Geometrical isomers are compounds with the same molecular formula but different arrangements of functional groups on either side of a double or ring bond with restricted rotation. There are several types of geometrical isomers including cis-trans isomers, E-Z isomers, and syn-anti isomers. Cis isomers have functional groups on the same side of the carbon chain while trans have them on opposite sides. The configuration of double bond substituents is described as E or Z depending on the priority of the groups. Geometrical isomers can have different physical and chemical properties as well as biological activity.

1. Geometrical isomers
Presented by-
Ranadeep Borgohain
M.Pharm 2nd Semester
Department of Pharmacy
Tripura University
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2. CONTENT
• What is isomer?
• Classification of isomer
• What is geometrical isomer?
• Characteristics of geometrical isomer
• Cis-tran isomer
• E-Z isomer
• Rules for finding E-Z isomer
• Syn-anti isomers
• Use of geometrical isomer
• Reference
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3. What is isomer?
• Compounds that have the same molecular
formula.
1
2 3
4
H
H
H
H
H
H
H H
H
H
butane
CH3 CH3
CH3
isobutane
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4. CONSTITUTIONAL
ISOMERS
STERIOISOMERS
CONFORMATIONAL
ISOMERS
CONFIGURATIO
NAL ISOMERS
ROTATION ABOUT
SINGLE BODIES AMINE INVERSION
GEOMETRIC
AL ISOMERS
ISOMERS
CONTAINING CHIRAL
CENTRES
CIS-TRANS
ISOMERS
E-Z ISOMERS SYN ANTI ISOMERS
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5. CIS-TRANS
ISOMERS
E-Z ISOMERS
SYN-ANTI
ISOMERS
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6. What is geometrical isomers?
• Compounds with different arrangements of
groups on either side of a bond with restricted
rotation, such as a double bond or a single
bond in a ring
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7. Characteristics of geometrical isomer
• Different physical properties
- Different density
- Polarity
- solubility
- melting point
- boiling point
• Different arrangement
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8. CIS-TRANS ISOMERS
• Cis isomers are the isomers where functional
group are on the same side of the carbon
chain.
CH3 CH3
H H
cis-but-2-ene
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9. • Trans isomers are the isomers where the
functional groups are on opposing sides of the
carbon chain.
CH3
CH3H
H
trans-but-2-ene
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10. E-Z ISOMERS
• It is an extension of Cis–trans isomer notation
that can be used to describe double bonds
having two, three or four substituent.
• If the two groups of higher priority are on
opposite sides of the double bond, the bond is
assigned the configuration E .
E-But-2-ene
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11. • If the two groups of higher priority are on the same
side of the double bond, the bond is assigned the
configuration Z .
(Z)-But-2-ene
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12. RULES FOR FINDING E-Z ISOMERS
• Rule 1: high atomic number high priority
CH3
Br Cl
H
The z isomer
Cl
Br CH3
H
The E isomer
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13. • Rule 2: If an atom is doubly bonded to another
atom, the priority system treats it as if it were singly
bonded to two of those atoms. If an atom is triply
bonded to another atom, the priority system treats
it as if it were singly bonded to three of those
atoms.
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14. • Rule3: In the case of isotopes (atoms with the
same atomic number, but different mass
numbers), the mass number is used to determine
the relative priorities
CH3
CH3
CH2
H
D
The Z isomer
CH2
CH3
CH3
H
D
The E isomer
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15. SYN- ANTI ISOMERS
• This type used for stereoisomeric oxime.
Anti isomer Where H and OH is trans syn isomer Where H and OH is ciz
N
OH
H NOH
H
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16. USE OF GEOMETRICAL ISOMERS
H
H
OH
OH
H
H
OH
OH
trans-DEC cis-DES
(Estrogenic) (non estrogenic)
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17. H
N
NCH3
Triprolidine (E)
Trans isomer, i.e., E, is 1000-times more histaminic than cis, Z
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18. Me
MeMe
OH
Vitamin A has all E double bonds, any Z
would make it inactive!
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19. REFERENCE
• https://www.slideshare.net/dragnerkar
• https://www.slideshare.net/sofiamubashir
• https://m.youtube.com/watch?v=hyWgF6Dnit
Y
• https://www.chemguide.co.uk/basicorg/isom
erism/geometric.html
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