1
ORGANIC MOLECULES
NOMENCLATURE OF ORGANIC COMPOUNDS
TERMS AND DEFINITIONS
An organic compound in which H atoms in an alkane have been substituted
Alcohol with hydroxyl groups (-OH groups). General formula: CnH2n + 1OH
Organic compounds having the general structure RCHO where R = H or alkyl.
Aldehydes
General formula: RCHO (R = alkyl group)
An organic compound containing only C-H and C-C single bonds.
Alkane
General formula: CnH2n + 2
A compound of carbon and hydrogen that contains a carbon-carbon double bond.
Alkene
General formula: CnH2n
Alkyl group A group formed by removing one H atom from an alkane.
Alkyne A compound of carbon and hydrogen that contains a carbon-carbon triple bond.
Carbonyl group Functional group of ketones (>C=O)
Carboxyl group Functional group of carboxylic acids (-COOH)
An organic compound containing a carboxyl group (-COOH group).
Carboxylic acid
General formula: CnH2n + 1COOH (or RCOOH)
Chain isomers Compounds with the same molecular formula, but different types of chains.
Condensed structural A formula that shows the way in which atoms are bonded together in the molecule but
formula DOES NOT SHOW ALL bond lines.
A bond or an atom or a group of atoms that determine(s) the physical and chemical
Functional group
properties of a group of organic compounds.
Functional isomers Compounds with the same molecular formula, but different functional groups.
An organic compound in which one or more H atoms in an alkane have been
Haloalkane
replaced with halogen atoms.
(Alkyl halide)
General formula: CnH2n + 1X (X = F, Cℓ, Br or I)
A series of organic compounds that can be described by the same general formula
and that have the same functional group.
Homologous series OR
A series of organic compounds in which one member differs from the next with a CH 2
group.
Hydrocarbon Organic compounds that consist of hydrogen and carbon only.
A chemical nomenclature (set of rules) created and developed by the International
IUPAC naming Union of Pure and Applied Chemistry (IUPAC) to generate systematic names for
chemical compounds.
A chemical formula that indicates the type of atoms and the correct number of each in
Molecular formula
a molecule, e.g. CH4.
Organic chemistry Chemistry of carbon compounds.
Compounds with the same molecular formula, but different positions of the side
Positional isomer
chain, substituents or functional groups on the parent chain.
The C atom bonded to the hydroxyl group is bonded to ONE other C atom.
Example:
Primary alcohol
C C O H
H H
, MAFSCIENCE PRIVATE TUTORING
H
H H
The C atom bonded to the halogen is bonded to ONE other C atom.
Example:
Primary haloalkane H H
C C HBr
H H
Compounds in which there are no multiple bonds between C atoms in their
hydrocarbon chains.
Saturated compounds
OR
Compounds with only single bonds between C atoms in their hydrocarbon chains.
TERMS AND DEFINITIONS
The C atom bonded to hydroxyl group is bonded to TWO other C atoms. Example:
H H
H C C O H
Secondary alcohol H
H C H
H
The C atom bonded to the halogen is bonded to ONE other C atom.
Example:
H H
H C C Br
Secondary haloalkane
H
H C H
H
A structural formula of a compound shows which atoms are attached to which within
Structural formula the molecule. Atoms are represented by their chemical symbols and lines are used to
represent ALL the bonds that hold the atoms together.
Structural isomer Organic molecules with the same molecular formula, but different structural formulae.
Substituent A group or branch attached to the longest continuous chain of C atoms in an organic
(branch) compound.
The C atom bonded to the hydroxyl group is bonded to THREE other C atoms.
Example:
H
H C H
H
Tertiary alcohol
H C C O H
H
H C H
H
, MAFSCIENCE PRIVATE TUTORING
The C atom bonded to the halogen is bonded to THREE other C atoms.
Example:
H
H C H
H
Tertiary haloalkane
H C C Br
H
H C H
H
Unsaturated Compounds in which there are multiple bonds (double or triple bonds) between C
compounds atoms in their hydrocarbon chains.
WRITING IUPAC NAMES OF ORGANIC COMPOUNDS
The name of each organic molecule has three parts:
prefix parent suffix
Type and position of Number of C atoms Type of functional group
substituents in the longest chain? or homologous series
Step 1: Suffix
• Determine the functional group in the structure of the given compound or the homologous series
to which the compound belongs.
• The functional group or homologous series determines the suffix (last part of the name).
Step 2: Parent name
• The number of C atoms in the longest carbon chain that contains the functional group determines
the parent name.
• Count the number of C atoms in the longest chain containing the functional group.
Number of carbon atoms 1 2 3 4 5 6 7 8
Parent name meth eth prop but pent hex hept oct
• Alkanes and haloalkanes: Number from the side that will give the substituents the smallest
numbers.
• Alkenes, alkynes, alcohols, ketones: Number from the side that will the functional group the
smallest number. The functional group receives a number that is written between parent name and
suffix.
