MODULE 3:
ORGANIC CHEMISTRY
Organic Chemistry
- l
Development of Organic Chemistry
Friedrich Wohler
- Father of Organic Chemistry
- First scientist that isolated an organic compound
- Ammonium cyanate (Inorganic)→Urea (Organic)
Carbon atoms link together to form chains of varying
length, branched chains and rings of different sizes
Catenation
- Ability of atoms in forming stable bonds with itself,
hence joining up into chains or rigs
- C—C>Si—Si>Ge—Ge>Sn—Sn
- Bond strength as bond length
- C—C>N—N>O—O
- Bond strength
- As the number of lone pairs
-
CnH2n+2n = 1,2,3,… (no limit for n)
Sin H2n+2n = 1 to 6 only, silanes
GenH2n+2n = 1 to 3 only, germanes
SnnH2N+2* Only SnH4 (stagnate) exists
Structure and Bonding
ATOMIC STRUCTURE
Organic compounds found in living things:
- Sugars
- Lipids
- Protein
- Nucleic acids
Differences between Inorganic Chemistry and
Organic Chemistry
Organic Compounds
Inorganic Compounds
1. Organic compounds
usually do not dissolve in
water
1. Inorganic compounds
usually dissolve in water
2. Organic compounds
generally dissolve in
organic solvents like ether,
alcohol, benzene and
chloroform
2. Inorganic compounds
generally do not dissolve in
organic solvents
3. Organic compounds
have usually low melting
points and boiling points,
and they usually
decompose on heating
- Ernest Rutherford - Goldfoil experiment
- Neihl Bohr - Planetary
- Nucleus - Proton & Neutron
- Electron
- Atomic number: Number of protons
- Atomic mass: number of protons + neutrons in
varying isotopes
3. Inorganic compounds
usually have high melting
points and boiling points.
They usually do not
decompose on heating
4. Organic compounds are 4. Inorganic compounds
inflammable; they catch fire are usually noneasily
inflammable; they do not
burn easily
5. Organic compounds
5. Most of the inorganic
exist as covalent
compounds are ionic, so
molecules, so they are non- they are electrolytes
electrolytes
The Unique Nature of Carbon:
- ability to form four strong covalent bonds
- Electron configuration of carbon (ground state):
1s²2s²2p²
- [↑↓] [↑↓] [↑ ][↑ ][ ]
- Each carbon atom has four unpaired electrons
when excited
- Tend to form four strong covalent bonds
- [↑↓][↑ ][↑ ][↑ ][↑]
- 4 atoms — tetrahedron — can hold another carbon
Ability to Catenate
- Mass number: number of protons + neutrons
Carbon
Atomic number: 6
Atomic mass: 12.011
Mass number: 12
Protons: 6
Neutrons: 6
Electrons: 6
ISOTOPES:
- Same atomic numbers BUT different mass numbers
Carbon-12
98.9%
6 protons
6 neutrons
Carbon-13
1.1%
6 protons
7 neutrons
Carbon-14
6 protons
8 neutrons
ISOBARS
- same mass number but contain different elements
ISOTONES
- same number of neutron but different elements
Name
Atomi
c
Numb
er
Proto
ns
Neutr
ons
Electr
ons
Mass
Numb
er
Atomi
c
Mass
Hydro
gen
1
1
1
1
1
1.008
Heliu
m
2
2
2
2
4
4.003
Lithiu
m
3
3
3
3
7
6.941
Berylli
um
4
4
4
4
9
9.012
Boron
5
5
5
5
11 10.811
Carbo
n
6
6
6
6
12 12.011
Ionic Bond
- bond between two atoms caused by electrostatic
attraction of plus and minus charged ions
- Involves complete transfer of electrons between two
atoms of widely different electronegativities to form
ions
- Positively charged ions are called cations
- Negatively charged ions are called anions
- Sign and magnitude of the charge on an ion is
called ionic charge
Covalent Bond
- bond formed by sharing of electrons (in pairs)
between two atoms
- A single covalent bond between elements is called
single bond or sigma bond
- Elements can share MORE than one pair of
electrons between each other four electrons are
shared (two bonds): double bond
- Six electrons are shared (three bonds): triple bond
- Sigma bond: 1st bond made with any other atoms,
made of hybridized orbitals
- Pi bond: any 2nd or 3rd bond made with other
atoms, made from leftover pi bonds
Electronegativity
- ability of an atom to attract its outer shell electrons
and electrons in general (Linus Pauling)
- Electronegativity increases from the left to the right
of the periodic table and from the bottom to the top
Formal Charge
- difference between the number of outer-shell
electrons “owned” by a neutral free atom and the
same atom in a compound
Ownership of electrons
- unshared electrons “belong” to the parent atom 1/2
of bonded electrons between a pair of atoms is
assigned to each atom
- Formal charge = [# of valence e-] - [# of nonbonding e-] - 1/2 [# of bonding e-]
- Formal charge = Valence electron - {bonds + dots)
Resonance Theory
- electrons that are fixed between two atoms are
called localized
- A single lewis structure can describe a molecule. In
some molecules a single Lewis structure CANNOT
describe the electronic structure adequately
- The negative charge is NOT localized at one atom
but delocalized over several atoms
Resonance Structures
- valid Lewis structure with the same connectivity,
differing only in the location of the electrons.
