Introduction to Organic Nomenclature (IUPAC System made-easy)

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INTRODUCTION TO

ORGANIC

NOMENCLATURE (IUPAC System Made - Easy) BY

ANTHONY O. NWOBOSI

Edited by:

EDET ODOKWO

INTRODUCTION TO

ORGANIC

NOMENCLATURE (IUPAC System Made - Easy)

Published by:

Fine Organic Limited 36, Adeola Road, Sapele, Delta State, Nigeria. 07069598610, 08118813920 [email protected]

c 2017 ANTHONY O. NWOBOSI Published November 2017 All right reserved. No part of this publication may be reproduced in a retrieval system or transmitted in any form or by any electronic, mechanical, photocopying, recording or otherwise without the prior permission of the copyright owners.

Graphic illustration by: Msquaregraphix 09023564969 [email protected]

Printed and distributed nation wide.

...INTRODUCTION TO ORGANIC NOMENCLATURE

CONTENTS Acknowledgement

iv

Dedication

v

Preface

vi

CHAPTER ONE

1

Introduction

1

Nomenclature The IUPAC System Definition of Relevant Terms Isomerism EXERCISE 1

1 1 6 13

CHAPTER TWO Nomenclature of the Alkanes Common/First Term Members Common Substituents Naming of Alkanes Naming of Cycloalkanes EXERCISE2

14 14 14 15 16 27 33

CHAPTER THREE Nomenclature of the Alkenes

34 34

CONTENTS

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...INTRODUCTION TO ORGANIC NOMENCLATURE

CONTENTS Nomenclature of Cycloalkenes EXERCISE3

36 39

CHAPTER FOUR Nomenclature of Alkynes EXERCISE4

41 41 44

CHAPTER FIVE Nomenclature of Other Functional Groups (Part A) Alkanols Alkanoic Acids The Carbonyls (Alkanals and Alkanones) Alkanoates Amines Amides Ethers EXERCISE 5 (Part A) Nomenclature of Other Functional Groups (Part B) Nitriles Acyl Halides Nitro Alkanes

45 45 45 48 51 58 63 66 69 69 69 71 72

CONTENTS

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CONTENTS HaloAlkanes Sulphides Sulphones Thiols Arenes (Aromatic Compounds) EXERCISE5 (Part B)

72 73 73 74 74 76

CHAPTER SIX 80 Naming of Organic Compounds with Different Functional 80 The IUPAC Order of Priority 80 IUPAC Rules and Examples 81 EXERCISE 6 85 Answers 87 References 91 Appendix 92

CONTENTS

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ACKNOWLEDGEMENT Firstly, I want to sincerely thank the Lord Jesus Christ for His incessant wisdom and enablement I enjoyed all through the process of this work. In addition, I extend my sincere appreciation to Dr. Daniel Christmas of the Christmas Publishing Press, whose concern and interest contributed hugely to this work. To my affable lecturer Mr. Edet Odokwo (Mr. Bayo) of the Department of Chemistry, Federal University Otuoke, Bayelsa State, I greet you Sir. Furthermore, I wish to extend my greetings to my lovely family members, who stood by me both financially and otherwise. To my able Daddy, Daddy James Ighama, I salute you Sir, To Mummy Florence Ighama (Nwobosi), Mummy Chinwe Nwobosi, Mr. Ugochukwu Nwobosi (Hugo Clifford), Mr. & Mrs. George Ighama, Mr. Emeka Ighama, Mr. & Mrs. Michael Orikpete, Mr. & Mrs. Roland Ogirigbo, Miss Blessing Ighama (IBE),Uju Faith(Nwobosi), Nnamdi Nwobosi and Favour Ighama (Chichi), How can I forget, my great friend Mr. Ifeanyi Chigbata C.E.O Smart Olive Games, I greet you sir. Also to my amiable friends and well wishers; Sunday Ogbekile, Marvelous Baradi, Ikakitie Elisha,Grace Anthony, to mention but a few, I thank you all for your contributions in one way or the other. Anthony O. Nwobosi

ACKNOWLEDGEMENT

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DEDICATION This book is dedicated to Almighty God, our Heavenly Father; for his wisdom and guidance in the course of writing this book.

DEDICATION

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...INTRODUCTION TO ORGANIC NOMENCLATURE

PREFACE This book, “Introduction To Organic Nomenclature (IUPAC System made-easy)”, was written to help students master the use of IUPAC (International Union of Pure and Applied Chemistry) system, in naming organic compounds.. In this book a deliberate attempt was made to ensure that the need of O'level and A'level students as well as Early-level Higher Institution students whose interests are in the field of Pure Sciences, Engineering and Medicine are satisfied. This book is also written for teachers, lecturers and other authors who may want to use it as a reference text. Students are enjoined to enjoy IUPAC system of naming organic compounds to the fullest.

PREFACE

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1

INTRODUCTION Nomenclature - The IUPAC System

The increasing number of organic compounds has led to the development of a systematic method of nomenclature.Based on the fact that, it would be cumbersome for one to know the names of all the numerous number(s) of organic compounds. A body known as International Union of Pure and Applied Chemistry (IUPAC) came up with this simple and clear method of naming organic compounds. Organic compounds are named after the corresponding hydrocarbons from which they are assumed to be derived. The IUPAC system relates the name of the compound to its molecular structure implying that every compound has a unique name. This unique name comprises of either a suffixed root (base) or/and a prefixed substituent(s). The suffixed root is either an open chain or a closed (ring) of carbon atoms, known as the parent chain which bears the functional group. The prefix(es) signifying the name(s) of the substituent(s).

INTRODUCTION Nomenclature - The IUPAC System

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...INTRODUCTION TO ORGANIC NOMENCLATURE

RELEVANT TERMS There are some terms which are frequently used in the study of organic chemistry. Some of these terms are explained below to facilitate a better understanding of this course. HYDROCARBONS: These are Organic compounds that contain carbon and hydrogen only. It comprises of two main types: that is, aliphatic hydrocarbon and aromatic hydrocarbon. Aliphatic hydrocarbon: They are compounds with open (straight) chain as well as ring (cyclic) chain, and they do not have benzene ring in their structure.

