Effect of sample moisture content on XRD-estimated cellulose crystallinity index and crystallite size

Although X-ray diffraction (XRD) has been the most widely used technique to investigate crystallinity index (CrI) and crystallite size (L₂₀₀) of cellulose materials, there are not many studies that have taken into account the role of sample moisture on these measurements. The present investigation focuses on a variety of celluloses and cellulose containing materials—from loblolly pine wood to tunicin, and evaluated moisture-induced changes in CrI and L₂₀₀. It was observed that upon introduction of a small amount of water (5%) into P₂O₅ dried samples, for most samples, both absolute intensity of (200) reflection and its full width at half maximum declined. Moreover, (200) peak position (2θ max) increased when the samples became moist. Although the extent of such changes were material dependent, in general, a greater degree of change was associated with lower sample CrI. For CrI, maximum and minimum increases occurred for oven dried NaOH treated red pine holopulp and tunicin, respectively. For L₂₀₀, maximum and minimum increases were for wood and tunicin, respectively. Moreover, 2θ max position for (200) reflection increased most for the wood and oven dried NaOH treated red pine holopulp (acid chlorite delignified milled-wood) and least for tunicin. The nonparametric statistical test “sign test” further supported these results. Observations from longer duration drying experiments, post moistening, indicated that the changes to the XRD parameters were reversible to some degree. Based on the findings it is concluded that for most cellulose materials with Segal CrI < 90% the moisture content has a significant bearing on the XRD-estimated CrI and L₂₀₀ data. Consequently, it is essential that when such materials are compared, their diffractograms should be obtained under similar levels of sample moisture content.     

An Innovative Protocol for the Synthesis of 3‐(Pyridin‐2‐yl)‐5‐sec‐aminobiphenyl‐4‐carbonitriles and 9,10‐Dihydro‐3‐(pyridine‐2‐yl)‐1‐sec‐aminophenanthrene‐2‐carbonitriles

Herein, we present an innovative, novel, and highly convenient protocol for the synthesis of 3‐(pyridin‐2‐yl)‐5‐sec‐aminobiphenyl‐4‐carbonitriles ( 6a , 6b , 6c , 6d , 6e , 6f , 6g ) and 9,10‐dihydro‐3‐(pyridine‐2‐yl)‐1‐sec‐aminophenanthrene‐2‐carbonitriles ( 10a , 10b , 10c , 10d , 10e ), which have been delineated from the reaction of 4‐sec‐amino‐2‐oxo‐6‐aryl‐2H‐pyran‐3‐carbonitrile ( 4a , 4b , 4c , 4d , 4e , 4f , 4g ) and 4‐sec‐amino‐2‐oxo‐5,6‐dihydro‐2H‐benzo[h]chromene‐3‐carbonitriles ( 9a , 9b , 9c , 9d , 9e ) with 2‐acetylpyridine ( 5 ) through the ring transformation reaction by using KOH/DMF system at RT. The salient feature of this procedure is to provide a transition metal‐free route for the synthesis of asymmetrical 1,3‐teraryls like 3‐(pyridin‐2‐yl)‐5‐sec‐aminobiphenyl‐4‐carbonitriles ( 6a , 6b , 6c , 6d , 6e , 6f , 6g ) and 9,10‐dihydro‐3‐(pyridine‐2‐yl)‐1‐sec‐aminophenanthrene‐2‐carbonitriles ( 10a , 10b , 10c , 10d , 10e ). The novelty of the reaction lies in the creation of an aromatic ring from 2H‐pyran‐2‐ones and 2H‐benzo[h]chromene‐3‐carbonitriles via two‐carbon insertion from 2‐acetylpyridine ( 5 ) used as a source of carbanion.     

Green synthesis of pyranopyrazoles via biocatalytic one-pot Knoevenagel condensation–Michael-type addition–heterocyclization cascade in non-aqueous media

Research on Chemical Intermediates - An efficient, green and facile route for the one-pot four-component synthesis of pyranopyrazole derivatives through the condensation of the aromatic aldehydes,...     

