[Indranil (OP)]

How to find sigma and pi bond? please tell me the methods, please.

[Kryptid]

Under most circumstances (I think there are some exceptions, like disulfur dinitride), any single bond will be a sigma bond, whereas any bond order greater than one will have a sigma bond plus some amount of pi bonding. So double bonds and triple bonds have pi bonds in them, as do resonance bonds like in nitrogen dioxide and aromatic bonds like in benzene rings.

In your particular example, count the number of double bonds in the whole molecule. That will tell you how many electron pairs are present in the pi bonds.

[Indranil (OP)]

Under most circumstances (I think there are some exceptions, like disulfur dinitride), any single bond will be a sigma bond, whereas any bond order greater than one will have a sigma bond plus some amount of pi bonding. So double bonds and triple bonds have pi bonds in them, as do resonance bonds like in nitrogen dioxide and aromatic bonds like in benzene rings.

In your particular example, count the number of double bonds in the whole molecule. That will tell you how many electron pairs are present in the pi bonds.
There are three pi bonds in the molecule in the diagram If I count but why 4 pi bonds are written there in the diagram?

[Indranil (OP)]

Under most circumstances (I think there are some exceptions, like disulfur dinitride), any single bond will be a sigma bond, whereas any bond order greater than one will have a sigma bond plus some amount of pi bonding. So double bonds and triple bonds have pi bonds in them, as do resonance bonds like in nitrogen dioxide and aromatic bonds like in benzene rings.

In your particular example, count the number of double bonds in the whole molecule. That will tell you how many electron pairs are present in the pi bonds.

There are three pi bonds in the molecule in the diagram If I count but why 4 pi bonds are written there in the diagram?

[Indranil (OP)]

Under most circumstances (I think there are some exceptions, like disulfur dinitride), any single bond will be a sigma bond, whereas any bond order greater than one will have a sigma bond plus some amount of pi bonding. So double bonds and triple bonds have pi bonds in them, as do resonance bonds like in nitrogen dioxide and aromatic bonds like in benzene rings.

In your particular example, count the number of double bonds in the whole molecule. That will tell you how many electron pairs are present in the pi bonds.

If I count there are 3 pi bonds in the molecule but 4 is written in the diagram. so how is it possible?

[chiralSPO]

The COOH part has a pi bond between the C atom and one of the O atoms. That is the fourth.

[Kryptid]

There was no need for you to ask the same question three times in a row.

[loosi007]

Usually, all bonds between atoms in most organic compounds contain one sigma bond each. If it is a single bond, it contains only sigma bond. Double and Triple bonds, however, contains sigma and pi bonds. Double bonds have one each, and triple bonds have one sigma bond and two pi bonds.

1 single bond = 1 sigma bond

1 double bond = 1 sigma bond + 1 pi bond

1 triple bond = 1 sigma bond + 2 pi bonds