Effect of Solvent Upon the Vicinal Proton Coupling Constants of Complex Substituted Ethanes. II. Anomalous Results for 1-Phenyl-1,2,2-trihaloethanes

Abstract

The n.m.r. spectra of 11 tetra-substituted ethanes have been obtained in a number of solvents. Changes in the vicinal coupling constants of 1-phenyl-l,2,2-trihaloethanes with solvent do not fit the electrostatic model for solvent effects. It is concluded that the theory breaks down because solute-solvent hydrogen bonding specifically favors the trans rotamers of these compounds. The conditions under which the theory would be expected to break down are also discussed in more general terms.Les spectres r.m.n. de 11 Cthanes tetra-substitub ont CtC obtenus dans un certain nombre de solvants. Des changements, avec le solvant, des constantes de couplage vicinales des phCny1-1 trihalo-1,2,2 ethanes ne peuvent Ctre accomodCs avec le modele Clectrostatique des effets de solvant. I1 en est conclu que la theorie ne tient pas parce que des ponts hydrogenes entre le solvant et le solute favorisent le rotamere trans de ces composes. Les conditions oh la thCorie ne serait pas approprite sont aussi discutkes en termes plus gCnCraux.

Dichlorination of Alkenes Using 1,3‐Dichloro‐5,5‐Dimethylhydantoin and ZnCl2

“…Although the product of solvent addition 3 b no longer could be produced, two undesired products were detected: vinyl chloride 4 b [6b] and the trichloride 5 b. [20] The former probably produced from proton abstraction of the chloriranium ion 1b' (or its carbocation resonance structure) and the latter by the dichlorination of 4 b. Considering this, we attempted the use of acidic additives to circumvent the selectivity issue.…”

“…The first attempt to dichlorinate 1 b with DCDMH and 5 equivalents of LiCl in DCM was not encouraging (Table , Entry 1). Although the product of solvent addition 3 b no longer could be produced, two undesired products were detected: vinyl chloride 4 b and the trichloride 5 b . The former probably produced from proton abstraction of the chloriranium ion 1b’ (or its carbocation resonance structure) and the latter by the dichlorination of 4 b .…”

Effect of Solvent Upon the Vicinal Proton Coupling Constants of Complex Substituted Ethanes. III. 1,2-Dihaloalkanes

“…spectroscopy. Compounds were dissolved in freshly distilled where strong 'pecific hydrogen bonding can Occur ACS grade solvents with 5% tetramethylsilane added as (7,8). Consequently, these systems should be lock and reference signal.…”