IUPAC Rules for Nomenclature of Organic Compounds
IUPAC Rules for Nomenclature of Alkanes
1. The unbranched alkanes are named according to the number of alkanes of carbons. Examples: Methane, Ethane, Propane etc.
2. For alkanes containing branched carbon chains, the principal chain of the compound needs to be determined. This is the longest continuous carbon chain in the molecule.
3. In determining the principal chain sometimes, two or more chains in the molecule may have same number of carbons in their chains. In such a case, the chain having the greater number of branches is chosen as the principal chain of the molecule.
4. Numbers have to be given for the carbon atoms, to which the branches are attached. To give numbers, principal chain of the carbon atoms is numbered from the direction that gives the lower number to the first branching point.
5. Branching groups are in general termed as substituents. Each group is to be given an IUPAC name (prefix name) and is prefixed to the name of the principal chain of the molecule.
6. Compound is named according to the pattern “number- alkyl group prefix name principal chain name”. Name of the group (prefix) and name of the principal chain are written together as one word.
7. Where there are more than one substituent groups, each substituent group must be given its own number depending on the carbon to which it was attached.
8. In case of identical substituents, prefixes di, tri, tetra etc., are used before the group prefix name to indicate number of identical groups.
9. Substituent groups are written in alphabetical order regardless of their location in the principal chain but the prefixes di, tri… as well as the prefixes tert- and sec- are ignored in deciding the alphabetical order, and the prefixes iso, neo, and cyclo are considered.
10. If the number of carbon atoms of the principal chain from either gives identical numbers to the substituent attachment carbons, the direction which gives the lower number to the first written group (according to the alphabetical order) is chosen.
Showing posts with label Nomenclature. Show all posts
Showing posts with label Nomenclature. Show all posts
Wednesday, December 24, 2008
Wednesday, July 23, 2008
Nomenclature - Carboxylic Acids
Nomenclature
The common names of carboxylic acids are based on their source of origin. Formic acid was first obtained from red ants (Latin formica means red ants) and it was named from that. Acetic acid was obtained from vinegar (Latin aceum means vinegar) and so got that name.
In the common system the position of substituents is indicated by the Greek letters α, β, γ, ō.
α, β, γ, ō Carbon atoms
The carbon atom next to the carboxyl carbon is assigned the letter α. The carbon next to α-carbon is the β-carbon. The carbon next to β-carbon is the γ-carbon. The carbon next to γ-carbon is the ō Carbon.
ō-γ-β-α carbons
C-C-C-C-COOH
IUPAC System
According to IUPAC system, the name of the monocarboxylic acid is derived by changing the final 'e' from the name of the corresponding hydrocarbon with 'oic' and adding the word acid.
Formic acid - Methanoic acid
Acetic acid - Ethanoic acid
n-Butyric acid - Butanoic acid
Isobutyric acid - 2-Mehtylpropanoic acid
Dicarboxylic acids
Oxalic acid - Ethanedioic acid
Malonic acid - Propanedioic acid
The position of substituents is indicated by the following rules.
1. The longest chain of carbon atoms containing the carboxylic group(-COOH) is selected.
2. The numbering of carbons starts from the carboxylic acid group and the carbon of carboxyl group is given number 1.
3. The position of the substituents is indicated by the number of carbon atom to which they are attached.
Aromatic carboxylic acids
The simplest aromatic carboxylic acid is benzoic acid.
The IUPAC names of substituted aromatic carboxylic acids are derived by prefixing the name of the substituent to the name of the parent acid i.e., benzoic acid and the position is indicated by an Arabic numeral with the carbon atom carrying the –COOH group being numbered as 1.
The common names of carboxylic acids are based on their source of origin. Formic acid was first obtained from red ants (Latin formica means red ants) and it was named from that. Acetic acid was obtained from vinegar (Latin aceum means vinegar) and so got that name.
In the common system the position of substituents is indicated by the Greek letters α, β, γ, ō.
α, β, γ, ō Carbon atoms
The carbon atom next to the carboxyl carbon is assigned the letter α. The carbon next to α-carbon is the β-carbon. The carbon next to β-carbon is the γ-carbon. The carbon next to γ-carbon is the ō Carbon.
ō-γ-β-α carbons
C-C-C-C-COOH
IUPAC System
According to IUPAC system, the name of the monocarboxylic acid is derived by changing the final 'e' from the name of the corresponding hydrocarbon with 'oic' and adding the word acid.