Individual resonance structure DO NOT exist
Resonance Hybrid
- “average” of the resonance forms used to describe
a molecule or ion that cannot be described by a
single structure
Hybrid Orbitals
Carbon undergoes 4 covalent bonds
- however it does not only has two single occupied p
orbitals and one filled s orbital in its outer shell
- When it undergoes four bonds it is tetrahedral
(bond angle of 109.5)
Hybridization
- mixing of two or more non-equivalent atomic
orbitals to form a new set of equivalent orbitals.
Sp3 : when a carbon is bonded to form 4 other atoms
with no lone electron pair (tetrahedral) - 109.5º
Sp2 : when a carbon atom bond to 3 atoms (2 single
bonds, 1 double bond) - 120º
Sp : when a carbon is bound to two other atoms (2
double bonds/1single bond + triple bond) - 180º
Group
Hybridization
1
S
2
Sp
3
Sp2
4
Sp3
PHYSICAL PROPERTY
- A property that does not affect the chemical identity
of a compound
- Can be observed and measured without changing a
compound’s composition of matter (Qualitative
Assessment)
• Any substance that has and can occupy space
Three Physical States of Matter
SOLID
- Particles are tightly packed and close together
- Particles do move but not very much
- Definite shape and definite volume (because
particles are packed closely and do not move)
- Most solid are crystals
- Crystals are made of unit cells (repeating patterns)
- The shape of a crystal reflects the arrangement of
the particles within the solid
LIQUID
- Particles are spread apart
-
Particles move slowly through a container
No definite shape but do have a definite volume
Flow from one container to another
Viscosity - resistance of a liquid to flowing
• Thixotropy - fluids whose viscosity decreases upon
application of stress (shear stress). Ex. Honey,
Gelatin, Xanthan Gum
• Rheopexy - anti-thixotropy, fluids whose viscosity
increases upon application of stress (shear
stress). Ex. Gypsum, Pastes, Lubricants, Printer’s
Ink
GASES
- Particles are very far apart
- Particles move very fast
- No definite shape and no definite volume
- Kinetic molecular theory of gas
• Total volume of gas molecules is negligible as
compared to the volume of space in which they
are confines
• Gas particles do not attract one another but rather
move independently from each other
• Particles exhibit continuous random movement
due to kinetic energy
• Gas particles exhibit perfect elasticity
PHYSICAL CHANGES
Solubility
- if the solvent is polar, like water, then a smaller
hydrocarbon component and/or more charged,
hydrogen bonding, and other polar groups will tend
to increase the solubility
- The number of carbons. More carbons means more
of a non-polar/hydrophobic character, and thus
lower solubility in water
- Anything with a charged group (eg. Ammonium,
carboxylate, phosphate) is almost certainly water
soluble, unless it has large non polar group, in
which case it will most likely be soluble in the form
of micelles, like a soap or detergent
- Solubility - maximum amount of solute expressed in
grams that can be dissolved 100g of water. (SolidLiquid)
- Miscibility - ability of one substance to mix to
another substance. (Liquid-Liquid)
- Any functional group that can donate a hydrogen
bond to water (eg. Alcohols, amines) will
significantly contribute to water solubility
- Any functional group that can only accept a
hydrogen bond from water (eg. ketones, aldehydes,
ethers) will have a somewhat smaller but significant
effect on water solubility
- Other groups that contribute to polarity (eg. Alkyl
halides, thiols sulfides) will make a small
contribution to water solubility
Solubility according to United States Pharmacopoeia
(USP)
Term
Solubility Factor (solute 1g)
Very soluble
<1
Freely soluble
1-10
Soluble
10-30
Sparingly soluble
30-100
Slightly soluble
100-1000
Very slightly soluble
1000-10000
