Nomenclature of Organic Compounds - PowerPoint Presentation

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Nomenclature of Organic Compounds

Dr.V.Jeevana

Jyothi

Associate Professor

Department of Chemistry

RBVRR Women’s College

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Organic ChemistryIt is the study of carbon compounds.It is studied as a separate discipline because of the following reasons

1. large number of compounds

2.Unique Physical & chemical properties

3. Unique character of Carbon-Catenation- carbon has the ability to bond successively to other carbon atoms to form chains.

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Importance of Organic Chemistry in Everyday life

Food: Proteins, Fats,

Carbohydrates

Clothing: Cotton, Silk, Wool, Nylon, rayon

Shelter: wood, paints, Varnishes

Power & Transportation: Natural gas, petroleum products, Coal

Medicines & Drugs: Penicillin, Streptomycin, Aspirin

Insecticides: DDT

Herbicides:

Treflan

Hormones & Steroids

Vitamins & Enzymes

Antiseptics

Pigments & Dyes

Paper & Inks

Photographic films &

Developers

Perfumes

&

Flavours

Plastics, rubber & resin

Propellants & Explosives

Soaps & Detergents

Refrigerants

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Types of Organic Compounds

Aliphatic Compounds

:

Compounds which consist of open chain of carbon atoms .

Ethane CH

3

-CH3 Ethyl alcohol CH3-CH2-OH Acetic acid CH3-COOHSaturated & Unsaturated Compounds: Compounds which contain only carbon & Hydrogen are called Hydrocarbons. A Hydrocarbon is said to be saturated if it contains only C-C single bonds. Eg: CH3-CH3 Ethane A Hydrocarbon is said to be unsaturated if it contains C=C or C≡C multiple bonds Eg: CH2=CH2 Ethylene HC≡CH AcetyleneAromatic compounds: a. Benzenoid Compounds: Benzene and all compounds that have structure and chemical properties similar to Benzene Eg:

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b

.

Non

benzenoid

compounds:

Alicyclic or Carbocyclic Compounds:

Cyclic compounds which consist only of

carbon & hydrogen atoms 5. Heterocyclic Compounds: Cyclic compounds in which ring atoms are C & Heteroatoms like N,S, OHomologous Series: series of organic compounds each containing a characteristic functional group forms a homologous series & members are called as homologues. They differ by a –CH2 group.Ex: alkanes, alkenes, alkynes, haloalkanes, alcohols, carboxylic acids etc.

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Representations of Organic Molecules

n-Pentane: C5H12

Long Hand formula

:

CH3-CH2-CH2-CH2-CH3

Short hand formula:

Skeletal formula:

C-C-C-C-CCondensed Formula: CH3-(CH2)3-CH3

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Structural formula:

Three dimensional:

Lewis –dot formula:

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Principles of Nomenclature

In early days , each new compound was given an individual name. Such name was based on the source, some property or some other trivial reason.

Eg

: Formic acid, it was named as it was obtained by distillation of red

ants.

Methane from marsh gas

Citric acid from citrus foods Nitrobenzene, it is named as oil of mirbane Curcumin from turmeric & many more……An ordinary name given to a compound without reference to its structure is called a common name or trivial name

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IUPAC System of Nomenclature:

With the rapid growth of organic chemistry, over 6 million of compounds were

discovered.It

was impossible to give common names.

In 1957, the

International Union of Pure and Applied Chemistry

proposed rules to give a systematic naming to organic compounds based on their structure. Each organic compound has only single IUPAC name.

According to IUPAC, name of an organic compound has the following parts1. Prefix: Indicates the identity, location, and number of substituents attached to the carbon chain eg: Chloro, alkyl, amino, hydroxy etc.2. Root word : Represents the no. of carbon atoms in the continuous longest chain3.Primary suffix: Indicates the presence or absence of saturation4.Secondary Suffix: Indicates the functional group present

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Root Word:

1-Meth

2-Eth

3-Prop

4-But

5-Pent

6-Hex7-Hept8-Oct9-Non10-Dec20-EicosPrimary Suffix:Saturated with all single bonds: -aneUnsaturated with = bond: -eneUnsaturated with ≡ bond: -yneSecondary Suffix: indicates the functional group present

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Functional Groups: A functional group

is an atom or group of atoms in a molecule that gives the molecule its chemical properties.