EXAMPLES

Hexane

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1. Aromatic hydrocarbon: They are special type of carbocyclic compounds with benzene ring. These compounds have unique smell hence known as aromatic hydrocarbons/compounds. EXAMPLES

benzene

OH

CH3

NH 2

phenol

toluene

aniline

CATENATION: It is the ability of carbon to form straight, branched or cyclic chain of atoms with itself or other atoms. This ability of carbon makes it unique and interesting to study. Carbon atoms can be classified into four different types, namely: i. Primary carbon: It has one or no carbon atom directly attached to it.

H

H

H

C

C

H

H H Either of the two Carbon atoms is a primary carbon atom INTRODUCTION Nomenclature - The IUPAC System

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ii. Secondary carbon: It has two carbon atoms directly attached to it. H

H

H

H

C

C

C

H

H H H The middle carbon atom is a Secondary carbon atom.

iii. Tertiary carbon: it has three carbon atoms directly attached to it.

CH3

H3 C

CH

CH3

The middle carbon atom is a tertiary carbon atom. iv. Quaternary carbon: It has four carbon atoms directly attached to it.

CH3

CH3 C

CH3

CH3 The Middle carbon atom is a quaternary carbon atom. HOMOLOGOUS SERIES: These are organic compounds that have the same general molecular formula (Alkanes(C H ), n

INTRODUCTION Nomenclature - The IUPAC System

4

2n-2

...INTRODUCTION TO ORGANIC NOMENCLATURE

Alkenes (C H ), Alkynes (C H ) etc.) and whose successive n

2n

n

2n-2

member differs from it preceding member by a -CH2- unit or a constant atomic mass unit of 14 FUNCTIONAL GROUPS: These are specific groups (moieties) of atoms or bonds within molecules that are responsible for the characteristic chemical reactions of those molecules. List of some examples include; C-C in alkanes, C=C in alkenes and C=C in alkynes, haloalkanes (R-X), Alkanols (-R- OH), Ethers (R-O-R), Alkanal, (-CHO), Alkanones (-CO-), Carboxylic acid (-COOH), Esters (RCOOR), Amines (-NH2), Amides (CONH2 Nitrile(R-C=N) etc. Note: R stands for alkyl group STRUCTURAL FORMULA: This Shows the orientation of atoms of a molecule/compound in space and how they are bonded to each other. Due to the fact that different organic compounds may possess the same molecular formula, which often makes their identification some worth difficult. It is now necessary to represent compounds with their structural formulae. INTRODUCTION Nomenclature - The IUPAC System

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ISOMERISM: This is the existence of two or more compounds, molecules or radicals with the same molecular formula but with different chemical structures. Such compounds, molecules or radicals are known as isomers. Thus, an isomer contains the same number of atoms (carbon, hydrogen, oxygen etc) as another, but has different arrangement in space. E.g. Isopentane (2-methylbutane) is an isomer of n-pentane.

H

H

H

H

H

H

C

C

C

C

C

H

H

H

H

H

H

H

n -p en t ane

H

H

H

H

C

C

C

C

H

H

H

H

H

C

H

H

2-m eth y lb u tan e

This phenomenon also shed light on the fact, that different compounds may contain the same numbers of carbon atoms but of different structural arrangement, as shown above. There are two main forms of isomerism; Structural or Constitutional Isomerism and Sterioisomerism or Spatial isomerism, and each of these types has other forms or types as shown in the diagram below. INTRODUCTION Nomenclature - The IUPAC System

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...INTRODUCTION TO ORGANIC NOMENCLATURE

TYPES OF ISOMERISM

1.

STRUCTURAL/ CONSTITUTIONAL ISOMERISM

It is the existence of two or more compounds having the same molecular formula but different structural formula. Types are as follows: A. Functional group isomerism This explains the constitutional isomerism usually encountered between two organic compounds belonging to different homologous series, having the same molecular formula but whose structural formulae differ in the functional group moieties.

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...INTRODUCTION TO ORGANIC NOMENCLATURE

EXAMPLES

B.

Chain isomerism

This type of isomerism form isomers that have different arrangement in their carbon skeleton. It occurs mostly in hydrocarbons.

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...INTRODUCTION TO ORGANIC NOMENCLATURE

H

H

H

H

H

H

C

C

C

C

C

H

H

H

H

H

H

H

H

H

H

H

C

C

C

C

H

H

n-pentane

H

H

H

C

H

H

2-methylbutane

C.

Position isomerism

They have the same carbon skeleton but differ in the position of their substituents. E.g. Propanol and propan-2-ol, 2methylpentane and 3- methylpentane, 1,2 dichlorobenzene and 1,3-dichlorobenzene. Cl

Cl Cl

1,2-dichlorobenzene

Cl

1,3-dichlorobenzene

2. STEREOISOMERISM OR SPATIAL ISOMERISM This is the phenomenon that molecules may have the same molecular formula and sequence of bonded atoms, but differ in INTRODUCTION Nomenclature - The IUPAC System

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...INTRODUCTION TO ORGANIC NOMENCLATURE

their orientation in space. In other words, molecules that are stereoisomers represent the same structural isomer. Types are as follows: A. Geometrical isomers They have the same properties and same functional group but different spatial arrangement and physical properties (i.e. different density, polarity, solubility, melting and boilingpoint. Note: This kind of isomerism exist in molecules where there is restriction (steric obstruction) of rotation. This restriction or obstruction gives rise to Cis- and -Trans isomers. Cis-isomer: This is the isomer which has two similar groups on the same side of the double bond. Trans-isomer: This type of isomer has its two similar groups on the opposite sides of the double bond. EXAMPLES

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...INTRODUCTION TO ORGANIC NOMENCLATURE

B. optical isomerism This type of isomerism occurs only in compounds that has the ability to rotate plane polarized light. Optical Isomers have the same chemical and physical properties. And also the same functional group. These type of isomers can only be distinguished by how they rotate plane polarized light.

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...INTRODUCTION TO ORGANIC NOMENCLATURE

Types are as follows: 1. Enantiomers: These are optical isomers whose mirror images are non-super imposable.

An enantiomer that can cause a plane polarized light to rotate clockwise is known as dextrorotatory and the one that can cause plane polarized light to rotate anticlockwise is known as laevorotatory. A mixture of dextrorotatory and laevorotatory in equal amount is known as racemic mixture. II. Diastereomers: They are not mirror image of one another. This includes all the non-enantiomers. Example

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EXERCISE 1

1.

