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Equilibrium constants between boron trifluoride etherate and carbonyl compounds in chloroform solution
1Department of Chemistry, Indiana University, Bloomington, Indiana 47401, USA. gajewski@indiana.edu
Organic Letters
|August 31, 2000
Summary
Boron trifluoride (BF(3)) complexation with carbonyl compounds was studied. BF(3) shows a preference for deuterated benzaldehyde, and complexation strength correlates with Taft
Area of Science:
- Chemistry
- Physical Chemistry
- Organic Chemistry
Background:
- Lewis acid-base interactions are fundamental in chemistry.
- Boron trifluoride (BF(3)) is a potent Lewis acid widely used in organic synthesis.
- Understanding the factors governing BF(3) complexation with carbonyls is crucial for predicting reaction outcomes.
Purpose of the Study:
- To quantify the equilibrium constants for BF(3) complexation with various carbonyl compounds.
- To investigate the influence of isotopic substitution (deuterium) on BF(3) binding affinity.
- To correlate complexation strengths with electronic parameters of substituted benzaldehydes and other carbonyls.
Main Methods:
- Determination of equilibrium constants in CDCl(3) using NMR spectroscopy.
- Measurement of heats of addition for BF(3) to carbonyl compounds.
- Correlation analysis using Taft's beta and beta' values.
Main Results:
- Equilibrium constants for BF(3) complexation with benzaldehyde, cyclohexanone, and isobutyraldehyde were determined relative to diethyl ether.
- A 1.28-fold preference for BF(3) bonding to benzaldehyde-D over benzaldehyde-H was observed.
- A rho(+) value of -2.0 indicated the electronic effects of substituents on benzaldehyde complexation.
- Heats of addition correlated well with Taft's beta and beta' values.
Conclusions:
- The study provides quantitative data on BF(3) complexation with carbonyls.
- Isotopic effects and substituent electronic properties significantly influence BF(3) binding.
- Heats of addition offer a predictive tool for BF(3) complexation strength with carbonyls.
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