Hydroxyl groups chloroacetic acid

Figure 1.89 Chloroacetic acid can be used to create a carboxylate group from a hydroxyl.

Another approach uses reactive alkyl halogen compounds containing a terminal carboxylate group on the other end to form spacer arms off the dextran polymer from each available hydroxyl. In this manner, Brunswick et al. (1988) used chloroacetic acid to modify the hydroxyl groups to form the carboxymethyl derivative. The carboxylates then were aminated with ethylene diamine to create an amine-terminal derivative (Inman, 1985). Finally, the amines were modified with iodoacetate to form a sulfhydryl-reactive polymer (Figure 25.14). 

Figure 25.14 An amine derivative of dextran may be prepared through a two-step process involving the reac-tion of chloroacetic acid with the hydroxyl groups of the polymer to create carboxylates. Next, ethylene diamine is coupled in excess using a carbodiimide-mediated reaction to give the primary amine functional groups.

Sodium starch glycolate is the sodium salt of a poly-ot-glucopyranose in which some of the hydroxyl groups are in the form of the carboxymethyl ether (Fig. 6). Starch is carboxymethylated by reacting it with sodium chloroacetate in an alkaline medium followed by neutralization with acid. Cross-linking is achieved by physical or chemical methods. The sodium starch... 

A method for replacing thiol by hydroxyl groups consists of treating them with chloroacetic acid, which converts them into sulfide groups these products are hydrolysed to the hydroxy compound and mercaptoacetic acid, partly already in hot water but completely only under the action of hot concentrated hydrochloric acid ... 

In the previous chapters the preparation and properties of certain important classes of compounds have been discussed, and the principles which are illustrated in their transformations into one another have been emphasized. These principles are of wide application and can be employed in the preparation of compounds of more complex structure than any met with so far. For example, the method of preparing an alcohol by the treatment of an alkyl halide with water or an alkali, is very general in its application. The reaction consists in the replacement of a halogen atom by a hydroxyl group, and such replacement takes place not only with alkyl halides, but with other compounds which contain halogen. Thus, chloroacetic acid can be transformed into hydroxyacetic acid by water —... 

Halogen-substituted acids are also prepared by the action of the halides of phosphorus on hydroxy-acids hydroxyacetic acid, CH2OH.COOH, for example, is converted into chloroacetyl chloride by phosphorus pentachloride, both hydroxyl groups taking part in the reaction. The substituted acetyl chloride reacts readily with water and chloroacetic acid and hydrochloric acid are formed —... 

Besides the above amine reactions for chitosan, alkylation can take place as well. However, this reaction is able to occur at both the C2 amino group and the C6 primary hydroxyl group of chitosan. Zhu et al. synthesized O-carbojymethyl chitosan (OCMCS) via the reaction of chitosan and mono-chloroacetic acid, where major carboxymethyl substitutions were located at the C6 position. The resulting materials showed better water solubility and ampholytic behavior. Beyond a critical aggregation concentration, the... 

Chemical. A large number of chitin and chitosan derivatives have been synthesized through modification of the primary (C-6) and secondary (C-3) hydroxyl groups present on each repeat imit, including amine (C-2) functionality existing on deacetylated imits (31). Reactions typical of hydroxyl and amine groups (such as acylations with acid chlorides and anhydrides) including urethane and urea formation respectively, are feasible with isocyanates. The primary amine can be quatemized by alkyl iodides or converted to an imine with a variety of aldehydes and ketones that can subsequently be reduced to an N-alkylated derivative. Chitin and chitosan are reactive with a variety of alkyl chlorides after treatment with concentrated NaOH. Important derivatives such as carboxymethylated chitin and chitosan are commonly produced in this manner with the addition of sodium chloroacetate. 

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