The functional groups present in the compound above are

(a) Alkene and halo-group (b) Hydroxyl and chloro-group (C) Alkene and chloro-group (d) Hydroxylandhalo-group 2. _____is the phenomenon that describes compounds with the same molecular formula but with different structural formula. (a) Hybridization (b) Isotopy (c) Isomerism (d) Allotropy. 3. ,_____and_____ are the molecular formulae of the alkanes, alkenes and alkynes respectively. 4. List and explain the two basic types of isomerism. 5. What is catenation? 6.What are the possible isomers of hexane?

INTRODUCTION Nomenclature - The IUPAC System

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2

THE ALKANES

Alkane is an Aliphatic hydrocarbon with the general molecular formula C H . Alkanes contain only single bonds, in other words, all members of the alkanes are tetrahedrally bonded i.e. Sp hybridized. Alkanes are unreactive (stable) but they undergo substitution reaction due to their saturated nature. It is usually advisable to be acquainted with the first ten (10) members of the alkane homologous family. And each member differ from the following member with CH2- and with atomic mass unit of 14. n

2n+2

3

Common/First Ten Members

THE ALKANES

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...INTRODUCTION TO ORGANIC NOMENCLATURE

Decane

COMMON SUBSTITUENTS OF THE ALKANES The alkyl group (R): Alkyl groups are simply alkane that has lost one proton (hydrogen atom).For example, methane (CH4) loses hydrogen and become methyl (CH3) and Ethane (C2H6) to Ethyl (C2H5). Hence, the general formula for the alkyl group is CnH2n+1. THE ALKANES

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Further illustration:

The halogens: these are group seven (7) elements which replaces/displaces one or more hydrogen atom(s) in a hydrocarbon. Examples of these halogens include: Fluorine (Fluoro), Chlorine (Chloro), Bromine (Bromo) and Iodine (Iodo). IUPAC RULES FOR NAMING ALKANES 1. Name should end with ane 2. Identify and name the longest continuous chain (parent chain) which could either be horizontal, vertical or otherwise. THE ALKANES

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3. Name each group attached to the parent chain as substituent. This substituent could be alkyl or halogen or even both. 4. Number the chain appropriately, starting with the end nearest the substituent(s) group, in order to give it/them the lowest possible number(s). 5. Show the location or position of all substituents with an appropriate number. E.g.2-methylpropane, this shows that methyl group is attached to carbon at locant 6.Assemble/collate the name and start by listing the substituted groups alphabetically e.g ethyl before methyl. And add it up to the parent chain and hence obtain the full name. 7.Prefixes like di, tri, tetra, etc. are used if there are multiples of the same kind of substituent. But the di, tri, tetra are not considered when arranging substituents in alphabetical order. Eg. Tri -ethyl before di -methyl. 8.Dash (-) is used to separate numbers from letters and comma to separate numbers. Eg. 2,2 Dimethyl.

THE ALKANES

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EXAMPLES I

Rule 1 Name ends with ane. Rule 2 Propane (3 carbon atoms) Rule 3 Methyl Rule 5 2-Methyl Rule 4 - not applicable because either way will give the same result. Rule 6 The full name is 2 Methylpropane NOTE: Just as a compound is obtained, it is taken as one word generally; therefore, once the first letter of the substituent is capitalized the next or the parent name should not be capitalized

II

CH3 CH3

CH

CH3

CH3 Rule 1 - name ends with - ane Rule 2 - The longest chain is propane (3 - Carbon atoms) Rule 3 - Methyl, Methyl

Rule 4 - not applicable. Rule 5 - 2 - Methyl, 2 - Methyl Rule 6,7 & 8 - The full name is 2, 2 - Dimethylpropane THE ALKANES

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III CH3 4

CH3 CH

3

CH3

C

CH3

2

1

CH3

Rule 1 - name ends with - ane Rule 2 - The parent chain is Butane (4-Carbon atoms) Rule 3 - Methyl, Methyl, Methyl Rule 4 - Count right-left Rule 5, 2 - Methyl, 2 - Methyl, 3 - Methyl Rule 6, 7 & 8 - The full name is 2,2,3 -Trimethylbutane 1

IV

CH3 6

2

CH2 5

3

CH2 4

4

CH

3

5

6

H2 C

2

1

CH2

CH3

CH3

Rule 1 - name ends with - ane Rule 2 - the longest chain is hexane (6 - carbon atoms) Rule 3 - Ethyl Rule 4 - Count to give ethyl group lowest number Rule 5 - 3 - Ethyl Rule 6 & 8 - The full name is 3 - Ethylhexane

THE ALKANES

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V (open chain form)

CH CH CH CH(Cl)CH (Condensed Form) 3

2

2

3

Rule 1 Single (-) bond, hence name ends with ane Rule 2 Pentane (5 carbon atoms) Rule 3 Chloro Rule 4 Recount to give the substituent lowest number Rule 5 2-chloro (counting right to left) Rule 6 the full name is 2 chloropentane

VI CH3 CHCH(CH3 )CH(f)CH3 It is interesting to know that compounds can also be named in their condensed form, but the groups in parenthesis should be considered as substituents therefore should be treated as such. 5

4

3

2

1

CH CH CH(CH )CH (F) CH 3

2

3

3

The methyl group in parenthesis should not be counted among the long / parent chain, since it is a substituent. THE ALKANES

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Considering the relevant rules. Rule 1 name end with ane Rule 2 Longest chain is (5 carbon) Ie Pentane Rule 3 Fluoro and methyl Rule 4/5 2-Fluoro 3 methyl Rule 6 Full name is 2-Fluoro-3-methylpentane VII. CH3 CH(CH3)CHBrCHFCH2CH3 NOTE: The halogens may not be in parenthesis, however in any formula written like the one above each halogen present should be treated as substituent.

Br CH3 1

CH 2

CH 3

CH3

CH 4

CH2

5

CH3 6

F

Rule 1 name ends with ane Rule 2 Longest chain is 6 carbon (hexane) Rule 3 Bromo, fluoro and methyl Rule 4&5 3 Bromo, 4-fluoro and 2-methyl THE ALKANES

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Rule 6 full name is 3-Bromo-4-fluoro-2-methylhexane

VIII.

