GENERAL INSTRUCTIONS:

Read carefully and follow the instruction in each part.

Write your answer in a separate sheet of paper. DO NOT write anything on the module.
Pray first before anything else.

What I Need to Know

In this module, the learner shall be able to:

1) become familiar with the functional groups present in aldehydes, ketones and carboxylic acids;
2) draw the structure of and name various aldehydes, ketones and carboxylic acids; and
3) recognize the biologic importance of various aldehydes, ketones and carboxylic acids.

What’s In

OTHER FUNCTIONAL GROUPS

The ability of organic compounds to react is attributed to particular atoms or groups of atoms within the molecules. The
site of reactivity of an organic compound is referred to as functional group because it controls how the molecules behaves or
functions. For the unsaturated hydrocarbons, the functional groups are the sites of the double and triple bonds. The functional
group may contain elements other than C and H; most often, it contains O, N or a halogen.
In describing the remaining hydrocarbon structure, it is convenient to use the designation R to represent any alkyl group.
If another alkyl group is present, the other alkyl group is represented by R’.
Table below summarizes the common functional groups. Several organic compounds contain the carbonyl group, C=O.
The compounds that contain the carbonyl group are aldehydes, ketones, carboxylic acids and esters. The organic compounds
that contain oxygen (but not in the carbonyl group) are alcohols and ethers. amines and amines are nitrogen-containing organic
compounds. This time, we will be focusing on aldehydes, ketones, and carboxylic acids.

Table. Common Functional Groups of Hydrocarbon Derivatives

1
Page
 What Is It

ALDEHYDES

Aldehydes are characterized by the presence of a carbon atom that is doubly bonded to any oxygen atom and
located at the terminal portion of the carbon chain.
Recall that a primary alcohol has the –OH functional group bonded to a carbon with one or no other carbon
atom attached to it. The following equation represents the oxidation of methyl alcohol (CH 3OH), a primary alcohol.
H H

H – C – OH → H – C = O + H2O

H
methyl alcohol formaldehyde
Observe that during the oxidation one H was removed from the –OH group and another H from the carbon to
which the –OH group was attached (the only carbon in this compound). Water is one product of this reaction; the
other product is a new kind of compound called an aldehyde. In this example, the product is called formaldehyde. The
formula for formaldehyde can also be written as HCHO.
The following reaction indicates the oxidation of ethyl alcohol.
.H H H H .

H – C – C – OH + [O] → H – C – C = O + H2O

. H H H
ethyl alcohol acetaldehyde
The oxidation of ethyl alcohol, a primary alcohol, yields acetaldehyde, whose formula can also be written as
CH3CHO. (Acetaldehyde is partially responsible for the damage to the liver in cirrhosis.) In general,
oxidation
primary alcohol aldehyde
Aldehydes all have the –CHO (called a carbonyl) group at the end of the chain. The general formula for an
aldehyde is RCHO, which indicates some aliphatic alkyl group (R) is attached to a – CHO group at the end of the
molecule.

NAMING ALIPHATIC ALDEHYDES

As we have seen, the oxidation of methyl alcohol, a primary alcohol of one carbon atom, yields an aldehyde
of one carbon atom, HCHO, formaldehyde. The oxidation of ethyl alcohol, a primary alcohol of two carbon atoms,
yields an aldehyde of two carbon atoms, CH3CHO, acetaldehyde. Note that the term aldehyde comes from the words
alcohol dehydrogenation.
The IUPAC names for all aldehydes end in -al. To name an aldehyde according to the IUPAC system, take the
name of the longest chain containing the aldehyde group, drop the ending -e, and replace it with the ending -al. Thus,
the following aldehyde, which contains four carbons, is called butanal.
CH3–CH2–CH2–CHO
The aldehyde group is always at the end of the chain, at carbon 1, with that number being understood and
not written.
Example 1: Name the compound
Br
CH3 – CH – CH – CH – CH2 – CH2 – CH2 – CHO
CH3 CH3
Solution: The largest chain containing the aldehyde group contains eight carbon atoms, so it is an octanal.
The chain is numbered with the aldehyde group at carbon number 1.
Br
8 7 6 5 4 3 2 1
CH3 – CH – CH – CH – CH2 – CH2 – CH2 – CHO
CH3 CH3
There are methyl groups at carbon numbers 5 and 7 and a bromine at carbon number 6. Therefore, naming
the groups in alphabetical order we have 6-bromo-5,7-dimethyloctanal.
2
Page
Example 2: Draw the structure of 4,4-dichloro-2,3-dimethylpentanal.
Solution: Pentanal indicates a five-carbon aldehyde, with the –CHO group at carbon number 1, or
5 4 3 2 1
C – C – C – C – CHO
4,4-dichloro- indicates two chlorines, both at carbon 4.
2,3-dimethyl- indicates two methyls, one at carbon number 2 and one at carbon number 3, or
Cl
5 4 3 2 1
C – C – C – C – CHO

