Methylation of Chitosan with Iodomethane: Effect of Reaction Conditions on Chemoselectivity and Degree of Substitution

Abstract

N,N,N‐trimethylchitosan (TMC) was prepared by reacting purified chitosan with iodomethane, in the presence of sodium hydroxide, water and sodium iodide, at room temperature. The reaction medium was N‐methyl‐2‐pyrrolidone. Different samples of TMC were obtained by adding to the reaction medium a fixed volume (5.5 mL) of aqueous NaOH solutions at different concentrations (15, 20, 30 and 40 wt.‐%) and carrying out the reactions for 9 or 24 h. The features observed in the 1H and 13C NMR spectra of these chitosan derivatives, in respect of the chemical shift, number and relative intensity of the signals, depended strongly on the excess of NaOH and H3CI added to the reaction medium, but when the lowest excess was employed, the characteristics of the derivative were not affected by the reaction time to the same extent. The average degree of quaternization of these N‐methylated derivatives of chitosan ranged from 10.5% to 44.8%, according to the reaction conditions. Increasing the excess of NaOH, in reactions carried out for 9 h, resulted in TMC samples with progressively higher content of trimethylated sites however, the reaction yields were correspondingly lower and O‐alkylation was favored in these cases.1H NMR spectrum of sample [AX]24h dissolved in D2O (Cp = 10 g/L).magnified image1H NMR spectrum of sample [AX]24h dissolved in D2O (Cp = 10 g/L).

Derivative spectrophotometric method for determination of acyclovir in polymeric nanoparticles

“…All other chemicals and solvents used were of analytical grade. N,N,N-trimethylchitosan was synthesized by reductive methylation of chitosan based on a previously described method 24 and 1 H-nuclear magnetic resonance spectra was obtained ( Figure 1S, supplementary material).…”

Estudo das interações entre o complexo polieletrolítico trimetilquitosana/carboximetilcelulose e Cu+2, ácido húmico e atrazina em solução aquosa

“…25 De acordo com literatura, 26 a quitosana (0,01 g) foi dissolvida em 1 mL de D 2 O/HCl (100/1 v/v) e o valor de foi determinado a partir da razão de intensidades dos sinais dos hidrogênios metílicos do grupo acetamido (δ≈2,0) e do hidrogênio ligado ao carbono 2 do anel de glicopiranose (3, foi determinado a partir da razão de intensidades dos sinais dos hidrogênios metílicos dos sítios quaternizados (δ=3,3) e do hidrogênio ligado ao carbono 1 do anel de glicopiranose (4,2 <δ< 5,5), como descrito na literatura. 27 Todos os espectros foram adquiridos em espectrômetro Bruker AC200 à temperatura de 90 0 C. A espectroscopia no infravermelho com transformada de Fourier (IVTF) e a espectroscopia de energia dispersiva de raios X (EDX) também foram empregadas para a caracterização de carboximetilcelulose sódica, cloridrato de N,N,N-trimetilquitosana e complexo polieletrolítico TMQ/CMC. Para a aquisição dos espectros das amostras de carboximetilcelulose sódica e cloridrato de N,N,N-trimetilquitosana no infravermelho foram preparados filmes com espessura de 0,05 mm.…”

Antimicrobial analysis of films processed from chitosan and N,N,N-trimethylchitosan

“…Consequently, fewer charged sites will be available to bind to bacterial cell walls. At high polymer concentration, the solvent plays a fundamental role since the formation of clusters by entangled molecules may occur while in solution (Curti et al, 2003). In particular, for polyelectrolytes such as chitosan it is energetically favorable to establish electrostatic interactions between chains, leading to a stabilized ionic network (interchain coupling).…”

“…TMC can be obtained by the covalent addition of a substituent containing a quaternary ammonium group (Curti et al, 2003), or by an exhaustive methylation of the primary amine groups in the parent polymer (Britto and Assis, 2007a). TMC is soluble in a wide pH range and forms films with good mechanical properties (Britto and Assis, 2007b).…”