Rule 1 Single (-) bond, name ends with ane Rule 2 We count to get the longest chain 5 CH3 4

CH2

3

CH3

2

CH

1

2

1

CH

CH3

3

4

CH2 CH2 CH3

Again 1

CH3

2

CH2

3

CH3 6

4

CH 5

4

CH

CH3

5

3

CH2

2

CH2

1

CH3

6

7

THE ALKANES

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Though if counted up-down or down-up, same result will be obtained (7-carbon atoms), but according to rule 4, up down is the correct numbering. Rule 3 Methyl and methyl Rule 4/5 3, 4 Dimethyl Rule 6 fullname is 3,4-Dimethylheptane

IX.

CH3 3

H3C

CH

1

2

CH2 3

C

4

5

H2C

CH3

1

CH3

5

4

H2C

2

CH2 CH2

6

6

CH2

7

CH2

8

CH3

Again CH3

H3C

3

1

CH 2

2

H2C

4

CH2 3

5

C

CH2

4 6

H2C 5

7

CH2 6

CH3 8

CH2 7

9

CH2 8

10

CH3 9

1

CH3

5-Ethyl-3,5-dimethyldecane

(This is to buttress the fact that the longest/parent chain is not always horizontal)

THE ALKANES

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X.

Rule 1 name ends with ane Rule 2 Longest chain is Octane (8-carbon atoms) Rule 3 Ethyl, methyl and methyl Rule 4&5 6-ethyl, 2-methyl and 4-methyl Rule 6 6-Ethyl-2,4-dimethyloctane FURTHER EXAMPLES CONSIDERING THEIR RELEVANT IUPAC RULES

CH3 a.

CH3

CH

CH2

CH

CH2

CH3

Cl CH3 2 - Chloro - 4, 4 - dimethylhexane

THE ALKANES

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Br

b. CH3 — CH— C— CH2 — CH3 Cl Br 3,3 - Dib ro mo -2-chlo ro pen tan e

F

c.

C H3 — C— CH2 — CH — C H2 — CH3 I

CH 3

2-Floro -4-iodo-2- m ethylhexane

Some cases exist where there are substituents attached to other substituents, here the branched chain or substituent is numbered beginning with the carbon directly joined to the parent chain and the name of the side chain is put in parenthesis Case 1

3

CH3

2

CH2 CH CH2 CH CH3 CH2

CH3

CH2 CH2 CH2 CH3

THE ALKANES

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Rule 1 name ends with ane Rule 2 longest chain is 10-carbon atoms (decane) Rule 3&4 3methyl, 5-(methylpropyl) Rule 6 full name 3-Methyl-5-(methylpropyldecane) Case 2 CH3

CH2

CH2

CH2

CH

CH2 CH2

CH2

CH 3

CH— Cl CH 2 CH 3

Applying all the necessary rules; the full name is 4-(Chloropropyl)nonane Kindly repeat the whole RULE (method) for a thorough understanding

THE CYCLOALKANES (CYCLIC HYDROCARBONS) Cycloalkanes are ring structures with general molecular formula C H . They are named by adding cyclo as prefix. Sometimes n

2n

substituents are assigned to the ring and numbers are used to indicate the positions of these substituents and in a way that the

THE ALKANES

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lowest possible numbers are assigned to the substituents. EXAMPLES

C yclo pro pane

Cyclo b utane

C yclo pen tan e

C ycloh exan e

HOW TO NAME CYCLOALKANES This case is quite different from the straight chain alkane as the edges of the ring represent carbon atoms. Here each carbon atom is directly bonded to two hydrogen atoms hence the formula C H . n

eg. C H cyclopropane, C H Cyclobutane etc. 3

6-

4

8-

THE ALKANES

27

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Important notes;

is not same as Hexane

Benzene

1.

Cyclobutane The 'C' belongs to the ring and not to the ethyl substituted group. Example

CH3

Methylcyclohexane

THE ALKANES

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Where the substituent is attached to is counted first in order to give the substituent a lowest possible number. IUPAC RULES TO CONSIDER 1.

Cyclo is the prefix for the ring structure of alkanes(cycloalkanes)

2.

Number from point where a substituent is attached to give it the lowest number.

3.

If there are two or more substituents, number to give lowest possible numbers to all substituents and collate names alphabetically.

4.

If there are just two substituents on a ring and their stereochemistry can be determined, remember to indicate it.E.g. CH

H

3

CH

3

H

Cis1,2-Dimethylcyclopropane THE ALKANES

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EXAMPLES I. CH 3

Ii. Cl

1- Chloro - 3- methylcyclobutane

CH 3

CH3

Cl 2-Ch loro-1-ethyl-3-m eth ylcyclob utane F

iii.

CH 3

H3C

1-Floro-3,5-dimethylcyclohexane

6-carbon atoms

Br CH

3

CH

3

iv. Cl CH

3

CH

3

4-Bromo-2-chloro-1,5-diethyl-3-methyl-6-propylheptane THE ALKANES

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F

v.

NO2

Cl

4-Chloro-1-floro-2-nitrocyclohexane In a case where there is an alkyl long chain attached to the ring, The compound is either named as an alkyl substituted cycloalkane or as a cycloalkyl substituted alkane.

See few examples below.

CH 3

1-Buylcyclopentane

1-Cyclobutylpentane

CONDITIONS i.

If the number of carbon in the cycloalkane is higher than that in the long chain alkyl, then the compound is named as an alkyl substituted cycloalkane.

ii.

If the carbon in the straight chain is higher, then the compound is named as cycloalkyl substitute alkane. THE ALKANES

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iii.

But if they have equal number of carbon atoms, then the ring takes precedence over the straight chain. i.e. should be named as alkyl substituted cycloalkane.E.g.

Propylcyclopropane Cyclopropylpropane Cycloalkanes possessing sub-branch i.e. Substituent under substituent. F

Cl CH3

3

1 2

4

CH3

CH3

1-Fluoro-3-(methylpropyl)cyclohexane

1-(3-Chlorobutyl) cyclopetane

CH 3 CH 3

CH3

CH3 2

CH 3 3

1-Methyl-2-(methylpropyl) cyclohexane

THE ALKANES

1

I

1-Iodo (ethylmethyl) cyclopropane

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EXERCISE 2 1.

The structural formula of octane can be drawn in how many ways? (a)6 ways ( b) 9 ways (c) 18 ways (d) 16 ways

2.

The molecular formula of cycloalkanes is the same as that of (a)Alkanes (b)Alkenes( c) Alkynes( d)Alkanols

3.

