CHE E122 Lecture Notes - Lecture 23: Fluorine, Regioselectivity, Covalent Bond
Document Summary
Cracking is the breaking up of large hydrocarbon molecules into smaller molecules. This is achieved by using high pressures and temperatures without a catalyst, or lower temperatures and pressures in the presence of a catalyst. The source of the large hydrocarbon molecules is often the naphtha fraction or the gas oil fraction from the fractional distillation of crude oil (petroleum). These fractions are obtained from the distillation process as liquids, but are re- vaporised before cracking. The hydrocarbon molecules are broken up randomly to produce mixtures of smaller hydrocarbons, some of which have carbon-carbon double bonds. Alkanes react with halogens when heated or in the presence of visible light to form haloalkanes. This reaction (and the oxidation reactions) needs the input of energy either electrical, thermal, or radiant energy. Molecular fluorine, bromine and iodine can undergo the same reaction with light but f2 is explosively reactive and i2 barely reacts at all.
