How does a reaction change its mechanism. General base catalysis of the addition of alcohols to 1-phenylethyl carbocations
Structure-reactivity correlations are reported for general base catalysis of the addition of alcohols to 1-(4-(dimethylamino)phenyl)ethyl and 1-(4-methoxyphenyl)ethyl carbocations in 50:40:10 H/sub 2/O: CF/sub 3/CH/sub 2/OH:ROH. The addition of trifluoroethanol to the relatively stable ((dimethylamino)phenyl)ethyl cation is catalyzed by substituted acetate ions with ..beta.. = 0.33, which is larger than ..beta.. = 0.23 for addition to the (methoxyphenyl)ethyl cation. Catalysis is more important for the more stable carbocation, but it decreases faster with increasing alcohol basicity. For the water catalysis of alcohol addition to 1-phenylethyl carbocations there is an increased sensitivity to the basicity of ROH with increasing carbocation stability (a Hammond effect). This indicates a small involvement of proton transfer in the transition state and is consistent with simple hydrogen bonding of ROH to a base; it is described by a positive interaction coefficient p/sub yy'/ = delta..beta../sub nuc//-deltasigma. However, for the acetate-catalyzed reaction there is not significant increase in the sensitivity to ROH basicity with increasing carbocation stability.
- Research Organization:
- Brandeis Univ., Waltham, MA
- OSTI ID:
- 6953284
- Journal Information:
- J. Am. Chem. Soc.; (United States), Journal Name: J. Am. Chem. Soc.; (United States) Vol. 108:25; ISSN JACSA
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
400201* -- Chemical & Physicochemical Properties
ACETATES
ALCOHOLS
CARBOXYLIC ACID SALTS
CATALYSIS
CATALYSTS
CATALYTIC EFFECTS
CATIONS
CHARGED PARTICLES
CHEMICAL REACTIONS
DATA
EXPERIMENTAL DATA
HYDROXY COMPOUNDS
INFORMATION
IONS
NUMERICAL DATA
ORGANIC COMPOUNDS
PH VALUE