Practically insoluble/
Insoluble
>10000
Boiling Point and Melting Point
- melting and boiling are processes in which noncovalent interactions between identical molecules in
a pure sample are disrupted. The stronger the non
covalent interactions, the more energy that is
required, in the form of heat, to break them apart
- ↑Molecular Weight = ↑VanderWaals = ↑Boiling Point
- Length of Carbon Chains
• Molecules with higher molecular masses have
higher melting point, boiling point and density
• Higher molecular masses
- Large molecular sizes
- Stronger London dispersion forces among
molecules
• Molecules with branched chains
- Boiling point and density lower than its
straight-chain isomer
- Straight chain isomers have greater surface
area in contact with each other
- Greater attractive force among the molecules
- Within the branched series, increased
symmetry leads to higher melting point, lower
boiling point
• As a rule, larger molecules have higher boiling
(and melting) points
CHEMICAL PROPERTIES
- a chemical reaction occurs when one substance is
converted into another substance
- A chemical reaction is accompanied by breaking of
some bonds and by making of some others
Evidence of Chemical Changes
- evolution of gas
- Formation of precipitate
- Emission of light
- Generation of electricity
- Production of mechanical energy
- Absorption/liberation of heat
Processes involved in Chemical Changes
- Oxidation - chemical union of oxygen with another
substance; donation of electron
- Reduction - oxygen is removed from a compound;
H is added; receives electron
- Neutralization - ACID + BASE = SALT (Neutral
Compound)
- Hydrolysis - reaction of water on a salt forming
ACID and BASE
- Saponification- a reaction between Alkali (NaOH Hard Soap; KOH - Soft Soap) + fats/oils forming
SOAP
- Fermentation - reaction of microorganism on
organic substances resulting to the production of
ALCOHOL
Reaction Mechanism
- defined as the detailed knowledge of the steps
involved in a process in which the reactant
molecules change into products
- Chemical reactions involve breaking of one or more
of the existing chemical bonds in reactant
molecule(s) and formation of new bonds leading to
products
- The breaking of a covalent bond is known as bond
fission
- During bond breaking or bond fission, the two
shared electrons can be distributed equally or
unequally between the two bonded atoms
Hemolytic Fission
- the fission of a covalent bond with equal sharing of
bonding electrons - absence of charge
• Free radicals are neutral but reactive species
having an unpaired electron and there can also
initiate a chemical reaction
Heterolytic Fission
- the fission of a covalent bond involving unequal
sharing of bonding electrons
- This type of bond fission results in the formation of
ions. The ion which has a positive charge on the
carbon atom, is known as the carbonic ion or a
carbocation. On the other hand, an ion with a
negative charge on the carbon atom is known as
carbanion
- The charged species obtained by the heterolytic
fission initiate chemical reactions and they are
classified as electrophiles and nucleophiles
- Electrophiles - an electrophile is an electron
deficient species and it may be positively charged
or neutral.
- Examples are H+, N+O2, Br+, Cl+, Ag+, CH3+CO,
BF etc.
- Nucleophiles - a nucleophile is negatively charged
or electron rich neutral species
- Examples of nucleophiles are OH-, -NO2,
H2O, :NH3 etc.
The different types of reactions in organic compounds
are:
Substitution
- a substitution reaction involves the displacement of
one atom or group in a molecule by another atom or
group. Aliphatic compounds undergo nucleophilic
substitution reactions
- For example a haloalkane can be converted to a
wide variety of compounds by replacing halogen
atom(X) with different nucleophiles.