Formic acid - Methanoic acid
Acetic acid - Ethanoic acid
n-Butyric acid - Butanoic acid
Isobutyric acid - 2-Mehtylpropanoic acid
Dicarboxylic acids
Oxalic acid - Ethanedioic acid
Malonic acid - Propanedioic acid
The position of substituents is indicated by the following rules.
1. The longest chain of carbon atoms containing the carboxylic group(-COOH) is selected.
2. The numbering of carbons starts from the carboxylic acid group and the carbon of carboxyl group is given number 1.
3. The position of the substituents is indicated by the number of carbon atom to which they are attached.
Aromatic carboxylic acids
The simplest aromatic carboxylic acid is benzoic acid.
The IUPAC names of substituted aromatic carboxylic acids are derived by prefixing the name of the substituent to the name of the parent acid i.e., benzoic acid and the position is indicated by an Arabic numeral with the carbon atom carrying the –COOH group being numbered as 1.
Tuesday, February 5, 2008
Alcohols - Introduction, Nomenclature
The hydroxy derivatives of aliphatic hydrocarbons are termed alcohols. They contain one or more hydroxyl (OH) groups.
Example:
Methyl Alcohol CH-3OH
Ehtyl alcohol C-2H-5OH also written as CH-3CH-2OH
Propyl alcohol C-3H-7OH also written as CH-3CH-2CH-2OH
They are classified according to the number of hydroxyl groups in the molecule.
i. Monohydric alcohol contains one -OH group.
ii. A dihydric alcohol contains two -OH groups in the molecule
ex. ethylene glycol
CH2OH
|
CH2OH
iii. A trihydric alcohol contains three -OH groups in its molecules
ex.glycerol
CH2OH
|
CH2OH
|
CH2OH
Monohydric alcohols are represented by the general formula R-OH or CnH2n+1OH.
Monohydric alcohols are further classified according to the carbon atom to which the hydroxyl group is attached.
1. Primary alcohols: -OH group is attached to primary carbon atom. They contain the group -CH2OH
eg.: CH3CH2OH, CH3CH2CH2OH
2. Secondry alcohol: -OH group is attached to a secondary carbon atom. It contains a divalent >CHOH group.
Ex. iso-propyl alcohol
3. Tertiary alcohol: -Oh group is attached to tertiary carbon atom. C-OH group is present
Alcohols – Nomenclature
Common system
Alcohols are named as alkyl alcohols. The alkyl group attached to the –OH group is named and the word alcohol is added to it.
Ex: Methyl alcohol
IUPAC nomenclature system
‘e’ in the parent chain is replaced by ‘ol’
Ex: Methanol
Rules follow for arriving at the names of alcohols
1. The longest continuous chain containing the carbon bonded to the OH group is selected as the parent chain.
2. The carbon atoms in the chain are numbered in such a way that the carbon atom carrying the hydroxyl group gets the lowest number.
3. The position of substituents is indicated by suitable numbers.
Ex: 2-Methyl propan-1-ol
The alcohols with two –OH groups are named as diols and alcohols with three –OH groups are named as triols.
Ex: Ethane – 1,2 – diol, propane -1,2,3-triol
Example:
Methyl Alcohol CH-3OH
Ehtyl alcohol C-2H-5OH also written as CH-3CH-2OH
Propyl alcohol C-3H-7OH also written as CH-3CH-2CH-2OH
They are classified according to the number of hydroxyl groups in the molecule.
i. Monohydric alcohol contains one -OH group.
ii. A dihydric alcohol contains two -OH groups in the molecule
ex. ethylene glycol
CH2OH
|
CH2OH
iii. A trihydric alcohol contains three -OH groups in its molecules
ex.glycerol
CH2OH
|
CH2OH
|
CH2OH
Monohydric alcohols are represented by the general formula R-OH or CnH2n+1OH.
Monohydric alcohols are further classified according to the carbon atom to which the hydroxyl group is attached.
1. Primary alcohols: -OH group is attached to primary carbon atom. They contain the group -CH2OH
eg.: CH3CH2OH, CH3CH2CH2OH
2. Secondry alcohol: -OH group is attached to a secondary carbon atom. It contains a divalent >CHOH group.
Ex. iso-propyl alcohol
3. Tertiary alcohol: -Oh group is attached to tertiary carbon atom. C-OH group is present
Alcohols – Nomenclature
Common system
Alcohols are named as alkyl alcohols. The alkyl group attached to the –OH group is named and the word alcohol is added to it.
