Chemlab Practicals (Experiment 5-8) (FINALS) WITH PICTURES

Schiff’s Test

HCHO
=POSITIVE

Schiff’s solution (fuchsin decolorized by H2SO4) + HCHO —→

=ROSEPINK SOLUTION

Schiff’s Test

C6H5CHO
=POSITIVE (slow reaction)

Schiff’s solution (fuchsin decolorized by H2SO4) + C6H5CHO —→

=ROSEPINK SOLUTION

ACETONE (schiff’s test)

Schiff’s Test

CH3COCH3
=NEGATIVE (does not contain an aldehyde group)

Schiff’s solution (fuchsin decolorized by H2SO4) + CH3COCH3 —→

=COLORLESS SOLUTION

Resorcinol Test
(HCHO only)

HCHO
=POSITIVE

HCHO + .5% Resorcinol + H2SO4 —→

=RED FLOCCULENT PRECIPITATE AT THE JUNCTION OF TWO LAYERS
(sulfuric acid at the bottom, formaldehyde at top)

Tollen’s Test
(Silver Mirror Test)

HCHO (Formalin with 37-40% formaldehyde)
=POSITIVE

HCHO + Ag(NH3)2 —→

=SILVER MIRROR SOLUTION AT THE WALLS OF THE TEST TUBE

BENZALDEHYDE (tollen’s test)

Tollen’s Test
(Silver Mirror Test)

C6H5CHO
=POSITIVE

C6H5CHO + Ag(NH3)2 —→

=SILVER MIRROR SOLUTION AT THE WALLS OF THE TEST TUBE

ACETONE (tollen’s test)

Tollen’s Test
(Silver Mirror Test)

CH3CO3CHO
=NEGATIVE (does not contain an aldehyde group)

CH3CO3CHO + Ag(NH3)2 —→

=COLORLESS SOLUTION

Fehling’s Test

HCHO (Formalin with 37-40% formaldehyde)
=POSITIVE

HCHO + Cu(OH)2 —→

=Cu2O (CUPROUS (I) OXIDE) BRICK RED PRECIPITATE

Fehling’s Test

C6H5CHO
=NEGATIVE

C6H5CHO + Cu(OH)2 —→

=REMAINED BLUE

Fehling’s Test

CH3COCH3
=NEGATIVE

CH3COCH3 + Cu(OH)2 —→

=REMAINED BLUE

Formaldehyde on Protein Substances

1 ml FORMALIN + 1 ml H2O + GELATIN SHEET
=GELATIN SHEET HARDENED
=insoluble in solution with formalin
=due to crosslinking between molecules

2 ml H2O
=GELATIN SHEET SOFTENED
=soluble in water

C6H5CHO in watch glass

Auto-Oxidation of Benzaldehyde

=WHITE CRYSTALS (BENZOIC ACID)
=C6H5CHO turned to C6H5COOH due to oxidation from the exposure to the atmosphere

C6H5C=O —[O]—>C6H5C-O-OH —[O]—>
|| ||
O O

C6H5C-OH
|| (BENZOIC ACID)
O

Addition of Sodium Bisulfite

=WHITE PRECIPITATE (ACETONE SODIUM BISULFITE)

CH3COCH3 + NaHSO3 ——>

CH3COHCH3
|
SO3Na

Addition of Phenyl hydrazine

=YELLOW-ORANGE PRECIPITATE (ACETONE 2,4-DINITROPHENYLHYDRAZONE)

CH3COCH3 + C6H5NHNH2——>

CH3CCH3
||
NHNHC6H5

Iodoform Test

=Acetone + 10% NaOH + Iodine Solution

CH3COCH3 + 3I₂ + 4NaOH——>

CHI3 +CH3COONa + 3Nai + 3H₂O

Biuret Test

1% Egg Albumin Solution + CuSO4 + 10% NaOH —→

=ROSEPINK SOLUTION

Xanthoproteic Test

1% Egg Albumin Solution + Conc. HNO3 + Conc. NH4OH—→

=YELLOW-ORANGE PRECIPITATE

• YELLOW with HNO3

• ORANGE with NH4OH after being neutralized

Millon’s Test
-Millon’s solution: dissolving mercury in nitric acid, mercurous or mercuric nitrates