Some Functional groups with prefixes & suffixes are given below:

Class

Functional group

IUPAC group Prefix

IUPAC group Suffix

ExampleAlkaneC-C-aneCH3-CH3AlkeneC=C-eneCH2=CH2AlkyneC≡C-yneHC≡CHArenesC6H6BenzeneHalides-X (X=F,Cl,Br,I)haloCH3-CH2-BrAlcohol-OHhydroxy-olCH3-CH2-OHEther

-O-alkoxyCH3-O-CH3

Aldehyde

R-CHO

formyl

-al

Ketone

Oxo-

-one

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Class

Functional group

IUPAC group Prefix

IUPAC group Suffix

Example

Carboxylic acid

-COOH

carboxy-oic acidEster-COORalkoxy carbonyl-oateAcid halides-COX( X=F,Cl,Br.I)halo carbonyl-oyl chlorideAcid anhydride-anhydideAmide-CONH2carbamoyl-amideAmine-NH2Amino-amineCH3-NH2Nitriles-C≡Ncyanonitrile

CH3-C≡NIsonitrilesN≡Cisocyano

Iso

nitrile or

carbyl

amine

CH

3

-N≡C

Nitro Compounds

-NO

2

Nitro

-

CH

3

-NO

2

Sulphonic

acids

-SO

3

H

sulpho

Sulphonic

acids

CH

3

-SO

3

H

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Alkyl groups: By removing one hydrogen from alkane

R-H - 1H

→

-R

alkyl group

CH

4 - 1H → -CH3 methyl groupn-alkyl group: Iso- alkyl group: Neo-pentyl group:

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Classification of Carbon atoms

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Alkyl group

Structure

IUPAC name

( Prefix)

Abbreviation

CH

3

- CH3-methylMe-CH3CH2-

ethyl

Et-

CH

3

CH

2

CH

2

-

n

-propyl

n

-

Pr

CH

3

CHCH

3

isopropyl or

i

-propyl

i

-

Pr

CH

3

CH

2

CH

2

CH

2

-

n

-butyl

n

-Bu

CH

3

CH

2

CHCH

3

sec

-butyl

s

-Bu

(CH

3

)

2

CHCH

2

-

isobutyl or

i

-butyl

i

-Bu

(

CH

3

)

3

C-

tert-butyl or t-butylt-BuC6H5-phenylPh

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ALKANESNames of first 10 straight chain alkanes

Carbon atoms

Name

Molecular formula

1

Methane

CH

42EthaneC2H63PropaneC3H84butaneC4H105PenatneC5H126HexaneC6H147HeptaneC7H168OctaneC8H189NonaneC9H2010DecaneC10H

22

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IUPAC Rules for Naming Alkanes

Rule 1: Select the longest continuous carbon chain

Note

that

it

does not matter if the chain is straight or it bends

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Also

note that if there are two chains of equal length, pick the chain with

more

substituents

.

In

the following example, two different chains in the same alkane have seven C atoms. We circle the longest continuous chain as shown in the diagram on the left, since this results in the greater number of substituents.

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Rule 2 : Number the atoms in the carbon chain to give the first substituent the lowest number.

If the first substituent is the same distance from both ends, number the chain to give the second substituent the lower number.

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When

numbering a carbon chain results in the same numbers from either end of the chain, assign the lower number alphabetically to the first substituent.

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Rule 3 : Name and number the substituents.

Name the substituents as alkyl groups

.

Every

carbon belongs to either the longest chain or a substituent, not both

.

Each

substituent needs its own number.If two or more identical substituents are bonded to the longest chain, use prefixes to indicate how many: di- for two groups, tri- for three groups, tetra- for four groups, and so forth.

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Rule 4: Combine substituent names and numbers + parent and suffix

Precede the name of the parent by the names of the substituents.

Alphabetize the names of the substituents, ignoring all prefixes except

iso

, as in isopropyl and isobutyl.

Precede the name of each substituent by the number that indicates its location.

Separate numbers by commas and separate numbers from letters by hyphens. The name of an alkane is a single word, with no spaces after hyphens and commas.

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1. Cycloalkanes are named by using similar rules, but the prefix

cyclo

- immediately precedes the name of the parent.

Example:

CYCLO ALKANES

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3. For rings with more than one substituent, begin numbering at one substituent and proceed around the ring to give the second substituent the lowest number.

2. Name and number the substituents. No number is needed to indicate the location of a single substituent.

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Note the special case of an alkane composed of both a ring and a long chain. If the number of carbons in the ring is greater than or equal to the number of carbons in the longest chain, the compound is named as a cycloalkane.

4.

With two different substituents, number the ring to assign the lower number to the substituents alphabetically.

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Naming compounds containing both Ring & side alkyl chains

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ALKENES

Select the longest carbon chain containing the double bond

Name the longest chain- the name is obtained by dropping the final-

ane

from the name of corresponding alkane, & adding the ending

–

ene

Number the chain from the end closer to the double bondIndicate the position of the double bond by the number of the first (lowest numbered) carbon atom involved in the db.Alkyl groups and other substituents are numbered, named and placed as prefixes in the alphabetical order.6. Alkenes containing two double bonds are named as alkadienes

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CYCLO ALKENES

Number the ring to give the double bonded carbons the number 1

& 2.