Cl CH3 CH3
Adding H’s to complete all the bonds, we have
Cl
CH3 – C – CH – CH – CHO

Cl CH3 CH3

USES OF ALDEHYDES
Formaldehyde, a colorless gas at room temperature, has a suffocating pungent odor. Its aqueous solution
(about 37% by mass) is called formalin, a poisonous liquid used as a disinfectant and preservative of biological
specimens, and an embalming liquid.
Acetaldehyde, a colorless gas or a volatile liquid ( boiling point, 20.8˚C) with a pungent and fruity odor, results
when ethanol is oxidized. The acetaldehyde in the person’s blood causes nausea, vomiting, sweating, facial flushing,
rapid heartbeat and reduction in blood pressure. Acetaldehyde is used mainly in organic synthesis.
When the functional group of an aldehyde is attached to benzene, a benzaldehyde is formed. The benzaldehyde
found in bitter almonds and in the roots of peach trees is called amygdalin. Amygdalin is poisonous. It hydrolyzes in
the digestive tract to produce hydrocyanic acid, HCN. Amygdalin, is found in some plants that are used as food like
cassava.

Write your answers in a ½ crosswise.

I. Give the name of the following compounds.
1) CH2CH3
. 2) N , N CH3
CH3–CH– CH2–CHO CH3–CH–CH–CH–C–CH2–CHO
F CH3
II. Draw the structures of the following.
1) 2,3-dichloropropanal
2) 3,5,7-trimethyldecanal
3) 5,5-dibromo-3,4-diethyl-7-methyloctanal

KETONES

Recall that a secondary alcohol is one in which the –OH group is bonded to a carbon atom that is also bonded
to two carbon atoms. Isopropyl alcohol is an example of a secondary alcohol. The oxidation of isopropyl alcohol is
indicated by the equation
H

CH3 – C – CH3 + [O] → CH3 – C – CH3 + H2O

‖
OH .O

isopropyl alcohol acetone

(2-propanol) (propanone)
As before, the oxygen atom from the oxidizing agent reacts with the H from the –OH group and with the H
attached to the same carbon as the –OH group forming water and a new class of compounds called ketones.
The oxidation of a secondary alcohol yields a ketone, of the general formula RCOR. That is, a ketone has two
alkyl groups attached to a C=O, carbonyl group. This carbonyl group is present in both aldehydes and ketones.
However, the carbonyl group is at the end of the chain in an aldehyde and not at the end in a ketone.
3
Page
NAMING KETONES
In the IUPAC system, the names of ketones and end in -one. To name a ketone according to this system,
take the name of the longest alkane containing the carbonyl group, drop the ending -e, and add -one. Thus, the four-
carbon ketone is called butanone.
In the common system for naming ketones, each alkyl group attached to the carbonyl group is named and
the word ketone is added afterward. Thus, the name of the preceding compound, according to the common system,
is methyl ethyl ketone, since there is a methyl group attached to one end of the carbonyl group and an ethyl group
attached to the other end.

Example 1: Name the compound using both IUPAC and common systems.
CH3 – CH2 – C – CH2 – CH2 – CH3
‖
.O

Solution: The largest chain containing the ketone (carbonyl) group has six atoms, so it is a hexanone. The
carbonyl group should be given the lowest number, so it is on carbon number 3. Therefore, the
IUPAC name is 3-hexanone. In the common system, there is an alkyl group on either side of
the carbonyl group or,
CH3 – CH2 – C – CH2 – CH2 – CH3
‖
ethyl .O
propyl

The common name for the compound is ethylpropylketone.

Example 2: Name the compound according to the IUPAC system.