1% Egg Albumin Solution +Millon’s Reagent (HgNO3)

=FLESH TO RED PRECIPITATE

Molisch’s Test
-Molisch Reagent: Alpha naphthol in ethanol

1% Egg Albumin Solution + Molisch Reagent + H2SO4

=VIOLET RING AT THE JUNCTION OF TWO LAYERS

Sulfur Test

1% Egg Albumin Solution + NaOH + Ch3COOH
(Cover with filter paper dipped in Pb(Ch3COO)2——>

=BLACK PRECIPITATE (LEAD (II) SULFIDE PbS

Effect of Heat on Proteins

=PROTEIN COAGULATES

Heller’s Ring Test

1% Egg Albumin Solution + HNO3——→

=WHITE PRECIPITATE AT THE CENTER OF TWO LATERS.

Heavy Metal Salts

• Copper (I) Sulfate

  = BLUE PRECIPITATE

• Lead (II) Acetate

  = WHITE RECIPITATE

• Silver Nitrate

  = WHITE PRECIPITATE

Alkaloidal Reagent

• 5% Tannic Acid

  =BROWN PRECIPIATE

• 5% Potassium Ferrocyanide

  = BLUE PRECIPIATE

• conc. Picric Acid

  =YELLOW PRECIPIATE

Molisch’s Test
-Molisch Reagent: Alpha naphthol in ethanol

H2O

=NEGATIVE
(water does not contain carbohydrates)

=UNMIXED SOLUTION

Molisch’s Test
-Molisch Reagent: Alpha naphthol in ethanol

C6H12O5 (glucose)
=POSITIVE

C6H12O5 + Molisch Reagent + H2SO4—→

=VIOLET RING AT THE JUNCTION OF TWO LAYERS

Molisch’s Test
-Molisch Reagent: Alpha naphthol in ethanol

C12H22O11 (sucrose)
=POSITIVE

C12H22O11 + Molisch Reagent + H2SO4—→

=VIOLET RING AT THE JUNCTION OF TWO LAYERS

Molisch’s Test
-Molisch Reagent: Alpha naphthol in ethanol

C6H10O5 (starch)
=POSITIVE

C6H10O5 + Molisch Reagent + H2SO4—→

=VIOLET RING AT THE JUNCTION OF TWO LAYERS

Moore’s Test

C6H12O5 (glucose)
=POSITIVE

C6H10O5 + 25% NaOH —→

=CARAMEL ODOR (DARK BROWN RESINOUS SUBSTANCE)

Moore’s Test

C12H22O11 (Sucrose)
=NEGATIVE
- sucrose is a non-reducing sugar

C6H10O5 + 25% NaOH —→

= COLORLESS SOLUTION

Benedict’s Test
-Benedict’s solution: CuSO4 + Na2CO3 + Sodium Citrate

C6H12O5 (glucose)
=POSITIVE

C6H12O5 (lactose)
=POSITIVE

C6H12O5+ Cu(OH)2 —→

=C6H12O6 + H2O + Cu2O (CUPROUS (I) OXIDE) BRICK RED PRECIPITATE

Benedict’s Test
-Benedict’s solution: CuSO4 + Na2CO3 + Sodium Citrate

C12H22O11 (sucrose)
=NEGATIVE

C6H10O5 (starch)
=NEGATIVE

-both are non-reducing sugars

C6H12O5+ Cu(OH)2 —→

=REMAINED BLUE

HYDROLYSIS OF SUCROSE (C12H22O11)

SUCROSE (C12H22O11) + HCL —→

HYDROLYZED SUCROSE
(broken down into GLUCOSE and FRUCTOSE)

