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  • 1.
    Blomkvist, Björn
    KTH, Skolan för kemivetenskap (CHE).
    The application of reversible covalent bonds in catalysis2014Independent thesis Advanced level (professional degree), 20 poäng / 30 hpOppgave
    Abstract [en]

    This work has been concerned with the study of ligand exchange of trimethylborate and its  ability to induce temporary intramolecularity. Experiments aimed at understanding the affinity of various alcohols and amines to boron centers by studying the formation of mixed borate species during equilibrium. Furthermore, a variety of reactions has been screened with the aim to perform catalysis by induced intramolecularity through the trimethylborate.

  • 2.
    Rydergren, Sara
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - BMC, Syntetisk organisk kemi.
    Chemical Modifications of Hyaluronan using DMTMM-Activated Amidation2013Independent thesis Advanced level (professional degree), 20 poäng / 30 hpOppgave
    Abstract [en]

    An alternative approach to chemically modifying hyaluronan (HA) has been investigated. The triazine derivative 4-(4,6-dimethoxy-1,3,5-triazin-2-yl)-4-methylmorpholinium (DMTMM) has been used to activate carboxylic groups on HA, which react further to form stable amide bonds with primary and secondary amines. The reaction can either be used to couple monoamines to HA or to produce hydrogels by using diamines that form crosslinks between the HA chains. The reaction between HA and DMTMM has been investigated and optimized in regard to degree of substitution (DS). Analysis using SEC-LC-UV demonstrated that the reaction was successful in coupling benzylamine to HA with a DS of 40%. Gel formation was successful using hexamethylene diamine as a crosslinker. Results also show that the reaction can be controlled by either the DMTMM or the amine concentration so that a specific degree of substitution or crosslinking is achieved. The stability of DMTMM has also been examined, and degradation studies of DMTMM in H2O at 50 °C with 1H NMR analysis show that 11% of the starting material remains after 48 hours. The reaction has proven to be an effective alternative to other modification methods with cheap reagents, simple procedures and the ability to control the amount of modification. Further investigations are nonetheless required in order to determine the full potential the DMTMM-activated amidation of HA.

  • 3.
    Waltersson, Johanna
    Mälardalens högskola, Akademin för hållbar samhälls- och teknikutveckling. Mälardalens högskola, Institutionen för biologi och kemiteknik.
    The metal binding properties of kraft lignin2009Independent thesis Advanced level (professional degree), 20 poäng / 30 hpOppgave
    Abstract [en]

    There is a strong driving force to increase the competitiveness of the pulping industry by finding new business opportunities. In this context full utilisation of the wood raw material used in conventional pulping mills is of vital importance. One focus area is to increase the utilisation areas of lignin. LignoBoost is a new method to obtain kraft lignin of high purity.

    The aim of the project was to investigate and increase the ability of LignoBoost kraft lignins to bind metals in aqueous solutions.

    The metal binding property of kraft lignins was evaluated using copper (II) ions. The metal binding capacities were 1.76 mg Cu2+/g LignoBoost softwood kraft lignin, 0.96 mg Cu2+/g LignoBoost hardwood kraft lignin and 1.12 mg Cu2+/g condensed softwood kraft lignin. The metal binding capacities of the softwood and hardwood kraft lignins from LignoBoost were lower than expected, when compared to the metal binding capacities of other lignins found in literature. The highest copper binding capacity of a kraft lignin found in literature was almost 50 times greater than that of the LignoBoost softwood kraft lignin.

     

    The Mannich reaction was used to increase the nitrogen content in softwood lignin, and thereby increase its electron-donating capacity. An increase in electron-donating capacity should promote its metal binding capacity.

     

    The Mannich reaction occurs in the vacant ortho position of the phenolic groups of lignin, introducing an aminomethyl group at that position. The only vacant ortho position in the phenol unit for reaction is in the guaicyl unit. Softwood lignin underwent a Mannich reaction, since softwood contains a greater number of guaiacyl units than hardwoods.

     

    A screening of the products from this Mannich reaction on LignoBoost softwood kraft lignin was performed to optimise the reaction conditions. The reaction time, temperature, amount of formaldehyde and dimethylamine were varied. The Mannich products were evaluated by elemental analysis. The conditions giving the highest nitrogen content in the product were used further in a Mannich reaction of condensed softwood kraft lignin. The condensed softwood kraft lignin (7 g) was treated with dimethylamine (0.35 mol) and formaldehyde (0.35 mol) at 80°C for 24 hours.

     

    The metal binding experiment could not be carried out with Mannich-modified condensed softwood kraft lignin since the lignin dissolved in the copper solution.

     

    When introducing nitrogen functionalities into lignin the electron-donating capacity should increase. An increase in donor groups should promote the metal binding capacity of the lignin. A problem that occurred when introducing aminomethyl groups was an increase in solubility of the lignin. Water solubility of the lignin derivative is undesirable in the envisaged utilization area, metal binding in, for example mine deposits, from where contaminated water may be a concentrated source of heavy metals.

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