SynopsisThere is a rapid and a slow stage in the decrease of reduced specific viscosity versus time (aging) for a solution of a high intrinsic viscosity polyacrylamide in water. The rapid stage is irreversible and has a fairly high temperature coefficient. Results of the latter type are usually associated with a weak-link scission mechanism, but they can also be reconciled with a disaggregation mechanism. A disaggregation mechanism is also indicated for the rapid stage by an increase in the first-order rate constant with a decrease in the polymer concentration or an increase in the shear rate and by the absence of the rapid stage during the aging of the same sample in formamide. Chemical changes in the polymer are suspected as being responsible for the Its\,* change during the slow stage in the aging of the high intrinsic viscosity polyacrylamide and also in the aging of a polyacrylamide of low intrinsic viscosity. The aging of the polyacrylamide of high intrinsic viscosity is paralleled by a decrease in the ability of the polymer to increase the subsidence of kaolin suspensions. This decrease in the flocculation activity is attributed to a weakening of the interparticle bridging by a change from a strong adsorption of the bridging polymer to two particles to a strong adsorption of the bridging polymer to one particle but weak adsorption of the bridging polymer to the other particle.

Reaction of equivalent amounts of pentaacetyl-P-D-glucopyranose and methanol in benzene or chloroform solution in the presence of 0.5 or more moles of stannic chloride oer mole of methanol pave 50-60Yn vields of methvl tetra-acetyl-8-u-gl~~copyranosidc. a-Xcetocl~lorogl~~cose was ;I by-protltlct of thc rcaction. The mechanisn~ of the reaction is disct~ssed. 'l'he n~etl~otl was applicaClle for the preparation of phenyl tetraacetyl-13-D-glucopyranoside. INTRODUCTIONLemieux and Brice (3) have shown that the treatment of pentaacetyl-0-Dglucopyranose (I) with stannic chloride in chlorofornl solutiol~ resulted in a rapid dissociation of the C1 to acetoxy group bond to yield carbonium ions of which the resonance stabilized 1,2-cyclic ion (11) is the predominant type. Treatment of 1,2,3,4-tetraacetyl-/3-D-glucose under these conditions yielded the internal glucoside, triacetyl-D-glucosan (1,5) P (1, 6) (3). Thus, it was reasonable to expect that treatment of pentaacetyl-/3-D-glucopyranose with stannic chloride in cl~loroform containing an alcohol \srould lead to glucoside formation. Since the ion I1 would predominate and the reaction of this ion with the alcohol under the ,prevailing acidic conditions would be accon~panied by an inversion of the anomeric center, it was expected that the initial reaction 0-0-0-HC-OAcproduct would be the acetylated P-D-glucopyranoside (111). Since pentaacetyl-P-~glucopyranose was found to be rapidly dissociated by stannic chloride (3), it was anticipated that the p-glucoside would be fonned rapidly a t the boiling point of the reaction mixture. Pacsu (8) has shown that stannic chloride can catalyze the anomerization of methyl tetraacetyl-p-D-glucopyranoside only slowly. Consequently, it was expected that the reaction of pentaacetyl-P-D-glucopyranose with methanol in the presence of stannic chloride would afford a good yield of methyl tetraacetyl-P-D-glucopyranoside. Lindberg (5) has shown that the rate of anomerization of a P-glucopyranoside depends greatly on the nature of theaglucon.

Three monosubstituted hydroxyethyl ethers of D-glucoSe have been synthesized by a novel method involving reduction of the corresponding carboxymethyl derivatives with lithium aluminum hydride. This technique also allowed introduction for the first time of hydroxyethyl substituents containing polyethyle~le oxide chain5 of a definite length in the glucose molec~~le, as exemplified by the synthesis of 3-0-hydroxyethoxyethyl-D-glucose.T h e quantitative paper chromatographic technique has recently been applied to distribution studies on hydroxyethylcellulose (I). In order to obtain the hydroxyethyl derivatives of glucose which were needed as reference compounds, a glucose derivative with the appropriate hydroxyl groups unsubstituted was reacted with ethylene oxide in the presence of alltali. This nlethotl of preparation was, however, hampered by the fact that further reaction of the l~~d r o x y e t h y l group t o give polyethylene oxide substituents could not be con trolled. 0T h e synthesis of some carboxgnlethyl derivatives of glucose has recently been described (3). I t has been found that the intermediates which were used for this purpose can be converted b y reduction with lithium aluminum hydride into the corresponding hydroxyethyl derivatives of glucose. By repeated carboxymethylation and reduction of the latter, polyethylene oxide substituents of definite length can also be introduced.Thus, reduction of 3-O-carboxyn~ethyl-l,2;5,6-di-0-isopropylidene-~-glucofuranose methyl ester (3) with lithium aluminum hydride in ethyl ether gave the correspondiilg hydroxyethyl derivative as a sirup. T h e latter was hydro- For personal use only.

