Kinetic investigations on the modified chitosan catalyzed solvent-free synthesis of jasminaldehyde

Facile fabrication of chitosan Schiff bases from giant tiger prawn shells (Penaeus monodon) via solvent-free mechanochemical grafting

Fabrication of chitosan Schiff bases (ChSB) from giant tiger prawn shells (Penaeus monodon) using an environmentally friendly method has been conducted successfully. Transformation of Prawn Shells (PS) as raw material into chitin then chitosan was executed under ambient temperature. Later, three Ch Schiff bases (ChSB-A, ChSB-S, and ChSB-V) were successfully synthesized for the first time via solvent-free mechanochemical grafting with 2-hydroxy benzaldehyde, 4-methoxy benzaldehyde, and 3-methoxy-4-hydroxy benzaldehyde, respectively. Synthesis was carried out with Shaker Mill-Ultimate Gravity equipped with a Teflon jar with zirconia balls; then the product was characterized. FTIR analysis proved the conversion of free amine to imine groups. The degree of substitution (DS) and crystallinity index (CrI) were determined by elemental analysis and X-ray diffraction. The DS values obtained were about 0.343, 0.795, and 0.055 for ChSB-A, ChSB-S, and ChSB-V, respectively. The CrI of ChSB-A, ChSB-S, and ChSB-V was 53.3, 51.7, and 46.9 %, respectively. The thermal gravimetric analysis showed that the mechanochemical grafting of Ch improves the thermal stability of ChSB. This developed method provides a novel potential technique to convert PS into ChSB products by solvent-free mechanochemical grafting.

A single-step protocol for closing experimental atom balances

Molar balances are considered to be closed if they are within 95–105%. It was shown in the companion paper “https://doi.org/10.1016/j.cej.2018.12.113; Chem. Eng. J., 361, 805–811 (2019)” that even this condition can give rise to pronounced deviations in conversion or selectivity data (Heynderickx, 2019). This manuscript offers a very simple a posteriori calculation procedure to address these deviations via simple linear algebra. The specific details of this procedure, called ‘CLOBAL’, after ‘closing the balances’, are shared (1) by showing the mathematics behind-the-scene and (2) by showing the specific programming code with an itemized guideline through the code.

Key benefits of proposed procedure CLOBAL script are:

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Physical quantities such as molar flow rates, concentrations or absolute number of moles are updated via a one-step linear procedure to close the corresponding atom balances;

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The presented CLOBAL procedure, is executed in Excel®, which is accessible and practical for every user – no need for special license and the code is provided; and

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Parameter estimation, using treated data, results in smaller confidence intervals and lower residual sum of squares (RSSQ).

Activity Coefficients for Liquid Organic Reactions: Towards a Better Understanding of True Kinetics with the Synthesis of Jasmin Aldehyde as Showcase

The aldol condensation of benzaldehyde and heptanal is taken as an example of reversible liquid phase organic reactions to show that inclusion of activity coefficients reveal distinct differences in conversion and product distribution when different solvents methanol, ethanol, n-propanol, or n-butanol are used. The purpose of this work is to show a pronounced solvent effect for a given set of identical kinetic parameters, i.e., the same liquid phase kinetics can result in different conversion and yield values, depending on the choice of solvent. It was shown that subsequent parameter estimation without inclusion of the activity coefficients resulted in a pronounced deviation from the 'true' kinetics, up to a factor of 30. It is proposed that the usage of average activity coefficients gives already a significant improvement, resulting in acceptable parameter estimates.

Efficient Ullmann C–X coupling reaction catalyzed by a recoverable functionalized-chitosan supported copper complex

Three different types of functionalized-CS were prepared and anchored with copper salts for use as the catalyst for the Ullmann C–X coupling reaction.

Chitosan as a sustainable organocatalyst: a concise overview

Increased demand for more sustainable materials and chemical processes has tremendously advanced the use of polysaccharides, which are natural biopolymers, in domains such as adsorption, catalysis, and as an alternative chemical feedstock. Among these biopolymers, the use of chitosan, which is obtained by deacetylation of natural chitin, is on the increase due to the presence of amino groups on the polymer backbone that makes it a natural cationic polymer. The ability of chitosan-based materials to form open-network, macroporous, high-surface-area hydrogels with accessible basic surface sites has enabled their use not only as macrochelating ligands for active metal catalysts and as a support to disperse nanosized particles, but also as a direct organocatalyst. This review provides a concise overview of the use of native and modified chitosan, possessing different textural properties and chemical properties, as organocatalysts. Organocatalysis with chitosan is primarily focused on carbon-carbon bond-forming reactions, multicomponent heterocycle formation reactions, biodiesel production, and carbon dioxide fixation through [3+2] cycloaddition. Furthermore, the chiral, helical organization of the chitosan skeleton lends itself to use in enantioselective catalysis. Chitosan derivatives generally display reactivity similar to homogeneous bases, ionic liquids, and organic and inorganic salts. However, the introduction of cooperative acid-base interactions at active sites substantially enhances reactivity. These functional biopolymers can also be easily recovered and reused several times under solvent-free conditions. These accomplishments highlight the important role that natural biopolymers play in furthering more sustainable chemistry.