C

hoose

the direction of numbering so that the substituents get the

lowest numbers.

The position of the double bond is not indicated because it is known to be between C1 & C2.3-methyl cyclopentene

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ALKYNES

Select the longest carbon chain containing the

triple bond

Name the longest chain- the name is obtained by dropping the final-

ane

from the name of corresponding alkane, & adding the ending

–

yneNumber the chain from the end closer to the triple bondIndicate the position of the triple bond by the number of the first (lowest numbered) carbon atom involved in the db.Alkyl groups and other substituents are numbered, named and placed as prefixes in the alphabetical order.6. Alkynes containing two triple bonds are named as alkadiynes

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Alkyl Halides

1.Select the longest chain to which the halogen is attached and give it the

name of the corresponding alkane

2. Prefix the name of the alkane by

chloro

, bromo, iodo or fluoro3. Number the chain so as to give the carbon carrying the halogen atom the lowest possible number4. Other substituents are numbered, named and placed as prefixes in alphabetic order. If there are two or more identical halogen substituents, the prefixes di, tri, tetra , etc.. are used 2-bromopropane

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Alcohols

Select the longest chain to which hydroxyl group is attached.

Name the longest chain. The name is obtained by dropping the final –e from the name of the alkane that contains the same number of carbon atoms, and adding the ending –

ol

Number the chain to give the lowest number to the carbon attached to the –OH group

Indicate the position of the hydroxyl group by the number of the carbon attached to the hydroxyl group

Other substituents are numbered, named and placed as prefixes in alphabetic order. For example,

CH3-OH Methanol CH3-CH2-OH Ethanol6. Alcohols containing two or three –OH groups are named as alkanediols and alkanetriols. Notice that –e of the corresponding alkane name is retained

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Ethers

1. Ethers are compounds in which an oxygen atom is bonded to two organic groups ( R-O-R).

2. In the IUPAC system, ethers are named as

Alkoxy

alkanes.

The smaller alkyl group plus the oxygen atom is called an

alkoxy

substituent. CH3-CH2-CH2-O-CH31- Methoxy PropaneCyclic Ethers ( Epoxides)These are also known as oxiranes In IUPAC system, they are named as alkyl oxiranes. Substituents on the oxirane ring require a numbering system. The oxygen atom is given the number-1

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Aldehydes

In the IUPAC system, aldehydes are named as

alkanals

Select the longest chain-the name is obtained by dropping the final -e from the name of the corresponding alkane, and adding–

a

l at the end.

Number the chain by assigning the number 1 to the aldehyde carbon. The number 1 is not used to indicate the position of the carbonyl carbon, since it is always located at the end of the chain

Other substituents are numbered, named & placed as prefixes in alphabetic order.When there are two aldehyde groups in a molecule, it is named as alkanedial. Notice that –e of the corresponding alkane is retained.

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Ketones

In the IUPAC system ketones are named as

Alkanones

.

Select the longest chain containing the carbonyl carbon atom

Name the longest chain -the

name is obtained by dropping the final -e from the name of the corresponding

alkane and adding–one at endingNumber the chain to give the lowest number to the carbonyl carbon.Other substituents are numbered, named & placed as prefixes in alphabetic order. 5. When there are two carbonyl groups in a molecule, it is named as alkanedione. Notice that –e of the corresponding alkane is retained.

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Carboxylic acids

Select the longest chain containing carboxyl group

Name the longest chain. The name is obtained by dropping the final –e from the name of the corresponding alkane & adding the ending

–

oic

acid

Number the chain starting with carboxyl carbon as number 1. the number 1 is not used to indicate the position of the carboxyl carbon, since it is always located at the end of the chain.

Other substituents are numbered, named & placed as prefixes in alphabetic order.5. When there are two carboxyl groups in a molecule, it is named as alkanedioic acid . Notice that –e of the corresponding alkane is retained.

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Carboxylic acid derivatives: hydroxyl part of the carboxyl group is replaced by other groups

Acid Chlorides:

T

hese are derived from acids by replacing –OH group by

Cl

atom. They are named by changing the ending

-

oic acid of the corresponding carboxylic acid by –oyl chloride.2. Esters: These are derived from acids by replacing –OH group by –OR group. Their names consist of two words. The first word is the name of the alkyl group attached to the oxygen atom. The second word is derived from the carboxylic acid name with –oic acid changed to –oate

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Carboxylic acid derivatives: contd

…

3. Acid Anhydrides:

These are derived from acids by replacing –OH by –OCOR. They are named by changing the suffix acid of the parent acid to

anhydride.

Asymmetric

anhydrides are named in a similar fashion listing the alkyl groups in alphabetical order.4. Amides: These are derived from acids by replacing –OH by –NH2 . These are named as alkane amides.

