a carboxylate + AH2 + H(+) => an aldehyde + A + H2O
a carboxylate + ah2 + h(+) => an aldehyde + a + h2o
a carboxylate + AH2 + H(+) => an aldehyde + A + H2O
a carboxylate + ah2 + h(+) => an aldehyde + a + h2o