Ex: Methyl alcohol
IUPAC nomenclature system
‘e’ in the parent chain is replaced by ‘ol’
Ex: Methanol
Rules follow for arriving at the names of alcohols
1. The longest continuous chain containing the carbon bonded to the OH group is selected as the parent chain.
2. The carbon atoms in the chain are numbered in such a way that the carbon atom carrying the hydroxyl group gets the lowest number.
3. The position of substituents is indicated by suitable numbers.
Ex: 2-Methyl propan-1-ol
The alcohols with two –OH groups are named as diols and alcohols with three –OH groups are named as triols.
Ex: Ethane – 1,2 – diol, propane -1,2,3-triol
Alkyl and Aryl Halides - Introduction, Nomenclature
When hydrogen atom or atoms of alkanes are replaced by the corresponding number of halogen atoms, the compounds are called halogen derivatives of alkanes.
They are classified according to the number of halogen atoms that replace hydrogen atoms in the alkane.
Monohalogen derivatives: They contain only one halogen atom.
e.g. CH-3Cl Methyl chloride
CH-3-CH-CH-3 2-Bromopropane
!
Br
Monohalogen derivatives of alkane are called alkyl halides
Dihalogen alkanes contain two halogen atoms.
Trihalog alkanes contain three halogen atoms.
Monohalo alkanes
The general formula is RX where is a alkyl group and X is a halogen.
Classification of Haloalkanes
A. Type of halogen atoms; Fluorides, chlorides, bromides, iodides
B. Number of halogena atoms, monohalo, dihalo, trihalo, tetra halo.
Classification of Haloalkanes
1. Compounds containing sp3 hybridization
2. Compounds containing sp2 hybridization
Compounds containing sp3 hybridization
a) halo alkances or alkyl halides
(i)Primary halogenoalkanes
In a primary (1°) halogenoalkane, the carbon which carries the halogen atom is only attached to one other alkyl group.
Secondary halogenoalkanes
In a secondary (2°) halogenoalkane, the carbon with the halogen attached is joined directly to two other alkyl groups, which may be the same or different.
Tertiary halogenoalkanes
In a tertiary (3°) halogenoalkane, the carbon atom holding the halogen is attached directly to three alkyl groups, which may be any combination of same or different.
b) Allylic halides: Halogens attached to alkenes to a carbon atom next to carbon-carbon double bond.
c) Benzylic halide (aralalkyl halide): Halogens attached to alkenes to a carbon atom next to to an aromatic ring (not to a carbon atom in the aromatic ring). It is attached to a carbon atom which is inturn attached to a carbon atom in the aromatic ring.
2. Compounds containing sp2 hybridization
a) Vinylic halides: Halogens attached to alkenes to a carbon atom of one of the carbon atoms of a double bond.
B) Aryl halides: Halogens attached to alkenes to a carbon atom of an aromatic ring
Nomenclature – Alkyl and Aryl halides
Nomenclature of alkyl halides
Common system
The monohalogen derivatives of alkanes are called alkyl halides. These are named by naming the alkyl group attached to halogen and adding the name of the halide.
Ex: Methyl halide, Isobutyl halide
The name of the alkyl group and halide are written as two separate words. The prefixes used to distinguish alkanes like n-, iso-, sec-, tert, etc. are also written.
IUPAC System
The monohalogen derivatives of alkanes are called haloalkanes.
The names of haloalkanes are written by prefixing the word ‘halo’ (bromo or chloro or iodo or fluoro) to the name of the alkane corresponding to the longest continuous carbon chain holding the halogen atom.
Ex: Bromoethane
Rules for naming haloalkanes having branches in carbon chains
1. The longest continuous chain containing the carbon attached to halogen group is selected as the parent alkane (principal chain or parent chain). In naming alkanes all rules that apply to alkane names are to be followed.
2. The carbon atoms are numbered in such a way that the carbon atom carrying the halogen atom gets the lowest number.
3. The position of the halogen atom and other substituents are indicated by numbers 1,2,3… etc.
Ex: 1-Iodo-2-methylpropane
Dihalo derivatives
1. When both the halogen atoms are attached to the same C-atom, these are called geminal dihalides. Alkylidene dihalides or alkylidene halides are also names used for such compounds.
Ex: ethlydine dichloride
2. When the two halogen atoms are in adjacent C-atoms, they are called vicinal dihalides. They are prepared from alkenes and hence they are named as the dihalide of the alkene from which they are prepared.
