Preparation of Alkenes Part 2

 Pyrolytic Eliminations

Pyrolytic elimination reactions are those in which the elimination occurs through heating and involves a cyclic transition state. These reactions occur without requiring the addition of external reagents like acids or bases. Instead, the heat provides the necessary energy to facilitate the elimination.

Preparation of Alkenes

Preparation of Alkenes

1. Dehydrohalogenation of alkyl halides:

Alkenes can be prepared by the elimination of hydrogen halide from an alkyl halide. Hydrogen and halogen are removed from adjacent carbon atoms, resulting in the introduction of a carbon-carbon double bond in the molecule.

Nomenclature of Alkenes

 Nomenclature of Alkenes

Introduction to Alkenes

 Alkenes

Introduction

Alkenes are hydrocarbons that contain at least one carbon-carbon double bond. They follow the general formula C_nH_2n. A double bond makes them unsaturated and more reactive than alkanes.

Olefins is another name for alkenes, derived from "olefiant gas" (oil-forming gas). This term historically referred to ethene () because it reacts with chlorine to form an oily liquid.

Reactions of Alkanes

 Reactions of Alkanes

1. Halogenation of Alkanes

Halogenation is a substitution reaction where hydrogen atoms in alkanes are replaced by halogens (Cl, Br). The reaction occurs via a free-radical mechanism involving initiation, propagation, and termination steps.

Preparation of Alkanes

Preparation of Alkanes:

1. Hydrogenation

Hydrogenation involves the addition of hydrogen to unsaturated hydrocarbons (alkenes or alkynes) in the presence of a metal catalyst such as Ni, Pd, or Pt, under elevated temperature (250°C).

Synthesis of Tris(ethylenediamine)cobalt(III) Chloride

Synthesis of Tris(ethylenediamine)cobalt(III) Chloride

Objective:

To synthesize tris(ethylenediamine)cobalt(III) chloride [Co(en)₃]Cl₃ ​, an octahedral coordination compound of cobalt(III) that exhibits optical activity.