nitrolic acid
Nitrolic acids are organic compounds with the functional group RC(NO2)=NOH. They are prepared by the reaction of nitroalkanes with base and nitrite sources:Matt, C.; Wagner, A.; Mioskowski, C., "Novel Transformation of Primary Nitroalkanes and Primary Alkyl Bromides to the Corresponding Carboxylic Acids", The Journal of Organic Chemistry 1997, 62, 234-235. {{doi|10.1021/jo962110n}}
:RCH2NO2 + HNO2 → RC(NO2)=NOH + H2O
The conversion was first demonstrated by Victor Meyer using nitroethane.Meyer, V.; Locher, J. "Untersuchungen über die Constitution der Nitrolsäuren (Researches on the constitution of the nitrolic acids)" Deut. Chem. Ges. Ber., 1874, volume 7, pp. 670-5. {{doi|10.1002/cber.187400701211}} The reaction proceeds via the intermediacy of the nitronate anion.
Occurrence
Most nitrolic acids are laboratory curiosities. One exception is the compound HO2C(CH2)4C(NO2)=NOH, which is produced by the oxidation of cyclohexanone with nitric acid.{{cite book | first = M. T. | last = Musser | chapter = Adipic Acid | title = Ullmann's Encyclopedia of Industrial Chemistry | publisher = Wiley-VCH | location = Weinheim | year = 2005 | doi = 10.1002/14356007.a01_269| isbn = 3527306730 }} This species decomposes to adipic acid and nitrous oxide:
:HO2C(CH2)4C(NO2)=NOH → HO2C(CH2)4CO2H + N2O
This conversion is thought to be the largest anthropogenic route to N2O, which, on a molecule-to-molecule basis, has 298 times the atmospheric heat-trapping ability of carbon dioxide.{{cite web|title=Overview of Greenhouse Gases – Nitrous Oxide |url=http://www.epa.gov/ghgreporting/documents/pdf/2013/documents/2013-data-elements.pdf |publisher=US EPA |access-date=19 March 2014 | at= Page 164 (document header listing)}} Adipic acid is a precursor to many nylon polymers. In the end, nitrous oxide is produced in about one to one mole ratio to the adipic acid.{{cite journal |last1=Parmon |first1=V. N. |last2=Panov |first2=G. I. |last3=Uriarte |first3=A. |last4=Noskov |first4=A. S. |title=Nitrous oxide in oxidation chemistry and catalysis application and production |journal=Catalysis Today |year=2005 |volume=100 |issue=2005 |pages=115–131 |publisher=Elsevier |language=English|doi=10.1016/j.cattod.2004.12.012}}