chirality centers in the following molecules (blue = N)

Assign R or S configurations to the chirality centers in the following molecules (blue = N)

Which, if any, of the following structures represent meso compounds? (Blue = N, green = Cl.)

Which, if any, of the following structures represent meso compounds? (Blue = N, green = Cl.)

Which, if any, of the following structures represent meso compounds? (Blue = N, green = Cl.)

Assign R or S configuration to each chirality center in pseudoephedrine, an over-the-counter decongestant found in cold remedies (blue = N)

Orient each of the following drawings so that the lowest-ranked group is toward the rear, and then assign R or S configuration

Orient each of the following drawings so that the lowest-ranked group is toward the rear, and then assign R or S configuration

Orient each of the following drawings so that the lowest-ranked group is toward the rear, and then assign R or S configuration

Which of the following objects are chiral?

 (a) A basketball 

 (b) A fork

 (c) A wine glass

 (d) A golf club 

(e) A spiral staircase 

(f) A snowflake

(c)

Which of the following objects are chiral?

 (a) A basketball 

 (b) A fork

 (c) A wine glass

 (d) A golf club 

(e) A spiral staircase 

(f) A snowflake

(e)

Which of the following objects are chiral?

 (a) A basketball 

 (b) A fork

 (c) A wine glass

 (d) A golf club 

(e) A spiral staircase 

(f) A snowflake

(f)

Which of the following objects are chiral?

 (a) A basketball 

 (b) A fork

 (c) A wine glass

 (d) A golf club 

(e) A spiral staircase 

(f) A snowflake

(b)

Q 31 Which of the following objects are chiral?

 (a) A basketball 

 (b) A fork

 (c) A wine glass

 (d) A golf club 

(e) A spiral staircase 

(f) A snowflake

Eight alcohols have the formula C₅H₁₂O. Draw them. Which are chiral?

Which of the following objects are chiral?

 (a) A basketball 

 (b) A fork

 (c) A wine glass

 (d) A golf club 

(e) A spiral staircase 

(f) A snowflake

(d)      

Which of the following pairs of structures represent the same enantiomer, and which represent different enantiomers?

What is the relationship between the specific rotations of (2R,3R)-dichloropentane and (2S,3S)-dichloropentane? Between (2R,3S)-dichloropentane and (2R,3R)-dichloropentane?

What is the stereochemical configuration of the enantiomer of (2S,4R)-2,4-octanediol? (A diol is a compound with two -OH groups.)

What are the stereochemical configurations of the two diastereomers of (2S,4R)-2,4-octanediol? (A diol is a compound with two -OH groups.)

Orient each of the following drawings so that the lowest-ranked group is toward the rear, and then assign R or S configuration:

a.

b.

c.

Assign R or S configurations to the chirality centers in the following molecules:

a.

b.

c.

Question: Assign R or S configurations to each chirality center in the following biological molecules:

Draw examples of the following:

(a) A meso compound with the formula 

(b) A meso compound with the formula 

(c) A compound with two chirality centers, one R and the other S

Draw the meso form of each of the following molecules, and indicate the plane of symmetry in each:

(a)

(b)

(c)

Draw the meso form of each of the following molecules, and indicate the plane of symmetry in each:

(a)

(b)

(c)

Draw the meso form of each of the following molecules, and indicate the plane of symmetry in each:

(a)

(b)

(c)

Draw the structure of a meso compound that has five carbons and three chirality centers.

The reactions shown below are unlikely to occur as written. Tell what is wrong with each, and predict the actual product.

Ribose, an essential part of ribonucleic acid (RNA), has the following structure:

(a) How many chirality centers does ribose have? Identify them.

(b) How many stereoisomers of ribose are there?

(c) Draw the structure of the enantiomer of ribose.

(d) Draw the structure of a diastereomer of ribose.