2040-03-1Relevant academic research and scientific papers
Gas-phase and solution basicities of some alkyl 2,6-dialkylphenyl ketones: A comparative analysis
Dell'erba, Carlo,Gruttadauria, Michelangelo,Mugnoli, Angelo,Noto, Renato,Novi, Marino,Occhiucci, Giorgio,Petrillo, Giovanni,Spinelli, Domenico
, p. 4565 - 4573 (2000)
The gas-phase basicity of a number of alkyl 2,6-dialkylphenyl ketones (2,6-R2C6H3COR') has been found to be almost insensitive to structural variations, as a result of a compensation of steric and electronic effects associated with the bulkiness and to the polarizability, respectively, of R and/or R'. On the contrary, the basicity in concentrated sulfuric acid undergoes, along the same series of compounds, a variation of nearly 8 pK units, as a consequence of steric inhibition of solvation of the protonated carbonyl as the main effect played by R and/or R'. The results in the condensed phase agree very nicely with recent findings relevant to some 4- substituted 2,6-dimethylacetophenones and 4-substituted acetophenones as well as with data for a large number of dialkyl or alkyl aryl ketones (either from the literature or determined herein) leading to an overall pK(BH+) vs. m* correlation (slope = 8.8, n = 31, r = 0.996; Eq. (3)) which appears to be of general significance and identifies steric inhibition of solvation as a common prevailing factor influencing the carbonyl basicity, at least in the absence of strong conjugative interactions. (C) 2000 Elsevier Science Ltd.