Cl
CH3 – C – CH2 – C – CH3
‖
Cl .O

Solution: The largest chain containing the carbonyl group is five, so this is a pentanone. The carbonyl
group is at carbon number 2, so it is a 2-pentanone.
Cl
5 4 3 2 1
CH3 – C – CH2 – C – CH3
‖
Cl .O

There are two chlorine atoms, both at carbon number 4, so the name is 4,4-dichloro-2-
pentanone.

Example 3: Draw the structure of methylethylketone.

Solution: Ketone indicates a carbonyl group attached to two alkyl groups. Methyl indicates an alkyl group
with one carbon atom (CH3–), ethyl indicates an alkyl group with two carbon atoms (CH 3 CH2–),
so the structure is
CH3 – C – CH2 – CH3
‖
.O

USES OF KETONES
Acetone (propanone), is the simplest ketone. It is a colorless, volatile and flammable liquid (boiling point
56.2˚C). Acetone is a good solvent for fats and oils. It is also frequently used in fingernail polish and in polish remover.
Acetone is normally present in small amounts in the blood and urine. In diabetes, it is present in larger amounts in the
blood and urine and even in the experiments. Dihydroxyacetone is an intermediate in carbohydrate metabolism.

Write your answers in a ½ crosswise. O .

I. Give the IUPAC name of the following compounds. ‖

1) CH3 – C – CH2 – CH – CH – CH3 3) CH3 – CH – CH2 – C – CH2 – CH3
‖
.O CH3 CH3 CH2CH3
2) CH3 – CH2 – CH2 – C – CH2 – CH2 – CH2 – CH3
‖
.O

II. Draw the structures of the following.

4

1) 3-chlorobutanone 2) 2,2-dimethyl-3-pentanone 3) hydroxyacetone

Page
CARBOXYLIC ACIDS

The oxidation of a primary alcohol yields an aldehyde. Aldehydes in turn can be easily oxidized. When an
aldehyde is oxidized, the resulting compound is acidic because it yields hydrogen ions (H +) in solution. The functional
group of an organic acid is –COOH.

NAMING KETONES
The IUPAC names for organic acids end in -oic acid. To name an acid according to the IUPAC system. Take
the longest alkane containing the acid group, drop the ending -e and add -oic acid. The common names of acids are
derived from the names of the aldehydes from which they may be prepared. Thus, ethanoic acid derived from
acetaldehyde, is called acetic acid. The general formula for an acid is RCOOH. All carboxylic acids contain at least one
–COOH group. This group is called carboxyl group and it is this group that yields hydrogen ions. Organic acids
containing two carboxyl groups are called dicarboxylic acids. Those containing three carboxyl groups are called
tricarboxylic acids.

Example 1: Name the compound

CH3–CH2–CH2–CH–COOH
Cl
Solution: The compound contains a COOH group, so it is a carboxylic acid. The longest chain contains five
carbon atoms, so it is a pentanoic acid, numbered with the acid at carbon number 1.
5 4 3 2 1
CH3–CH2–CH2–CH–COOH
Cl
Attached to the chain is a chlorine at carbon 2, so the name is 2-chloropentanoic acid.
Example 2: Name the compound
CH3
CH3–CH–CH–COOH
CH3
Solution: The compound contains a COOH group, so it is a carboxylic acid. The longest chain contains four
carbon atoms, so it is a butanoic acid, numbered with the acid at carbon number 1.
CH3
4 3 2 1
CH3–CH–CH–COOH
CH3
Attached to the chain are two methyls at carbon 2 and 3, so the name is 2,3-
dimethylbutanoic acid.
Example 3: Draw the structure of 2,4-difluoro-3-nitropentanoic acid.
Solution: Since it is pentanoic acid so the longest chat contains five carbon atoms. Attached to the chain
are two fluorine at carbons 2 and 4, and nitrogen at carbon 3. So the structure is
F F
CH3–CH–CH–CH–COOH
N

Write your answers in a ½ crosswise.

I. Give the IUPAC name of the following compounds. CH3 CH3
1) CH3–CH–CH2–CH–COOH 2) CH3–CH–CH2–CH–CH2–CH–CH–CH2–COOH
CH2CH3 Cl CH3 CH3

II. Draw the structures of the following.

1) 2,3-dibromo-3-ethylpentanoic acid 2) 3,3-dimethylhexanoic acid

Give 2 examples of aldehydes, ketones and carboxylic acids and give its uses. Make a table for your answers. Write
your answer in a 1 whole sheet of paper.

God Bless!
5

-End-
Page