11
General
Chemistry 1
Quarter 2 – Module 6:
Structural Isomerism in Organic
Compounds
General Chemistry 1 – 11
Self-Learning Module (SLM)
Quarter 2 – Module 6: Structural Isomerism in Organic Compounds
First Edition, 2020
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11
General
Chemistry 1
Quarter 2 – Module 6:
Structural Isomerism in Organic
Compounds
Introductory Message
For the facilitator:
Welcome to the
General Chemistry 1 - 11
Structural Isomerism in Organic Compounds!
Self-Learning Module (SLM) on
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For the learner:
Welcome to the General Chemistry 1 - 11 Self-Learning Module (SLM) on Structural
Isomerism in Organic Compounds!
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What I Know
What’s In
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What I Have Learned
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into real life situations or concerns.
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Assessment
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What I Need to Know
This module was designed and written with you in mind. It is here to help you master
the (Structural Isomerism in Organic Compounds). The scope of this module permits
it to be used in many different learning situations. The language used recognizes the
diverse vocabulary level of students. The lessons are arranged to follow the standard
sequence of the course. But the order in which you read them can be changed to
correspond with the textbook you are now using.
The module is composed of one lesson, namely:
●
Lesson 3 – Structural Isomerism in Organic Compounds
After going through this module, you are expected to:
1. define isomerism;
2. name and define different kinds of structural isomerism;
3. identify molecules that exhibit structural isomerism
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What I Know
Choose the letter of the best answer. Write the chosen letter on a separate sheet of
paper.
1. A compound may have two or more structural isomers. True or false?
a. True
b. False
2. Structural isomers may come from different families of organic compounds.
True or false?
a. True
b. False
3. N-butane and isobutane are examples of ________.
a. chain isomers
b. functional isomers
c. positional isomers
d. none of these
4. Isomers with the same bond structure but the geometrical position of the
atoms and functional groups differ are known as:
a. Structural isomers
b. Stereoisomers
c. Tautomers
d. Chain isomers
5. What
a.
b.
c.
d.
is the functional group with a symbol of RCHO?
amine
aldehyde
ketone
carboxylic acid
6. What
a.
b.
c.
d.
is the functional group with a symbol of RCOOH?
amine
aldehyde
ketone
carboxylic acid
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7. What
a.
b.
c.
d.
is the functional group with a symbol of RCOR?
amine
aldehyde
ketone
carboxylic acid
8. What
a.
b.
c.
d.
is the functional group with a symbol of RCOOR?
amide
ether
alcohol
ester
9. What
a.
b.
c.
d.
is the functional group with a symbol of ROR?
amide
ether
alcohol
ester
10. What
a.
b.
c.
d.
functional group is present in ethanol?
amide
ether
alcohol
ester
11. What
a.
b.
c.
d.
functional group is present in citric acid?
amide
ether
alcohol
carboxylic acid
12. What
a.
b.
c.
d.
functional group is present in acetamide?
amide
ether
alcohol
carboxylic acid
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Lesson
3
Structural Isomerism in
Organic Compounds
What’s In
Isomerism is a phenomenon in which more than one compound have the
same formula but have different chemical structures. There are 2 kinds of isomerism:
Stereoisomerism, where compounds have different spatial arrangement of atoms and
Constitutional isomerism, where compounds have different connections of atoms. In
this topic, we will focus on constitutional isomerism/structural isomerism.
Alkanes are hydrocarbons with a general formula of C nH2n+2. Most of these
hydrocarbons are straight-chained. However, there are alkanes that are branched.
In the last chapter, we discussed that C5H12 is named as pentane. Do you know that
an alkane having a formula of C5H12 can still be drawn in two specific manners?
These compounds have the same formula (C5H12) but different arrangement of
atoms in the molecule. They are called isomers.
Source: Brown, 2009
Take note that each isomer has distinct characteristics from one another. Straight
chained alkanes have higher boiling and melting points than their branched isomers.
Notes to the Teacher
This topic is quite tricky. Use several
analogies and examples for better
understanding of the students.
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What’s New
Activity 1
Write YES if the given set of molecules are isomers and NO if not. Write your answers
in a separate sheet of paper.
1.
2.
3.
4.
5.
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What is It
Isomerism
Isomerism is a phenomenon in which more than one compound have the same
formula but have different chemical structures. Isomers are groups of compounds
having the same molecular formula but different structural formula. Different
structures mean different bond patterns, different space orientation or different
connectivity of atoms. As the number of carbon increases, the number of isomers in
a given compound also increases.