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Sulfonic acids: These contain –SO

3

H group. Their IUPAC names are obtained by adding the suffix

sulphonic

acid to the alkane name

Nitro Compounds:

T

hese contain –NO2 group. Their IUPAC names are obtained by adding prefix –nitro to the alkane name.Cyanides or Nitriles: These contain –CN group. In the IUPAC system they are named as Alkane nitriles. Numbering includes the nitrile carbon atom.The prefix cyano used for the nitrile group when it occurs as a substituent. In that case, the carbon of the –CN group is not numbered.

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Isocyanides/Isonitriles

/

carbyl

amines:

T

hese contain –NC (

isocyano

) group. In IUPAC system, they are named as Alkyl carbylamines. The numbering does not include carbon of the isocyano group.Amines: These are derivatives of ammonia in which one or more hydrogen atoms have been replaced by alkyl or aryl groups.Amines are classified as primary, secondary & tertiary amines.R-NH2 Primary amineR2NH Secondary amineR3N Tertiary amineIn the common system they are named as alkyl amines. If two different alkyl groups are present, write in the alphabetical order.Eg: CH3-NH2 Methyl amine CH3-NH-CH3 Dimethyl amineCH3-NH-CH2CH3 ethyl methyl amineMethyl carbylamine

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Amines: contd

….

In the IUPAC system, primary amines are named by replacing the final –e of the parent alkane by –

amine.

If necessary, a number is added to indicate the position of –NH

2

group.

Secondary or tertiary amines are named as N-Substituted derivatives of primary amines. The largest of the groups attached to nitrogen is chosen as the organic group of the primary amine. The remaining alkyl groups are named as substituents by using the prefix N-to indicate that they are attached to nitrogenCH3-CH2-NH-CH3 N-Methyl EthanamineWhenever it is necessary to name –NH2 as a substituent, it is called the amino group

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Nomenclature of Poly functional compounds

When a compound contains two or more different types of functional groups ( poly functional compound), the functional group which specifies its class is called the

Principal Functional group.

The other functional groups are referred to as

substituents.

4-hydroxy

butanoic

acid

Slide43

The IUPAC system has laid down priority of functional groups for determining the class of a polyfunctional

compound.

The table below shows a list of functional groups in decreasing order of priority for citation as the principal functional group.

Class

Functional group

Suffix used

Carboxylic acid

-COOH-oic acidSulphonic acid-SO3H-sulfonic acidEster-COOR-oateAcid Halide-COX-oyl halideAmide-CO-NH2-amideNitrile-CN-nitrileAldehyde-CHO-alketone-CO--oneAlcohol-OH-olamine-NH2AmineEthers-O-Alkoxy alkanesAlkene-C=C-

-eneAlkyne-C≡C--yne

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Prefixes used for functional groups

F.G

Prefix

F.G

Prefix

F.G

Prefix

-BrBromo-RAlkyl-C=OOxo-FFluoro-ORAlkoxy-NO2Nitro-ClChloro-OHhydroxy-NONitrosoIIodo-NH2Amino-CNcyano

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IUPAC Rules for naming Poly functional compounds

Rule 1 :

I

dentify the principal functional group.

eg

:

The two functional groups in the above structure are –COOH & -OH. Since –COOH ranks higher in the priority table, the structure is named as a carboxylic acidRule 2: Number the longest chain containing functional group from the end closer to it.Rule 3: Write the parent name corresponding to the number of carbons in the longest chain.Longest chain= 5 carbonsParent name = Pentanoic acid

Slide46

contd…..

Rule 4 :

Arrange the substituent names with position numbers in alphabetic order

4-hydroxy-2-methyl

Rule 5 :

prefix substituent names with the parent name

4-hydroxy-2-methyl pentanoic acidRule 6: C-C double or triple bonds are usually indicated by integrating –ene or –yne into the suffix, as in –enoic acid or –ynoic acidRule 7: compounds containing both db & tb in the main chain are named as alkeneynes. The position number of db is inserted before-alken- & that of tb before -yne. Rule 8: The following functional groups are always named as substituents.-X ( all halo groups), -CN, -R, -OR, -NH2, -NO2, -NO

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Excercises

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Excercises

Example-1

The functional groups are –Br,-

Cl

, -NO2 .these are not Principal F.G, but taken as substituents

Example-2

The functional groups are –CHO & C=C . The –CHO is the Principal functional group & it ranks higher in the priority and number for –CHO group is not indicated as it is always 1.

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Example:3

As –CHO group is highly preferred than Ketone. Compound is named as aldehyde and ketone is taken as

substituent..so

named as the prefix –Oxo.

Example:4

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Example:5

Example:6

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Example: 7

Example: 8

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Example:9

Example: 10

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Any queries????????

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THANK YOU