TOJC
Andrew Glandon (glandoal@PLU.edu)
Mon, 23 Sep 1996 18:56:21 -0800 (PST)
Hello all. Today while living the organic chemistry adventure, I learned
that the acidity of carboxylic acids can be explained two different ways
which more than likely work together. Resonance effects and inductions
effects both take place on the carboxylic acids.
When the double bond in the carboxyl group is moved to form resonant
structures, they are not equal because of the hydrogen atom present.
This resonance requires that the charge is separated and that does'nt
make that atom relatively more stable. When the hydrogen is given up in
solution, the leftover ion (whatever it is, the book uses acetic
acid/acetate ion) has equal resonance hybrids. This is a stable state
(for an ion) and the equilibrium tends to shift this way, producing a
carboxylic acid that is stronger than its corresponding alcohol.
Inductive effects are due to the carbonyl group. The book divides the
carboxyl group into its repective parts. The O-H bond is polarized
because of the oxygen's electronegativity. The carbonyl group is also
very polarized and it behaves like the resonance structures shown in the
book. (page 109) Anyway the carbon is very positive and it induces its
charge on the O-H bond and increases the polarity of it. This causes the
hydrogen atom to be very positive and it separates easier. Neat stuff,
huh?
Andy Glandon