Ex: ethylene dichloride
Polyhalo derivatives
Ex: Trichloromethane
Fully halogenated hydrocarbons are also called perhalohydrocarbons under common system.
Nomenclature of aryl halides
Aryl halides are termed Haloarenes in IUPAC systems. The prefix ‘halo” ((bromo or chloro or iodo or fluoro) is placed before the name of the aromatic hydrocarbon. In case of disubstituted compounds, the relative positions are indicated by (1,2), (1,3) or (1,4). Ortho, meta and para are also used to indicate the positions.
Ex: Chlorobenzene, Bromobenzene
They are classified according to the number of halogen atoms that replace hydrogen atoms in the alkane.
Monohalogen derivatives: They contain only one halogen atom.
e.g. CH-3Cl Methyl chloride
CH-3-CH-CH-3 2-Bromopropane
!
Br
Monohalogen derivatives of alkane are called alkyl halides
Dihalogen alkanes contain two halogen atoms.
Trihalog alkanes contain three halogen atoms.
Monohalo alkanes
The general formula is RX where is a alkyl group and X is a halogen.
Classification of Haloalkanes
A. Type of halogen atoms; Fluorides, chlorides, bromides, iodides
B. Number of halogena atoms, monohalo, dihalo, trihalo, tetra halo.
Classification of Haloalkanes
1. Compounds containing sp3 hybridization
2. Compounds containing sp2 hybridization
Compounds containing sp3 hybridization
a) halo alkances or alkyl halides
(i)Primary halogenoalkanes
In a primary (1°) halogenoalkane, the carbon which carries the halogen atom is only attached to one other alkyl group.
Secondary halogenoalkanes
In a secondary (2°) halogenoalkane, the carbon with the halogen attached is joined directly to two other alkyl groups, which may be the same or different.
Tertiary halogenoalkanes
In a tertiary (3°) halogenoalkane, the carbon atom holding the halogen is attached directly to three alkyl groups, which may be any combination of same or different.
b) Allylic halides: Halogens attached to alkenes to a carbon atom next to carbon-carbon double bond.
c) Benzylic halide (aralalkyl halide): Halogens attached to alkenes to a carbon atom next to to an aromatic ring (not to a carbon atom in the aromatic ring). It is attached to a carbon atom which is inturn attached to a carbon atom in the aromatic ring.
2. Compounds containing sp2 hybridization
a) Vinylic halides: Halogens attached to alkenes to a carbon atom of one of the carbon atoms of a double bond.
B) Aryl halides: Halogens attached to alkenes to a carbon atom of an aromatic ring
Nomenclature – Alkyl and Aryl halides
Nomenclature of alkyl halides
Common system
The monohalogen derivatives of alkanes are called alkyl halides. These are named by naming the alkyl group attached to halogen and adding the name of the halide.
Ex: Methyl halide, Isobutyl halide
The name of the alkyl group and halide are written as two separate words. The prefixes used to distinguish alkanes like n-, iso-, sec-, tert, etc. are also written.
IUPAC System
The monohalogen derivatives of alkanes are called haloalkanes.
The names of haloalkanes are written by prefixing the word ‘halo’ (bromo or chloro or iodo or fluoro) to the name of the alkane corresponding to the longest continuous carbon chain holding the halogen atom.
Ex: Bromoethane
Rules for naming haloalkanes having branches in carbon chains
1. The longest continuous chain containing the carbon attached to halogen group is selected as the parent alkane (principal chain or parent chain). In naming alkanes all rules that apply to alkane names are to be followed.
2. The carbon atoms are numbered in such a way that the carbon atom carrying the halogen atom gets the lowest number.
3. The position of the halogen atom and other substituents are indicated by numbers 1,2,3… etc.
Ex: 1-Iodo-2-methylpropane
Dihalo derivatives
1. When both the halogen atoms are attached to the same C-atom, these are called geminal dihalides. Alkylidene dihalides or alkylidene halides are also names used for such compounds.
Ex: ethlydine dichloride
2. When the two halogen atoms are in adjacent C-atoms, they are called vicinal dihalides. They are prepared from alkenes and hence they are named as the dihalide of the alkene from which they are prepared.
Ex: ethylene dichloride
Polyhalo derivatives
Ex: Trichloromethane
Fully halogenated hydrocarbons are also called perhalohydrocarbons under common system.
