General Organic Chemistry (GOC) For JEE

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GOC in Chemistry

We know that organic chemistry is the study of carbon compounds. However, organic chemistry comes under GOC. Now, what is GOC?

GOC stands for General Organic Chemistry.

General organic chemistry is the gateway to organic chemistry which talks about the following things:

  1. How does any reaction happen?

  2. Determines which reaction occurs at pace among the two reactions.

  3. Probability of any short-lived species, i.e., reaction intermediate forming a product.

  4. Determines whether the reaction is acidic or basic.

To understand GOC, it’s necessary to know IUPAC nomenclature.


GOC Chemistry

General Organic Chemistry Class 11 includes the following organic chemistry topics that we will study in this article:

  1. Electron displacement effects

  2. Species: Intermediates between the reactions

  3. Reaction mechanism


Electron Displacement Effects

The types of electron displacement effects are:

  1. The inductive effect (An important concept)

  2. Resonance effect 

  3. Hyper-conjugation effect or Baker-Nathan effect

The effects mentioned above are permanent except for the electromeric effect.

Let’s discuss these one-by-one

1. Inductive Effect

The inductive effect is of two types:

  1. - I effect

  2. + I effect

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Here, X is an electronegative element. So a partial negative charge δ develops on X.

This effect is also known as an electron-withdrawing effect or a negative inductive effect. Since Y is less electronegative than C, δ develops on Y. Here, Y is an electron-donating group. That’s why it is known as the electron-donating inductive effect.


Acidic Order

HA ⇌ \[H^+\] + \[A^Θ\]

Let’s take an example to determine the acidic order among the four species:

  1.  (CH3)3 -  C -OH

  2. H - C - (CH3)2 - OH

  3. CH3 - CH2 - OH

  4. CH3 - OH

Here, (CH3)3 -  C -OH has a tertiary alkyl group, and three CH3 gives electrons to the C-atom, and this C-atom, in turn, displaces electrons to the O-atom.

Here, O is already electronegative, on getting more electrons in its cloud, 

(CH3)3 - C -OH becomes unstable because of which O doesn’t allow the release of H+ ions.

In H - C - (CH3)2 - OH, chances of the release of H+ ions are there but very less in number.

However, in CH3 - CH2 - OH is more and the maximum release of H+ ions in CH3 - OH.


According to the Inductive Effect Order

-C(CH3)3 > - H - C - (CH3)2 > -CH2 - CH3 > - CH3

The acidic order of these elements is 4 > 3 >2 >1.

This means, more the + I effect is, the acidic nature decreases.


Resonance Effect

The resonance effect is a hypothetical phenomenon in which the shifting/displacement or movement of π-electrons occurs within the compound. It is an intra-molecular phenomenon that occurs on a double bond only. As we can see in the diagram below:

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All these resonating structures are imaginary.

The resonance occurs when there is a conjugation, i.e.,

  1. π-bond, σ-bond, and ⊕/vacant orbital

           CH2 = CH - CH2 ↔️ CH2 -CH = CH2 (Hybrid structure -  CHδ+2 = CH= CH2δ+   

  1. π-bond, σ-bond, and lone pair

  2. π-bond, σ-bond, and free radical

  3. π, σ, π-bond

  4. lp, σ-bond, and ⊕


Hyper-Conjugation Effect

It is a no-bond resonance, also known as a σ-bond p-orbital resonance.

Hyper-conjugation in the following species:

  1. Carbocation: CH3 - CH2

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  1. Free Radical: CH3- CH2.

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  1. Alkene: CH3 - CH = CH2

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  1. Carbanion: CH3 - CH2

Practically, hyper-conjugation doesn’t take place in carbanion because of the absence of a vacant orbital. Therefore, the inductive effect decides its stability.  

 

 Reaction Intermediate

The reaction intermediates formed during the reaction are hypothetical. Moreover, they have a brief period, i.e., \[10^{-6}\]sec- few seconds.

Reaction intermediates decide the final product and one of the most famous reaction intermediates is the ‘Carbocation’. After carbocation, we have:

  1. Carbanion

  2. Free radical

  3. Carbenes

  4. Nitrenes

  5. Benzene.

We will study Carbocation. Let’s take an example for the same:

H3C - X where X is an electronegative element.

X captures both the electrons between itself and the C-atom. Then,

                 H3C - X → - X-→  H3C

Here, the species,  H3C is a carbocation.

This means an atom more electronegative than a C-atom breaks the bond and captures the electrons from it and goes away. This is how carbocation forms. Since C and X are different, so this is Heterolysis.


Reaction Mechanism

This will include the following:

Any reaction occurring has such type of expression: S + R = P,  i.e., S and R forms P.

Where,

S = substrate or reactant, which is the main molecule on which reaction happens or the changes occur. The following effects can happen in the substrate, i.e.,

  1. Inductive Effect

  2. The resonance or the mesomeric effect.

R = Attacking reagent; this R makes changes in the substrate.

P = Product

Types of attacking reagents are: 

  1. Electrophile

  2.  Nucleophile


Electrophile

An electrophile is an electron-deficient species that attacks at the electron-rich centre. The types of electrophile are:

  1. Positively Charged Electrophile

Examples: \[H^⊕\] , \[Cl^⊕\] , \[Br^⊕\] , \[Cl^⊕\] ,\[H_3C^⊕\]

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  1. Incomplete Octet Electrophile (neutral)

The strength order of bonding: BF3 > BCl3 > BBr3 > BI3

The strongest bond forms in BF3 because F is smaller in size and wishes to share the electron with B to complete its octet.

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Nucleophile

A nucleophile is an electron-rich species that attacks the electron-deficient centre.

Types of nucleophiles

1. Neutral Nucleophiles

H2O , NH3 , RNH2 , R2NH , R3N , ROH , RCOOH , RSH and PR3

2. Charged Nucleophiles

RO- , -NH2 , R\[\overline{N}\]H , R2N- , HS-  , RS-  , RSe- , CL-  , Br- , I-  , F-  , CN- , -OH , RCO2-

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Example for two types of nucleophiles

FAQ (Frequently Asked Questions)

Q1: Is GOC important for JEE?

Ans: Yes, GOC is very important for exams like NEET, JEE and many other competitive examinations. As it covers the entire fundamental concepts of organic chemistry, you need to have a thorough knowledge. You need to spend considerable time understanding the Ins and Outs of this topic and solve problems related to the same. Then only you can gain mastery over it.

Q2: How can I master GOC for JEE?

Ans: Following are the tips for mastering GOC for JEE:

  1. Build a grip on the fundamental concepts of General Organic Chemistry or GOC.

  2. Understand the reaction mechanisms and practice these mechanisms.

  3. For understanding GOC, the knowledge of IUPAC nomenclature becomes important.

  4. Spend considerable time, and practice a lot of problems each day.

Q3: Is Organic Chemistry Difficult?

Ans: A famous quote says that many things seem unachievable only as long as one does not attempt them. The same is with organic chemistry. All it requires is 3Ps: patience, persistence and practice.

Q4: Is NCERT enough for JEE Main?

Ans: NCERT builds up your base. However, to be up-to-date with JEE Main preparation, you need to look out for external resources like online tutorials.