Recuperation yield

Abstract New acylation techniques were developed for the fabrication of fatty estos of cellulose and starch. They exclude the use of organic solvents and are readily achieved. Emulsification of the fatty acid in water allowed die intimate contact between the tty recent and die polysaccharide. Fatty acid salts (soap) were used as both catalyst and emulsifying agent. Reaction conditions were optimized using an experimental design. Starch and cellulose octanoates were obtained having a DS of 0.52 and 0.23 with a recuperation yield of 70 and 85 %, respectively. Both polysaccharide esters showed a marked hydrophobic character. 

Conventional synthesis of such materials employs fiitty-acid chlorides or anhydrides in organic solvents. Recently, a fiee-solvent method to esterify starch was developed in our laboratory using formic acid and octanoyl chloride as the gelatinizing and acylating agents respectively. After optimization of reaction conditions, starch octanoate with DS of 1.7 was obtained with a recuperation yield of 89 %. ... 

Figure I. Effect of the reaction time and NaOH catalyst concentration on die (a) degree of substitution and (b) recuperation yield of amylose ester obtained from reaction between amylose and octanoic acid at 195°C. XI (Time) 2 to 6 h X2 ([Catalyst]) 1.5 to 23 meq/eq OH...

The optimization of the reaction conditions was done by using a central composite experimental design. In this case, the variables studied were the catalyst, reagent and water concentrations. The maximum DS (0.23) was obtained with a recuperation yield (RR) of 8S% at the following conditions [potassiiun laurate] = 0,01 eq/eq OH [octanoic acid] = 10 eq/eq OH and [H2O] = 3 eq/eq OH. 

Conditions and results of polyrecombination reaction of /)-dibromoxylene in ATRC and ATRP conditions were collected in Table 2. First experiment was performed under typical ATRC condition at 110 °C for 20 h. Although the precipitate was extracted with toluene and THF, soluble polymer fraction or umeacted monomer could not be separated. At lower temperature and concentration, umeacted monomer was recuperated from the solution and the yield was calculated as 15%. Also, ATRP condition is efficient for this polyrecombination even at relatively low monomer and catalyst concentration. 

The following is observed. Only Method III (and to a lesser extent Method II with r = 16) was capable of recuperating the fine details of the tme MMD, while all the other techniques yielded unimodal solutions. Methods 111 and 11 considerably improve the highly oscillatory direct pseudoinverse solution (not presented here for space reasons). The recuperated average molar masses of Table 1 are in aU cases quite acceptable. 

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