Nomenclature of aryl halides
Aryl halides are termed Haloarenes in IUPAC systems. The prefix ‘halo” ((bromo or chloro or iodo or fluoro) is placed before the name of the aromatic hydrocarbon. In case of disubstituted compounds, the relative positions are indicated by (1,2), (1,3) or (1,4). Ortho, meta and para are also used to indicate the positions.
Ex: Chlorobenzene, Bromobenzene
Aldehydes - Ketones - Introduction and Nomenclature
Aldehydes contain carbonyl group C=O as functional group and the carbonyl atom carries at least one H atom.
Ketones
In ketones, also carbonyl group C=O is the functional group. But the carbonyl carbon does not contain any H atoms, but it is attached to two alkyl or aryl groups.
Getting an aldehyde from methylbenzene - by oxidation
Getting ketone from alcohols - By oxidation of secondary alcohols
Aldehydes and ketones are polar molecules because the C=O bond has a
dipole moment:
• Their polarity makes aldehydes and ketones have higher boiling points than
alkenes of similar molecular weight.
Aldehydes and Ketones – Nomenclature
Nomenclature of Aliphatic Aldehydes
Common system
Aldehydes are named according to the name of the corresponding acid which they form on oxidation.
The suffix –ic acid of the name of the acid is replaced by aldehyde.
Ex: The aldehyde that gives acetic acid is termed as acetaldehyde.
Braching in the aldehyde chain, is indicated by carbon atom positions α, β, γ, δ.
The carbon atom next to the carbonyl carbon is assigned the letter α. The carbon next to α-carbon is the β-carbon. The carbon next to β-carbon is the γ-carbon. The carbon next to γ-carbon is the δ Carbon.
δ - γ- β- α carbons
C-C-C-C-CHO
Ex: α-Methyl butyraldehyde
IUPAC system
Aldehydes are termed alkanals. The terminal ‘e’ of the name of corresponding alkane is replaced by ‘al’.
Ex: methanal, ethanal, propanal.
Nomenclature for Aldehydes with Branches
1. The longest chain containing –CHO group is considered as the parent chain and the name is derived as an alkanal.
2. To determine the number of the carbon where a substituent is attached to the aldehyde chain, the carbons in the chain are numbered in such a way that the aldehydic group carbon gets lowest number (i.e 1). In other words number of the aldehydic chain carbons is started from the carbon in the carbonyl group.
Nomenclature of Aromatic Aldehydes
The simplest aromatic aldehyde is benzaldehyde. In aromatic aldehydes, -CHO group is directly attached to the benzene ring.
In case of substituted aromatic aldehydes, the positions of the substituents in benzene ring with respect to –CHO group are indicated either by suffixes ortho, meta or para or by numbers 1,2,3… etc. with the carbon bearing the –CHO group as number 1.
Ex; 2-Hydroxybenaldehyde – OH is the substituent at the 2 carbon from CHO group.
The aldehydic group (CHO) can be a part of the side chain. In other words, an aldehydic group may be attached to benzene ring.
The name will be as an example 2-Phenylethanal. In this compound CH2CHO is attached to a benzene ring. The substituent is ethanal group, and the numbering of carbon atoms still starts from CHO group carbon and the terminology indicates that a benzyl group is attached to ethanal at 2nd carbon.
Nomenclature of Ketones
Common system
Ketones are named by using the names of alkyl groups present in the molecule.
Ex: Dimethyl ketone, Methyl isopropyl ketone
IUPAC system
Ketones are termed as alkanones.
Rules for arriving at names
1. The longest chain carrying the carbonyl groupis considered as the parent chain and the name is derived by replacing the terminal ‘e’ of the name of the corresponding alkane by letters ‘one’.
Ex: Propanone
2. In case of substituted ketones, theparent chain is numbered in such a way that the ketone group carbon gets the lowest number (but the numbering does not start from ketone group carbon – caron attached with a double bond to oxygen).
3. The position of carbonyl group and the substituents is indicated by numbers.
Ex: 3-methylbutan-2-one (indicated that there is methyl group at 3rd carbon and carbonyl group at 2nd carbon on butanone.
Compounds having both aldehyde and ketone groups.
For compounds having both aldehyde and ketone groups, the aldehyde group is considered as the principal functional group and ketonic group is regarded as substituent. It is named as prefix oxo- along with a number to indicate its position.
Ex: 2-Methyl-4-oxohexanal
Aromatic Ketones
Purely aromatic or mixed aromatics ketones are know by their common names.
