Editing Theophylline (section)

== Spectroscopy ==
=== UV-visible  ===
Theophylline is soluble in 0.1N NaOH and absorbs maximally at 277&nbsp;nm with an extinction coefficient of 10,200 (cm<sup>−1</sup> M<sup>−1</sup>).<ref name="pmid15392550">{{cite journal | vauthors = Schack JA, Waxler SH | title = An ultraviolet spectrophotometric method for the determination of theophylline and theobromine in blood and tissues | journal = The Journal of Pharmacology and Experimental Therapeutics | volume = 97 | issue = 3 | pages = 283–291 | date = November 1949 | pmid = 15392550 | doi =  }}</ref>

=== Proton NMR ===
The characteristic signals, distinguishing theophylline from related methylxanthines, are approximately 3.23δ and 3.41δ, corresponding to the unique methylation possessed by theophylline. The remaining proton signal, at 8.01δ, corresponds to the proton on the imidazole ring, not transferred between the nitrogen. The transferred proton between the nitrogen is a variable proton and only exhibits a signal under certain conditions.<ref name="pmid27320965">{{cite journal | vauthors = Shelke RU, Degani MS, Raju A, Ray MK, Rajan MG | title = Fragment Discovery for the Design of Nitrogen Heterocycles as Mycobacterium tuberculosis Dihydrofolate Reductase Inhibitors | journal = Archiv der Pharmazie | volume = 349 | issue = 8 | pages = 602–613 | date = August 2016 | pmid = 27320965 | doi = 10.1002/ardp.201600066 | s2cid = 40014874 }}</ref>

=== <sup>13</sup>C-NMR ===
The unique methylation of theophylline corresponds to the following signals: 27.7δ and 29.9δ. The remaining signals correspond to carbons characteristic of the xanthine backbone.<ref>{{cite journal | vauthors = Pfleiderer W | title = Pteridines. Part CXIX. A New Pteridine–Purine Transformation. | journal = Helvetica Chimica Acta | date = February 2008 | volume = 91 | issue = 2 | pages = 338–353 | doi = 10.1002/hlca.200890039 }}</ref>