- Another type of substitution reaction which takes
place in an aromatic hydrocarbons. In this case, an
electrophilic reagent attacks the aromatic ring
because the latter is electron rich. The leaving
group in this case, is always one of the hydrogen
atom of the ring
Elimination
- an elimination reaction is characterized by the
removal of a small molecule from adjacent carbon
atoms and the formation of a double bond
Addition
- unsaturated hydrocarbons such as alkenes and
alkynes are extremely reactive towards a wide
variety of reagents. The carbon-carbon double bond
(—C=C—) of an alkene contains two types of
bonds. In alkynes, three carbon-carbon bonds.
Molecular Rearrangements
- a molecular rearrangement proceeds with a
fundamental change in the hydrocarbon skeleton of
the molecule. During this reaction, an atom or group
migrates from one position to another.
MODULE 3:
ISOMERISM
Steriochemistry
- branch of chemistry that is concerned with 3D
arrangement of atoms and molecules and its effect
on chemical reaction
Isomers
- compounds having the same molecular formula
and same molecular weight but different structural
formula, thus differ in physical and chemical
properties
- “Iso” - Same/equal, “Meros” - parts same
molecular formula but different in structural
formula.
Structural arrangement
- arrangement of atoms which gives the compound a
particular structure
Spatial arrangement
- arrangement of atoms in 3D geometry in a
particular atom
Structural Isomerism (Constitutional)
- compounds which have the same molecular
formula but differ in their structure are called
structural isomers
- The phenomenon is called structural isomerism
1. Chain Isomerism
- These isomers differ in the chain of the carbon
atoms
2. Functional Isomerism
- These isomers differ in the type of functional
group
3. Positional Isomerism
- these isomers differ in the attachment of the
functional group to the chain at different
positions
4. Metamerism
- Exhibited by those compounds in which
functional group comes in between the carbon
chain and breaks the continuity of the chain
- This breaking occurs at different positions and
different isomers are formed which are called
meters
Sterioisomerism
- exhibited by the compounds which have similar
attachment of atoms but differ in their arrangement
in space
1.Geometrical Isomerism
2. Optical Isomerism
Geometric Isomerism
- a cis-isomer is the one having identical groups on
same side of double bond
- A trans-isomer has identical groups on opposite
side
- Geometrical Isomerism in Drugs
• Geometrical isomers have different
physicochemical proper and pharmacological
activity (e.g. cis-diethylbestrol has only 7% of the
estrogenic activity of trans-diethylbestrol —
“morning after pill”)
- Entgegen - Apart; Zusammen - Same
Optical Isomerism
- compounds having at least one carbon atom joined
to four different atoms or groups
- Such a carbon atom is called asymmetric or chiral
carbon atom; and those which are not chiral (do
not have four different groups) are called achiral.
- The optical isomers have identical physical
properties except optical activity
- They rotate the plane of plain polarized light
opposite directions
- The plain polarized light is defined as the light that
vibrates in one plane only
- The rotation of the plane of polarized light is called
optical activity
- Those substances that can rotate the plane of
polarized light are said to be optically active
Enantiomer
- non-superimposable mirror image
- Same physicochemical property
Cahn-ingold-prelog priority
- atomic number of individual atoms attached to
chiral carbon
1. Rank atoms (1,2,3,4)
2. Ensure that #4 is at the back
3. Cross out #4
4. Trace arc 1→2→3
• S-Counterclockwise
• R-Clockwise
Polarimeter (Dextro-Right; Levo-left)
Dextrorotatory Compounds
- compounds that rotate the plane of plane polarized
light to the right (clockwise)
- Denoted by “d” or (+) before the name of the
compound
Levorotatory Compounds
- compounds that rotate the plane to the left (anti
clockwise)
- This is denoted by placing “l” or (-) before the name
of the compound
Racemic Mixture
- a mixture containing equal amounts of d- and lisomers
- Optically inactive denoted by dl or +
Importance of Chirality in Drugs
- Approximately 50% of marketed drugs are chiral.