Examples
Acetophenone – Methyl phenyl ketone
Propiophenone – Ethyl phenyl ketone
Benzophenone - Diphenyle ketone
IUPAC 1993 recommendation for 3 same functional groups
If an unbranched chain is directly bonded to more than two same functional groups, the organic compound is named as a derivative of parent alkane which does not include the carbon atoms of the functional groups. These compounds are named by use of suffix tricarboaldehyde (for three –CHO groups).
Ex: Butane-1,2,4-tricarbaldehyde
If three groups are not directly bonded to the unbranched carbon chain, the two like groups are considered in the parent chain and are named by using di before the name of the functional group. The third group forming the side chain is considered as a substituent group.
Ex: 3-Formylmethylhexane-1,6-dial (three –CHO groups are there. But at 1 and 6 they are directly bonded. At three there is a branching of the alkane chain and –CHO is attached to the methyl group of the branch).
Ketones
In ketones, also carbonyl group C=O is the functional group. But the carbonyl carbon does not contain any H atoms, but it is attached to two alkyl or aryl groups.
Getting an aldehyde from methylbenzene - by oxidation
Getting ketone from alcohols - By oxidation of secondary alcohols
Aldehydes and ketones are polar molecules because the C=O bond has a
dipole moment:
• Their polarity makes aldehydes and ketones have higher boiling points than
alkenes of similar molecular weight.
Aldehydes and Ketones – Nomenclature
Nomenclature of Aliphatic Aldehydes
Common system
Aldehydes are named according to the name of the corresponding acid which they form on oxidation.
The suffix –ic acid of the name of the acid is replaced by aldehyde.
Ex: The aldehyde that gives acetic acid is termed as acetaldehyde.
Braching in the aldehyde chain, is indicated by carbon atom positions α, β, γ, δ.
The carbon atom next to the carbonyl carbon is assigned the letter α. The carbon next to α-carbon is the β-carbon. The carbon next to β-carbon is the γ-carbon. The carbon next to γ-carbon is the δ Carbon.
δ - γ- β- α carbons
C-C-C-C-CHO
Ex: α-Methyl butyraldehyde
IUPAC system
Aldehydes are termed alkanals. The terminal ‘e’ of the name of corresponding alkane is replaced by ‘al’.
Ex: methanal, ethanal, propanal.
Nomenclature for Aldehydes with Branches
1. The longest chain containing –CHO group is considered as the parent chain and the name is derived as an alkanal.
2. To determine the number of the carbon where a substituent is attached to the aldehyde chain, the carbons in the chain are numbered in such a way that the aldehydic group carbon gets lowest number (i.e 1). In other words number of the aldehydic chain carbons is started from the carbon in the carbonyl group.
Nomenclature of Aromatic Aldehydes
The simplest aromatic aldehyde is benzaldehyde. In aromatic aldehydes, -CHO group is directly attached to the benzene ring.
In case of substituted aromatic aldehydes, the positions of the substituents in benzene ring with respect to –CHO group are indicated either by suffixes ortho, meta or para or by numbers 1,2,3… etc. with the carbon bearing the –CHO group as number 1.
Ex; 2-Hydroxybenaldehyde – OH is the substituent at the 2 carbon from CHO group.
The aldehydic group (CHO) can be a part of the side chain. In other words, an aldehydic group may be attached to benzene ring.
The name will be as an example 2-Phenylethanal. In this compound CH2CHO is attached to a benzene ring. The substituent is ethanal group, and the numbering of carbon atoms still starts from CHO group carbon and the terminology indicates that a benzyl group is attached to ethanal at 2nd carbon.
Nomenclature of Ketones
Common system
Ketones are named by using the names of alkyl groups present in the molecule.
Ex: Dimethyl ketone, Methyl isopropyl ketone
IUPAC system
Ketones are termed as alkanones.
Rules for arriving at names
1. The longest chain carrying the carbonyl groupis considered as the parent chain and the name is derived by replacing the terminal ‘e’ of the name of the corresponding alkane by letters ‘one’.
Ex: Propanone
2. In case of substituted ketones, theparent chain is numbered in such a way that the ketone group carbon gets the lowest number (but the numbering does not start from ketone group carbon – caron attached with a double bond to oxygen).
3. The position of carbonyl group and the substituents is indicated by numbers.
Ex: 3-methylbutan-2-one (indicated that there is methyl group at 3rd carbon and carbonyl group at 2nd carbon on butanone.
