Chapter E, Problem E.32P

Interpretation Introduction

(a)

Interpretation:

For the given molecule, the complete IUPAC name is to be written.

Concept introduction:

To write the IUPAC name, first, it is important to determine the highest-priority functional group present that requires a suffix referring to Table E-1. For the molecules having two or more highest-priority functional groups, the rules are slightly different. In the IUPAC name of such molecules, the final ‘e’ of ‘ane’, ‘ene’, or ‘yne’ is not removed in the suffix.. Prefixes such as ‘di’, ‘tri, etc are written immediately before the suffix to specify the number of highest-priority functional groups. Add a locator number for each of the highest-priority functional groups immediately before the prefixes.

The main chain or ring containing the highest-priority functional group is to be determined. The next step is to number the main chain or ring such that carbon atoms involving highest-priority functional group receive the lowest possible numbers. The locator number for the highest-priority functional group is written immediately before the suffix unless needed. All other functional groups in the molecule are treated as substituents and appear in the name as a prefix. Prefixes such as ‘di’, ‘tri’, ‘tetra’... etc. are used to indicate the number of identical substituents attached. The substituents are named in alphabetical order.

In the IUPAC name of the molecule, the stereochemical configurations at the chiral centers are included as R/S. When assigning priorities to substituents, the atom having the greater atomic number has higher priority.

When the fourth priority substituent is pointing away (it is attached by a dash bond) and the first, second, and third priority substituents are arranged clockwise, the configuration is R.

When the fourth priority substituent is pointing away (it is attached by a dash bond) and the first, second, and third priority substituents are arranged counterclockwise, the configuration is S.

If the fourth priority substituent is attached by a wedge bond, then the clockwise or counterclockwise arrangement of the first, second, and third priority substituents is determined and that arrangement is reversed before assigning R or S.

If the fourth priority substituent is in the plane of the page, then it is switched with the substituent that points away. Then, the clockwise or counterclockwise arrangement of the first, second, and third priority substituents is determined, and that arrangement is reversed before assigning R or S.

When writing the IUPAC name, the R or S designation is written in parenthesis for each asymmetric carbon atom and hyphens are used to separate those designations from the rest of the IUPAC name.

Answer to Problem E.32P

The complete IUPAC name for the given molecule, considering the given stereochemistry, is $\text{(3S, 4R)-3, 5-dichloropentane-1, 4-diol}$.

Explanation of Solution

The given molecule is:

The molecule above contains two $\text{OH}$ functional groups. Thus, a prefix ‘di’ is added immediately before the suffix $\text{'ol'}$ of the functional group. The numbering of the chain starts from the carbon atom on the left to which the $\text{OH}$ group is attached. The numbering is shown below:

The corresponding locator numbers are also added before the prefix ‘di’. Thus, the name of the root is $\text{pentane-1, 4-diol}$; note that the ‘e’ in pentane is retained because the molecule contains more than one highest-priority functional group. The carbon atoms C3 and C5 of the root has one chlorine substituent attached. The prefix ‘di’ is added before the name of the substituent to indicate that it has appeared twice. Thus, the complete IUPAC name for the compound is $\text{3, 5-dichloropentane-1, 4-diol}$.

There are two chiral centers in the given molecule at C3 and C4 carbon atoms.

The C3 carbon attached to Chlorine atom by a wedge bond has the S configuration, while the C4 carbon attached to the $\text{OH}$ group by a dash bond has the R configuration. Thus, for the compound, the IUPAC name considering the given stereochemistry is: $\text{(3S, 4R)-3, 5-dichloropentane-1, 4-diol}$

Conclusion

The complete IUPAC name for the given molecule considering the given stereochemistry

is written above.

Interpretation Introduction

(b)

Interpretation:

For the given molecule, the complete IUPAC name is to be written.

Concept introduction:

To write the IUPAC name, first, it is important to determine the highest-priority functional group present that requires a suffix referring to Table E-1. For the molecules having two or more highest-priority functional groups, the rules are slightly different. In the IUPAC name of such molecules, the final ‘e’ of ‘ane’, ‘ene’, or ‘yne’ is not removed in the suffix. Prefixes such as ‘di’, ‘tri, etc are written immediately before the suffix to specify the number of highest-priority functional groups. Add a locator number for each of the highest-priority functional groups immediately before the prefixes.

The main chain or ring containing the highest-priority functional group is to be determined. The next step is to number the main chain or ring such that carbon atoms involving the highest-priority functional group receive the lowest possible numbers. The locator number for the highest-priority functional group is written immediately before the suffix unless needed. All other functional groups in the molecule are treated as substituents and appear in the name as a prefix. Prefixes such as ‘di’, ‘tri’, ‘tetra’… etc. are used to indicate the number of identical substituents attached. The substituents are named in alphabetical order.

In the IUPAC name of the molecule, the stereochemical configurations at the chiral centers are included as R/S. When assigning priorities to substituents, the atom having the greater atomic number has higher priority.

When the fourth priority substituent is pointing away (it is attached by a dash bond) and the first, second, and third priority substituents are arranged clockwise, the configuration is R.

When the fourth priority substituent is pointing away (it is attached by a dash bond) and the first, second, and third priority substituents are arranged counterclockwise, the configuration is S.

If the fourth priority substituent is attached by a wedge bond, then the clockwise or counterclockwise arrangement of the first, second, and third priority substituents is determined and that arrangement is reversed before assigning R or S.

If the fourth priority substituent is in the plane of the page, then it is switched with the substituent that points away. Then, the clockwise or counterclockwise arrangement of the first, second, and third priority substituents is determined and that arrangement is reversed before assigning R or S.