Draw the correct structure of 2-Floro-4-methylpentane and 1-Bromo-3-ethylcyclopropane

4.

Name the following a.

b. H3 C

CH3

THE ALKANES

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3

NOMENCLATURE OF ALKENES

Alkenes are straight chain hydrocarbons with molecular formula C H . They are double bond with one sigma bond and one pie (??) n

2n

bond. Their double bond account for their unsaturation. The first member isEthene.

IUPAC RULES FOR NAMING ALKENES 1.

Name ends with ene

2.

The longest chain chosen must have the double bond(=)

3.

Use numbers to indicate the positions of double bond as well as that of substituents.

4.

Carbon atom with the double bond must be given the lowest number.

5.

If the double bond is equidistance from each other, then number to give the first substituent lowest possible number. E.g. CH - CHCl- CH= CH- CH - CH3 2-chloro-3-hexene or 2-chlorohex-3-ene 3

2

NOMENCLATURE OF ALKENES

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...INTRODUCTION TO ORGANIC NOMENCLATURE

6.

If there are more than one double bond in the compound indicate their position by using the number of the first carbon atom present in each double bond and use the suffix diene, -triene for two double bonds, for three double bond respectively.

EXAMPLES

CH3 -CH=CH2 Propene

CH2=CH2 Ethene

4-Ethylhept-1-ene Number the longest continuous chain such that it contains the double bond functional group and take the outnumbered parts as substituents.

3,3-Dimethylpent-1,4-diene NOMENCLATURE OF ALKENES

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In the case above, one can number from either sides, since thesumofthe number of substituents will give the same value for any side. More examples:

2, 2, 3-Trimethyl-3-hexene

But-1,3-diene

Pent-1, 2, 4-trien

THE CYCLOALKENES (RING STRUCTURES) This also is a little different from the open chain alkene. Their molecular formula is C H n

2n-2

Cycloalkenes are numbered to give the double bond numbers 1& 2 (they are numbered head to tail) and their substituents are given the lowest numbers.

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EXAMPLES

Cyclopropene 1

Cyclobutene

Cyclohexene

C2 H5 3

4

2 1 6

4 5 2

3

CH3

Cl

3-Methylcyclobut-1-ene

5-Chloro-3-ethylcyclohexen

ALKENES AS SUBSTITUENTS IN THE RING (ALKYLENE) CH

2

CH Methylenecyclopropane

1-Ethynylcyclohexane

CH3

1-Propynylcyclopentane

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Further IUPAC rule for naming cycloalkene If the carbon-carbon double bond is carrying a substituent then numbering must start from the end having the substituent, irrespective of what number will be given to another substituent attached to the ring. EXAMPLE 4

CH 3

5 3

CH 3

1

2

1,5-Dimethylcyclepentane 6

CH 3

1 5

4

2

CH 2

5

2-Ethyl-1,3-dimethylcyclohexene

3

CH3

C2H5 1

CH3

2 5

3 4

C3H7

1-Ethyl-2-methyl-4-propylcyclopentene

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EXERCISE 3 1.

The IUPAC name for CH =CH-CH2-CH 2

3

(a) but-1-ene (b) 1-pentene (c)but-3-ene (d) 3-pentene 2.

Alkenes have the same molecular formula with

(a)Alkanes (b) Propane (c) Cycloalkanes (d) Halo-alkanes 3.

CH

3

(a)3-Ethylcyclopropane (b)3-Methylcyclopropane (c)3-Ethylcyclopropene (d)2-Methylcyclopropane 4. What is the name of the compound below

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a.

(a)

2-methyl,3-ethylbut-2-ene

(b)

. 2, 3, 4trimethylbut-2-ene

(c)

1, 1-dimethyl,1-ethylprop-1-ene

(d)

.2,3-Dimethylpent-2-ene

What is the IUPAC name of the compound with the following structure?

(a) 2-methylbutane (b) 2-methylprop-2-ene (c) 2-methylprop-1-ene (b)But-1-ene 5. Give the IUPAC name of the structure shown below

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4

NOMENCLATURE OF ALKYNES

Alkynes are triple (º) bond hydrocarbon with general molecular formula C H -2. They are open chain (acyclic compounds) n

2n

hydrocarbons.

IUPAC RULES FOR NAMING ALKYNES 1. Name should end with yne 2. Longest chain chosen, should contain triple (º )bond. 3. The first carbon of the triple bonds should be given the lowest number. 4. If there are more than one substituent; they should be numbered in such a way that they have the lowest possible sum. 5. Appropriate numbers should be used to indicate the position of each substituent group.

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6. If the triple bond is equidistance from each side we number to give the first substituent lowest possible number. Example 3

2-Ethylhex-3-yne 7.

If there are multiple bonds in the compound each bond must be given a number according to IUPAC system.

8.

If there are more than one triple/double bond, the prefixes di, tri, tetra, etc is used.

EXAMPLES

Heptyne(parent chain) 2-ethyl 5-chloro 5-methyl Collate names alphabetically to obtain the full name. Thus, NOMENCLATURE OF ALKYNES

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5-Chloro-2-Ethyl-5-Methylhept-3-yne II. H C=CH-CºCH 2

But-3-en-1-yne or But-1-en-3-yne (because alkene and alkyne have equal preference) III.

3-Bromopent-3-en-1-yne In the case above alkyne functional group is preferred because it is closer to the terminal. IV.

3-Methylbut-1-yne or 3-methyl -1-butyne NOMENCLATURE OF ALKYNES

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EXERCISE 4 1.

Alkyne belong to what class of hydrocarbon?

a.

Cyclic

b.

Aromatic

c.

Ring

d.

Aliphatic

2.

Name the followingcompounds.

a.

CH -CºCH

b.

HCºC-CH CH

c.

CH -IC-CºC-CH

3

2

3

3

3

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NOMENCLATURE OF OTHER FUNCTIONAL GROUPS (PART A)

5

THE ALKANOLS Alkanols are commonly known as alcohol. They are derivatives of the alkane homologous family. They have the general molecular formula C H OH n

2n+1

Alkanols can be classified into primary, secondary and tertiary alkanols . 1.

Primary alkanol: This is when two or three hydrogen is attached to the carbon bearing the -OH group. EXAMPLE:

H

C

OH

CH2

CH3

and

OH

H

Methanol

Ethanol

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2.

