Reactivity Of Carboxyl Groups Research Articles

A novel, mild and selective methylation of carboxyl groups in cellulosic pulps 10th EWLP, Stockholm, Sweden, August 25–28, 2008

Abstract A method for selective, fast, and near-quantitative methylation of carboxyl groups in the presence of aliphatic hydroxyl groups of cellulose was developed. The main advantage of the method is the complete maintenance of cellulose integrity; no degradation of cellulose whatsoever during the methylation procedure was observed, making the protocol extremely useful in advanced cellulose analytics. Trimethylsilyl diazomethane (TMS-DAM) was used as the methylation agent. The methylation conditions were pre-optimized by means of carbohydrate model compounds with low-molecular weight, such as derivatives of glucuronic acid and hexenuronic acid, and then re-optimized for methylation of cellulose. The influence of reaction parameters, such as time, temperature, solvents, and concentration, was also determined. The reaction kinetics was monitored by fluorescence labeling of the remaining carboxyl groups according to the common FDAM protocol. A general protocol for the fast methylation of carboxyl groups in pulp samples is presented. The methylation with TMS-DAM is a very fast process, both in comparison to general heterogeneous reactions on cellulosic pulps, and especially in comparison to other methylation approaches. In dissolving and paper grade pulps, methylation of xylan carboxyls proceeded faster than methylation of cellulosic carboxyls. The methylation rate and kinetics are dependent on the pulp type. As application examples, electrokinetic measurements were used to demonstrate the “blocked” reactivity of carboxyl groups in spin-coated films of methylated pulp samples, and ICP-MS was used to demonstrate the drastically decreased metal ion binding capacity of pulp after such methylation.

Reactivity of Carboxylic Groups on Armchair and Zigzag Carbon Nanotube Tips: A Theoretical Study of Esterification with Methanol

A theoretical study of gas-phase esterification of monocarboxy fragments of armchair (10,10) and zigzag (16,0) single-walled carbon nanotubes (SWNTs) with methanol was performed by using a two-leve...

Grafting of Polymers onto a Crosslinked Polymer Carrying Carboxyl Groups as a Model Compound for Carbon Black

Abstract A cation-exchange resin (a crosslinked polymer carrying carboxyl groups) was used as a model compound for carbon black, and the grafting of several polymers to the resin was investigated. Reaction of acyl chloride groups that had been placed on the ion-exchange resin with polymers having hydroxyl or amino groups, such as polypropylene glycol, polyethylene glycol, polybutadiene glycol, polyvinyl alcohol, silicone diol, silicone diamine, and polyethyleneimine, resulted in grafting to the ion-exchange resin. In further experiments, primary amino groups were placed on the cation-exchange resin by reaction of acyl chloride groups with ethylenediamine. It was found that ring-opening polymerization of γmethyl L-glutamate N-carboxyanhydride is initiated by the amino groups on the resin, and polypeptide was grafted from the cation-exchange resin. Therefore, the reactivity of carboxyl groups on the resin was found to be similar to that on carbon black. However, carboxyl groups on the resin failed to initia...

Gel formation of soybean 7S and 11S proteins.

Rheological properties of soybean 7S and 11S proteins were investigated at the concentrations in which both could form the heat-induced gel. It was recognized that 7S protein formed gel at the lower concentration than that of 11S protein. In forming gel, 11S protein seems to have the ability to form more hydrogen bonds and ionic attractions and less hydrophobic interactions than those of 7S protein. In the presence of salts, the gel of 7S protein was formed at the lower protein concentration compared with the absence of salts. But the addition of salts to 11S protein suppressed the formation of gel even with high protein concentration. The reactivity of carboxyl groups was determined by the dye-binding method. The 11S protein contained reactive carboxyl groups.

The reactivity of carboxyl groups in chymotrypsinogen

Recent work from this laboratory reported the functional and structural consequences of the modification of carboxylates in chymotrypsinogen (ChTg), chymotrypsin (ChTi), trypsinogen (Tg) and trypsin (Ti) [l] with glycine ethyl ester (GEE) under the influence of l-ethyl-3<3-dimethylaminopropyl) carbodiimide (EDC) by the method of Hoare and Koshland [2]. The results of a similar and independent study were published at about the same time by Carraway et al. [3]. We present in this paper complementary information and the results of our sequence studies*.