Electronic Displacement Effects (aka General Organic Chemistry or GOC) – A brief review from the desk of Mohit Ryan (Senior Chemistry Faculty, guru of AIR 95 and an alumnus of IIT Kharagpur)
Let me begin with a short story —->
4th april 2014….
One of my students called me and said “Sir, I have completed all chapters of organic but I’m not confident enough in any chapter because I am unable to get the correct answers specially in GOC ( General Organic Chemistry) and end up scoring negative marks in every other question”
I asked him – “Where do you think the problem is? What are the weak areas??”
He replied, “Sir general organic chemistry mein approach kaise lena hai aur uska use kaise karna hai samajh nhi aa raha (Translation : I’m unable to understand the approach that I should take and how to utilize it in GOC). So, I’m not having confidence in any unit of organic ”
I was taken aback on hearing this from one of my good students because JEE MAIN was just around the corner … it is fatal to suffer from low confidence at this crucial time!
The truth was a tad different. He was really panic-stricken as he knew not having high confidence in organic can cost him terribly. High self confidence actually implies high probability of choosing correct option otherwise you suffer from the 50-50-90 RULE which works pretty well in organic chemistry 😛
[50-50-90 rule – anytime you have 50-50 chance of choosing correct option there is a 90% chance that you will get it wrong 😉 ]
What happened next?
He sat with me on that very same day for straight six hours (his studying capacity was tremendous….almost equal to my yet another student, Aakash Kapoor (Founder, Prepsera), and completed each and every bit of the concepts related to GOC. That gave a tremendous surge to his confidence. I WAS FINALLY HAPPY TO SEE HIM CONFIDENT. He practiced a lot (which supposedly is the prime requirement to do well in organic chemistry). He solved around 300+ problems on that day itself. That cheered him up 🙂
On 9th April in the JEE MAIN examination, he scored 115/120 in chemistry and that too in 15-16 minutes! INSPIRATIONAL… isn’t it?
Below are my tips which will enable you to achieve this feet
WHAT IS THE IMPORTANCE OF THIS CHAPTER ?
- Undoubtedly, this is the basic building block of entire organic chemistry. Quite obviously, to strengthen organic chemistry, the first step is to know all the concepts of this chapter and then, of course, isomerism. ISOMERISM = IMAGINATION. 3-D visualization ability is something you must develop over the time by working out loads of questions.
- For any reaction mechanism, say roughly around 70% of organic chemistry requires quick and correct application of electronic displacement effects (EDEs).
- Without having a good grip over EDEs, you will certainly follow what we can call a poor-muggle-way of learning organic chemistry – “memorization way”. Mark my words, you can never grasp concepts of organic chemistry with this method. Concepts have to be made and strengthened to understand Organic Chemistry.
- An inconvenience – NCERT also forces you to study organic chemistry without Mechanism. Therefore, you don’t find specific chapters on Electronic Displacement Effects and Isomerism in NCERT. The few mechanisms given in NCERT don’t require in-depth knowledge of displacement effects. Sadly, all this forms only a small fraction of JEE syllabus. Hence, NCERT fails here.
WHICH BOOKS TO FOLLOW ?
If you are a student of some coaching institute, then first revise your class-notes. Solving worksheets is important. They are sufficient for the required practice on this chapter. If you are doing self-study and have gone through this blog, then I’m sure you have already gone through the recommended book section by Aakash (AIR 95) – the same books are to be followed.
‘Your desire to succeed and the passion can drive you crazily towards your goal’.
The boy in this story was, no doubt, weak in organic chemistry. However, as soon as he gained his confidence by working on his conceptual knowledge, he actually came out as a WINNER. Driven by his strong desire, he kept working hard – day and night. I would also emphasize on the fact that he prepared for JEE in just 5 months. Surprisingly, he cleared JEE IN JUST 5 MONTHS!!
IMPORTANT CONCEPTS OF THE CHAPTER
We can easily conclude here that anyone who wants to keep organic chemistry at their finger tips must first be strong in GOC .
Important permanent electronic effects are:
- Inductive effect
- Mesomeric effects
- Steric inhibition of protonation
- Steric inhibition of resonance
Out of these, mesomeric effect is very important. This is because it is an effect related to pi electrons/movable electrons. Well, movement of electrons is the deciding factor in any mechanism. It would be really fruitful if you master inductive effect first and then move on to mesomeric effect. This will actually let you understand the difference between these two effects and how to apply them properly.
To catch the concepts of this chapter the topic-by-topic preferred order is-
- Mastering Inducticve Effect — Inductive effect is of two types +I and -I. Students often tend to miss the real concept and they take it as something easy. Of course it is easy, but you should and you must understand this effect through the concept of ELECTONEGATIVITY THAT WORKS well for sigma bonds than for pi or movable electrons. If you don’t understand inductive effect from the electronegativity point of view, it will be quite tough for you. (I will definitely try to give some examples in future articles )
- Mesomeric effect — The most important effect of all and it must be mastered by first learning about the +M and -M groups and then by learning about the conjugated systems which must be present for resonance to occur. Learn this effect from point of view of “FLOW OF ELECTRONS IS FROM HIGHER TO LOWER ELECTRON DENSITY “. This concept might ease your work.
- Hyperconjugation — Works well for alkene and carbocation and questions are basically framed in which there is stability to be compared. Also if we have aromatic rings carrying an alkyl group (infact YOU SHOULD BE HUNTING FOR THIS SITUATION RIGHT FROM THE START when you come across aromatic rings based questions 😉 ] then that ring is bound to have extra electron density due to the effect of +H.
Learning point of view:
The strength of MESOMERIC EFFECT > HYPERCONJUGATION > INDUCTIVE EFFECT. This pattern, however is not followed by HALOGENS, things get reversed in such a case. Basically, to sum up, whenever your heart says think about ” inductive effect” your brain should instantly recall that HYPERCONJUGATION needs to be checked out first (not considering the halogens).
Quite obviously, I can’t make you visualize everything. I’m not lecturing you in my classroom (which, I wish, should be the case to make you understand it completely) but what I’m trying to tell you is that you should follow these subtle tips and the point of view or the approach to solve any problem of organic chemistry should be in the same way as I discussed above. I will write later about a yet another important part i.e. how to command the logical approach to organic chemistry!!
Steric inhibition of protonation and Steric inhibition of resonance
Both of these effects are called ortho effects and are useful if one has to understand the relative comparison of acidic and basic strengths of organic compounds. In fact, they break the usual pattern in which acidic an basic strength appears to be when viewed through the general concepts.
THE BOY IN THE STORY IS RITVIK RAWAT. HE SECURED AIR 948 IN JEE ADV 2014 WITH ALMOST FULL MARKS IN ORGANIC AND IS STUDYING COMPUTER SCIENCE AT IIT GUWAHATI AT PRESENT. ONE OF THE COOLEST PERSON I have ever seen and one who has always been an INSPIRATION.
If by any means, you think that I forgot to mention any topic, or if you still have problems in ANY part of organic, feel free to mention it in your comments.
All the Best…