Secondary alkanol: When one hydrogen atom is attached to the carbon bearing the OH group. E.g.propan-2-ol

CH3

CH

CH3

OH 3.

Tertiary alkanol: When no hydrogen atom is attached to the carbon bearing the OH group.E.g.

CH3 CH3— C— CH2— CH3 OH 2-Methylbutan-2-ol

IUPAC RULES FOR NAMING ALKANOLS 1.

Name ends with the base word ol which replaces e in the corresponding alkane.

2.

The parent chain chosen should contain the OH functional group.

3.

Number to give the carbon atom bearing the OH group the lowest possible number. NOMENCLATURE OF OTHER FUNCTIONAL GROUPS (PART A)

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4.

Use number 1, 2, 3 … to indicate the position of the OH group in the chemical structure.

EXAMPLES 1.

CH -CH -OH

2.CH -CH CH OH

Ethanol

Propanol

3

2

3

2

2

For examples above it can be seen that alkanols are derivatives of alkanes, Just a matter of displacing/replacing hydrogen atom(s) with hydroxyl (-OH) group. 3. 2

OH

3

OH

Propan-1,2-diol 4

Propan-1, 2, 3-triol (Glycerol).

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5

4-Chloro-5-ethylnonan-3-ol

6. 3

2

Br

CH3

3-Bromo-2-methylbutan-1-ol THE ALKANOIC / CARBOXYLIC ACIDS These are organic acids; they can be represented with the carboxylic functional group COOH. The molecular formula for the carboxylic is C H COOH. n

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Carboxylic functional group has the highest preference among other functional groups, as such the base or suffix of any organic compound that contains more than one functional group including the carboxylic (-OOH) group, should be named as alknaoic acid, with the suffix oic acid.

IUPAC RULES FOR NAMING ALKANOIC ACIDS (CARBOXYLIC GROUP) 1.

Suffix is oic acid (which replace the e in the corresponding alkane)

2.

The parent chain must have the COOH group.

3.

Numbering should start from the carbon atom bearing the COOH group.

4.

Numbers are used to indicate the positions of the COOH group in organic compounds where there are two COOH groups at both ends. Otherwise no need.

5.

Numbers are used to indicate the positions of substituents.

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EXAMPLES H3C-H2C-COOH

H

H

OR

H

H

C

C

H

H

C

Propanoic acid

OH

Methanoic acid

C OH

3

CH—CH—CH— CH—C 3 2 CH3 2

OH 2, 3-Dimethypentanoic acid

C2H5

5

CH—CH—CH—C— COOH 3 2 2

CH3—CH2—C— COOH

CH 3 2 Ethyl-2-methylpentanoic acid

CH3 2-Ethyl-2-methylbutanoic acid

O

Benzoic acid NOMENCLATURE OF OTHER FUNCTIONAL GROUPS (PART A)

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THE CARBONYLS Carbonyls (pronounced car-bo-neel) are carbon-oxygen double bond organic compounds. Carbonyl comprises of alkanals also known as aldehydes with functional group CHO and alkanones also known as ketones with functional group CO. Alkanals and alkanones have the following general molecular formula.

R

C Alkanal

H

R

C

R1

Alkanone

Alkanals have one R group (alkyl group) and a hydrogen atom attached to the carbon bearing the oxygen, but alkanones have two R groups attached to both sides of the carbon bearing the oxygen.

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NOMENCLATURE OF ALKANALS Here the carbonyl group is always at the terminal. IUPAC RULES FOR NAMING ALKANALS 1. Suffix is al 2. The longest chain chosen should contain CHO (carbonyl group) 3. Numbers 1, 2, 3… are used to indicate the positions of their branched groups or substituents. 4. Numbering should start with carbon bearing the carbonyl functional group, since it's always at the terminal. 5. 'di' should be used in a case where there are up to two (2) CHO functional group in a compound. EXAMPLES

H

CH3— CH2— CHO

C H

Propanal

Methanal NOMENCLATURE OF OTHER FUNCTIONAL GROUPS (PART A)

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H2C— CH—CH 2—CHO

CH—CH— C 3 2 CH—CH—CH— 2 Cl

CH2

H

CH2

CH3

CH2

CHO CH3 3-Ethylhex-1,6-dial

2-Chloro-4-ethyl-4-methylhexanal

H3C—CH—CH—CH— CHO 2 CH3 CH3 2, 3 Dimethylpentanal

C2 H5 CH—CH—CH—CH— C 3 2 Br

H

3 Bromo-2-ethylpentanal

HC—C=CH— CHO 3 CH3 3-Methylbut-2-enal

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NOMENCLATURE OF ALKANONES Here the carbonyl group (C=O) is always in between two carbon atoms. IUPAC RULES FOR NAMING ALKANONES 1.

Name ends with one (which replaces the e in the corresponding alkanes).

2.

The longest continuous chain chosen should contain ketone groupCO-.

3.

Numbering should start from the end nearest to the ketone functional group.

4.

Numbers such as 1, 2, 3… should be used to indicate the position of ketone group and the position of all the substituent groups.

5.

Di, tri, etc should be used when there are up to two or moreCO- functional groups present in a compound.

EXAMPLES

CH 3 —CH 2—CH 2— CO—CH 3 Pentan-2-one NOMENCLATURE OF OTHER FUNCTIONAL GROUPS (PART A)

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CH3 HC— CH— CH— CH– C— CH3 3 CH3 O

C2 H 5

5-Ethyl-3, 4-dimethylhexan-2-one

H H O O H H C C C C C H H H

H

Pentan-2,3-dione CH CH (CH )CH COCH 3

3

2

3

Arrange

O

CH— CH— CH— C— CH 3 3 2 CH 3 4-methylpentan-2-one 2-methylpentan-4-one

H 3C

CH2

C

Heptan-3, 4-dione

C

CH2 CH2

CH3

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O CH— CH—C— CH = CH — CH—CH—CH 3 2 3 CH3

CH3

2, 7-Dimethyloct-4-en-3-one Cl CH— CH—C— CH—CO— CH 3 3 2 2 CH3

4-chloro-4-methylhexan-2-one NOMENCLATURE OF ALKANOATES Alkanoates are also known as esters, which is formed from the reaction of alkanol with alknoic acid. i.e alkanol +alknoic acid gives ester +water. Eg.CH COOH +C H OH 3

(aq)

Ethanoic acid

2

5

Ethanol

CH COOC H +H O 3

2

Ethylethanoate

5

2

Water

They have the general formula RCOOR where R and R may not be of the same alkyl group. And it (alkyl group) has a molecular formula C H 1

n

2n+1

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IUPAC RULES FOR NAMING ALKANOATES 1.