• Aldehydes and carboxylic acids: Number from the C atom that forms part of the functional group.
• Esters: To determine the first part of the name, count the C atoms attached to the single bonded
O atom of the functional group. Add –yl to this part e.g. ethyl.
To determine the last part of the name, number from the C atom bonded to the O atom with a
double bond. Add the -anoate to this part e.g. butanoate.
Step 3: Prefix
• Identify substituents on the parent chain. Substituents can be methyl (one C atom i.e. –CH3) or
ethyl (2 C atoms i.e. –CH2CH3).
, MAFSCIENCE PRIVATE TUTORING
• Use numbers on the parent chain to indicate the position of the substituents on the parent
chain.
• Arrange substituents in alphabetical order in the IUPAC name (bromo, chloro, ethyl, methyl)
• If two or more of the same substituents occur, use di- and tri- in front of the name of the substituent
e.g. dimethyl or tribromo. (Di- and tri are ignored when arranging substituents in alphabetical order.)
• When there are two (or more) identical groups on the same C atom, the number of the C atom is
repeated with commas between the numbers e.g. 2,4,4-trimethylhexan-3-one
• Final IUPAC names, except those of esters, are written as one word with COMMAS BETWEEN
NUMBERS and HYPHENS BETWEEN NUMBERS AND WORDS e.g. 2,4,4-trimethylhexan-3-
one. IUPAC names of esters and carboxylic acids are written as two words e.g. ethyl methanoate
and pentanoic acid.
EXAMPLES
Step 2: Parent Step 3:
Compound Step 1: Suffix
name Substituents
H H H A hydrocarbon Three C atoms in Methyl group on C2.
H C C C H with C-C single longest chain:
3 2 1 bonds only, thus prop- 2-methylpropane
H H an alkane. Ends
H C H propane
on -ane
H
H A triple bond Five C atoms in One methyl group
H H longest chain: on C4.
between C
H C C C C C H atoms, thus -pent-
5
4 3 2 1
an alkyne. 4-methylpent-1-yne
H H
H C Ends on -yne Triple bond after
H C1.
H
pent-1-yne
H An –OH group, Six C atoms in Methyl group on C4.
thus an alcohol. longest chain.
H C H Ends on –ol
6 4-methylhexan-2-ol
-OH group on
H C H C2.
5
H H H H hexan-2-ol
H C C C C C H
4 3 2 1
H H H O H
H
ORGANIC MOLECULES
NOMENCLATURE OF ORGANIC COMPOUNDS
TERMS AND DEFINITIONS
An organic compound in which H atoms in an alkane have been substituted
Alcohol with hydroxyl groups (-OH groups). General formula: CnH2n + 1OH
Organic compounds having the general structure RCHO where R = H or alkyl.
Aldehydes
General formula: RCHO (R = alkyl group)
An organic compound containing only C-H and C-C single bonds.
Alkane
General formula: CnH2n + 2
A compound of carbon and hydrogen that contains a carbon-carbon double bond.
Alkene
General formula: CnH2n
Alkyl group A group formed by removing one H atom from an alkane.
Alkyne A compound of carbon and hydrogen that contains a carbon-carbon triple bond.
Carbonyl group Functional group of ketones (>C=O)
Carboxyl group Functional group of carboxylic acids (-COOH)
An organic compound containing a carboxyl group (-COOH group).
Carboxylic acid
General formula: CnH2n + 1COOH (or RCOOH)
Chain isomers Compounds with the same molecular formula, but different types of chains.
Condensed structural A formula that shows the way in which atoms are bonded together in the molecule but
formula DOES NOT SHOW ALL bond lines.
A bond or an atom or a group of atoms that determine(s) the physical and chemical
Functional group
properties of a group of organic compounds.
Functional isomers Compounds with the same molecular formula, but different functional groups.
An organic compound in which one or more H atoms in an alkane have been
Haloalkane
replaced with halogen atoms.
(Alkyl halide)
General formula: CnH2n + 1X (X = F, Cℓ, Br or I)
A series of organic compounds that can be described by the same general formula
and that have the same functional group.
Homologous series OR
A series of organic compounds in which one member differs from the next with a CH 2
group.
Hydrocarbon Organic compounds that consist of hydrogen and carbon only.
A chemical nomenclature (set of rules) created and developed by the International
IUPAC naming Union of Pure and Applied Chemistry (IUPAC) to generate systematic names for
chemical compounds.
A chemical formula that indicates the type of atoms and the correct number of each in
Molecular formula
a molecule, e.g. CH4.
Organic chemistry Chemistry of carbon compounds.
Compounds with the same molecular formula, but different positions of the side
Positional isomer
chain, substituents or functional groups on the parent chain.
The C atom bonded to the hydroxyl group is bonded to ONE other C atom.
