The in "MS Chauhan Organic Chemistry PDF 105" most likely refers to a specific page number (Page 105) in the book "Problems and Solutions in Organic Chemistry for JEE (Main & Advanced)" by M.S. Chauhan .

Here is an typically found on or around Page 105 of this specific book: Feature: The "Trick-Based Approach" to Elimination vs. Substitution (E1/E2/SN1/SN2) On Page 105, the book typically introduces a highly structured, decision-tree style logic chart for predicting whether a reaction will undergo E2 elimination or SN2 substitution . This is one of the most challenging conceptual hurdles in Organic Chemistry.