Part 3

Compound having the same
molecular formula and same molecular
weight but different structural formula, thus
differ in physical and chemical properties

Compound which have the same
molecular formula but differ in their structure
are called

The simplest hydrocarbons: methane
(CH4), ethane (CH3 CH3), and propane
(CH2CH2CH3)- have

there are two different butanes,
C4H10, and these two molecules, called

These isomers differ in the chain of the carbon atoms
- Increasing carbon = increased isomerism

These isomers differ in the type of functional group
- Ether and alcohols
- Carboxylic acid and ester
- Aldehyde and ketone
- Propanone and Propanal

These isomers differ in the
attachment of the functional group to
chain at different positions

This type of isomerism arises due to the presence of different alkyl chains on each side of the functional group
It is a rare type of isomerism and is generally limited to molecules that contain a divalent atom (sulfur or oxygen), surrounded by alkyl groups.
- Typically, on ETHERS
- Example: C4H10O can be represented as
ethoxyethane (C2H5OC2H5) and
methoxypropane (CHeOC3H7)

Isomer of the compound which only
differs in the position of protons and
electrons
It occurs via an intramolecular proton
transfer
- Equilibrium

An important example of this tauromers is

One of the isomers has an open-
chain structure whereas the other has a ring
structure

Are isomers that have the same
composition (that is, the same parts) but that
differ in the orientation of those parts in
space
- Geometrical
- Optical

It is popularly known as cis-trans
isomerism

These isomers have different spatial
arrangements of atoms in three-dimensional
space.

is the one having identical groups on same side of double bond

has identical groups on opposite side

Compounds having at least one
carbon joined to four different atoms or
groups

Such carbon atoms are called
asymmetric or chiral carbon atom; and
those which are not chiral (do not have four
different groups) are called

Optical Isomers =

no superimposable mirror
image; differ in optical activity (can be
rotated) (polarized light)

light rays in particular direction: controllable

The rotation of the plane of polarized light
is called

Compound that rotate the plane of plane
polarized light to the right (clockwise) are
said to be

is denoted by d or (+)
before the name of the compound

Compounds that rotate the plane to the
left (counterclockwise) are called

This is denoted by placing l or (-) before
the name of the compound

A mixture containing equal amounts of d-
and I- isomers us called _________and is optically inactive denoted by dl or ±

polarized light to the left

When a double bond is attached to 3
or 4 Non-hydrogen substituents, there are
some example where cis-trans
nomenclatures would be rendered ineffective
in describing the substituent’s orientation in
geometric isomers. In this situation, the
rigorous IUPAC system will use

High ranked substituents on opposite
sides

higher ranked substituents on the same
side