UNIT 2

Chemistry of Carbon and Carbon

Compounds

Lesson 4:
Aldehydes and Ketones
DESIRED LEARNING OUTCOMES (DLO):
At the end of the unit, the students must have:
1. Identified aldehydes and ketones from their formulas.
2. Wrote IUPAC and common names of aldehydes and ketones.
3. Wrote formulas for aldehydes and ketones when given their names.

Aldehydes and ketones are widespread in nature and are often combined with
other functional groups. Examples of naturally occurring molecules which contain a
aldehyde or ketone functional group are shown in the following two figures. The
compounds in Figure 9.7.19.7.1 are found chiefly in plants or microorganisms and
those in Figure 9.7.29.7.2 have animal origins. Aldehydes and ketones are known for
their sweet and sometimes pungent odors. The odor from vanilla extract comes from
the molecule vanillin. Likewise, benzaldehyde provides a strong scent of almonds and
is this author’s favorite chemical smell. Because of their pleasant fragrances aldehyde
and ketone containing molecules are often found in perfumes. However, not all of the
fragrances are pleasing. In particular, 2-Heptanone provides part of the sharp scent
from blue cheese and (R)-Muscone is part of the musky smell from the Himalayan
musk deer. Lastly, ketones show up in many important hormones such as
progesterone (a female sex hormone) and testosterone (a male sex hormone). Notice
how subtle differences in structure can cause drastic changes in biological activity. The
ketone functionality also shows up in the anti-inflammatory steroid, Cortisone.
https://chem.libretexts.org/Courses/Sacramento_City_College/SCC%3A_CHEM_330_-_Adventures_in_Chemistry_(Alviar-
Agnew)/09%3A_Organic_Chemistry/9.07%3A_Aldehydes_and_Ketones#:~:text=Summary-,An%20aldehyde%20is%20an%20organic
%20compound%20in%20which%20the%20carbonyl,atom%20within%20the%20carbon%20chain.

4.1 ALDEHYDE AND KETONE

• Closely related classes of organic compound
• Their structures contain the carbonyl group,

The difference between aldehydes and ketones is the placement of the carbonyl
group within the molecule. An aldehyde is an organic compound in which the
carbonyl group is attached to a carbon atom at the end of a carbon chain. A ketone is
an organic compound in which the carbonyl group is attached to a carbon atom within
the carbon chain. The general formulas for each are shown below.

Table 4.1 Name of Selected Aldehyde

Formula IUPAC Name
H - CHO Methanal
CH3CHO Ethanal
CH3CH2CHO Propanal
CH3CH2CH2CHO Butanal
CH3CH2CH2CH2CHO Pentanal
4.2 NAMING ALDEHYDES AND KETONES

ALDEHYDES
___________________________________________________________
IUPAC Rules for Naming Aldehydes
1. To establish the parent name, select the longest continuous chain of carbon
atoms that contains the aldehyde group.
2. The carbons of the parent chain are numbered starting with the aldehyde group.
Since the aldehyde group is at the beginning (or end) of a chain, it is
understood to be the number 1.
3. Form the parent aldehyde name by dropping the -e from the corresponding
alkane name and adding the suffix -al.
4. Other groups attached to the parent chain are named and numbered as we
have done before.
___________________________________________________________

The first member of the homologous series, H2C=O is methanal. The name methanal
is derived from the hydrocarbon methane, which contains one carbon atom. The
second member of the series is ethanal, the third member is propanal, and so on.
(Table 4.1) the following diagrams illustrate how the name is formed for the first two
members of the series.

The longest carbon chain containing the aldehyde group is the parent compound.
Other group attached to this chain are numbered and named as before, as the
following structural formula shows
Practice 4.1
Name each compound, using the IUPAC System:

1. CH3-CH2-CH2-CHO

CH3

2. CH3-CH2-CH-CH-CH2-CHO

CH3

Cl

3. CH3 – C - CHO

Cl
Practice 4.2
Write structure for the following carbonyl compounds:

1. Pentanal
2. 4-bromo-5-methylhexanal
3. 3,4,5-trichloroheptanal
_____________________________________________________________________
KETONES

IUPAC Rules for Naming Ketones

1. To establish the parent name, select the longest continuous chain of carbon
atoms that contains the ketone group.
2. Form the parent name by dropping the -e from the corresponding alkane
name and adding the suffix -one.
3. If the chain is longer than four carbons, it is numbered so that the carbonyl
group has the smallest number possible; this number is prefixed to the parent
name of the ketone.
4. Other group attached to the parent chain are named and numbered as we
have done before.

