First Point of Difference Rule | Organic Chemistry | Explained by IITian | Jee Mains, Advance | NEET - Videos


Hello guys, In this Video we will discuss “First point of Difference Rule” in organic chemistry.

Don’t sum locants!
Simply put, there is NO IUPAC rule based on summing the locants despite what you may have been taught elsewhere!

However, to be honest, the sum idea works in most cases (unfortunately). But, learning the “sum rule” typically means one doesn’t take the time to learn the first point of difference rule which is required in several other situations. Therefore, it is recommended that you learn the first point of difference rule as you will probably need to learn it at some point anyway, and it really isn’t any more difficult to learn!

(summing a list of numbers versus comparing a list of numbers written in numerical order).


for each possible numbering scheme, list out the locants in numerical order
compare the “lists” to locate the first point of difference, i.e. the first time you encounter a low number
at the first point of difference, select the lower locant choice.

In this video we are discussing some examples of the application of the first point of difference rule to generate the correct name where the “sum rule” fails.

Hope you will enjoy the lecture.

Team IITian Explains
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  1. Thank u very much sir …I can't say how much ur video are help me….ap chem se love hone loga ..he ……ur teaching style are just osm….. 😘😘😘😘 …love u sir

  2. Sir vaise to mera neet 2018 m selection ho gya h VMMC,Delhi m but jab aapki video ka notification dekha to khudh Ko video dekhne s nahi rok paya
    Thankyou so much sir


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