Suffix is oate (which replaces e in the corresponding alkanes).

2.

The longest chain chosen should bear the oate group.

3.

Counting should start from the point nearest to the oate group.

NOTE: In naming the alkanoates, the alkyl group of the alkanol is named first before the oic group which is replaced by oate. EXAMPLES

C2 H5

CH3 — C H2 — CO O C 2H 5

Ethyl propanoate

—COOCH3 H3C—CH— 2 CH— 2 CH

2- Ethylmethylpentanoate

CH3— CH2 —COOC3H7 Propyl propanoate

Ethylbenzoate NOMENCLATURE OF OTHER FUNCTIONAL GROUPS (PART A)

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CH3 — COOC8 H17 Octylethanoate (smells like orange)

CH3 — COOC5 H11 Pentylethanoate (smells like banana)

NOMENCLATURE OF THE AMINES Amines are derivatives of ammonia (Nh ). 3

Amine is formed when and alkyl group replaces one hydrogen atom in ammonia(NH )and forms RNH , R NH and R N for 3

2

2

3

primary, secondary and tertiary amines respectively. STRUCTURAL REPRESENTATION

IUPAC RULES FOR NAMING AMINES 1.

Amines are named as alkanamine

2. The e in the corresponding alkane is replaced by amine as the suffix. 3. Amines are classified by number of alkyl chain i.e primary, secondary and tertiary. NOMENCLATURE OF OTHER FUNCTIONAL GROUPS (PART A)

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4. The parent chain is numbered from the side nearest the amino group. 5. Numbers are used to indicate their position in the structure. EXAMPLES Primary amines

Secondary amines Hints: Determine the longest / parent chain and number it. Any alkyl group attached or bonded to nitrogen is named as Nalkyl. E.g. N methyl, N ethyl, N Propyl, etc. NOMENCLATURE OF OTHER FUNCTIONAL GROUPS (PART A)

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(a)

N-methylpropan-2-amine ii.

N-propylheptan-3-amine iii.

2-Bromo-N-ethylhexan-3-amine i.

3-Chloro-N-methyl-1-butanamine

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Tertiary amines Here it's almost same with the secondary amine, the little difference is that tertiary amines are named as N, N-dialkylyalkanamine or N alkyl-N- alkylalkanamine unlike secondary which is named as N-alkylalkanamine.

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WHEN AMINES ARE USED AS SUBSTITUENT. Hints: - When they are found in compounds containing oxygen the e in amine changes to o, giving it amino. If it is in the form -

H 3C

NH amino 2

-

NHRN-alkylamino

-

NR N,N-dialkylamino 2

CH

CH2

CH2 C

NH2

OH

4-Aminopentanoic acid

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C H

C OH

NOMENCLATURE OF AMIDES Amides are derived from alkanoic acid. The suffix is amide. The oic in alkanoic acid is replaced by amide i.e. COOH

CONH

2

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They are also classified into primary, secondary and tertiary amides.

EXAMPLES

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WITH DOUBLE BOND

NOMENCLATURE OF ALKYL ETHERS (ALKOXYALKANES)

Ethers are organic compounds with general formula R-O-R, Ar-O-R or Ar-O- Ar. Where Ar is a phenyl group. Ethers are named either as alkylether or alkoxyalkane. EXAMPLES

i. CH3 — CH2 —O— CH2 — CH3 Diethylether or Ethoxyethane ii. CH3 — CH2 — CH2 —O— CH2 — CH3 Ethylpropylether (The alkyl group are arranged in alphabetical order)

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iii. CH 3 — CH2 — CH 2 —CH 2 O Butylmethylether or methoxybutane

— CH3

NOTE: if it should be named as alkoxyalkane, then the side of Owith lower number of carbon atom is named as alkoxy while the side with higher number as alkane. iv. CH3

— CH2 — CH2 —O— CH2 — CH3

Ethoxypropane(Ethylpropylether) v.

CH3 — O— CH2 — CH2 — CH2 — CH3 Methoxybutane(Butylmethylether)

EXERCISE 5 A 1. Which of the following formula is that of a dicarbxylic acid. (a). (CH CH ) CHCOOH 3

2

(b). CH (OH) 2

2

2

(c) CH CH(OH)COOH 3

(d) CH (COOH) 2

2

(e) CH COCOOH 3

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2. State the functional groups present in the structure below H

O

H OH H

OH H OH OH

H CH3

(a) OH and COOH (b). CHO and COOH (c). OH and CHO (d). CO and CHO 3. The organic compound with the following structure represents___ CH CH2 C H OH 3

2

5

(a) Primary alkanol (b) Secondary alkanol (c) Tertiary alkanol (d) Quaternary alkanol 4.

The IUPAC nomenclature of the compound CH CH COOCH CH is: 3

2

2

3

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(a)

Propylethanoate

(b)

Ethylbutanoate

(c)

Ethylpropanoate

(d)

Methylbutanoate

5.

The IUPAC name for the structure below is

6.

Draw the structural formula of Decan-2-enol Name the following compounds:

7.

CH3 — CH2 — C2 H5 — OH 9. CH3 —O— CH3

8. 10.

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NOMENCLATURE OF OTHER FUNCTIONAL GROUPS (PART B) NITRILES: They have the general molecular formula R-C = N Nitriles have equal priority with the straight chain alkanes therefore organic compounds containing only nitriles or cyanides in the alkane structure as the only substituent are either named as Nitriles or Alkanes. The base word or suffix is either -onitrile or ane. If named as alkane the 'c' in C=N should not be counted but should be taken as substituent (called cyano), but if as nitrile it should be counted and the suffix -e in alkane should be replaced with onitrile. NB: Nitrile becomes cyano if we name the compound as Alkane.

1. CH3C = N Ethanonitrile(as Nitrile) OR

Cyanomethane( as Alkane)

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H

6 - Bromo-4-ethyl-4,5-dimethylheptanonitrile

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ACYL HALIDES It is a group of organic compound with general molecular formula R-CO-X where x can be any halogen.

