Chapter 14, Problem 14.11E

Each of the following names is wrong. Give the structure and correct name of

each compound.

a $\text{3-ethyl-2-butanone}$

b $\text{2-ethyl-propanal}$

c. $\text{4-methyl-5-propyl-3-hexanone}$

d. $\text{2-methyl-2-phenylethanal}$

Interpretation Introduction

(a)

Interpretation:

The structural formula of $\text{3-ethyl-2-butanone}$ is to be drawn and its correct name is to be stated.

Concept introduction:

The systematic naming of organic compound is given by IUPAC. The naming of organic compound is done in such a way that the structure of organic compound is correctly interpreted from the name.

Rules for writing the structural formula from IUPAC are:

• First identify the word root for the given compound.

• The suffix used in the compound like –ane, ene, yne, ol, al and so on.

• Identify the position, location, and number of the substituent bonded to the carbon chain.

Aldehydes and ketones contain carbonyl functional group in their parent chain and are named by adding suffix –al and –one to the name of the parent alkane.

Answer to Problem 14.11E

The structural formula of $\text{3-ethyl-2-butanone}$ is,

The correct name is $\text{3-methyl-2-pentanone}$.

Explanation of Solution

The given name is $\text{3-ethyl-2-butanone}$. The root word used in this is ‘but’. It means structure contains four carbon atoms. The hydrocarbons that are attached to the longest chain are called substituents and they are written as prefix in alphabetical order. One ethyl substituent is attached to the third carbon atom. The functional group present in the given compound is ketone $\left(\text{R-CO-R}\right)$ because the suffix used for ketone is –one. It is present at the second carbon atom. Therefore, the structure corresponding to $\text{3-ethyl-2-butanone}$ is shown below.

Figure 1

The longest carbon chain contains five carbon atoms. One methyl substituent is attached to the third carbon atom. The functional group present in the given compound is ketone $\left(\text{R-CO-R}\right)$ present at the second carbon atom. Therefore, the correct name of this compound is $\text{3-methyl-2-pentanone}$.

Conclusion

The structural formula is shown in Figure 1.

The correct name of the compound is $\text{3-methyl-2-pentanone}$.

Interpretation Introduction

(b)

Interpretation:

The structural formula of $\text{2-ethyl-propanal}$ is to be drawn and its correct name is to be stated.

Concept introduction:

The systematic naming of organic compound is given by IUPAC. The naming of organic compound is done in such a way that the structure of organic compound is correctly interpreted from the name.

Rules for writing the structural formula from IUPAC are:

• First identify the word root for the given compound.

• The suffix used in the compound like –ane, ene, yne, ol, al and so on.

• Identify the position, location, and number of the substituent bonded to the carbon chain.

Aldehydes and ketones contain carbonyl functional group in their parent chain and are named by adding suffix –al and –one to the name of the parent alkane.

Answer to Problem 14.11E

The structural formula of $\text{2-ethyl-propanal}$ is,

The correct name is $\text{2-methylbutanal}$.

Explanation of Solution

The given name is $\text{2-ethyl-propanal}$. The root word used in this is prop. It means structure contains three carbon atoms. One ethyl substituent is attached to the second carbon atom. The functional group present in the given compound is aldehyde $\left(\text{R-COH}\right)$ because the suffix used for aldehyde is –al. It is present at the first carbon atom. Therefore, the structure corresponding to $\text{2-ethyl-propanal}$ is shown below.

Figure 2

The longest carbon chain contains four carbon atoms. One methyl substituent is attached to the second carbon atom. The functional group present in the given compound is aldehyde $\left(\text{R-COH}\right)$ present at the first carbon atom. Therefore, the correct name of this compound is $\text{2-methylbutanal}$.

Conclusion

The structural formula is shown in Figure 2.

The correct name of the compound is $\text{2-methylbutanal}$.

Interpretation Introduction

(c)

Interpretation:

The structural formula of $\text{4-methyl-5-propyl-3-hexanone}$ is to be drawn and its correct name is to be stated.

Concept introduction:

The systematic naming of organic compound is given by IUPAC. The naming of organic compound is done in such a way that the structure of organic compound is correctly interpreted from the name.

Rules for writing the structural formula from IUPAC are:

• First identify the word root for the given compound.

• The suffix used in the compound like –ane, ene, yne, ol, al and so on.

• Identify the position, location, and number of the substituent bonded to the carbon chain.

Aldehydes and ketones contain carbonyl functional group in their parent chain and are named by adding suffix –al and –one to the name of the parent alkane.

Answer to Problem 14.11E

The structural formula of $\text{4-methyl-5-propyl-3-hexanone}$ is,

The correct name is $\text{4, 5-dimethyl-3-octanone}$.

Explanation of Solution

The given name is $\text{4-methyl-5-propyl-3-hexanone}$. The root word used in this is hex. It means structure contains six carbon atoms. One methyl substituent is attached to the fourth carbon atom and one propyl group is attached to the fifth carbon atom. The functional group present in the given compound is ketone $\left(\text{R-CO-R}\right)$ because the suffix used for ketone is –one. It is present at the third carbon atom. Therefore, the structure corresponding to $\text{4-methyl-5-propyl-3-hexanone}$ is shown below.

Figure 3

The longest carbon chain contains eight carbon atoms. One methyl substituent is attached to the fourth carbon atom and the other methyl group is attached to the fifth carbon atom. The functional group present in the given compound is ketone $\left(\text{R-CO-R}\right)$ present at the third carbon atom. Therefore, the correct name of this compound is $\text{4, 5-dimethyl-3-octanone}$.

Conclusion

The structural formula is shown in Figure 3.

The correct name of the compound is $\text{4, 5-dimethyl-3-octanone}$.

Interpretation Introduction

(d)

Interpretation:

The structural formula of $\text{2-methyl-2-phenylethanal}$ is to be drawn and its correct name is to be stated.

Concept introduction:

The systematic naming of organic compound is given by IUPAC. The naming of organic compound is done in such a way that the structure of organic compound is correctly interpreted from the name.

Rules for writing the structural formula from IUPAC are:

• First identify the word root for the given compound.

• The suffix used in the compound like –ane, ene, yne, ol, al and so on.

• Identify the position, location, and number of the substituent bonded to the carbon chain.

Aldehydes and ketones contain carbonyl functional group in their parent chain and are named by adding suffix –al and –one to the name of the parent alkane.

Answer to Problem 14.11E

The structural formula of $\text{2-methyl-2-phenylethanal}$ is,

The correct name is $\text{2-phenylpropanal}$.

Explanation of Solution

The given name is $\text{2-methyl-2-phenylethanal}$. The root word used in this is eth. It means structure contains two carbon atoms. One methyl and one phenyl substituents are attached to the second carbon atom. The functional group present in the given compound is aldehyde $\left(\text{R-COH}\right)$ because the suffix used for aldehyde is –al. It is present at the first carbon atom. Therefore, the structure corresponding to $\text{2-methyl-2-phenylethanal}$ is shown below.

Figure 4

The longest carbon chain contains three carbon atoms. One phenyl substituent is attached to the second carbon atom. The functional group present in the given compound is aldehyde $\left(\text{R-COH}\right)$ present at the first carbon atom. Therefore, the correct name of this compound is $\text{2-phenylpropanal}$.

Conclusion

The structural formula is shown in Figure 4.

The correct name of the compound is $\text{2-phenylpropanal}$.