- The two enantiomers of a chiral drug may differ
significantly
• The two enantiomers may have pharmacokinetic
differences or pharmacodynamic differences
Stereoisomerism in Drugs
- (+) Warfarin - loger half-life, less distributed, less
potent
- (-) Warfarin - shorter half-life, more distributed,
more potent
- (S)-(+)- Ibuprofen - pharmacologically active
- (R)-(-)- Ibuprofen - pharmacologically inactive (no
anti-inflammatory activity
- (-) Thalidomide - Teratogenic - causes phocomelia
- (+) Thalidomide - has therapeutic activity, used for
morning sickness and as a sedative
Diasteriomer
- Non-mirror image, non-superimposable
- Different physic-chemical properties
- With at least 2 chiral center
Epimer
- a special type of diastereomer
- Identical in all aspect except one chiral center
Anomer
- differ only in carbonyl C or anomeric carbon
- Alpha - opposite
- beta - same
MODULE 3:
INTRODUCTION TO
ORGANIC MOLECULES AND
FUNCTIONAL GROUPS
Functional Groups
- this pertains to a specific group of atoms that bond
within a compound that is responsible for the
characteristic chemical reaction of a chemical
compound
- The same functional group will behave in a similar
fashion by undergoing similar reaction regardless of
the compound of which it is a part of.
- Members in the same series can be represented by
a general formula
• alkanes (hydrocarbon): CnH2n+2
• alkenes (hydrocarbon): CnH2n
•
•
•
•
alkynes (hydrocarbon): CnH2n-2
alkanols (alcohol): CnH2n+1OH
alkanals (aldehydes-carbonyl): CnH2n+1CHO
alkanoic acids (carboxylic acid): CnH2n+1COOH
Hydrocarbons
Alipathic - chains
a. Saturated - Single bond only
- Alkene (single)
• General formula: CnH2n + 2
b. Unsaturated - contains multiple bonds (double,
triple)
- Alkene (double)
• General formula: CnH2n
- Alkyne (triple
• General formula: CnH2n-2
Aromatic - presence of ring
Alcohol
- R-OH
13
Tridec-
14
Tetradec-
15
Pentadec-
16
Hexadec-
17
Heptadec-
18
Octadec-
19
Nonadec-
20
Eichos-
Alkane - Prefix # + -ane
Factors Affecting the Physical Properties of
Organic Compounds
Structure of Functional Group
- Molecules having a polar functional (two atoms do
not share equally in covalent bond) group have a
higher b.p. than others with a non-polar functional
group of similar molecular masses
Carbonyl (Aldehyde/Ketone)
Aldehyde
- R-CHO
Ketone
- R-COR
Carboxylic Acid
- R-COOH
Homologous Series
- the physical properties change gradually along the
homologous series e.g. the longer the carbon chain
in the molecule ( or the greater the molecular mass)
• The greater the attractive force between molecules
the higher the melting point, boiling point and
density
- members of a homologous series have similar
chemical properties
Number of Carbons
Prefix
1
Meth-
2
Eth-
3
Prop-
4
But-
5
Pent-
6
Hex-
7
Hept-
8
Oct
9
Non-
10
Dec-
11
Undec-
12
Dodec-
Solubility of Organic Molecules
- Depends on the polarity of organic molecules and
the solvent
• Non-polar or weakly polar compounds dissolve
readily in non-polar or weakly polar solvents
• Highly polar compounds dissolve readily in highly
polar solvents
• “Like dissolves like”
- Molecules having OH or NH2 groups are able to
form hydrogen bonds
- Hydrogen bonds affect the physical properties of
alcohols and amines with low molecular masses
- Formation of Hydrogen Bonding
• it also affect the solubility of a molecule
• Molecules with OH groups are able to form
hydrogen bonds with surrounding water molecules
- Length of Carbon Chains
• Molecules with higher molecular masses have
higher m.p., b.p. and density
• Higher molecular masses
- Large molecular size
- Stronger London dispersion forces among
molecules
Molecules with branched chains
Intermolecular - bond between 2 or more
molecules
Van der Waals
A. Induced dipole-induced dole (London
- b.p. and density lower than its straight-chain isomer
(straight-chain isomers have greater surface area in
contact with each other)
- Greater attractive force among the molecules
- m.p. ihigher than its straight-chain isomer
Branched-chain isomers are more spherical
- packed more efficiently in solid state
- Extra energy is needed to break down the efficient
packing
NOMENCLATURE OF
ORGANIC COMPOUNDS
Nomenclature
- a scientific way of naming compounds for
identification
MODULE 3:
Types of Nomenclature
Systermatic Name/IUPAC Name (Refers to structures)
- Name composed wholly or especially coined or
selected syllables (hexane, thiazole)
