<span style="font-size:12.0pt;font-family: "Times New Roman";mso-fareast-font-family:"Times New Roman";mso-ansi-language: EN-IN;mso-fareast-language:EN-IN;mso-bidi-language:AR-SA" lang="EN-IN">Kinetics and mechanism of the oxidation of aliphatic aldehydes by benzyltrimethylammonium dichloroiodate</span>

Abstract

The oxidation of six aliphatic aldehydes by benzyltrimethylammonium dichloroiodate (BTMACI) in glacial acetic acid, in the presence of zinc chloride, results in the formation of the corresponding carboxylic acids. The reaction is first order

<span style="font-size:12.0pt;font-family:" times="" new="" roman";="" mso-fareast-font-family:"times="" roman";mso-ansi-language:en-in;mso-fareast-language:="" en-in;mso-bidi-language:ar-sa"="" lang="EN-IN">with respect to BTMACI, the aldehyde and zinc chloride. The oxidation of deuterated acetaldehyde shows the presence of a substantial kinetic isotope effect <i>(k</i>_{<span style="mso-bidi-font-style:italic">H</span>}<i>/k</i>_{<span style="font-size:8.0pt;mso-bidi-font-size:12.0pt;font-family:" times="" new="" roman";="" mso-fareast-font-family:"times="" roman";mso-ansi-language:en-in;mso-fareast-language:="" en-in;mso-bidi-language:ar-sa;mso-bidi-font-style:italic"="" lang="EN-IN">D</span>}<i><span style="font-size:12.0pt;font-family:" times="" new="" roman";mso-fareast-font-family:="" "times="" roman";mso-ansi-language:en-in;mso-fareast-language:en-in;="" mso-bidi-language:ar-sa"="" lang="EN-IN"> </span></i><span style="font-size:12.0pt; font-family:" times="" new="" roman";mso-fareast-font-family:"times="" roman";="" mso-ansi-language:en-in;mso-fareast-language:en-in;mso-bidi-language:ar-sa"="" lang="EN-IN">= 6.32 at 288 K). Addition of benzyltrimethylammonium chloride enhances the reaction rate. It is proposed that the reactive oxidizing species is [PhCH₂Me₃N]⁺ [IZn₂Cl₆]^-. The rates correlate well with Taft's σ^{<span style="font-size:8.0pt;font-family:" times="" new="" roman";="" mso-fareast-font-family:"times="" roman";mso-ansi-language:en-in;mso-fareast-language:="" en-in;mso-bidi-language:ar-sa"="" lang="EN-IN">●</span>}<span style="font-size: 12.0pt;font-family:" times="" new="" roman";mso-fareast-font-family:"times="" roman";="" mso-ansi-language:en-in;mso-fareast-language:en-in;mso-bidi-language:ar-sa"="" lang="EN-IN"> substituent constants, with negative reaction constant. A mechanism involving a hydride-ion transfer from the aldehyde to the oxidant in the rate-determining step, has been postulated.<span style="font-family:Symbol;mso-ascii-font-family:" times="" new="" roman";="" mso-hansi-font-family:"times="" roman";mso-char-type:symbol;mso-symbol-font-family:="" symbol"="" lang="EN-IN"><span style="font-size:12.0pt;font-family:" times="" new="" roman";="" mso-fareast-font-family:"times="" roman";mso-ansi-language:en-in;mso-fareast-language:="" en-in;mso-bidi-language:ar-sa"="" lang="EN-IN"><span style="font-size:12.0pt; font-family:Symbol;mso-ascii-font-family:" times="" new="" roman";mso-fareast-font-family:="" "times="" roman";mso-hansi-font-family:"times="" roman";mso-bidi-font-family:="" roman";mso-ansi-language:en-in;mso-fareast-language:en-in;="" mso-bidi-language:ar-sa;mso-char-type:symbol;mso-symbol-font-family:symbol"="" lang="EN-IN"><span style="font-size:12.0pt;font-family:" times="" new="" roman";mso-fareast-font-family:="" "times="" roman";mso-ansi-language:en-in;mso-fareast-language:en-in;="" mso-bidi-language:ar-sa"="" lang="EN-IN"></span></span></span></span></span></span></span>