The entire portion of organic chemistry could be easily understood if you are well versed with the general topics in organic chemistry that includes nucleophiles, electrophiles, type of reactions, basicity, acidity, etc and the remaining portion of organic chemistry is just its application part. These topics are covered in the general organic chemistry part of the JEE syllabus.
a. Named Reactions: There are several standard named reactions in organic chemistry and you should know all these named reactions along with their mechanisms so that, you could easily solve any similar type of problem asked in the question paper.
b. Organic Synthesis: It is one of the important and conceptual aspects of organic chemistry and every year in JEE Exams, around 2 to 3 questions are asked from this section that includes writing certain steps to synthesize any particular compound by the provided set of reagents with as little efforts as possible. Sometimes, you have to write the missing chemicals in any particular step of the synthesis. Therefore, it is very important to know some of the common chemical reactions.