- Internation Union of Pure and Applied Chemistry
Trivial Name/Common Name (refers to compounds,
independent of structure and sometime given before
the structure is known
- a name no part of which is used in a systematic
sense (furan, xanthophyll)
Semisynthetic-Semitrivial Name
- a name of which only a part is used in a systematic
sense
- Most organic compounds belong to this class
(methane, butane)
Classification of Hydrocarbons
- all organic compounds may be divided into two
broad classes based upon the pattern of chain of
carbon atoms
- Open-chain or Alipathic compounds - no ring
• Saturated - single bond (alkane)
• Unsaturated - double (alkene) or triple (alkyne)
bond
- Closed-cahin or Cyclic compounds
• Alycyclic compounds - has the presence of ring
but behave like alipathic
• Aromatic compounds - benzene is the ring
- 2 benzene rings - naphthalene
- 3 benzene rings - anthracene
Open-chain or Alipathic compounds
- This class includes all hydrocarbons (saturated and
unsaturated) and their derivatives which have openchain structures
- Saturated hydrocarbons are those which contain
single bonds between all carbon atoms (Alkane CnH2n+2 —- aka Paraffin)
- Unsaturated compounds contain a double (Alkene CnH2n —- Olefins) or a triple (Alkyne - CnH2n-2 —Acetylene)
Closed-chain or Cyclic compound
- these compounds have at least one ring (cyclic)
system. These are further divided into two subclasses: homocyclic and heterocyclic based on the
atoms present in the ring
- Homycyclic (carbocyclic)
• Alicyclic compounds:
- This group includes saturated and unsaturated
cyclic hydrocarbons which resemble with the
aliphatic hydrocarbons in properties
- Prefix “cyclo”
• Aromatic compounds:
- The group homocyclic compounds having
special set of properties are called aromatic
compounds. They also have characteristic
smell or aroma and hence called aromatic
- Homologous Series
• A series of compounds in which the molecular
formula of a compound differs from those of its
neighboring compounds by the CH2 group, is
known as a homologous series. Each of such
homologous series is given a general name
IUPAC Nomenclature of Acyclic Hydrocarbons
- in order to bring uniformity and rationality in naming
the organic compounds throughout the world,
International Union of Chemistry (in 1951) came out
with a system of nomenclature later known as
IUPAC (International Union of Pure and Applied
Chemistry) system
- The purpose of the IUPAC system of nomenclature
is to establish an international standard of naming
compounds to facilitate communication
- The goal of the system is to give each structure a
unique and unambiguous name, and to complete
each name with a unique and unambiguous
structure
Straight chain Hydrocarbons
- The names of these hydrocarbons consists of two
parts
- The first one is word root and second one is suffix.
- ROOT WORD - it indicates the number of carbon
chain also known as parent chain chosen by a set
of rules. The root words used for different length of
carbon chain (up to 20).
Number of Carbons
Prefix
1
Meth-
2
Eth-
3
Prop-
4
But-
5
Pent-
6
Hex-
7
Hept-
8
Oct
9
Non-
10
Dec-
11
Undec-
12
Dodec-
13
Tridec-
14
Tetradec-
15
Pentadec-
16
Hexadec-
17
Heptadec-
18
Octadec-
19
Nonadec-
20
Eichos-
- SUFFIX - it is again divided into two types: I)
Primary suffix and II) Secondary suffix
• Primary suffix: It is used to indicate the degree of
saturation or unsaturation in the main chain. It is
added immediately after the root word
Type of carbon chain
Primary suffix
Saturated (all C-C bonds)
-ane
Unsaturated: one C=C
-ene
Unsaturated: two C=C
-diene
Unsaturated: one C=C
-yne
Unsaturated: two C=C
-diyne
Unsaturated: one C=C &
one C=C
-enyne
• Secondary suffix: It is used to indicate the main
functional group in the organic compound and is
added immediate after the 1 o suffix
Branched chain Hydrocarbons
- In branched chain hydrocarbons, one or more alkyl
groups are present as side chain attached to the
main straight chain of carbon atoms
- The carbon atoms of the side chain constitute alkyl
groups
- These alkyl groups are written as prefixes in the
IUPAC name
- An alkyl group is obtained from an alkane by
removing one hydrogen atom
- Since the general formula of alkane is CnH2n+2,
the general formula of alkyl group is CnH2n+1
- The alkyl groups are generally represented by R—
and named by replacing the suffix and of the
corresponding alkane by yl.