The following examples of the rules for naming ketones are illustrative:

Note that in 4-methyl-3-hexanone, the carbon chain is numbered from left to

right to give the carbonyl group the lowest possible number.

Practice 4.3
Name the following ketone, using the IUPAC System:

O
║
1. CH3-CH2 – C – CH3

CH3

2. CH3 – CH – CH2- CH – C – CH2-CH3

║
CH3 O

Practice 4.4
Write structure for the following carbonyl compounds:

1. 2-butanone
2. 3,4-dimethyl-2-hexanone
3. 4,4-dichloro-2-pentanone
_____________________________________________________________________
4.3 PHYSICAL PROPERTIES OF ALDEHYDE AND KETONE
1. They are polar
2. Have lower boiling points
3. Low-molar-mass aldehyde and ketone are soluble in water, but for five or
more carbons, the solubility decreases.
4. Ketone are highly efficient organic solvents.
5. Lower-molar-mass aldehyde have a penetrating, disagreeable odor and are
partially responsible for the taste of some rancid and stale foods
6. As the molar mass increases, the odor of both aldehyde and ketone –
becomes more fragrant (used as flavorings and perfumes)

4.4 CHEMICAL PROPERTIES OF ALDEHYDE AND KETONE

4.4.1. Oxidation
• aldehydes are easily oxidized to carboxylic acid
• Ketones – variety of products are formed

4.4.2 Reduction
• Aldehyde and Ketone are easily reduced to alcohol
 For example, hardworking muscles generate an excess of a specific ketones,
which is then reduced to an alcohol before being secreted into the
bloodtstream:
o The product, lactic acid, contributes to the burning sensation of
hardworking muscles and is removed from the blood by the liver.
The first reaction of lactic acid in the liver is a conversion back to
the ketone. This reversible reaction completes a cycle: the ketone
is reduced to lactic acid, which is them oxidized to the ketone once
again. In this case, the oxidation of lactic acid by the liver
accelerates glucose production – glucose that the muscle needs to
do more work.

4.4.3 Addition Reaction

• Addition of Alcohols

Aldehyde/ketone + alcohol hemiacetals/hemiketals (compound

that contain an alkoxy group and
hydroxyl group)

• Addition of Hydrogen Cyanide

Aldehyde/ketone + HCN aldehyde/ ketone cyanohydrins

 • Aldol Condensation (Self-addition)

Acetone + acetone diacetone alcohol

4.5 COMMON ALDEHYDES AND KETONES

4.5.1 Formaldehyde (Methanal)

• Is made from methanol by reaction
with oxygen (air) in the presence of a
silver or copper as catalyst
• A poisonous, irritating gas that is highly
soluble in water
• Marketed as a 37% aqueous solution
called formalin
• Used in the manufacture of polymers
• Vapors are intensely irritating to the
mucous membranes
• Ingestion may cause severe abdominal
pains, leading to coma and death
• Is believed to have been a component of the primitive atmosphere of the
earth
• Has been used to preserve biological specimens, in fumigation, and in a
number of other polymers
4.5.2 Acetaldehydes (Ethanal)
• Is a volatile liquid with a pungent, irritating odor
• It has a general narcotic action and, in large doses, may cause respiratory
paralysis
• Principal use is as an intermediate in the manufacture of other chemicals
(e.g. acetic acid and butanol)

4.5.3 Acetone
• Is used in very large quantities as organic solvent
• As a solvent in the manufacture of drugs, chemicals and explosives; for the
removal of paints, varnishes, and fingernail polish ; and as a solvent in the
plastic industry
• Is formed in the human body as a by-product of lipid metabolism. Normal
concentrations of acetone in the body are less than 1mg/100mL of blood.
In patient with diabetes
mellitus, the
concentration of
acetone may rise,
and it is excreted
in the urine,
where it can be
detected on the
breath of these
patients.
4.4.4 Methyl Ethyl Ketone
Butanone, also known as methyl ethyl ketone (MEK), is an organic
compound with the formula CH3C(O)CH2CH3. This colorless liquid ketone has a sharp,
sweet odor reminiscent of acetone. It is produced industrially on a large scale, but
occurs in nature only in trace amounts. It is partially soluble in water, and is commonly
used as an industrial solvent.

