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A novel method to accurately determine the carbonyl content in cellulosic materials by fluorescence labeling with carbazole-9-carboxylic acid [2-(2-aminooxyethoxy)ethoxy]amide has been developed. The procedure can readily be incorporated into a gel permeation chromatography (GPC) system with refractive index and multiple-angle laser light scattering detection. Both a homogeneous procedure, working in DMAc/LiCl (2.5%, w/v), and a heterogeneous derivatization approach, using aqueous buffer pH 4.0, for determination of carbonyls in pulps have been optimized with regard to reaction conditions, presence of catalysts, reproducibility, and completeness of conversion. The homogeneous labeling requires prolonged reaction times and removal of excess marker prior to GPC analysis by a time-consuming precipitation-washing-redissolution sequence, which is not needed in the heterogeneous approach. The heterogeneous procedure offers the additional advantages of higher efficiency, shortened analysis times, increased simplicity, and widest applicability.

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The regioselectivity of the oxidation of alpha-tocopherol (the main component of vitamin E) to an ortho-quinone methide (oQM) has been explained in the literature mostly by the ill-defined term "Mills-Nixon effect". In this paper we describe the preparation of eleven alpha-tocopherol derivatives, different from each other by the sum of annulation angles, but keeping the electronic factors unchanged. These compounds underwent Ag(2)O oxidation, forming two isomeric oQMs that were trapped by vinylmethyl ether. It was found that the isomeric product ratio changes smoothly as a function of the annulation angles, not abruptly from one regioisomer to the other on going from five- to six- and seven-membered rings, as predicted by the Mills-Nixon effect. The relative amounts of the products were determined at four different temperatures, and assuming that the product ratio represents the relative rates ratio, the relative enthalpy of activations could be obtained. Theoretically (at B3LYP/6-31G* theoretical level) four different intermediates were considered. Each of these underwent angular angles deformations to model the two regioisomers. At each deformation angle the energy difference between the two intermediates models was correlated to the experimental data for each of the four intermediates. It was found that the angle-deformed lithium (6-methyl-2-benzylium)phenolate correlated best (R>0.994) to the experimental data. This study confirms that the regioselectivity of the two isomeric oQMs in the oxidation of alpha-tocopherol and related compounds is simply a function of angular strain, best explained by the SIBL (strain-induced bond localization) model. In addition, this study provides evidence that the highest energy intermediate in the oxidation of vitamin E is a phenolate-benzyl cation.

The thermal degradation products of 1-alkyl-3-methyl-imidazolium-type ionic liquids (e.g., BMIM, EMIM), which are commonly used in cellulose chemistry, were identified. Imidazole (5), N-methylimidazole (6), and N-alkylimidazoles (7, 8) are the main products. Moreover, dimeric substituted imidazoles (9–11) were found carrying a methylene bridge formed from the N-methyl structure. The former 1-alkyl group (butyl or ethyl) was not present in any of the dimeric compounds. The N-methylene intermediate (12) acts as a precursor for the substituted imidazoles linked by a methylene group. All thermal degradation products are bases and catalyze the previously described reaction between the reducing end of celluloses and 1-alkyl-3-imidazolium cations. To minimize this side reaction, ionic liquids have to be liberated from such basic compounds prior to application as cellulose solvents. In this regard, the usage of “recycled” (and unpurified) ionic liquids has to be treated with caution.