Author Topic: benzaldehydes from benzoic acids  (Read 1190 times)

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3base

  • Guest
benzaldehydes from benzoic acids
« on: June 04, 2002, 09:03:00 AM »
this thread is dedicated to the direct conversion
of benzoic acid derivatives to the corresponding benzaldehydes

3base

  • Guest
vanillic acid --> vanillin
« Reply #1 on: June 04, 2002, 09:05:00 AM »
vanillic acid --> vanillin
electroreduction
j org chem, 1972 37(10), 1513-6
"the electrochemical reduction of aromatic acids to
the corresponding aldehydes"; john h wagenknecht
abstract: a number of aromatic carboxylic acids have been found
to undergo electrochemical reduction of aromatic acids to the
corresponding aldehydes. electrondonating substituents in the
para position inhibit the reaction. it is possible to predict
from the pKa value of the acid or, more accurately, from the
polarographic half-wave potential of the corresponding methyl
ester whether or not the method is applicable for the preparation
of an aldehyde.

3base

  • Guest
benzoic acid --> benzaldehyde
« Reply #2 on: June 04, 2002, 09:08:00 AM »
benzoic acid --> benzaldehyde
calcium benzoate, formic acid, calcium formate
(1) justus liebigs ann chem, 1856 100, 105; piria
(2) jahresber fortschr chem verw theile anderer wiss, 1856, 431


benzoic acid --> benzaldehyde
vacuum ultraviolet irradiation
journal of physical organic chemistry, 2001 14(5), 300-309
"reactions of carbon dioxide radical anion with substituted benzenes"
janina a rosso, sonia g bertolotti, andré m braun,
daniel o mártire, mónica c gonzalez
abstract: we report mechanistic studies on the reactivity of CO2.- radicals
towards substituted benzenes, XPh, with X = NO2, COOH, COH, CH3, H,
Cl and HO. vacuum ultraviolet (VUV, 172 nm) irradiation of aqueous solutions
containing formate was used as a method of CO2.- radical generation for the
study of the reaction products, which were determined by gas chromatography-
mass spectrometry and high-performance liquid chromatography. the nature
of some of the reaction intermediates was studied by laser flash photolysis of
aqueous solutions of peroxodisulfate in the presence of formate. the observed
products and intermediates of reaction are discussed and rationalized by a
dual reactivity of the CO2.- radical anion with substituted benzenes: a one-
electron reduction and radical addition to the aromatic ring. for substituted
benzenes with X = NO2, COOH and COH, the observed products support an
electron transfer from CO2.- to the substrates as the primary reaction channel,
while the reactions with toluene follow the channel of radical addition. benzene
and chlorobenzene react with CO2.- by both routes, electron transfer and
radical addition. our experimental results indicate that H abstraction by the
CO2.- radical is negligible under the chosen experimental conditions.