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Oxidation Reactions
Published in Michael B. Smith, A Q&A Approach to Organic Chemistry, 2020
A vicinal diol is a dihydroxy compound with OH units on adjacent carbon atoms. An example is ethanediol, HOCH2CH2OH. What is the major product when dilute KMnO4 reacts with cyclopentene in aqueous KOH?
Oxidized demethylated lignin as a bio-based adhesive for wood bonding
Published in The Journal of Adhesion, 2021
Xinyi Chen, Xuedong Xi, Antonio Pizzi, Emmanuel Fredon, Guanben Du, Christine Gerardin, Siham Amirou
Oxidation is a commonly used method in starch-based wood adhesives production.[33] Recently, the specific oxidation of plant flours has attracted the attention of some researchers as regards their effectiveness for adhesives application.[34,35] Periodate is a specific oxidant cleaving carbon to carbon bonds presenting vicinal aliphatic hydroxyl groups to form aldehydes and dialdehydes.[34–38] Often the structural units within lignin presents on their aliphatic part both hydroxyl groups vicinal to the β-O-4 bonds to another lignin unit. The β-O-4 linkage is easily cleaved by an oxidant so that aldehydes and possibly also dialdehydes are generated. In addition, the greater proportion of aromatic hydroxyl groups have generated by demethylation thereby increasing aromatic ring reactivity. Hence, the aldehydes generated by periodate oxidation are likely to react with hydroxyl-activated reactive phenolic sites contributing to form a stronger hardened network. Such an adhesive could be classified as a biobased product.
Cyclosulfenylation of N-(1(2)-naphthyl) styrylacetamides as a synthetic route to 4(2)-arylthio naphtho[1,2-b]([2,1-b])azepin-2(4)-ones
Published in Journal of Sulfur Chemistry, 2021
Ivanna Yu. Danyliuk, Alla I. Vaskevych, Ruslan I. Vaskevych, Eduard B. Rusanov, Mykhailo V. Vovk
The azepine nucleus formed in the cyclization manifests itself in the 1H NMR spectra of compounds 3a-h by the multiplets of the H3 (2.26–2.71 ppm) and H4 protons (4.53–4.78 ppm), and the doublets of the H5 protons (4.30–4.37 ppm, 3JHH = 10.4–12.6 Hz). The large values of the vicinal H4 - H5 spin–spin coupling constants 3JHH imply the dihedral angle close to 180° between the corresponding C–H bonds [24] thus pointing to the trans-configuration of the substituents at the C4 and C5 positions and supporting the structure of azepines 3a-h. The 1H NMR spectra of compounds 5a,b show, along with the signals similar to those of 3a-h (multiplets of the H3 and H4 protons at 2.62–2.77 and 4.27–4.32 ppm, respectively, and the doublets of the H5 protons at 4.43–4.44 ppm, with 3JHH of 11.2 Hz), the additional multiplets of the protons of the phenylthio group (in the aromatic region). However, such spectral characteristics are evidently insufficient for reliable structural determination and, therefore, X-ray diffraction analysis of compound 5a was performed (see Figure 2). The crystallographic data obtained are equally relevant to 4,7-di(phenylthio) substituted azepinones 5a,b and their mono-substituted precursors 3b,c unambiguously confirming the proposed structure of the two types of products.
Bromine-terminated azobenzene liquid crystals
Published in Liquid Crystals, 2019
Sergio A. A. Sanches, Wallison C. Costa, Ivan H. Bechtold, Renato A. P. Halfen, Aloir A. Merlo, Leandra F. Campo
The effect of the flexible spacer group can be estimated from the population levels of the conformers of the flexible spacer group containing a bromine atom connected to the end of the spacer group. ChemBio3D Ultra® (PerkinElmer Inc., Waltham, MA) with a MM2 force field was used to evaluate the conformation of the flexible spacer and was correlated to the mesomorphic properties of the azocompounds. Thus, despite the large number of conformational states that the molecules can assume, the analysis was restricted to the dihedral angles between selected carbon atoms of the spacer group, bromine atoms and oxygen atoms bonded to the aromatic ring. Dihedral angles of the long alkyl chain on the other side of the rigid core did not greatly impact the final shape and energy level of the molecules in this series. 5a, 5b and 5c were analysed. Some conformers of 5a, 5b and 5c are shown in Figure 2. Hydrogen atoms were omitted. Conformers were optimised in their most-extended conformations where the antiperiplanar arrangement was considered and analysed for all chemical bonds. Thus, the long and linear alkyl chains are shown in all-trans conformations and the flexible spacer was also considered in an all-trans conformation, except for 5a, where a gauche conformation was also analysed due to the polar bromine group vicinal to the oxygen atom.