Unimolecular Solvolyses in Ionic Liquid: Alcohol Dual Solvent Systems

Molecules

Elizabeth D. Kochly¹  Nicole Jean Lemon¹  Anne Marie Deh-Lee¹ 

关键词: ionic liquids;    organic synthesis;    green chemistry;    solvolysis;    carbocation;    nucleophile;    dual solvent;    Kamlet–Taft parameters;    hydrogen bonding;   

DOI  :  10.3390/molecules21010060

来源: mdpi

【 摘 要 】

A study was undertaken of the solvolysis of pivaloyl triflate in a variety of ionic liquid:alcohol solvent mixtures. The solvolysis is a k_Δ process (i.e., a process in which ionization occurs with rearrangement), and the resulting rearranged carbocation intermediate reacts with the alcohol cosolvent via two competing pathways: nucleophilic attack or elimination of a proton. Five different ionic liquids and three different alcohol cosolvents were investigated to give a total of fifteen dual solvent systems. ¹H-NMR analysis was used to determine relative amounts of elimination and substitution products. It was found, not surprisingly, that increasing the bulkiness of alcohol cosolvent led to increased elimination product. The change in the amount of elimination product with increasing ionic liquid concentration, however, varied greatly between ionic liquids. These differences correlate strongly, though not completely, to the Kamlet–Taft solvatochromic parameters of the hydrogen bond donating and accepting ability of the solvent systems. An additional factor playing into these differences is the bulkiness of the ionic liquid anion.

【 授权许可】

CC BY   
© 2016 by the authors; licensee MDPI, Basel, Switzerland.