When writing the IUPAC name, the R or S designation is written in parenthesis for each asymmetric carbon atom, and hyphens are used to separate those designations from the rest of the IUPAC name.

Answer to Problem E.32P

The complete IUPAC name for the given molecule is $\text{(2R, 3S, 4S)-5-bromo-2-propylpentane-1, 3, 4-triamine}$.

Explanation of Solution

The given molecule is:

The molecule above contains three ${\text{NH}}_2$ functional groups. Thus, a prefix ‘tri’ is added immediately before the suffix $\text{'amine'}$ of the functional group. The numbering of the chain starts from the carbon atom on the top-right to which the ${\text{NH}}_2$ group is attached, and the numbering continues such that all the carbon atoms directly bonded to ${\text{NH}}_2$ functional group receive lowest possible locator numbers. The numbering is shown below:

The corresponding locator numbers are also added before the prefix ‘tri’. Thus, the name of the root is $\text{pentane-1, 3, 4-triamine}$; note that the ‘e’ in pentane is retained because the molecule contains more than one ${\text{NH}}_2$ functional group.

The carbon atoms C2 and C3 have two substituents attached.

One propyl group is attached to the C2 carbon atom of the root, while one bromine atom is attached to the C5 carbon atom of the root. The substituents are named in alphabetical order.

Thus, the complete IUPAC name for the compound without considering the stereochemistry is $\text{5-bromo-2-propylpentane-1, 3, 4-triamine}$.

There are three chiral centers in the given molecule.

The C2 carbon atom has R configuration.

The C3 carbon attached to ${\text{NH}}_2$ group by a dash bond has the S configuration.

The C4 carbon attached to ${\text{NH}}_2$ group by a wedge bond has the S configuration.

Thus, the IUPAC name of the compound, considering the given stereochemistry is,

$\text{(2R, 3S, 4S)-5-bromo-2-propylpentane-1, 3, 4-triamine}$

Conclusion

The complete IUPAC name for the given molecule considering the given stereochemistry

is written above.

Interpretation Introduction

(c)

Interpretation:

For the given molecule, the complete IUPAC name is to be written.

Concept introduction:

To write the IUPAC name, first, it is important to determine the highest-priority functional group present that requires a suffix referring to Table E-1. For the molecules having two or more highest-priority functional groups, the rules are slightly different. In the IUPAC name of such molecules, the final ‘e’ of ‘ane’, ‘ene’, or ‘yne’ is not removed in the suffix. Prefixes such as ‘di’, ‘tri, etc are written immediately before the suffix to specify the number of highest-priority functional groups. Add a locator number for each of the highest-priority functional groups immediately before the prefixes.

The main chain or ring is to be determined to be the one that contains the highest-priority functional groups. The next step is to number the main chain or ring such that carbon atoms involving highest-priority functional group receives the lowest possible numbers. The locator number for the highest-priority functional group is written immediately before the suffix unless needed. All other functional groups in the molecule are treated as substituents and appear in the name as a prefix. Prefixes such as ‘di’, ‘tri’, ‘tetra’… etc. are used to indicate the number of identical substituents attached. The substituents are named in alphabetical order.

In the IUPAC name of the molecule, the stereochemical configurations at the chiral centers are included as R/S. When assigning priorities to substituents, the atom having the greater atomic number has higher priority.

When the fourth priority substituent is pointing away (it is attached by a dash bond) and the first, second, and third priority substituents are arranged clockwise, the configuration is R.

When the fourth priority substituent is pointing away (it is attached by a dash bond) and the first, second, and third priority substituents are arranged counterclockwise, the configuration is S.

If the fourth priority substituent is attached by a wedge bond, then the clockwise or counterclockwise arrangement of the first, second, and third priority substituents is determined and that arrangement is reversed before assigning R or S.

If the fourth priority substituent is in the plane of the page, then it is switched with the substituent that points away. Then, the clockwise or counterclockwise arrangement of the first, second, and third priority substituents is determined and that arrangement is reversed before assigning R or S.

When writing the IUPAC name, the R or S designation is written in parenthesis for each asymmetric carbon atom and hyphens are used to separate those designations from the rest of the IUPAC name.

Answer to Problem E.32P

The complete IUPAC name for the given molecule is $\text{(1R, 2S, 4S)-2-amino-5-nitrocyclohexanol}$.

Explanation of Solution

The given molecule is:

The molecule above contains one $\text{OH}$ and one ${\text{NH}}_2$ group and one nitro group. According to Table E-1, the higher priority goes to $\text{OH}$ group. Thus, the suffix $\text{'ol'}$ is added in the root name. The numbering of the ring starts from the carbon to which the $\text{OH}$ group is attached, and the numbering continues such that all the substituents get the lowest possible locator numbers.

The numbering is shown below:

The name of the root is $\text{cyclohexanol}$. The locator number is not added for the functional group if the root is a ring.

There is one ${\text{NH}}_2$ substituent attached to the C2 carbon atom of the root and one nitro substituent attached to the C5 carbon atom of the root. Each is named as ‘amino’ and ‘nitro’ respectively.

Thus, the complete IUPAC name without considering the stereochemistry for the compound is $\text{2-amino-5-nitrocyclohexanol}$.

There are three chiral centers in the molecule.

The C1 carbon atom attached to the $OH$ functional group by a wedge bond has R configuration.

The C2 carbon attached to the ${\text{NH}}_2$ group by a wedge bond has the S configuration.

The C5 carbon attached to the ${\text{NH}}_2$ group by a dash bond has the S configuration.

Thus, the IUPAC name of the compound considering the given stereochemistry is

$\text{(1R, 2S, 4S)-2-amino-5-nitrocyclohexanol}$

Conclusion

The complete IUPAC name for the given molecule considering the given stereochemistry

is written above.