Compounds having both aldehyde and ketone groups.
For compounds having both aldehyde and ketone groups, the aldehyde group is considered as the principal functional group and ketonic group is regarded as substituent. It is named as prefix oxo- along with a number to indicate its position.
Ex: 2-Methyl-4-oxohexanal
Aromatic Ketones
Purely aromatic or mixed aromatics ketones are know by their common names.
Examples
Acetophenone – Methyl phenyl ketone
Propiophenone – Ethyl phenyl ketone
Benzophenone - Diphenyle ketone
IUPAC 1993 recommendation for 3 same functional groups
If an unbranched chain is directly bonded to more than two same functional groups, the organic compound is named as a derivative of parent alkane which does not include the carbon atoms of the functional groups. These compounds are named by use of suffix tricarboaldehyde (for three –CHO groups).
Ex: Butane-1,2,4-tricarbaldehyde
If three groups are not directly bonded to the unbranched carbon chain, the two like groups are considered in the parent chain and are named by using di before the name of the functional group. The third group forming the side chain is considered as a substituent group.
Ex: 3-Formylmethylhexane-1,6-dial (three –CHO groups are there. But at 1 and 6 they are directly bonded. At three there is a branching of the alkane chain and –CHO is attached to the methyl group of the branch).
Tuesday, January 29, 2008
IIT JEE Revision Alkanes Nomenclature
1. The unbranched alkanes are named according to the number of alkanes of carbons. Examples: Methane, Ethane, Propane etc.
2. For alkanes containing branched carbon chains, the principal chain of the compound needs to be determined. This is the longest continuous carbon chain in the molecule.
3. In determining the principal chain sometimes, two or more chains in the molecule may have same number of carbons in their chains. In such a case, the chain having the greater number of branches is chosen as the principal chain of the molecule.
4. Numbers have to be given for the carbon atoms, to which the branches are attached. To give numbers, principal chain of the carbon atoms is numbered from the direction that gives the lower number to the first branching point.
5. Branching groups are in general termed as substituents. Each group is to be given an IUPAC name (prefix name) and is prefixed to the name of the principal chain of the molecule.
6. Compound is named according to the pattern “number- alkyl group prefix name principal chain name”. Name of the group (prefix) and name of the principal chain are written together as one word.
7. Where there are more than one substituent groups, each substituent group must be given its own number depending on the carbon to which it was attached.
8. In case of identical substituents, prefixes di, tri, tetra etc., are used before the group prefix name to indicate number of identical groups.
9. Substituent groups are written in alphabetical order regardless of their location in the principal chain but the prefixes di, tri… as well as the prefixes tert- and sec- are ignored in deciding the alphabetical order, and the prefixes iso, neo, and cyclo are considered.
10. If the number of carbon atoms of the principal chain from either gives identical numbers to the substituent attachment carbons, the direction which gives the lower number to the first written group (according to the alphabetical order) is chosen.
Examples
2,2,4,4-Tetramethylhexane
3-Ethyl-2,2-dimethylpentane
2. For alkanes containing branched carbon chains, the principal chain of the compound needs to be determined. This is the longest continuous carbon chain in the molecule.
3. In determining the principal chain sometimes, two or more chains in the molecule may have same number of carbons in their chains. In such a case, the chain having the greater number of branches is chosen as the principal chain of the molecule.
4. Numbers have to be given for the carbon atoms, to which the branches are attached. To give numbers, principal chain of the carbon atoms is numbered from the direction that gives the lower number to the first branching point.
5. Branching groups are in general termed as substituents. Each group is to be given an IUPAC name (prefix name) and is prefixed to the name of the principal chain of the molecule.
6. Compound is named according to the pattern “number- alkyl group prefix name principal chain name”. Name of the group (prefix) and name of the principal chain are written together as one word.
7. Where there are more than one substituent groups, each substituent group must be given its own number depending on the carbon to which it was attached.
8. In case of identical substituents, prefixes di, tri, tetra etc., are used before the group prefix name to indicate number of identical groups.
9. Substituent groups are written in alphabetical order regardless of their location in the principal chain but the prefixes di, tri… as well as the prefixes tert- and sec- are ignored in deciding the alphabetical order, and the prefixes iso, neo, and cyclo are considered.
10. If the number of carbon atoms of the principal chain from either gives identical numbers to the substituent attachment carbons, the direction which gives the lower number to the first written group (according to the alphabetical order) is chosen.