First total synthesis of medicinally important 3,4,7-trimethoxy-9,10-dihydrophenanthrene-1,5-diol

The first total synthesis was successfully achieved for biologically active 9,10-dihydrophenanthrene-1,5-diol. The key features of our synthetic approach are Perkin condensation, followed by bromination, palladium mediated intramolecular C-C bond coupling, and selective isopropyl ether cleavage. Synthesized compounds were purified and characterized by IR, ¹HNMR, ¹³CNMR and HRMS/LC-MS.     

Bis(2-Hydroxy-3-Isopropyl-6-Methyl-Benzaldehyde)Ethylenediamine: A Novel Cation Sensor

Novel substituted phenol-based new symmetrical bis(2-hydroxy-3-isopropyl-6-methyl-benzaldehyde)ethylenediamine (1) has been designed and synthesized. The compound 1 fluorometrically recognized Cu²⁺ ion in CH₃OH/H₂O (90:10, v/v) by exhibiting an increase in emission upon complexation. In addition, Cu²⁺ gave rise to a change in colour of the solution of compound 1, which was clearly visible to the naked eye under UV irradiation. The association constant (K) of compound 1 with Cu²⁺ ion was computed with the Benesi-Hildebrand plot and Scatchard plot at 43,000 M^?1 and 43,011 M^?1 respectively.     

Determination of the chemical states of impurities in natural kyanite by the ionoluminescence technique

Ionoluminescence (IL) of natural kyanite crystals was studied during 120 MeV Au⁹⁺ ion irradiation in the fluence range 1.50?12 × 10¹¹ ions/cm². The IL spectrum exhibits sharp peaks at ～689, 694, 705, 713 and 716 nm, along with a broad emission peak at 530 nm recorded for all samples investigated. The sharp emission peaks at 689 and 694 nm are attributed to R₂ and R₁ lines of Cr³⁺ impurities, and they are related to the transition ²E_g → ⁴A_2g. The peaks at 705–716 nm are attributed to Fe³⁺ impurities and are related to the transition ⁴T_1g → ⁶A_1g. It was observed that up to a given fluence, the IL peak intensity grows, reaches a maximum and gradually decreases with increase of Au⁹⁺ ion fluence. The decrease in IL intensity might be attributed to disorder produced by dense electronic excitation under swift heavy ion irradiation. The stability of the chemical species was studied both with and without irradiation by means of FTIR spectroscopy. The results confirm that the Si?O?Al, Al?O and Si?O (2ν₃) type species are destroyed due to amorphization.     

Ethyl 2‐[N‐(tert‐butyl­oxy­carbonyl)‐l‐alanyl­amino]‐4‐methyl‐1,3‐thia­zole‐5‐carboxyl­ate reveals a trans orientation of the preceding amide N—H with respect to the thia­zole‐ring sulfur

The title mol­ecule, C₁₅H₂₃N₃O₅S, was prepared as a synthetic precursor to 4‐methyl­thia­zole‐based DNA minor groove binders which would bear chiral amino acids in the sequence. The crystallographic evidence presented herein shows that the aromatic amide NH group preceding the thia­zole ring points away from the direction of sulfur. The mol­ecule is biplanar, with the dihedral angle between the N‐terminus peptide moiety and the thia­zole‐containing plane being 49.7 (5)°, with a bend at the Cα carbon.     

Chiral amide from (1S,2R)-(+)-norephedrine alkaloid in the enantioselective addition of diethylzinc to aryl and heteroaryl aldehydes

Chiral amide synthesized from (1S,2R)-(+)-norephedrine and furoic acid was found to catalyze the enantioselective ethylation of aromatic and heteroaromatic aldehydes to secondary alcohols with 99.8% enantioselectivity at 0 °C without the addition of a promoter such as titanium tetraisopropoxide.