CHEM 0310 Lecture Notes - Lecture 3: Hyperconjugation, Pyrolysis, Zeolite
Document Summary
Combustion of alkanes releases most of the energy that powers modern industrialized society. Alkanes lack functional groups so they do not undergo the kinds of electrophile-nucleophile reactions typical of functionalized molecules. Alkanes are typically unreactive undergo homolytic bond cleavage. The energy needed to break bonds is called bond-dissociation energy (dho) Heterolytic cleavage breaking a bond in which the entire bonding electron pair is donated to one of the atoms - these fragments form ions. Homolytic cleavage occurs in nonpolar solvents while heterolytic cleavage occurs in polar solvents. Dissociation energies, dho, refers only to hemolytic cleavages. The larger the dho, the stronger the corresponding bond. Bonds are strongest when made by overlapping orbitals that are closely matched in energy and size (ch3-f>ch3-i) Bond strength decreases as carbons have more attachments (primary>secondary) Radical stability increases along the series from primary secondary; consequently the energy to create them decreases.