Examples

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NITRO ALKANES They have the general molecular formula R-NO2 Examples CH3-NO2Nitromethane CH3 CH2 NO2Nitroethane CH3-CH2-CH2-NO2Nitropropane CH3-CH2-CH (CH3)-CH2-NO2 2-Methylnitrobutane.

HALO-ALKANES They have the general molecular formula R-X

Examples

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SULPHIDES The general molecular formula (M.F) is R-S-R.

EXAMPLES CH3-S-CH2-CH3 Ethylmethylsulphide

CH3-CH2-S-CH2-CH3 Diethylsulphide

CH3-CH2-S-CH2-CH2-CH3 Ethylpropylsulphide SULPHONES The general molecular formula is R2 So2or Examples [CH3]2SO2Dimethylsulphone CH3

CH2

S CH2-CH3 NOMENCLATURE OF OTHER FUNCTIONAL GROUPS (PART A)

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[CH3CH2CH2]2SO2 Dipropylsulphone THIOLS The have the general molecular formula R-SH. Examples CH3-SH Methane thiol or methyl mecantan

CH3-CH2-SH

CH3-CH2-CH2-CH2-SH

Ethane thiol

Butanethiol.

THE ARENES (AROMATIC COMPOUNDS) They are benzene compounds. The formula for benzene is C6H6

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Benzene as substituent (Phenyl Ar group)S

NB: Benzene is named as substituent only when the ring is attached somewhere in-between the long chain or straight chain hydrocarbon.

2-Phenylpropene

3-Chloro-3-phenylpent-1,4-diene

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PHENOLS (Ar - OH)

i.e 2= ortho 3= meta 4=para

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ANILINE (Ar-NH2)

Other examples of Benzene

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EXERCISE 5B Name the following compounds:

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6

ORGANIC COMPOUNDS WITH DIFFERENT FUNCTIONAL GROUP

Organic compounds with more than one functional group have their own unique way of naming. For one to successfully name a compound that has not only one functional group, the other of preference/priority series according to IUPAC system must be understood and followed. THE IUPAC ORDER OF PRIORITY (in descending order)

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IUPAC RULES TO CONSIDER IN SUCH CASES 1.

Select the longest chain, so that it contains the functional group of highest priority.

2.

Other functional group are taken as substituents.

3.

The ane in the corresponding alkane must be replaced by the base/suffix of the functional group with the highest priority and the base of the lower ones are written before that of the highest one

EXAMPLES

CH3 — CH2 — CH2 — CH = CH — COOH Hex-2-enoic acid

H2 C— CH2 — CH — CH = C — CH3 O

CH2 CH3

5-Methylhept-4-en-3-one

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3-Propylhex-2-en-4-yne (correct) 4-Propylhex-4-en-2-yne is wrong because alkenes and alkynes have equal priority, and so the compound is numbered/counted to give the substituent the lowest number since both functional groups are equidistant to each other.

HC º C CH = CH

2

But -3-en-1-yne

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4-Methylhex-5-en-2-ol (-ol is the base word because OH group is higher than C=C in the priority series)

CH3

OH

H

4-Hydroxypentanal

(-ol of OH group changes to hydroxy when it is used as a substituent)

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CH3 CH— CH — CH — CH 2 3 Cl

(Number to give OH the lowest possible number since it's of higher priority) Hence the name of the compound is

Hex-4-en-3-ol

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EXERCISE 6 1.

Which of the following is in other of decreasing priority?

(a). OR>C=C>-OH> -CHO (b) C=C>-OR>-OH>-CHO (d) CHO>-OH>-OR>C=C (d). CHO>-OH>C=C>-OR 2.

Name the structure below is

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3.

Draw the structure of 1, 1, 2,2-tetrabromoethane

4.

Give the IUPAC name of the compound above 5.

Name the following compounds.

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ANSWERS EXERCISE 1 1. b

2. c

3.CnH2n+2, CnH2n and CnH2n-2

EXERCISE 2 1. c

2. b

3.a 1-Ethyl-2-propylcyclohexane b 4-Ethyl-2-methylhexane EXERCISE 3 1. a 2. d Cycloalkanes

5. c 6. cis 1,2-Dichloroethene

3. c 4. d ANSWERS

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EXERCISE 4 1. d 2. a. Propyne b. But-1-yne c. 4-iodopent-2-yne EXERCISE 5 A 1.

D

2. C Alkanal (-CHO) and Alkanol(-OH) 3. A 4. C 5. 3-Propylbenzaldehyde 6. C10H21OH 7. Butanol 8. 2, 3,4-Tripentanol 9. Dimethylether 10. 3-Methylethylpentanoate ANSWERS

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EXERCISE 5B 1.

2-Bromo-3-chlorobutanonitrile

2.

Propanonitrile

3.

Ethanoylchloride

4.

Methanoylbromide

5.

1-Ethyl-3-methylbenzene

6.

3-Propylnitrobenzene

7.

Diethylsulphone

8.

Dimethylsulphone

9.

4-Phenylbut-1,3-diene

10.

3-Ethyl-4-phenylheptane

11.

Ethylpropylsulphide

EXERCISE 6 1.

c

2.

3-Iodobenzenol

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3.

Br

Br

H—C—C—H Br

4.

Br

Benzoicacid

5. A. But-3-enal B. Butan-2,3-dione C. But-3-en-2-ol D. Methylethanoate E. EthylpropyletherorEthoxypropane F. Ethanamine G. But-2-enamide

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REFERENCE Ababio, O.Y (…) New School Chemistry 5th Edition Egbonoje, T.O. (2012). Quick Review Chemistry Fundamentals of Chemistry, Unizik Prescience, (2015/16) session. Powell, WH. (2014). New edition of the “IUPAC Blue Book” Http://www.britannica.com/iupacsystem http://www.britannica.com>science>IUPACnom... http://web.chemdoodle.com/demos/IUPACHttp://chem.libretexts.org>...>alkanes Http://en.m.wikibooks.org>wiki>alkane Http://pabehem.nehi.nim.nih.gov/compound Http://www.chemistry.msu.edu/faculty/reusch/virttyjml/ nomen/.htmwww.utdallas.edu/scartes/ochem.

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APPENDIX

THE FIRST TWENTY MEMBERS OF THE ALKANE FAMILY

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Hexadecane

APPENDIX

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