Chapter 21, Problem 5RQ

What functional group distinguishes each of the following hydrocarbon derivatives?

a. halohydrocarbons

b. alcohols

c. ethers

d. aldehydes

e. ketones

f. carboxylic acids

g. esters

h. amines

Give examples of each functional group. What prefix or suffix is used to name each functional group? What are the bond angles in each? Describe the bonding in each functional group. What is the difference between a primary, secondary, and tertiary alcohol? For the functional groups in a–h, when is a number required to indicate the position of the functional group? Carboxylic acids are often written as RCOOH. What does —COOH indicate and what does R indicate? Aldehydes are sometimes written as RCHO. What does —CHO indicate?

Interpretation Introduction

Interpretation: The given hydrocarbon derivatives are to be distinguished on the basis of functional groups present. Various question based upon the functional groups are to be answered.

Concept introduction: A functional group is a group of elements that changes the physical as well as chemical properties of a compound. They play a significant role in naming and reactivity of a chemical reaction. Some of the common examples of functional groups are alcohol, carboxylic acid, amine, aldehyde, ketone and many others.

To determine: The functional groups that distinguishes the given hydrocarbon derivatives and the answers for the questions asked.

The functional group that distinguishes halohydrocarbons.

Explanation of Solution

Explanation

The functional group present in halohydrocarbons is halogen

The hydrocarbons are the organic compounds that contain hydrogen and carbon. When halogen is attached to any hydrocarbon, then the compound is known as halohydrocarbons.

Chloropropane is an example of halohydrocarbon where the functional group “chlorine” is attached to the hydrocarbon propane. Structure of halohydrocarbon is,

Figure 1

Interpretation Introduction

Interpretation: The given hydrocarbon derivatives are to be distinguished on the basis of functional groups present. Various question based upon the functional groups are to be answered.

Concept introduction: A functional group is a group of elements that changes the physical as well as chemical properties of a compound. They play a significant role in naming and reactivity of a chemical reaction. Some of the common examples of functional groups are alcohol, carboxylic acid, amine, aldehyde, ketone and many others.

To determine: The functional group that distinguishes alcohols.

Explanation of Solution

Explanation

The functional group present in alcohols is $\left(\text{-OH}\right)$ group

When the functional group $\left(\text{-OH}\right)$ is attached to the hydrocarbons, the compound is known as alcohols. The example of alcohol is propanol. Structure of propanol is,

Figure 2

Interpretation Introduction

Interpretation: The given hydrocarbon derivatives are to be distinguished on the basis of functional groups present. Various question based upon the functional groups are to be answered.

Concept introduction: A functional group is a group of elements that changes the physical as well as chemical properties of a compound. They play a significant role in naming and reactivity of a chemical reaction. Some of the common examples of functional groups are alcohol, carboxylic acid, amine, aldehyde, ketone and many others.

To determine: The functional group that distinguishes ethers.

Explanation of Solution

Explanation

The functional group present in ethers is $\left(\text{-O-}\right)$ group.

In ethers, the oxygen atom is bonded with two alkyl or aryl group. The example of ether is diethylether. Structure of diethylether is,

Figure 3

Interpretation Introduction

Interpretation: The given hydrocarbon derivatives are to be distinguished on the basis of functional groups present. Various question based upon the functional groups are to be answered.

Concept introduction: A functional group is a group of elements that changes the physical as well as chemical properties of a compound. They play a significant role in naming and reactivity of a chemical reaction. Some of the common examples of functional groups are alcohol, carboxylic acid, amine, aldehyde, ketone and many others.

To determine: The functional group that distinguishes aldehydes.

Explanation of Solution

Explanation

The functional group present in aldehyde is $\left(\text{-CHO}\right)$ group.

In aldehydes, the hydrocarbon is attached to $\left(\text{-CHO}\right)$ group. The example of aldehyde is propanal. Structure of propanal is,

Figure 4

Interpretation Introduction

Interpretation: The given hydrocarbon derivatives are to be distinguished on the basis of functional groups present. Various question based upon the functional groups are to be answered.

Concept introduction: A functional group is a group of elements that changes the physical as well as chemical properties of a compound. They play a significant role in naming and reactivity of a chemical reaction. Some of the common examples of functional groups are alcohol, carboxylic acid, amine, aldehyde, ketone and many others.

Explanation of Solution

Explanation

The functional group present in ketones is $\left(-\text{C=O}\right)$ group.

In ketones, the hydrocarbon is attached to $\left(-\text{C=O}\right)$ group. The example of ketone is propan- $2$-one. Structure of propan- $2$-one is,

Figure 5

Interpretation Introduction

Interpretation: The given hydrocarbon derivatives are to be distinguished on the basis of functional groups present. Various question based upon the functional groups are to be answered.

Concept introduction: A functional group is a group of elements that changes the physical as well as chemical properties of a compound. They play a significant role in naming and reactivity of a chemical reaction. Some of the common examples of functional groups are alcohol, carboxylic acid, amine, aldehyde, ketone and many others.

Explanation of Solution

Explanation

To determine: The functional group that distinguishes carboxylic acid.

The functional group present in carboxylic acids is $\left(-\text{COOH}\right)$ group.

In carboxylic acids, the hydrocarbon is attached to $\left(-\text{COOH}\right)$ group. The example of carboxylic acid is propanoic acid. Structure of propanoic acid is,

Figure 6

Interpretation Introduction

Interpretation: The given hydrocarbon derivatives are to be distinguished on the basis of functional groups present. Various question based upon the functional groups are to be answered.

