General Formula of Carbohydrates C x ( H 2 O ) y \text{C}_x(\text{H}_2\text{O})_y C x ( H 2 O ) y Classical representation of carbohydrates as hydrates of carbon.
applies when Has exceptions: some carbohydrates (e.g., rhamnose, C6H12O5) do not fit, and some non-carbohydrates (e.g., acetic acid, C2(H2O)2) do.
carbohydrates general_formula
CHO − ( CHOH ) 4 − CH 2 OH + 5 ( CH 3 CO ) 2 O → CHO − ( CHOCOCH 3 ) 4 − CH 2 OCOCH 3 + 5 CH 3 COOH \text{CHO}-(\text{CHOH})_4-\text{CH}_2\text{OH} + 5(\text{CH}_3\text{CO})_2\text{O} \rightarrow \text{CHO}-(\text{CHOCOCH}_3)_4-\text{CH}_2\text{OCOCH}_3 + 5\text{CH}_3\text{COOH} CHO − ( CHOH ) 4 − CH 2 OH + 5 ( CH 3 CO ) 2 O → CHO − ( CHOCOCH 3 ) 4 − CH 2 OCOCH 3 + 5 CH 3 COOH Reaction with acetic anhydride yields glucose pentaacetate, confirming five -OH groups.
applies when Anhydrous conditions.
acetylation esterification pentaacetate
Mild Oxidation of Glucose CHO − ( CHOH ) 4 − CH 2 OH → Br 2 / H 2 O COOH − ( CHOH ) 4 − CH 2 OH \text{CHO}-(\text{CHOH})_4-\text{CH}_2\text{OH} \xrightarrow{\text{Br}_2 / \text{H}_2\text{O}} \text{COOH}-(\text{CHOH})_4-\text{CH}_2\text{OH} CHO − ( CHOH ) 4 − CH 2 OH Br 2 / H 2 O COOH − ( CHOH ) 4 − CH 2 OH Oxidation with bromine water yields gluconic acid, proving the carbonyl is an aldehyde.
applies when Requires a mild oxidizing agent like Br2 water.
oxidation mild gluconic_acid
Glucose reaction with HCN CHO − ( CHOH ) 4 − CH 2 OH + HCN → CH(OH)(CN) − ( CHOH ) 4 − CH 2 OH \text{CHO}-(\text{CHOH})_4-\text{CH}_2\text{OH} + \text{HCN} \rightarrow \text{CH(OH)(CN)}-(\text{CHOH})_4-\text{CH}_2\text{OH} CHO − ( CHOH ) 4 − CH 2 OH + HCN → CH(OH)(CN) − ( CHOH ) 4 − CH 2 OH Reaction forming a cyanohydrin, proving the presence of a carbonyl group.
applies when Occurs with the open-chain form of glucose.
cyanohydrin nucleophilic_addition glucose
Reduction of Glucose with HI CHO − ( CHOH ) 4 − CH 2 OH → Δ , HI CH 3 − ( CH 2 ) 4 − CH 3 \text{CHO}-(\text{CHOH})_4-\text{CH}_2\text{OH} \xrightarrow{\Delta, \text{HI}} \text{CH}_3-(\text{CH}_2)_4-\text{CH}_3 CHO − ( CHOH ) 4 − CH 2 OH Δ , HI CH 3 − ( CH 2 ) 4 − CH 3 Prolonged heating of glucose with hydrogen iodide yields n-hexane, proving its 6-carbon straight chain.
applies when Prolonged heating with concentrated HI.
reduction glucose structure_elucidation
Strong Oxidation of Glucose CHO − ( CHOH ) 4 − CH 2 OH → HNO 3 COOH − ( CHOH ) 4 − COOH \text{CHO}-(\text{CHOH})_4-\text{CH}_2\text{OH} \xrightarrow{\text{HNO}_3} \text{COOH}-(\text{CHOH})_4-\text{COOH} CHO − ( CHOH ) 4 − CH 2 OH HNO 3 COOH − ( CHOH ) 4 − COOH Oxidation with nitric acid yields saccharic (glucaric) acid, proving the presence of a primary alcohol.
applies when Requires a strong oxidizing agent like HNO3.