Examples
2,2,4,4-Tetramethylhexane
3-Ethyl-2,2-dimethylpentane
Monday, January 28, 2008
Revision Alkenes Nomenclature
Ethene
Propene
Butene
Pentene
The rules used for naming alkenes under IUPAC system are similar to alkanes with some special ones.
i)The suffix to be used is -ene.
ii)The longest continuous chain should include both the carbon atoms of the double bond.
iii) The chain is to be numbered from the end that gives the lower number to the first carbon atom of the double bond.
iv) If there are two or more double bonds, the suffix used is -adiene or -atriene.
Some more examples
Buta-1,3-diene
Propene
Butene
Pentene
The rules used for naming alkenes under IUPAC system are similar to alkanes with some special ones.
i)The suffix to be used is -ene.
ii)The longest continuous chain should include both the carbon atoms of the double bond.
iii) The chain is to be numbered from the end that gives the lower number to the first carbon atom of the double bond.
iv) If there are two or more double bonds, the suffix used is -adiene or -atriene.
Some more examples
Buta-1,3-diene
Sunday, January 27, 2008
Saturday, January 26, 2008
IIT JEE Revision - Amines Nomenclature
Nomenclature of aliphatic amines
Common system:
In the common system, amines are called alkylamines. The suffix amines is added to the name of the corresponding alkyl group.
Ex: Methylamine, Ethylamine, Propylamine
Second common system
In the second system of the common system, primary amines are named as the amino derivatives of the corresponding hydrocarbons and are names as aminoalkanes. The position of the amino group is indicated by Arabic numeral. The numbering of the primary chain is to be done in such a way that the carbon atom containing the amino group gets the lowest possible number.
Secondary and tertiary amines are named as nitrogen substituted primary amine.
Example: N-Methylaminoethane
Primary amine is aminoethane and N-Methyl is added to it. N- indicates that the methyl group is attached to the nitrogen atom.
IUPAC system
The aliphatic amines are called alkamines. The letter ‘e’ in the alkane is replaced by suffix amine.
Ex: methanamine, ethanamine
The position of the amino group is indicated by Arabic numeral. The numbering of the primary chain is to be done in such a way that the carbon atom containing the amino group gets the lowest possible number.
Ex: 1-propanamine, 2-propanamine
Aromatic Amines
Common system
Aromatic amines are called aryl amines. Suffix amine is added to the aryl group.
IUPAC System
The simplest aromatic amine C6H5NH2 is called benzanamine.
Other aromatic amines are named as derivatives of benzenamine and positions of other groups are indicated by numbers
Ex: Benzenamine
N-Methylbenzenamine, N,N-Dimethylbenzenamine, 2-Methylbenzenamine, 3-Methylbenzenamine
In IUPAC system, benzenamine may also be written as amino benzene.
Common system:
In the common system, amines are called alkylamines. The suffix amines is added to the name of the corresponding alkyl group.
Ex: Methylamine, Ethylamine, Propylamine
Second common system
In the second system of the common system, primary amines are named as the amino derivatives of the corresponding hydrocarbons and are names as aminoalkanes. The position of the amino group is indicated by Arabic numeral. The numbering of the primary chain is to be done in such a way that the carbon atom containing the amino group gets the lowest possible number.
Secondary and tertiary amines are named as nitrogen substituted primary amine.
Example: N-Methylaminoethane
Primary amine is aminoethane and N-Methyl is added to it. N- indicates that the methyl group is attached to the nitrogen atom.
IUPAC system
The aliphatic amines are called alkamines. The letter ‘e’ in the alkane is replaced by suffix amine.
Ex: methanamine, ethanamine
The position of the amino group is indicated by Arabic numeral. The numbering of the primary chain is to be done in such a way that the carbon atom containing the amino group gets the lowest possible number.
Ex: 1-propanamine, 2-propanamine
Aromatic Amines
Common system
Aromatic amines are called aryl amines. Suffix amine is added to the aryl group.
IUPAC System
The simplest aromatic amine C6H5NH2 is called benzanamine.
Other aromatic amines are named as derivatives of benzenamine and positions of other groups are indicated by numbers
Ex: Benzenamine
N-Methylbenzenamine, N,N-Dimethylbenzenamine, 2-Methylbenzenamine, 3-Methylbenzenamine
In IUPAC system, benzenamine may also be written as amino benzene.
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