Polarographic Behavior of Organic Compounds, XI. The 2-Bromo-n-alkanoic Acids. Influence of Substitution on Carbon-Halogen Bond Fission

Abstract

A polarographic study of the saturated straight‐chain alpha‐bromo acids (acetic to caprylic) indicates a similar pattern of behavior for all, involving fission of the carbon‐ halogen bond and conversion to the corresponding acid. As the chain length increases, the ease of reduction increases at all pH values, with the one exception that bromopropionic acid in the alkaline region is more difficultly reducible than bromobutyric acid.Maxima effects found with the acids can apparently be ascribed to the colloidal behavior of the acids upon dilution with buffers in which the reducible acid has a lower solubility than in pure water.The effects of ethanol on half‐wave potential, E 1/2, and diffusion current, i d. have been investigated with representative members of the series. In the alkaline region E 1/2 becomes more negative and i d decreases as the alcohol content increases. The evidence in the acid region, though not entirely conclusive, indicates the reverse effect with regard to E 1/2.The behavior of the 2‐bromo‐n‐alkanoic acids does not follow the rule that the ease of polarographic reduction increases with substitution of more electronegative groups. The influences of structure and inductive effect are considered relative to the ease of carbon‐halogen bond fission. The apparent differences between the present work and that reported by others is discussed.

Voltammetry and Electron Paramagnetic Resonance Spectra of Halonitrobenzene Anion Radicals.

“…In the case of the p-iodo compound, this is very likely the "extra" wave for iodide elimination (see Table I). While the present results are unexpected, they are consistent with the known ease of cleavage of carbon-halogen bonds (8) and, in the case of the o-bromonitrobenzene, with the steric effects of bulky ortho groups.…”

Determination of p-Chloroacetanilide in Phenacetin: A Polarographic Method.

“…as 1.60. Comparing this with the value of I for p-chloroacetanilide (3.49) in the present work, shows that n is most likely 2. The reduction mechanism for aliphatic halides at the dropping mercury electrode has been discussed (4,12,IS,22).…”

Effect of Chain Branching on Electrochemical Carbon-Halogen Bond Fission. Possible Mechanism for the Process

“…However, BE does not fit this correlation. Furthermore, the straight chain acids (1) do not correlate at all beyond the first three members, the deviations of the higher members being of such a trend as to indicate that E1/2 is becoming positive at too great a rate as the chain length increases. This and other attempts at similar correlation indicate that, if Taft's parameters are indeed reflections of the polar character of the substituents, a polar effect cannot be used to explain the continuing trend of E1/2 as the substituent size increases above that of ethyl.…”

“…Accordingly, the phenomenon of the S-shaped curve is given only brief attention in the present paper. Consequently, the polarographic behavior of bromoethanoie (HH), 2-bromopropanoic (MH), 2-bromobutanoic (EH), 2-bromo-2-methylpropanolc (MM), 2-bromo-2-methylbutanom (ME), 2-bromo-2-ethylbutanoic (EE), and 2-bromo-2-ethyl hexanoic (BE) acids was investigated, the first three for comparison with the previous study (1). 4 In order to complete the work, the ethyl esters of five of these acids were also investigated.…”