Essential Concepts in Organic Chemistry: Reactions and Mechanisms

Core Concepts in Organic Chemistry

Nucleophilic Substitution Reactions

SN1 Reaction: Unimolecular Substitution

SN1 stands for Substitution Nucleophilic Unimolecular reaction. It proceeds in two steps:

1. Slow Step: Dissociation of the substrate to form a carbocation intermediate.
2. Fast Step: The carbocation combines with the attacking nucleophile.

Characteristics of SN1 reactions:

• More stable carbocation leads to a faster reaction.
• Favored by polar solvents.
• Mostly given by tertiary alkyl halides.
• Occurs with racemization.
• Follows 1st-order kinetics: Rate = k[R-X].

SN2 Reaction: Bimolecular Substitution

SN2 stands for Substitution Nucleophilic Bimolecular reaction. It proceeds in a single step, which is the rate-determining step.

Characteristics of SN2 reactions:

• Favored by non-polar solvents.
• Mostly given by primary alkyl halides.
• Nucleophilic addition takes place from the opposite side of the leaving group.
• Occurs with 100% inversion of configuration.
• Follows 2nd-order kinetics: Rate = k[R-X][Nu].

Distinguishing Alcohols and Halides

The Victor Meyer Test for Alcohols

The Victor Meyer test is a chemical test used to distinguish between primary, secondary, and tertiary alcohols. The results are color-coded:

• Primary alcohols: Produce red color.
• Secondary alcohols: Produce blue color.
• Tertiary alcohols: Produce no color.

Understanding Haloarenes and C-X Bonds

The Carbon-Halogen (C-X) bond in haloarenes is polarized because halogens are more electronegative than carbon. Due to the high electronegativity of the halogen, it attracts the electron cloud more toward itself, thus gaining a slight negative charge. Conversely, the carbon atom obtains a slight positive charge.

Defining Alkyl Halides (Haloalkanes)

The replacement of one or more hydrogen atoms in an aliphatic hydrocarbon by halogen atoms results in the formation of an alkyl halide, also known as a haloalkane.

The Sandmeyer Reaction

The Sandmeyer reaction is a type of substitution reaction that is widely used in the production of aryl halides from aryl diazonium salts.

Key Organic Reactions and Compounds

Cross Cannizzaro Reactions

A Cross Cannizzaro reaction occurs if an aldehyde without any α-hydrogen is made to react with formaldehyde in the presence of a base, yielding sodium formate and an alcohol.

DDT: Dichlorodiphenyltrichloroethane

DDT, the abbreviation for dichlorodiphenyltrichloroethane, is also called 1,1,1-trichloro-2,2-bis(p-chlorophenyl)ethane. It is a synthetic insecticide belonging to the family of organic halogen compounds. DDT is highly toxic toward a wide variety of insects as a contact poison that apparently exerts its effects by disorganizing ..