The Nitric Acid Oxidation of Selected Alcohols and Ketones An Organic Laboratory Experiment Kurt W. Field, James P. Shields, Jean M. Standard, Craig K. Ash, Daniel J. Hoch, and Kenneth E. Kolb Bradley University, Peoria, IL 61625 This experiment illustrates that nitric acid can he used as a rapid, versatile, and economical oxidant for selected organic substances. For example, cycloalkanols or cycloalkanones are smoothlv converted to m.o-dioic acids in mod vields hv oxidation with hot nitric acid, eqn. (1).
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This same oxidant, when moderated with 1,2-dimethoxyethane (glyme), also provides an excellent method for the synthesis of benzaldehydes or benzophenones from henzyl alcohols, eqn. (2), or diarylcarhinols, eqn. (3), respectively.
Table 1. Nitric Acld Oxidation of Cycloalkanots and Cycloalkanones Substrate
Product (Acid)
Yield. % Mp, "Ce
Cyclopentanoi 13-Pentanedioic (Glutaric) Cyclopentan~ne~~~1.5-Pentanedioic(Giutaric) Cyclohexanol 1,GHexanedioic(Adipic) Cyclohexanones 1.6Hexanedioic(Adipic) Cycloheptanol 1.7-Heptanedioic(Pimeiic) Cyclaheptanoner 1.7-Haptanedioic(Pimeiia) 1,8-Octanedioic(Suberic) Cyclooctanoi Cyclooctanonee I,&Octanedioic(Suberic) Cyclododecanold 1.12-Dodecanedioic Cycbdodecanoner~* 1.12-Dodecanedioic a
65 60 70
97.5 97.5 153 153
52
43
106
41 45
106 140 140 128 128
47 50 44
Relerence (lo).
a A modilied work-uo Drocedure must be used because ofthe emerne waterrolubilm
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"""me* ranu*
X
These exoeriments reauire one 3-h laboratow how. period: . ever, they may serve as open-ended projects since suhrtrates not described herein could he oxidized. The reoorted viel(ls were determined by averaging student results; the organic compounds to he oxidized were ~ u r c h a s e dfrom Aldrich chemical Co. and used as received:
Part I. The preparation of a,o-Dioic Acids The alkanedioic acid usually synthesized in the undergraduate organic laboratory is 1,6-hexanedioic acid (adipic). Common laboratory procedures utilize strong oxidizing agents, e.g., permauganate (1-3), chromium (VI) (4, 5 ) , or nitric acid (6-8) with cyclohexene ( 5 ) ,cyclohexanol(4,6-8), or cyclohexanone (1-3) as the adipic acid precursor. The experiment described which is similar to the industrial process, demonstrates that nitric acid oxidations of cvcloalkanols and c)lcIonlkanonesare hruad in scope nnd afford a convenient and economical mcthud for the weoaration uf alkanedioir acids in moderate yields, Table 1: ~ h e s acids e are used in nylons, polyesters, urethanes, plasticizers, and synthetic luhricants. Experimental General Procedure for the Preparation of C6-CE a,o-Dioic Acids1 Caution: The oxidation should be performed in a hood. Avoid using cork because it is attacked by hat nitric acid. To a 50-mL round-bottomed flask, equipped with a thermometer and a boiling stone, add 15.0 mL of aqueous nitric acid2;however, if
a C12substrate is to be oxidized use 10.0 mL of eoncd. nitric acid as the oxidant. If a cycloslkanone is to he oxidized, also add 0.1 gof sodium nitrite (Caution: see footnote 3). After warming the mixture to 65-90', add the substrate (1.5-2.0 g) portionwise to maintain the temperature. During the addition, oxides of nitrogen are e~olved.~ When the addition is complete, heat the mixture to-90" for -5 mi". Finally, mol the material in an ice-water bath for -30 min. Isolate the prcduct by vacuum filtration and wash with three 5-mL portions of water;allow the solid to air dry overnight Determine the melting point and percent yield. Recrystallization of the product from the indicated solvent can be performed if desired (recrystallizationsolvents: adipic, pimelic, and suberic acid, ethanal-water;dodecanedioie acid, ethyl acetate). Modified Procedure for the Preparation of Glutaric Acids (Pentanedioic Acid) Oxldix t h p (!isubstrate ns descrlhed i r l the Grnrral Prwrdurc. ~\ftcrtlwa~lditicmalheatma, cool the rrnction mixture and naulralire the rrmain~n~ nitrica