The acetolyses of the alpha and beta methyl D-glucopyranoside tetraacetates in 1 : 1 acetic acid -acetic anhydride 0.5 11d with respect to sulphuric acid were followed a t 25'C. by isotopic dilution analysis of products isolated after various intervals of tirne. The reaction of the a-glucoside was found to proceed mainly with inversion of the anomeric center. On the other hand, the 0-glucoside was found to undergo acetolysis with retention of configuration concurrent with anomerization. I t was shown t h a t the polarimetric changes observed in the course of the reactions could be satisfactorily accounted for on the basis of these reaction routes. Reaction mechanisms are suggested. Montgomery et al. (15) investigated the use of either sulphuric acid or zinc chloride in acetic acid -acetic anhydride as a reagent for the acetolysis of glycosides. I t was shown that in many cases the glycoside was converted to a mixture of the anomeric sugar acetates in high yield and the procedure has been widely used for the cleavage of acetal bonds in carbohydrate chemistry. Studies on the acetolysis of the anomeric methyl D-arabinopyranoside triacetates showecl these reactions to be highly complex (15). A solution a t 20°C.of nlethyl a-D-arabinopyranoside triacetate in a mixture of 4y0 sulphuric acid in 7 : 3 acetic anhydride -acetic acid changed sharply in specific rotation from -lgO to -114O in one minute and declined to an equilibrium value of -ZO a t the end of 20 min. The hexaacetate of aldel~ydo-D-arabinose and p-D-arabinopyranose tetraacetate were isolated in yields of soy0 and 12%, 1-espectively, from the product. However, when the experiment was interrupted a t the rotation peak of -114", a 14% yield of methyl /3-D-arabinopyi-anoside triacetate was obtained. Thus, it was apparent that the rapid initial rise in rotation was d~~e to the anomerization of the a-anoiner to the more stable /3-form. This possibility was strengthenecl by the observ a t' loll that ~nethyl @-D-arabinopyranosicle triacetate under the same conditions gave a solution which changed in specific rotation from -184' t o a constant equilibrium value of -17" in three minutes. The hcxaacetate and the p-tetraacetate could be isolated in 56y0 and 11% yields, respectively, after 24 hr. The occurrence of the hexaacetate in the reaction products suggested that the C1 to ring-oxygen bond may cleave in preference to the C1 to methoxyl group bond. This idea was substantiated by the acetolysis of the p-arabinoside under the milder conditions of O.l6Y0 sulphuric acid in 7 : 3 acetic anhydride -acetic acid mixture. Both the anomeric forms of methyl hemiacetal pentaacetates (I) were isolated in good and approximately equal yields. I t is to be notecl that liLl~nz~script received September 7 , 1954 More recently, Lindberg (1, 2, 13) has obtained further evidence that the acetolysis of an unstable 0-acetylated allcyl glycopyranoside is accompanied by anomerization. This was shown to be so for a variety of glucosides (13), galactosides ( I ) , and a xyloside (2...

1,2‐Dimethyl‐5‐vinylpyridinium methyl sulfate is readily polymerizable in aqueous solution under mild free radical conditions to a high molecular weight, cationic polyelectrolyte. A three‐halves order dependence of the rate of polymerization on monomer concentration is indicated for about 75% of the polymerization of 1,2‐dimethyl‐5‐vinylpyridinium methyl sulfate in aqueous solution with potassium persulfate as initiator. A normal dependence of the polymerization rate on the square root of the initiator concentration is also indicated by these data. The overall activation energy is estimated to be about 17 kcal./mole. Preliminary experiments related to the effect of changing the ionic strength of the reaction medium by addition of sodium chloride led to a change in the kinetics with a dramatic slowing‐down of the polymerization. Copolymerization studies indicate that the reactivity of this cationic monomer is higher than that of acrylamide, methacrylamide, and methyl methacrylate, but close to that of methacrylic acid.