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|Type:||Artigo de periódico|
|Title:||Methanolysis (solvolysis) And Synthesis Of 4′'-substituted 4-benzyloxybenzyl Chlorides And Some Related Compounds: Comparisons With The Corresponding Benzoyl Compounds|
|Abstract:||The kinetics of methanolysis (solvolysis) in 97.4% MeOH-dioxan of a series of 4′-substituted 4-benzyloxybenzyl chlorides, and of 4-anisyl, 4-phenoxybenzyl, and benzyl chlorides have been studied and discussed, including comparisons with the data for the corresponding series of benzoyl chlorides, previously reported by us. The 4′-substituted precursor alcohols, chlorides, and product methyl ethers are all new compounds. 4-Anisyl chloride and the series of benzyloxybenzyl chlorides react by the SN1 mechanism, whereas benzyl chloride reacts by the SN2 mechanism. 4-Phenoxybenzyl chloride shows intermediate behaviour. A similar pattern was observed with the corresponding benzoyl compounds. In both series the reactivity order is CH3O > 4′-CH3C6H 4CH2O (-0.76) >C5H5CH 2O (-0.74) > 4′-ClC6H4CH2O (-0.69) > 4′-NO2C6H4CH2O (-0.60) > C6H5O > H (values in parentheses are new σ+ values). At 25° the overall range of rates is 4 290 in the benzyl series, compared with only 2.42 in the benzyl series. The Arrhenius parameters in the two series demonstrate, however, an underlying similarity with obvious differences superimposed. In both series, the introduction of 4-OR groups leads to a ΔS‡ increase of ca. 40 J mol-1 K -1. In the benzyl series this is accompanied by ΔE‡ decreases of ca. 6-10 kJ mol-1, whereas in the benzoyl series ΔE‡ values increase by ca. 10-15 kJ mol-1. The equation log k = log k0 + n[MeOH] in mixtures with increasing content of dioxan, was used to study the rate dependence on MeOH concentration. Values of n are ca. 5 between 97.4 and 8.3.% MeOH, and ca. 3 between 83.3 and 50.0% MeOH.|
|Appears in Collections:||Unicamp - Artigos e Outros Documentos|
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