Primary alcohols and aldehydes are normally oxidised to carboxylic acids using potassium dichromate(VI) solution in the presence of dilute sulphuric acid. During the reaction, the potassium dichromate(VI) solution turns from orange to green.
Primary alcohols are oxidised to carboxylic acids in two stages - first to an aldehyde and then to the acid. We often use simplified versions of these equations using "[O]" to represent oxygen from the oxidising agent.
Ketone or aldehyde synthesis by acylation
Phenylacetaldehyde and 3- and 4-chlorophenylacetaldehyde are effectively oxidized to the corresponding phenylacetic acid derivatives when incubated with rat hepatic microsomal dehydrogenase containing NAD+ as a coenzyme. The rates of oxidation for the 3- and 4-chloro derivatives were markedly slower than that of the parent phenylacetaldehyde (Martini & Murray, 1996). In dogs, 32% of a dose of 1900 mg/kg bw phenylacetaldehyde (No. 1002) was rapidly oxidized and excreted as the glycine conjugate within 48 h (Kay & Raper, 1922).
octanal (aldehyde C-8), 124-13-0
Two men excreted an average of 91% and 7% of an oral dose of 1 mg/kg bw of [carboxy-14C]phenylacetic acid within 24 h as glutamine and taurine conjugates, respectively. In contrast to most animals, humans have only traces of the glycine conjugate (James et al., 1972). The distribution and type of conjugation are virtually unaffected by continued ingestion of phenylacetic acid. One person fed 34 doses of 1000–10 000 mg of the acid over 97 days excreted > 90% of the administered dose as the phenylacetylglutamine conjugate (Ambrose et al., 1933). Like humans, Old and New World monkeys conjugate phenylacetic acid with glutamine and, to a lesser extent, taurine; however, significant quantities of acid (1–44%) are excreted free. In carnivores (e.g., dogs, cats and ferrets), glycine conjugation predominates, with no detectable glutamine conjugation. Likewise, in rodents and lagomorphs (rabbits), phenylacetic acid is excreted primarily as the glycine conjugate. Unconjugated phenylacetic acid and minute amounts of taurine conjugates are also excreted. In rats, > 94% of a dose of 80 mg/kg bw of phenylacetic acid given by intraperitoneal injection was excreted as the glycine conjugate (James et al., 1972).
Department of Chemistry | UMass Amherst
Once formed, phenylacetaldehyde is oxidized by inducible aldehyde dehydro-genases from rat liver cytosol. In rats, these isoenzymes can be induced by phenobarbital (Simpson et al., 1985). The Km and Vmax values of human mitochondrial ALDH (ALDH-2) and the cytosolic isoenzyme (ALDH-1) for oxidation of phenylacetal-dehyde (Table 3) indicate rapid conversion to phenylacetic acid (Klyosov, 1996).
Yield from pure aldehyde should ..
Phenylacetic acid given orally at a single dose of 20 mg/kg bw to each of five male volunteers resulted in a two- to fourfold increase in urinary indole-3-acetic acid concentration (Tashian, 1960). Presumably, the phenylacetic acid deactivated tryptophan decarboxylase, resulting in increased conversion of tryptophan to indole-3-acetic acid.