*Production
Butanone may be produced by oxidation of 2-butanol. The dehydrogenation of 2-
butanol using a catalyst is catalyzed by copper, zinc, or bronze:
CH3CH(OH)CH2CH3 → CH3C(O)CH2CH3 + H2
This is used to produce approximately 700 million kilograms yearly. Other
syntheses that have been examined but not implemented include Wacker
oxidation of 2-butene and oxidation of isobutylbenzene, which is analogous to the
industrial production of acetone.
*Application

As a Solvent
Butanone is an effective and common solvent[8] and is used in processes
involving gums, resins, cellulose acetate and nitrocellulose coatings and in vinyl
films. For this reason it finds use in the manufacture of plastics, textiles, in the
production of paraffin wax, and in household products such as lacquer, varnishes,
paint remover, a denaturing agent for denatured alcohol, glues, and as a cleaning
agent. It has similar solvent properties to acetone but boils at a higher temperature
and has a significantly slower evaporation rate. [12] Unlike acetone, it forms
an azeotrope with water, making it useful for azeotropic distillation of moisture in
certain applications. Butanone is also used in dry erase markers as the solvent of the
erasable dye.
As a Plastic Welding Agent

As butanone dissolves polystyrene and many other plastics, it is sold as "model

cement" for use in connecting parts of scale model kits. Though often considered
an adhesive, it is actually functioning as a welding agent in this context.

Other Users

Butanone is the precursor to methyl ethyl ketone peroxide, which is a catalyst for
some polymerization reactions such as crosslinking of unsaturated polyester
resins. Dimethylglyoxime can be prepared from butanone first by reaction with ethyl
nitrite to give diacetyl monoxime followed by conversion to the dioxime:
 Self
Assessment
Assessment 4.1
Aldehydes & Ketones

Name:___________________________ Score:_____________
Course, Year & Section:______________ Date:______________

Give what is ask in each of the following.

_________1. Have at least one hydrogen atom bonded to the carbonyl group;
R – CHO.
_________2. Have an alkyl group bonded to the carbonyl group; R – C – R’.

CHEMICAL PROPERTIES OF ALDEHYDE AND KETONE

3. ________________________
4. ________________________
5._________________________

__________6. Has been used to preserve biological specimens, in fumigation, and in

a number of other polymers.
__________7. Principal use is as an intermediate in the manufacture of other
chemicals (e.g. acetic acid and butanol)
__________8. As a solvent in the manufacture of drugs, chemicals and explosives;
for the removal of paints, varnishes, and fingernail polish ; and as a
solvent in the plastic industry.
__________9. In patient with ____, the concentration of acetone may rise, and it is
excreted in the urine, where it can be detected on the breath of these
patients.
__________10. Widely used as a solvent, especially for lacquers and made by
oxidation
 Activity
Activity 4.1
Aldehyde & Ketone

Name:__________________________ Rating:_______
Course, Year & Section:_____________ Date:_________

I. Objective:
1. To be able to name aldehydes and ketones using the IUPAC System and write
its the structural formula.

II.Name the following, using the IUPAC System

A. Aldehyde

1. CH3-CH2-CH2-CHO

CH3

2. CH3 – CH – CH - CHO

CH3

3. CH3-CH2-CH-CH-CHO

4. CH3 – C - CHO

CH3

5. CH3-CH3-CH-CH-CHO

CH3
 B. Ketone

6. CH3 – C – CH3
║
O

7. CH3 – CH2 – CH2 – C – CH3

║
O

CH3 Cl

8. CH3– C – CH – CH2 – C – CH3

║
O Cl

Br Br

9. CH3-CH2-CH – C – CH-CH2-CH3
║
O

O F
║
10. CH3– C – C – CH2-CH3

III.Write the structure of the aldehyde and ketone.

A. Aldehyde

1. Octanal
2. 2,4 – dimethylhexanal
3. 3,3 – dichloro-5-methylheptanal

B. Ketone

1. 3-octane
2. 2,4-dimethyl-3-hexanone
3. 3,3-dichoro-5-methyl-4-heptanone

***end***