Study of selective oxidation of starch

Corn starch was selectively oxidated by periodate sodium.The effect of acid category,reaction time,pH,temperature,the ratio of amount of substance of reactant on the oxidation reaction was studied in detail.And the conclusions were explained on the basis of thermodynamics and electrochemistry.The optimum reaction conditions are as follows: the ratio of amount of substance of periodate sodium to starch is 1∶1,pH is 3.5 by dilute H2SO4,temperature is 25 ℃,reaction time is 6 h,and the dialdehyde percentage of product is 99.7%.While the ratio of amount of substance of periodate sodium to starch is less than 1,the fit of dialdehyde content and the ratio of amount of substance of reactant to linearity is very good.Periodate sodium can react completely.Thus,the oxidation degree of product can strictly be controlled by ratio of amount of substance of periodate sodium to starch.The product was characterized by IR and SEM.The aldehyde groups of dialdehyde starch existed mainly in the forms of acetal or hemiacetal,which was confirmed by IR.The morphological changes of starch were analyzed by SEM.