XIilnJr color reactions iitilizccl ClUillit;ltivcly and rluantitativcly in biological chemistry are based upon the aldchyclc -phenol -acid reaction system. One component of this system may be clctcrmincd if the reagents furnish tlw other two components. 'l-tic aldcliydc and the phenol conclcnsc to form a chromogenic con~l&xx in tllc prescncc of a condensing ikgctlt sucli as conccntratccl 1~yclrocl~loric or sulfuric acid1-3.
'i'lw aldchydc -phenol -acid reaction system lxx5 furnishccl analytical proceclurcs for a large variety of compounds: I. Phenols z. Phcnologenic compounds, such ;ls cluinoncs, which on reduction proclucc phenols. 3. Aldelqxlcs 4. AldchydogT;cnic compounds, among which may lx mcnt ioncrl the following compounds :
Primary alcohols, which yield ;~lclcliydcs on osidation. Carbohydrates, which in thcmsclvcs contain a frw or combinctl aldehydc group, and which on treatment with hydrochloric acid or sulfuric acid of sufficient concentration, disrupt to form the iilClCllydC, furfural or its clcrivativcs. mcthylfurfural and hydrosymcthylfurfural. Glycol, glycerol, and higher polyalcohols, sugars, anti cc-arnirio alcohols, which yield aldchyclcs on oxidation with pcriodatc (Malapraclc reaction). Amino acids, which react with ninhydrin to libcratc carbon cliosidc and ammonia, and to ~woduce an iLltlClly<lc. Glycinc, prolinc ilnd hyclrosylxolinc proclucc aldchycles with ninhydrin. Carbosylic acids, such as citric acid, succinic acid, malic acid, tartaric acid, glycolic acid or lnctic acid, which react with conccntratccl sulfuric acid to yicltl an aldchydc. Glycolic acid procluccs formalclcl~ydc, and lactic acid yields acctaldehyclc. Alkaloids, such as narcotinc and hydri~stinc, which on osiclativc hydrolysis, yield the alclchyclc, opianic acid (z,q-climcthosy-o-alclchyclo-bcnzoic acid.)
- Inorganic acids, such as hydrochloric acid or sulfuric acid. * Part of a project, tho Microchemical Dctcrmination of Carbonyl Compounds, aided hy a grant from the United States Public Wealth Service. Iiejererrces p. x45/146 v. 15. LEVINE, I<. s. SI\SS VC)L. 20 (x()5()) I'OL. 20 (1959) COLOR REACTIOS FOR FYRIDOXAL 139