LECTURE NOTE SK025 (ORGANIC) KMKt

CHEMISTRY UNIT

Kolej Matrikulasi Kelantan

CHEMISTRY
STUDY GUIDE

SK025

ORGANIC Name :
CHEMISTRY

CHAPTER 4

Introduction
to Organic
Chemistry

1

WHAT IS ORGANIC CHEMISTRY?

Organic chemistry is the chemistry of carbon
compounds.

Organic compounds contain H as well as C,
while other common elements are O, N, the
halogens, S and P.

Examples of organic compound:

OCOCH3 CH2OH O CH3
CH3
H OH N
H N H

COOH OH H O N Caffeine
OH OH

H OH

methyl salicylic acid (aspirin) glucose CH3

LEARNING OUTCOMES

4.1 Molecular and Structural Formulae

At the end of the lesson, student should be able to:

a) define structural formula (C1)
b) show structural formula in the form of expanded,

condensed and skeletal structures based on
molecular formula (C2)
c) classify carbons into primary,secondary,tertiary or
quarternary and hydrogen into primary,secondary
or tertiary. (C2)

Structural Formula

Formula that shows how the atoms of a
molecule are bonded to one another

Structural
formula

Expanded Condensed Skeletal
structure structure structure

Expanded structure

A structural formula that shows all atoms in a

molecule and all bonds connecting the atoms.

Example: HO HH
H CC OH H C C C HH
HH
H CC CH H H C C CH
H
Cl H

HH

Skeletal structure

C chains are drawn zigzag, and rings are drawn
as polygons
C atoms and H atoms are usually not shown
Functional groups are shown

Example SKELETAL
Cl

Condensed structure

C–H and C–C single bonds are normally not
shown

Example

EXPANDED CONDENSED
(CH3)3CH
HH H

HC C C H

H C H
H H

H

USES OF ( ) IN
CONDENSED STRUCTURE

To show heteroatoms, functional groups,
alkyl groups, at the side chain

Example 2–propanol (C3H8O)

EXPANDED CONDENSED

HHH CH3CHCH3
H CCCH OH

HO H CH3CH(OH)CH3
H CH3CHOHCH3
(CH3)2CHOH

Example

EXPANDED CONDENSED
HHH
Multiple bond in
HCCCH CH2═CHCH3 condensed structure
(show double bond /

triple bond)

H
HO

H C CH CH3CHO Condensed structure
containing C = O
bond

H

HH CH2
H2C CH2
C H Condensed structure
C of cyclic compound
HC

HH

EXAMPLE 1:
Butane, C4H10 H H H H

Expanded HC C C C H
structure

H HHH

Condensed CH3CH2 CH2 CH3
structure
or

CH3(CH2)2CH3

Skeletal
structure

BACK

Exercise 1

Convert each molecule into skeletal structure.

(a) (CH3)2CHCH2CH2CH(CH3)2

(b) CH3CH(Cl)CH(OH)CH3

H

(c) H C H H

C C C CCH

C C HH H H
H HH

Exercise 2

Write a condensed structural formula

for each of the following compounds.

H H Cl H

(a) H CC CC H (b) H H Cl H
H Cl H H CC CC H
HC H H OH H H

H H Br
HH H
(c) C (d) C C H Br
H OH H C C C Br
CC

HH H H Br

CLASSIFICATION OF C ATOMS

CC C
CC

primary carbon (1o) secondary carbon (2o)
Number of C atoms Number of C atoms
attached to it = 1 attached to it = 2

C C

CC C CC
C
C
quaternary carbon (4o)
tertiary carbon (3o) Number of C atoms
attached to it = 4
Number of C atoms
attached to it = 3

No classification for C atoms in methane and in
multiple bonds
Only for sp3 C atom

Example 1o H correct
C
H H3C
C
1o
H CH3
H CH 2–butene 1o
H
H3C H
methane CC

H 2o 2o CH3

2–butene

Example 1

Identify the types of carbons (1o, 2o, 3o, or 4o)
in the following molecules. Label at each
C atom.

(a) CH3 (b) CH3
CH3CHCH2CH3

(c) (d)

Answer 2o 2o 3o 1o
CH3
1o (b)
(a) CH3
2o
C1Ho 3C3oHC2Ho 2C1oH3

(c) 1o (d) 2o 2o 2o
3o

1o 4o2o 3o 1o 2o 3o 2o
1o 1o 2o 2o
2o 2o

EXERCISE 3:

Count the amount of primary carbon, secondary
carbon, tertiary carbon and quaternary carbon present
in the following structure:

Primary Carbon = ___ Tertiary Carbon = __
Secondary Carbon = __ Quaternary Carbon =__

CHEMISTRY UNIT,
KELANTAN MATRICULATION COLLEGE

LEARNING OUTCOMES

4.2 Functional Group and Homologous
Series

At the end of the lesson, student should be able to:

a) define functional group (C1)
b) state functional groups of the following class of

compounds. (C1)
c) identify functional groups in a given

compound.(C1,C2)
d) define homologous series. (C1)
e) explain general characteristics of homologous

series. (C2)

Functional group

Definition

Is an atom or group of atoms in an organic
molecule which characterised the
molecule and enables it to react in specific
ways which determines its chemical
properties.