oxidation strong saccharic_acid
Glucose reaction with Hydroxylamine CHO − ( CHOH ) 4 − CH 2 OH + NH 2 OH → CH=NOH − ( CHOH ) 4 − CH 2 OH + H 2 O \text{CHO}-(\text{CHOH})_4-\text{CH}_2\text{OH} + \text{NH}_2\text{OH} \rightarrow \text{CH=NOH}-(\text{CHOH})_4-\text{CH}_2\text{OH} + \text{H}_2\text{O} CHO − ( CHOH ) 4 − CH 2 OH + NH 2 OH → CH=NOH − ( CHOH ) 4 − CH 2 OH + H 2 O Reaction confirming the presence of a carbonyl group via oxime formation.
applies when Occurs with the open-chain form of glucose.
carbonyl_addition oxime glucose
Enzymatic Hydrolysis of Maltose C 12 H 22 O 11 + H 2 O → Maltase 2 C 6 H 12 O 6 \text{C}_{12}\text{H}_{22}\text{O}_{11} + \text{H}_2\text{O} \xrightarrow{\text{Maltase}} 2\text{C}_6\text{H}_{12}\text{O}_6 C 12 H 22 O 11 + H 2 O Maltase 2 C 6 H 12 O 6 Hydrolysis of maltose catalyzed by the enzyme maltase.
applies when Physiological/enzymatic conditions.
enzyme maltose hydrolysis
Mutarotation Equilibrium Specific Rotation [ α ] eq = [ α ] α X α + [ α ] β X β [\alpha]_{\text{eq}} = [\alpha]_{\alpha} X_{\alpha} + [\alpha]_{\beta} X_{\beta} [ α ] eq = [ α ] α X α + [ α ] β X β Calculation of the specific rotation of an anomeric mixture at equilibrium.
applies when Aqueous solution allowed to reach dynamic equilibrium.
mutarotation anomers jee-advanced
C 6 H 12 O 6 + 3 PhNHNH 2 → Δ Glucosazone + PhNH 2 + NH 3 + 2 H 2 O \text{C}_6\text{H}_{12}\text{O}_6 + 3\text{PhNHNH}_2 \xrightarrow{\Delta} \text{Glucosazone} + \text{PhNH}_2 + \text{NH}_3 + 2\text{H}_2\text{O} C 6 H 12 O 6 + 3 PhNHNH 2 Δ Glucosazone + PhNH 2 + NH 3 + 2 H 2 O Reaction of reducing sugars with excess phenylhydrazine to form an osazone. Glucose, fructose, and mannose form the exact same osazone.
applies when Excess (3 equivalents) of phenylhydrazine is required.
osazone phenylhydrazine jee-advanced
Commercial Preparation of Glucose ( C 6 H 10 O 5 ) n + n H 2 O → 2 − 3 atm 393 K , H + n C 6 H 12 O 6 (\text{C}_6\text{H}_{10}\text{O}_5)_n + n\text{H}_2\text{O} \xrightarrow[2-3 \text{ atm}]{393\text{ K}, \text{H}^+} n\text{C}_6\text{H}_{12}\text{O}_6 ( C 6 H 10 O 5 ) n + n H 2 O 393 K , H + 2 − 3 atm n C 6 H 12 O 6 Hydrolysis of starch or cellulose yielding n molecules of glucose.
applies when Boiled with dilute H2SO4 at 393 K under 2-3 atm pressure.
hydrolysis starch polysaccharides
C 12 H 22 O 11 + H 2 O → H + C 6 H 12 O 6 ( Glucose ) + C 6 H 12 O 6 ( Fructose ) \text{C}_{12}\text{H}_{22}\text{O}_{11} + \text{H}_2\text{O} \xrightarrow{\text{H}^+} \text{C}_6\text{H}_{12}\text{O}_6 \, (\text{Glucose}) + \text{C}_6\text{H}_{12}\text{O}_6 \, (\text{Fructose}) C 12 H 22 O 11 + H 2 O H + C 6 H 12 O 6 ( Glucose ) + C 6 H 12 O 6 ( Fructose ) Hydrolysis of cane sugar yielding equimolar glucose and fructose (invert sugar).
applies when Boiled with dilute HCl or H2SO4 in alcoholic solution.
hydrolysis sucrose disaccharides