Benedict’s Test
-Benedict’s solution: CuSO4 + Na2CO3 + Sodium Citrate

HYDROLYZED C12H22O11 (sucrose)
=POSITIVE

=now positive, because sucrose has broken into GLUCOSE AND FRUCTOSE

HYDROLYZED C12H22O11+ NaOH —→ Neutralized Sucrose

HYDROLYZED C12H22O11+ Cu(OH)2 —→

=C12H22O12 + H2O + Cu2O (CUPROUS (I) OXIXDE) BRICK RED PRECIPITATE

Seliwanoff’s Test
-Seliwanoff’s solution: Resorcinol + HCl

HYDROLYZED C12H22O11 (sucrose)
=POSITIVE

=now positive, because sucrose has broken into GLUCOSE AND FRUCTOSE
=Seliwanoff is test for Fructose

HYDROLYZED C12H22O11+ NaOH —→ Neutralized Sucrose

HYDROLYZED C12H22O11+ Seliwanoff’s reagent (Resorcinol + HCl)—→

=MAHOGANY RED SOLUTION

HYDROLYSIS OF STARCH (C6H10O5)

STARCH (C6H10O5) + HCl ——> HYDROLYZED STARCH C6H10O5

=broken down into GLUCOSE

IODINE TEST (for starch)

SOLUBLE STARCH (blue) ——> AMYLODEXTRIN (purple) ——> ERYTHRODEXTRIN (red) ——> ACHRODEXTRIN (colorless) ACHROMATIC POINT——> MALTOSE (colorless) ——> GLUCOSE (colorless)

=once broken down into glucose, starch has fully hydrolyzed
=IODINE is used to test the presence of STARCH

Benedict’s Test
-Benedict’s solution: CuSO4 + Na2CO3 + Sodium Citrate

HYDROLYZED STARCH C6H10O5
=POSITIVE

=now positive, because sucrose has broken into GLUCOSE

C6H10O5+ Cu(OH)2 —→

=C6H10O6 + H2O + Cu2O (CUPROUS (I) OXIXDE) BRICK RED PRECIPITATE

MISCIBILITY TEST

H2O (POLAR)
-all oils was immiscible with H2O
-OIL is NONPOLAR, H2O is POLAR

CH3CH2OH (HAS BOTH POLAR AND NONPOLAR PROPERTIES)
-all oils was immiscible with CH3CH2OH
-OIL is NONPOLAR, CH3CH2OH is BOTH NONPOLAR AND POLAR

CHCl3 (NONPOLAR)
-all oils was miscible with CHCl3
-OIL is NONPOLAR, CHCl3 is NONPOLAR

Acrolein Formation

• Coconut Oil (has Lauric acid) + KHSO4

  =MILD IRRITATING ODOR

• Glycerol (CH2OHCHOHCH2OH) + KHSO4

  =PUNGENT IRRITATING ODOR/ ACROLEIN (2-PROPENAL) CH2CHCHO

EQUATIONS

• Coconut Oil + KHSO4 ——> Lauric Acid + CH2OHCHOHCH2OH

• CH2OHCHOHCH2OH + KHSO4 ——>

  CH2CHCHO (ACROLEIN)

SOLUBILITY TSET (HUBLE’S TEST)

=the more a substance discolorizes IODINE, the more UNSATURATED
=unsaturated substances ABSORB IODINE, fads the color the of the IODINE

• LINSEED OIL
  =Linolenic Acid
  =MOST UNSATURATED
  

• COTTONSEED OIL
  =Linoleic Acid
  =Unsaturated
  

• OLIVE OIL
  =Oleic Acid
  =Unsaturated
  

• COCONUT OIL
  =Lauric Acid
  =SATURATED / NOT UNSATURATED
  =did not discolorize I2 solution

• Coconut Oil + 10% NaOH ——>

• Glycerol+ 10% NaOH ——>

Saponification
=hydrolysis in a basic medium

• Coconut Oil + 10% NaOH ——> CH2OHCHOHCH2OH + 3C11H23COONa (soap/metallic salt)