(b) & (c) Identifying and Classifying Functional
groups of different class of compounds

Functional Group

Class of Structure Name Example
compounds none -
CH3-CH3
Alkane C=C carbon-carbon
CnH2n+2 double bond H2C=CH2

Alkene
CnH2n

Alkyne -C≡C- carbon-carbon HC≡CH
CnH2n-2
triple bond

21

Class of Functiona22l Group Example
compounds
Structure Name

Aromatic/Arene Aromatic ring CH3
CnH2n- 6

Alcohol -OH Hydroxyl CH3CH2OH
CnH2n+1OH

Haloalkane -X (F,Cl,Br,I) Halogen CH3CH2Cl
CnH2n+1X

Ether C-O-C Alkoxy H3COCH3
CnH2n+2O

Class of Functiona23l Group Example
compounds
Structure Name
Aldehyde
CnH2nO O Carbonyl O
CH Carbonyl H3C C H
Ketone O
CnH2nO O
Carboxylic acid R CR H3C C CH3
CnH2nO2
O Carboxyl O
Ester
CnH2nO2 C OH H3C C OH

Acyl chloride O Ester O
CnH2n+1COCl COR /carboalkoxy
O H3C C O CH3
Acyl
O

C Cl H3C C Cl

Class of Functiona24l Group Example
compounds
Structure Name OO
Anhydride H3C C O C CH3
(CnH2n+1CO)2O OO Anhydride

COC

Amide O Amide / O
CnH2n+1CONH2 RCN
carboxamide H3C C NH2

Amine CN Amino H
CnH2n+1NH2 H3C N CH3

Nitrile CN Cyano CH3 C N
CnH2n+1CN

1. Identify the function groups in the following molecules.

CH3 O Carboxamide / Amide

a) CH3CCH2 C
CH3 NH2

b) CH3

Carbon – carbon double bond

c) CH3OCH2CH3 Alkoxy

CH2 CH3 Aromatic ring

d)

e) H3C Carboalkoxy / Ester
C OCH2CH3

O

f) H3C cyano
CH C N

H3C

Identify the functional groups in the following molecule:

H2N OH
O O
Br
O

HO

28

Identify and name the O
functional groups in CH2COOH
the given organic
compound:

H2N
CH2CH2OH

O

29

Identify the functional groups in the following

structures. Name the functional group.

OH b. H H H H O
C

a. HN C C N C C OH

H H H H3C C O

OCH3
OH

General Formula
Homologous Series

SERIES GENERAL FORMULA ENDING NAME

ALKANE CnH2n+2 …ane
ALKENE CnH2n …ene
ALKYNE CnH2n-2 …yne
ALCOHOL R-OH …ol

ALDEHYDE RCHO …al

KETONE RCOR’ …one

CARBOXYLIC ACID RCOOH …oic acid

AMINE RNH2 …amine
AMIDE RCONH2 …amide

Note: R normally refer to alkyl group: CnH2n+1

Reduce 2 atom H for cyclic compound

R normally refer to alkyl group: CnH2n+1 (reduced 1 H atom from
alkane formula)

ALKANE CnH2n+2 ALKYL CnH2n+1
METHANE CH4 METHYL
─ CH3

ETHANE CH3CH3 ETHYL ─ CH2CH3

PROPANE CH3CH2CH3 PROPYL ─CH2CH2CH3

BUTANE CH3CH2CH2CH3 BUTYL ─CH2CH2CH2CH3

PENTANE CH3CH2CH2CH2CH3 PENTYL ─CH2CH2CH2CH2CH3

Reduce 2 atom H for cyclic compound
EXAMPLE: ALKANE AND CYCLOALKANE

ALKANE CnH2n+2 CYCLOALKANE CnH2n
METHANE CH4
─ ─
ETHANE CH3CH3 ─ ─

PROPANE CH3CH2CH3 CYCLOPROPANE C3H6

BUTANE CH3CH2CH2CH3 CYCLOBUTANE C4H8

PENTANE CH3CH2CH2CH2CH3 CYCLOPENTANE C5H10

Reduce 2 atom H for cyclic compound
EXAMPLE: ALKENE AND CYCLOALKENE

ALKENE CnH2n CYCLOALKENE CnH2n-2
ETHENE CH2 ═ CH2
─ ─

PROPENE CH2 ═ CH CH3 CYCLOPROPENE C3H4

BUTENE CH2 ═ CH CH2CH3 CYCLOBUTENE C4H6
1-BUTENE

CH3CH ═CH CH3
2-BUTENE

PENTENE CH2═CHCH2CH2CH3 CYCLOPENTENE C5H8
1-PENTENE

Alkanes and cycloalkanes belong to the
same class of compounds but
different homologous series