Example:
Primary alcohol
C C O H
H H
, MAFSCIENCE PRIVATE TUTORING
H
H H
The C atom bonded to the halogen is bonded to ONE other C atom.
Example:
Primary haloalkane H H
C C HBr
H H
Compounds in which there are no multiple bonds between C atoms in their
hydrocarbon chains.
Saturated compounds
OR
Compounds with only single bonds between C atoms in their hydrocarbon chains.
TERMS AND DEFINITIONS
The C atom bonded to hydroxyl group is bonded to TWO other C atoms. Example:
H H
H C C O H
Secondary alcohol H
H C H
H
The C atom bonded to the halogen is bonded to ONE other C atom.
Example:
H H
H C C Br
Secondary haloalkane
H
H C H
H
A structural formula of a compound shows which atoms are attached to which within
Structural formula the molecule. Atoms are represented by their chemical symbols and lines are used to
represent ALL the bonds that hold the atoms together.
Structural isomer Organic molecules with the same molecular formula, but different structural formulae.
Substituent A group or branch attached to the longest continuous chain of C atoms in an organic
(branch) compound.
The C atom bonded to the hydroxyl group is bonded to THREE other C atoms.
Example:
H
H C H
H
Tertiary alcohol
H C C O H
H
H C H
H
, MAFSCIENCE PRIVATE TUTORING
The C atom bonded to the halogen is bonded to THREE other C atoms.
Example:
H
H C H
H
Tertiary haloalkane
H C C Br
H
H C H
H
Unsaturated Compounds in which there are multiple bonds (double or triple bonds) between C
compounds atoms in their hydrocarbon chains.
WRITING IUPAC NAMES OF ORGANIC COMPOUNDS
The name of each organic molecule has three parts:
prefix parent suffix
Type and position of Number of C atoms Type of functional group
substituents in the longest chain? or homologous series
Step 1: Suffix
• Determine the functional group in the structure of the given compound or the homologous series
to which the compound belongs.
• The functional group or homologous series determines the suffix (last part of the name).
Step 2: Parent name
• The number of C atoms in the longest carbon chain that contains the functional group determines
the parent name.
• Count the number of C atoms in the longest chain containing the functional group.
Number of carbon atoms 1 2 3 4 5 6 7 8
Parent name meth eth prop but pent hex hept oct
• Alkanes and haloalkanes: Number from the side that will give the substituents the smallest
numbers.
• Alkenes, alkynes, alcohols, ketones: Number from the side that will the functional group the
smallest number. The functional group receives a number that is written between parent name and
suffix.
• Aldehydes and carboxylic acids: Number from the C atom that forms part of the functional group.
• Esters: To determine the first part of the name, count the C atoms attached to the single bonded
O atom of the functional group. Add –yl to this part e.g. ethyl.
To determine the last part of the name, number from the C atom bonded to the O atom with a
double bond. Add the -anoate to this part e.g. butanoate.
Step 3: Prefix
• Identify substituents on the parent chain. Substituents can be methyl (one C atom i.e. –CH3) or
ethyl (2 C atoms i.e. –CH2CH3).
, MAFSCIENCE PRIVATE TUTORING
• Use numbers on the parent chain to indicate the position of the substituents on the parent
chain.
• Arrange substituents in alphabetical order in the IUPAC name (bromo, chloro, ethyl, methyl)
• If two or more of the same substituents occur, use di- and tri- in front of the name of the substituent
e.g. dimethyl or tribromo. (Di- and tri are ignored when arranging substituents in alphabetical order.)
• When there are two (or more) identical groups on the same C atom, the number of the C atom is
repeated with commas between the numbers e.g. 2,4,4-trimethylhexan-3-one
• Final IUPAC names, except those of esters, are written as one word with COMMAS BETWEEN
NUMBERS and HYPHENS BETWEEN NUMBERS AND WORDS e.g. 2,4,4-trimethylhexan-3-
one. IUPAC names of esters and carboxylic acids are written as two words e.g. ethyl methanoate
and pentanoic acid.
EXAMPLES
Step 2: Parent Step 3:
Compound Step 1: Suffix
name Substituents
H H H A hydrocarbon Three C atoms in Methyl group on C2.
H C C C H with C-C single longest chain:
3 2 1 bonds only, thus prop- 2-methylpropane
H H an alkane. Ends
H C H propane
on -ane
H
H A triple bond Five C atoms in One methyl group
H H longest chain: on C4.
between C
H C C C C C H atoms, thus -pent-
5
4 3 2 1
an alkyne. 4-methylpent-1-yne
H H
H C Ends on -yne Triple bond after
H C1.
H
pent-1-yne
H An –OH group, Six C atoms in Methyl group on C4.
thus an alcohol. longest chain.
H C H Ends on –ol
6 4-methylhexan-2-ol
-OH group on
H C H C2.
5
H H H H hexan-2-ol
H C C C C C H
4 3 2 1
H H H O H
H