Rule 1. Longest chain Rule:
- According to this rule, the longest possible chain of
carbon atoms is considered and the compound is
named as the derivative of the corresponding
alkane
- If some multiple bonds are present, the selected
chain must contain the carbon atoms of the multiple
bonds. The number of carbon atoms in the selected
chain determines the word root and the saturation
or unsaturation
- If two equally long chains are possible, the chain
with maximum number of side chains is
Rule 2. Lowest number or lowest sum rule
- The longest carbon chain is numbered from one
end to another and the positions of the side chain
are indicated by the number of carbon atoms to
which these are attached. The numbering is done in
such a way that:
• The substituted carbon atoms have the lowest
possible number.
- the sum of numbers used to indicate the positions of
various alkyl groups must be the lowest
Rule 3.
- if some multiple bond is present in the chain the
carbon atoms involved in the multiple bond should
get the lowest possible numbers
Rule 4. Naming the compounds with one alkyl group
as the substituent (side chain)
- the name of a substituted hydrocarbon consists of
the following parts
- Position of substituent - Name of substituent, Word
root, Suffix
Rule 5. Naming the same alkyl groups at different
positions or more than one alkyl groups
- if the compound contains more than one identical
alkyl groups, their positions are indicated separately
and the prefixes di (for two), try (for three) etc. are
attached to the name of the substituents
- The positions of the substituents are separated by
commas (,)
Rule 6. Naming different alkyl substituents
- if there are different alkyl substituents present in the
compound their names are written in the
alphabetical order. However, the prefixes di, try, etc.
are not considered in deciding the alphabetical
order
Alicyclic Compounds
- Alicyclic compounds have closed chain i.e. cyclic
structures hence their names are derived by putting
prefix “cyclo” before the word root
- The suffix ane, ene or yne are written according to
the saturation or unsaturation in the ring structure
- If an alkyl substituent is present, it is indicated by
the appropriate prefix and its position is indicated by
numbering the carbon atoms of the ring in such a
way so as to assign the lease possible number to
the substituent
Aromatic Compounds
- the most important members of this class are
benzene and its derivatives
- For naming an alkyl substituted benzene, the
carbon atoms of benzene are numbered from 1 to 6
by giving the lowest possible number to the position
of the side chain or substituent
- Benzene forms only one mono substituted
derivatives like methylbenzene or ethylbenzene
- However, it can form three disubstituted compounds
namely 1,2 (oath); 1,3 (meta) and 1,4 (para)
derivatives
IUPAC Nomenclature of Alipathic Organic
Compounds Containing Functional Groups
- A functional group is an atom or group of atoms
which is responsible for characteristic properties of
a compound
Compound with one functional group
(Monofunctional Derivatives):
Rule 1:
- find the highest priority functional group. Determine
and name the longest continuous carbon chain that
includes this group
Rule 2:
- the longest continuous carbon atom chain is
numbered from that end which will give the lowest
number to the carbon atom bearing the functional
group
Rule 3:
- There is a specific suffix for each functional group
that replaces the ending -e in the name of the
corresponding parent alkane
Rule 4:
- if the carbon chain is branched, then the attached
alkyl groups are named and numbered as in
structure I (rule 1) main chain contains a branch of
two carbon atoms I.e., ethyl group at position 2.
