EFFECT OF CHAIN BRANCHING ON ELECTROCHEMICAL CARBON-HALOGEN BOND FISSION. POSSIBLE MECHANISM FOR THE PROCESS
Abstract
An attempt was made to ascertain the mechanism of the electrochemical process to establish a basis for correlating chemical activity with the polarographic behavior of C-halogen bonds. A group of branched-chain alpha- bromoalkanoic acids, their Et esters, and straight-chain isomers were examined polarographically. The relation between the half-wave potential (E sub1/2) and the pH for the acids had an S-shaped pattern with pH-invariant regions in the alkaline and acidic ranges; E sub1/2 in the latter region was more negative. The E sub1/2 values for the esters were independent of pH and were slightly more positive than those of the corresponding acids in the acidic region. The polarographic waves involved a 2-electron reduction process and were diffusion- controlled. In the acidic region, the branched-chain acids were more easily reducible than their straight-chain isomers by 0.2 to 0.13 v; larger differences were observed for the lower molecular weight acids. In the alkaline region, a similar behavior occurred with some anomalies. The electrode reaction was considered with respect to the influence of pH, chain length, and chain branching. A reaction mechanism is postulated in terms or organic reactivity theory and steric concepts. The possibilities of an elimination process of S subN i or S subN 2 pattern for the C-halogen bond fission and a free-radical mechanism are discussed. The anomalous behavior in the alkaline region is attributed to the formation of ring structures which become stabilized in the acids.
Document Details
- Document Type
- Technical Report
- Publication Date
- Jun 15, 1953
- Accession Number
- AD0013939
Entities
People
- Isodore Rosenthal
- Joseph M. Markowitz
- Philip J. Elving
Organizations
- Michigan State University