There are 2 kinds of isomerism in organic compounds: Stereoisomerism,
where compounds have different spatial arrangement of atoms and Constitutional
isomerism, where compounds have different connections of atoms. In this topic, we
will focus on constitutional isomerism/structural isomerism.
Structural Isomerism in organic compounds can be classified as:
1.
2.
3.
4.
5.
Chain Isomerism
Positional Isomerism
Functional Isomerism
Metamerism
Tautomerism
1. Chain Isomerism - isomerism in which 2 or more compounds have the same
number of atoms and functional groups but have different arrangements of
carbon skeleton in the parent chain or in the side chains. The picture below
shows the chain isomers of C5H12.
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2. Positional Isomerism - isomerism in which 2 or more compounds have the
same number of atoms and functional groups but differ in the arrangement of
functional groups in the parent carbon chain.
These are 2 compounds namely (from left to right) 1-bromopropane and 2bromopropane possess positional isomerism. They have the same molecular
formula of C3H9Br but different arrangement of bromine substituent groups.
3. Functional Isomerism - isomerism in which 2 compounds have the same
number of atoms but they differ in the arrangement of atoms which are
determined as different functional groups in the compounds.
Both of these compounds have a formula of C 4H8O2 but the first structure
contains a carboxylic acid (-COOH) group while the second contains an ester
(-COO-) group.
4. Metamerism - isomerism in which the isomers have different carbon chain
length along a functional group with hetero atom.
There are 2 identical (same length)
ethyl groups (CH3CH2-) attached to
central oxygen
There is 1 methyl (CH3-) group
(shorter) and 1 propyl (CH3CH2CH2-)
group (longer) attached to central
oxygen
Both ethoxyethane and 1-methoxypropane have the same formula but their
carbon chains differ in length along the O group. If we will compare the left
side of the O, ethoxyethane has longer alkyl chain than in 1-Methoxypropane,
however if we will compare the right side of the O, 1-Methoxypropane has
longer alkyl chain than in ethoxyethane.
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5. Tautomerism – isomerism in which 2 compounds differ only in the position
of the protons and electrons but carbon skeleton of the compound is
unchanged. Tautomers interconvert rapidly. Several types of tautomerism are:
keto-enol tautomerism, nitro-acinitro tautomerism, imine-en-amine
tautomerism, and cyano - isocyano tautomerism.
The two structures are examples of keto-enol tautomerism. The left structure
is composed of a ketone functional group which is in equilibrium with the
right structure which contains the combination of alkene-alcohol functional
groups in which enol is derived.
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Isomerism is a phenomenon in which more than one compound have the
same formula but have different chemical structures.
Isomers are groups of compounds having the same molecular formula but
different structural formula.
Different kinds of Structural Isomerism:
Chain Isomerism - isomerism in which 2 or more compounds have the same
number of atoms and functional groups but have different arrangements of
carbon skeleton in the parent chain or in the side chains.
Positional Isomerism - isomerism in which 2 or more compounds have the
same number of atoms and functional groups but differ in the arrangement of
functional groups in the parent carbon chain.
Functional Isomerism - isomerism in which 2 compounds have the same
number of atoms but they differ in the arrangement of atoms which are
determined as different functional groups in the compounds.
Metamerism - isomerism in which the isomers have different carbon chain
length along a functional group with hetero atom.
Tautomerism – isomerism in which 2 compounds differ only in the position
of the protons and electrons but carbon skeleton of the compound is
unchanged. Tautomers interconvert rapidly.
Straight chained alkanes have higher boiling and melting points than their
branched isomers.
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What’s More
Activity 2. Identifying Isomerism
I.
Identify the type of isomerism in the following set of compounds:
1.
2.
3.
4.
5.
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What I Have Learned
Summarize what you have learned from the very beginning by answering the
following questions. Write your answers in separate sheet of paper.
1. What is isomerism?
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
2. Give the types of structural isomerism and describe each. Give examples.
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
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What I Can Do
C6H12O6 has 23 isomers but it has 3 most biologically important isomers called
glucose, fructose and galactose. Glucose is our main source of energy, needed for
several metabolic processes. fructose is known as the sweetest sugar, typically
present in honey, when bonded to glucose makes a disaccharide called sucrose, a
typical table sugar. On the other hand, galactose, when bonded to glucose makes a
disaccharide called lactose, the milk sugar. Give the structure of these isomers and
tell whether they are chain, positional, functional, tautomeric or metameric isomers.
Write your answers on a separate sheet of paper.