HOMOLOGOUS SERIES HOMOLOGOUS SERIES

OF ALKANES OF CYCLOALKANES

methane CH4 cyclopropane C3H6

ethane C2H6 cyclobutane C4H8
propane C3H8 cyclopentane C5H10
butane C4H10 cyclohexane C6H12
pentane C5H12 cycloheptane C7H14

GENERAL CHARACTERISTICS OF HOMOLOGOUS SERIES

Has general formula EXAMPLE: alkane, CnH2n+2

Successive member differ by only a CH2 group
similar chemical properties (because same
functional group)

4.3 ISOMERISM

LEARNING OUTCOMES

4.3 Isomerism

At the end of the lesson, student should be able to:

a) define isomerism,constitutional isomerism and stereoisomerism.(C1)
b) construct constitutional isomers: (C3)

i. chain isomers
ii. Positional isomers
iii. Functional group isomers
c) describe cis-trans isomerism due to restricted rotation about: (C2)

i. C=C bond
ii. C-C bond in cyclic compounds
d) identify cis-trans isomerism of a given structural formula.(C1,C2)
e) define chirality centre and enantiomers.(C1)
f) identify chirality centre(s) in a molecule. (C1,C2)
g) determine optical activity of a compound. (C3)
h) draw a pair of enentiomers using 3-dimensional formula. (C3)
*restricted to molecules with one chirality centre

ISOMERISM

Definition

The existance of chemical compounds that
have same molecular formula but different
molecular structure or arrangement in space

TYPES OF ISOMER

Isomerism

Structural/ Stereoisomerism
Constitutional Isomerism
(same connectivity, but
(different in connectivity) different arrangement in

space)

Chain Positional Functional Group diastereomer
Isomerism Isomerism Isomerism
enantiomer

cis-trans
isomerism

STRUCTURAL ISOMERISM/
CONSTITUTIONAL ISOMERISM

molecules that have same molecular
formula but different structure.

3 types:

a) Chain isomerism
b) Positional isomerism
c) Functional group isomerism

Question 1

Draw structural isomers of compound with the
molecular formula C6H14

Answer 1

Strategy: First draw all possible skeletal structures
(without the H atoms), beginning with the
longest possible structure.

CCCCC CCCCC
C
C
C
CCCCCC CCCC

C C
CCCC

C

Answer 1

CH3—CH2—CH2—CH2—CH2—CH3
hexane

CH3—CH—CH2—CH2—CH3 CH3—CH2—CH—CH2—CH3

CH3 CH3
2–methylpentane 3–methylpentane
CH3
CH3—CH—CH—CH3
CH3—C—CH2—CH3

CH3 CH3 CH3
2,3–dimethylbutane 2,2–dimethylbutane

Total five
chain isomers

CHAIN ISOMERS

due to different in carbon skeleton

Question: How many structural isomers does
pentane, C5H12, have?

Step 1: draw the longest carbon skeleton, in this case 5-C

CH3 CH2 CH2 CH2 CH3 Condensed structure
of cyclic compound

Step 2: Shorten the carbon backbone to 4-C, so
now you will get one branch

CH3 CH2 CH CH3
CH3 Now you get one branch!

Step 3: Shorten it some more to 3-C carbon backbone, and
now you will get 2 branches!

CH3
CH3 C CH3

CH3

Can you further
shorten the carbon
backbone?

Example 1: Draw structural isomers of
alkene (C5H10)

CH3CH2CH2CH CH2

CH3
CH3CHCH CH2

CH3
CH3CH2C CH2

POSITIONAL ISOMERS

due to different position of functional group

Example

Molecular formula = C3H8O

32 1 32 1

CH3 C H2 CH2 OH CH3 C H C H3

1–propanol OH

2–propanol

Both isomers have same

carbon skeleton. They are only different
in the position of –OH group!

Example 1: C3H7Cl CH3CHCH3
CH3CH2CH2Cl Cl

Example 2: C4H8 CH3CH=CHCH3
CH2=CHCH2CH3
CH3
Example 3: C6H14O (alcohol) CH3CHCH2CHCH3

CH3 OH
CH3CHCH2CH2CH2 CH3
CH3CHCHCH2CH3
CH3 OH
CH3CCH2CH2CH3 OH

OH

iii) Functional Group I49somerism

➢ These isomers have different functional
groups and belong to different homologous
series with the same general formula.

Classes of compounds General Formula

Alcohol & Ether CnH2n + 2O
Aldehyde & Ketone CnH2nO
Carboxylic acid & Ester CnH2nO2
Alkene & Cycloalkane CnH2n