Concept introduction: A functional group is a group of elements that changes the physical as well as chemical properties of a compound. They play a significant role in naming and reactivity of a chemical reaction. Some of the common examples of functional groups are alcohol, carboxylic acid, amine, aldehyde, ketone and many others.

Explanation of Solution

Explanation

To determine: The functional group that distinguishes esters.

The functional group present in esters is $\left(\text{-COO-}\right)$ group.

When hydrogen of the carboxylic group is replaced by hydrocarbon group the formation of ester $\left(\text{RCOOR}\right)$ takes place. The example of ester is ethylpropanoate. Structure of ethylpropanoate is,

Figure 7

Interpretation Introduction

Interpretation: The given hydrocarbon derivatives are to be distinguished on the basis of functional groups present. Various question based upon the functional groups are to be answered.

Concept introduction: A functional group is a group of elements that changes the physical as well as chemical properties of a compound. They play a significant role in naming and reactivity of a chemical reaction. Some of the common examples of functional groups are alcohol, carboxylic acid, amine, aldehyde, ketone and many others.

Explanation of Solution

Explanation

To determine: The functional group that distinguishes amines.

The functional group present in amines is $\left(-{\text{NH}}_2\right)$ group.

In amines, $\left(-{\text{NH}}_2\right)$ group is attached to hydrocarbons. The example of amine is methylamine. Structure of methylamine is,

Figure 8

Interpretation Introduction

Interpretation: The given hydrocarbon derivatives are to be distinguished on the basis of functional groups present. Various question based upon the functional groups are to be answered.

Concept introduction: A functional group is a group of elements that changes the physical as well as chemical properties of a compound. They play a significant role in naming and reactivity of a chemical reaction. Some of the common examples of functional groups are alcohol, carboxylic acid, amine, aldehyde, ketone and many others.

To determine: The answers of the various questions based upon functional groups.

Explanation of Solution

Explanation

Example of each functional group is given below.

The examples of each functional group is,

1. a) Halohydrocarbon: Chloropropane.
2. b) Alcohols: propanol.
3. c) Ethers: diethylether.
4. d) Aldehydes: propanal.
5. e) Ketones: propan- $2$-one.
6. f) Carboxylic acids: propanoic acid.
7. g) Esters: ethylpropanoate.
8. h) Amines: methylamine.

Prefixes and suffixes for each functional group are given below.

Prefixes and suffixes for each functional group are,

1. a) Halohydrocarbon: Prefix “halo”.
2. b) Alcohols: Suffix “ol”.
3. c) Ethers: Suffix “oxy”.
4. d) Aldehydes: Suffix”al”.
5. e) Ketones: Suffix “one”.
6. f) Carboxylic acids: Suffix “oic acid”.
7. g) Esters: Suffix “oate”.
8. h) Amines: Suffix”amine”.

Bond angles in each of the functional group are,

1. a) Halohydrocarbon: $109.5°$ .
2. b) Alcohols: $109.5°$.
3. c) Ethers: $110°$
4. d) Aldehydes: $120°$ .
5. e) Ketones: $120°$.
6. f) Carboxylic acids: $120°$.
7. g) Esters: $120°$.
8. h) Amines: $109.5°$.

The bonding in each functional group and the difference between primary, secondary and tertiary alcohol have been rightfully described.

Halohydrocarbons have tetrahedral geometry. Halogen $\left(\text{F,Cl,Br,I}\right)$ is bonded covalently to a ${\text{sp}}^3$ hybridized carbon.

In alcohols, the oxygen atoms are ${\text{sp}}^3$ hybridized and have bent shape with bond angles less than $109.5°$ to each other. Alcohols are polar. When the carbon having the alcohol group is attached to only one alkyl group, then the alcohol is known as primary alcohol. When the carbon having the alcohol group is attached to two alkyl groups, then the alcohol is known as secondary alcohol. When the carbon having the alcohol group is attached to three alkyl groups, then the alcohol is known as tertiary alcohol.

The geometry of ethers is tetrahedral, i.e., oxygen is ${\text{sp}}^3$ hybridized. The $\text{C}-\text{0}-\text{C}$ angle is $110°$. The $\text{C}-\text{O}$ bonds are slightly polar.

In aldehydes and ketones, both the carbon and oxygen are ${\text{sp}}^2$ hybridized and the bond angle is $120°$.

In carboxylic acids, the carbon and oxygen in the carbonyl group are both ${\text{sp}}^2$ hybridized which gives basic trigonal shape to carbonyl group. The hydroxyl oxygen is also ${\text{sp}}^2$ hybridized which allows one of its lone pair to conjugate with the pi system of the carbonyl group. This makes the carboxyl group planar.

In esters, the $\text{C}-\text{C}-\text{O}$ bond angle is $120°$. In amines, the nitrogen is ${\text{sp}}^3$ hybridized and the bond angle between $-\text{NH}$ bonds is $109.5°$.

The significance of $\text{R}$ and $-\text{COOH}$ in carboxylic acid and $\text{R}$ and $-\text{CHO}$ in aldehydes have been rightfully stated.

The carboxylic acids are identified by the formula $\text{RCOOH}$.

The $\text{R}$ indicates the alkyl or aryl group attached to the carboxylic acids.

The $-\text{COOH}$ indicates the carboxylic acid functional group.

The aldehydes are identified by the formula $\text{RCHO}$.

The $\text{R}$ indicates the alkyl or aryl group in the aldehydes.

The $-\text{CHO}$ indicates the aldehyde functional group.