Carbonyls
Old name
1C - Form
2C - Acet
3C - Propio
4C - Butyr
5C - Valer
6C - Car
7C - Enanth
8C - Capry
9C - Pelargo
Naming of Organic compounds with more than one
functional group:
- in case of organic compounds containing more than
one functional group, one group is given preference
over the other(s) in deciding the parent compound
Family of
Compound
Prefix
Suffix
Carboxylic Acid
carboxy-
-oic acid (carbocylic acid)
Aldehyde
oxo- (formyl)
-al
(carbaldehyde)
Ketone
oxo-
-one
Alcohol
hydroxy-
-ol
Amine
amino-
-amine
Alkene
-
-ene
Alkyne
-
-yne
Amines (R-NH2)
- the root name is based on the longest chain with
the -NH2 attached
- The chain is numbered so as to give the amine unit
the lowest possible number
- The amine suffix is appended to the appropriate
10C - Capris acid
12C - Laurie acid
14C - Myristic acid
16C - Palmitic acid
18C - Stearic acid
20C - Arachidic acid
Rule 5:
- while writing the name of the compound, place the
substituents in the alphabetical order
alkyl root or alkane-root
Alcohols (R-OH)
- name the longest chain to which the hydroxyl group
is attached. Drop the -e (alkyl) then add -ol
- Number the longest chain to give the lower number
to the carbon with the attached hydroxyl group
- Locate the position of the hydroxyl group
- Locate and name any branches attached to the
chain
- Common: +yl alcohol
Polyols - (two or more -OH groups)
- the root name is based on the longest chain
containing both the alcohol groups
- The chain is numbered so as to give the one of the
alcohol groups the lowest possible number
- The appropriate multiplier (i.e. di- for two, try for
three etc.) is inserted before the -ol suffix or before
the root
Ketone (RC=OR)
- the root name is based on the longest chain
including the carbonyl group.
-The
chain
is
numbered so as to give the ketone carbonyl the
lowest possible number
• -ane + -one = -anone
•-ene + one =
-enone
alkyl group + ketone
Aldehyde (RC=OH)
- the
is
on
-common:
•
•
•
•
3C - Propio
4C - Butyr
5C - Valer
6C - Car
- Enanth
• 8C - Capry
• 9C - Pelargo
•7C
Carboxylic Acid (RC=OOH)
- the root name is based on the longest chain
including the carboxylic acid group
- Since the carboxylic acid group is at the end of the
chain, it must be C1
- -ane + -oic acid = -anoic acid
- Common: #C + ic acid
- Dicarboxylic acid
• 2C - Oxalic acid (Oh)
• 3C - Manolic acid (My)
• 4C - Succinic acid (Such)
• 5C - Glutaric acid (Good)
• 6C - Adipic acid (Apple)
• 7C - Pimelic acid (Pie)
• 8C - Suberic acid (Sweet)
• 9C - Azelaic acid (As)
• 10C - Sebacic acid (Sugar)
Example of Drug and their IUPAC name
• Generic/Trivial Name: Valproic acid
• Systematic name: 2-propylpentanoic acid
• Use: For the treatment of seizure disorder
• CI: pregnant women - may cause spinabifida
• Generic/Trivial Name: Aspirin, Acetylsalicylic acid
• Systematic Name: 2-acetoxybenzoic acid
• Use: relief of mild to moderate pain and
inflammation
root
name
based
the
longest
chain including the carbonyl group
- Since the aldehyde is at the end of the chain, it
must be C1
- -ane + -al = -anal or -ene + al = -enal
- Common: #C + aldehyde
• 1C - Form
• 2C - Acet
• Generic/Trivial Name: Thymol (isopropyl-m-cresol)
• Systematic Name: 2-isopropyl-5-methylphenol
• Use: Antiseptic in mouthwash, Anti-fungal
• Generic/Trivial Name: Diphenhydramine (Benadryl)
• Systematic Name: 2-(diphenylmethoxy)-N,Ndimethylethanamine
• Use: Relief of symptoms of allergy, Antihistamine
• Generic/Trivial Name: Cinnamaldehyde
• Systematic Name: 3-phenylprop-2-enal
• Use: flavoring, indicated for use as an aid in the
diagnosis of allergic contact dermatitis
1.
2.
3.
4.
3,8-dimethylnon-4-yne
2,6-dibromophenol
2-metheylhexanoic acid
Pentan-2-amine