Chemistry · Ch 14 — Biomolecules
Preparation of glucose from starch
Preparation of glucose from starch
On a commercial scale, glucose is manufactured by hydrolysing starch rather than sucrose, because starch (from grains such as maize) is a cheaper and more abundant raw material. Starch is boiled with dilute sulfuric acid at 393 K (120 C) under an elevated pressure of 2 to 3 atmospheres -- considerably harsher conditions than the simple warming used for sucrose, reflecting how much more resistant starch's many alpha-1,4-glycosidic linkages are to hydrolysis compared with sucrose's single linkage. Every repeating glucose unit along the starch polymer chain is released as one free glucose molecule: (C6H10O5)n + n H2O, with H+ catalyst at 393 K and 2-3 atm, gives n C6H12O6 (glucose). This acid hydrolysis of starch is the prin …
Worked out. Reaction scheme: (C6H10O5)n (starch) + n H2O, in the presence of H+ catalyst at 393 K and 2-3 atm pressure, gives n C6H12O6 (glucose). Each repeating glucose unit of the starch polymer is released as one free glucose molecule, so complete hydrolysis of n linked units consumes n water molecules and yields n glucose molecules -- this is the large-scale industrial route to …