Problems in Fluorocarbon Chemistry

Dartmouth College, Hanover NH

Investigators

Abstract

In extreme bonding situations the contrasts between fluorinated molecules and their hydrocarbon analogues are often especially sharp, resulting in novel properties and reactivity for the fluorocarbons. This project will explore the synthesis and properties of highly strained fluorocarbons - [2.2.2]propellanes, a [2.2.1]propellane, bicyclo[2.1.0]pentanes, bicyclo[1.1.0]butanes and a bicyclo[2.2.0]alkene - as well as highly fluorinated derivatives of an unusual aromatic system, the nonbenzenoid hydrocarbon azulene. These molecules are of interest not only for their reactivity, but especially for their electronic spectra and photophysics, which will be explored collaboratively. Methods for functionalization of fluorocarbon liquids will be applied to fluoropolymer surfaces. In contrast to other methods of functionalizing fluoropolymer surfaces, which are non-selective in nature, the approach to be used will introduce a specific functional group at specific sites on the surface. The result should be novel properties for the polymer, including the ability to chelate metals. Also to be explored is the synthesis of perfluorinated triplet carbenes that should display extraordinary thermal stability without the electron delocalization characteristic of the only known stable triplet carbenes. The synthetic plan is predicated on the size difference between alkyl and perfluoroalkyl groups, together with the great strength of carbon-fluorine bonds. Fluorocarbons and derived materials enjoy an wide variety of uses in our society, for many of which they are without equal. They owe their special character to the fact that substitution of fluorine for the hydrogens in organic molecules results in dramatic changes in properties and chemical behavior. With the support of the Organic and Macromolecular Chemistry Program, Professor David M. Lemal, of the Department of Chemistry at Dartmouth College, is extending what is known regarding the structure, reactivity and synthesis of highly fluorinated molecules. Through these studies, Professor Lemal is enhancing our understanding of the contrasts between these molecules and their better known hydrocarbon counterparts.