JEE Important Chapter - General Organic Chemistry (GOC)

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

\[HA\rightleftharpoons H^{+}+A^{\Theta }\]

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)₃H - C - (CH3)2 > -CH2 - CH3 > - CH3

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

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

2. 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.,

• π-bond, σ-bond, and ⊕/vacant orbital

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

• π-bond, σ-bond, and lone pair

• π-bond, σ-bond, and free radical

• π, σ, π-bond

• lp, σ-bond, and ⊕

3. 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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2. Free Radical: CH3- CH2.

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3. Alkene: CH3 - CH = CH2

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4. 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., 10−6sec- 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, 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 center. The types of electrophile are:

1. Positively Charged Electrophile

Examples: 

H^⊕, Cl^⊕,Br^⊕,Cl^⊕,H₃C^⊕

       2. 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.

Nucleophile

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

Types of nucleophiles

1. Neutral Nucleophiles

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

2. Charged Nucleophiles

RO-, -NH2, RNH , R2N- , HS-  , RS-  , RSe- , CL-  , Br- , I-  , F-  , CN- , -OH , RCO2-

Example for two types of nucleophiles

JEE General Organic Chemistry  (GOC)

GOC (General Organic Chemistry ) is a course that covers the fundamental ideas of organic Chemistry . In the study of somewhat complex topics, a good comprehension of the concepts covered by GOC is essential (such as the mechanisms of named reactions). Keeping this in mind, this essay explains all general organic Chemistry principles in a clear and straightforward manner. To get all of the notes in this article, click the link below (in PDF format).

GOC Important Topics

The following are some of the most important subjects in general organic Chemistry :

• Nucleophiles and Electrophiles

• (+I and -I Effects) Inductive Effect

• (+E and -E Effects) Electromeric Effect

• Hyperconjugation

• Mesomeric Influence

• The Resonance Effect and Resonance

• Stereoisomerism and structural isomerism are two types of isomerism.

GOC Fundamentals

Components of an Organic Reaction in General

The following is an example of a typical reaction mechanism:

Reactants + Catalyst or Energy → Intermediate (Transition State) → Product

The production of an intermediate from the chemical reaction between the reactants is aided by proper reaction conditions. These intermediates are usually unstable, and they react swiftly to produce a finished product.

An organic reaction's reactants are categorized as follows:

• Reagents are reactive chemical species that start a reaction by attacking another.

• In an organic reaction, the substrate is the species that is attacked by the reagent.

The location of reagent assault varies depending on whether the reagent is electrophilic or nucleophilic:

Electrophiles are electron-deficient organisms that assault the substrate in an area with a high electron density.

Nucleophiles are entities with a lot of electrons that like to donate them. Nucleophiles usually attack the reagent at an area with a low electron density.

Bond Cleavage and Reaction Intermediates

Existing chemical bonds are broken and new chemical bonds are formed in most chemical processes. A covalent bond can be broken in two ways:

Homolytic Fission occurs when a covalent connection is broken and each participating atom is left with one unpaired electron. Free radicals are chemical entities that are formed as a result of homolytic fission. They are quite receptive (due to their unstable electron configurations).

Heterolytic Fission occurs when a covalent connection is split such that one atom maintains both electrons while the other atom retains none. The creation of an ion pair — a positively charged cation and a negatively charged anion – is a feature of heterolytic fissions.

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