TYPE OF ISOMERISM:
Glucose
Fructose
Galactose
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Assessment
Multiple Choice. Choose the letter of the best answer. Write the chosen letter on a
separate sheet of paper.
1. Structural isomers are molecules with ___________
a. the same molecular formula
b. the same number of atoms
c. different arrangement of atoms
d. all of the above
.
2. Which of the following is not a type of structural isomerism?
a. Functional
b. Positional
c. Chain
d. Optical
3. How many structural isomers are possible for butane?
a. 1
b. 2
c. 3
d. 4
4. Functional isomers are molecules with the same molecular formula
___________.
a. but different functional group
b. but different arrangements of the carbon chain
c. but different geometric structures
d. and functional groups but different locations of the functional groups on
the carbon chain
5. Chain isomers are molecules with the same molecular formula _______.
a. but different functional group
b. but different arrangements of the carbon chain
c. but different geometric structure
d. and functional groups but different locations of the functional groups on
the carbon chain
6. Positional isomers are molecules with the same molecular formula ______.
a. but different functional group
b. but different arrangements of the carbon chain
c. but different geometric structure
d. and functional groups but different locations of the functional groups on
the carbon chain
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7. Is the boiling point of hexane lower or higher than the boiling point of 2,3dimethylbutane?
a. Higher
b. Lower
c. Both are isomers, they have the same boiling points
d. The two compounds are not comparable
8. Is the boiling point of 2-methylpentane lower or higher than the boiling point
of hexane?
a. Higher
b. Lower
c. Both are isomers, they have the same boiling points
d. The two compounds are not comparable
9. What is the relationship between two molecules shown below?
a. They are chain isomers.
b. They are positional isomers.
c. They are functional isomers.
d. There is no relationship between the two molecules.
10. Which of the following compounds is an isomer of CH 3CH2CH2CH2OH?
a. CH3CH2CH2OH
b. CH3CH(OH)CH3
c. CH3CH2CH2CH3
d. none of the above
11. Which of the following compounds is a functional group isomer of C2H5OH,
ethanol (ethyl alcohol)?
a. ethanal, CH3CHO
b. acetic acid, CH3COOH
c. diethyl ether, (C2H5)2O
d. dimethyl ether, (CH3)2O
12. Which of the following hydrocarbons does not have isomers?
a. C7H16
b. C6H14
c. C5H10
d. C2H6
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Additional Activities
Give 1 pair of molecules for each type of isomerism. Write your answers in a separate
sheet of paper.
CHAIN ISOMERISM
POSITIONAL ISOMERISM
FUNCTIONAL ISOMERISM
METAMERISM
TAUTOMERISM
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20
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What’s More
Positional
Isomerism
Functional
Isomerism
Metamerism
Chain Isomerism
Tautomerism
Assessment
1. d
2. d
3. b
4. a
5. b
6. d
7. a
8. b
9. b
10.d
11.d
12.d
What I know
What’s New
A
A
A
B
B
D
C
D
B
C
D
A
1. YES
2. YES
3. YES
4. YES
5. NO
Answers
References
Brown, Theodore L. ... et al, Theodore L. Brown, Jr H. Eugene. LeMay, Bruce E.
Bursten, Catherine J. Murphy, and Patrick Woodward. 2009. Essay.In Chemistry:
the Central Science - 12th Edition, 12th ed., 1004–21. Upper Saddle River, NJ:
Pearson Prentice Hall.
Chandanakota Follow. 2010. “Structural Isomerism.” LinkedIn SlideShare.
September 10. https://www.slideshare.net/chandanakota/structural-isomerism.
Chang, Raymond. 2010. “Organic Chemistry.” Essay. In Chemistry, 10th ed., 1026–
52. Boston: McGraw-Hill.
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EDITOR’S NOTE
This Self-Learning Module (SLM) was developed by DepEd
SOCCSKSARGEN with the primary objective of preparing for and addressing
the new normal. Contents of this module were based on DepEd’s Most
Essential Competencies (MELC). This is a supplementary material to be used
by all learners of SOCCSKSARGEN Region in all public schools beginning SY
2020-2021. The process of LR development was observed in the production of
this module. This is Version 1.0. We highly encourage feedback, comments,
and recommendations.
For inquiries or feedback, please write or call:
Department of Education – SOCCSKSARGEN
Learning Resource Management System (LRMS)
Regional Center, Brgy. Carpenter Hill, City of Koronadal
Telefax No.: (083) 228 8825 / (083) 228 1893