Deuterium isotope studies of the dehydration alcohols by reaction with triphenylphosphine-tetrachloromethane

Article abstract of DOI:10.1016/S0040-4020(01)80935-2

The reactions of 2-butanol, 2-butanol-2d₁, erythro-2-butanol-3d₁ (EB), 2-methyl-2-propranol (2M2P), and 1,1,1,3,3,3-hexadeuterio-2-methyl-2-propranol (HDMP), respectively, with CCL₄, and Ph₃P in a polar or non-polar solvent in the temperature range of 36-85°C was studied. For 2-butanol the fraction of dehydration products increased with temperature; the opposite temperature effect was observed for (2M2P). Dehydration was the dominant pathway for (2M2P) (85-95%) but substitution (of OH by Cl) was dominant for 2-butanol (75-95%). Deuterium retention in the butenes from the conversion of (EB) indicated that 98% or more of the dehydration followed an anti-elimination pathway, and there was a preference for Saytzeff elimination. An isotope effect for deuterium elimination (K(H)/k(D)) for the alkene-forming step for (EB) and (HDMP) was about 2.0, and neither temperature nor solvent polarity appeared to have an effect on (k(H)/k(D)) in the range investigated. Surprisingly, there was an isotope effect for the relative rate of the formation of alkyl halide from (EB) but not from (HDMP).