We show here for the first time that strongly correlated linear relationships exist between equilibrium bond lengths of the sulfonamide group and aqueous pKa values.

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In this work, we present a wide-range spectrochemical analysis of the degradation products from naturally aged paper. The samples obtained from wash waters used during the de-acidification treatment of leaves from a 16th-century-printed book were analysed through NMR, IR, Raman UV/Vis, EPR and X-ray fluorescence (XRF) spectroscopy and HPLC-MS and inductively coupled plasma (ICP) analysis. By these methods we also studied some of the previous samples treated by acidification (sample AP) and catalytic hydrogenation (sample HP). Crossing all the data, we obtained precise indications about the main functional groups occurring on the degraded, water-soluble cellulose oligomers. These results point out that the chromophores responsible for browning are conjugated carbonyl and carboxyl compounds. As a whole, we show that the analysis of wash waters, used in the usual conservation treatments of paper de-acidification, gives much valuable information about both the conservation state of the book and the degradation reactions occurring on the leaves, due to the huge amount of cellulose by-products contained in the samples. We propose therefore this procedure as a new very convenient general method to obtain precious and normally unavailable information on the cellulose degradation by-products from naturally aged paper.

A basic recipe for making a Cr logwood ink dating to 1847 was adapted in order to obtain hues varying from orange to dark brown. The inks synthesized were characterized by Raman spectroscopy, Fourier transform infrared spectroscopy, liquid chromatography-diode array detection-quadrupole time-of-flight-mass spectrometry, and liquid chromatography-inductively coupled plasma-mass spectrometry to gain insight into the spectroscopic properties of the compounds responsible for the inks colors and to obtain Raman spectra that can be used for their non-invasive identification in works of art and in historic documents. It was observed that hematein and logwood oxidation products are present in the inks and that their relative proportions determine the inks hues. It was also found that relatively small variations in the basic recipe, such as in the temperature that the logwood and K2CrO4 mixture were heated at, gave inks with different hues. The Raman spectra acquired in the laboratory samples were used to characterize the ink used by Vincent van Gogh in Street in Saintes-Maries-de-la-Mer

The accurate prediction of aqueous pK a values for tautomerizable compounds is a formidable task, even for the most established in silico tools. Empirical approaches often fall short due to a lack of pre-existing knowledge of dominant tautomeric forms. In a rigorous first-principles approach, calculations for low-energy tautomers must be performed in protonated and deprotonated forms, often both in gas and solvent phases, thus representing a significant computational task. Here we report an alternative approach, predicting pK a values for herbicide/therapeutic derivatives of 1,3-cyclohexanedione and 1,3-cyclopentanedione to within just 0.24 units. A model, using a single ab initio bond length from one protonation state, is as accurate as other more complex regression approaches using more input features, and outperforms the program Marvin. Our approach can be used for other tautomerizable species, to predict trends across congeneric series and to correct experimental pK a values.