Transcript hydrolysis-of-sucrose

Sucrose is non-reducing disaccharides,
therefore, it neither gives positive result
with Benedict’s, and Barfoed’s regeants,
nor does it form any Osazone crystals.
However, its components give these test
positive
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Heating of sucrose in the presence of concentrated
HCL causes its hydrolysis into glucose & fructose.
Because glucose have free aldehyde group and
fructose have free ketone group, therefore both are
strongly reducing sugars’ and hence Benedict’s
Selivanoff’s & Osazone test become positive.
Sodium carbonate is added to neutralize excessive
HCL, because the ability of reducing sugars is high in
alkaline medium, and hence gives good result of
Benedict’s, Selivanoff’s & Osazone tests.
Addition of sodium carbonate produces effervescence
(Formation of Bubble) because of CO2 production
Na2CO3 + 2HCl
→
2NaCl+H2O+CO2
Reagents of Hydrolysis
Concentrated Hydrochloric acid
Solid sodium carbonate
Reagents for Benedict’s qualitative test
Copper Sulphate
Sodium citrate
Anhydrous sodium carbonate
Reagents for Selivanoff’s test
Resorcinal
Concentrated hydrochloric acid
Reagents for Osazone test
Phenyl hydrazine hydrochloride
Sodium Acetate
Glacial acetic acid
 Take
two test tubes and lebal them as “T” (for
test) and “c” (for control)
 Take 15ml of sucrose solution in both test
tubes. Add 10 drops of concentrated
hydrochloric acid in test tube “T” and 1ml of
distilled water in test tube “C”
 Heat both test tubes for 2 minute and then cool
at room temperature. Add very small amount
of solid sodium carbonate in both test tubes.
Continue to add sodium carbonate till the
effervescence (formation of bubbles) stops in
“T” test tube
 Now from both test tube, take small quantity in
separates test tubes to perform benedicts’,
Selivanoff’s, Osazone tests.
In test tube “C” Benedicts’, Selivanoff’s,
Osazone tests remain negative, because the
sucrose is not hydrolyzed due to absence of
concentrated hydrochloric acid in this tube.
 In test tube “T” Benedicts’, Selivanoff’s,
Osazone tests become positive, because the
sucrose has hydrolyzed into glucose and
fructose (Strongly Reducing
Monosaccharide’s) due to presence of
concentrated hydrochloric acid in this tube.
