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PRACICAL ORGANIC CHEMISTRY

(A) FUNCTIONAL GROUP ANALYSIS

1. Unsaturation : Alkenes & alkynes :

(a) Bayer's test : Cold dil alk. KMnO₄ decolourisation test

       Purple colour to Colourless MnO₂ (Brown ppt).

(b) Br₂ water decolourisation test

      Violet colour of Br₂ → Colourless

2. Terminal alkynes :

Confirmed by ppt. of Acetylide ion with NaNH₂ or AgNO₂ or Cu₂Cl₂NH₄OH.

3. Alkyl halides :

(a) If they are capable of carbocation formation then they will give ppt with AgNO₃.

(b) Beilstein's test : A green colour is imported to the flame if small amount of organic compound is taken on copper wire.

4. Alcohol :

(a) Cerric ammonium nitrate → Give red colour

(b) Boil with acetic acid & conc. H₂SO₄ → fruity smell

(c) 2-alkanol & ethanol also give Iodoform test → Yellow ppt. of CH₃I on reaction with I₂  ^-OH

5. Aldehyde & ketones :

2,4-Dinitrophenyl hydrazize (or) Braddy's reagent give yellow, orange or red colour with ald. & Ketones (2, 4-DNP).

6. Aldehydes :

(a) Tollen's test _^→  Silver mirror

(b) Fehling's test {except benzaldehyde} → Red colour

(c) Benedict's test →  Red colour

(d) Schiff's dye colour regeneration test →  Pink colour

(e) Gly ppt. with HgCl₂.

7. Ketones :

(a) methyl ketones give haloform test

(b) a-hydroxy Ketones give Tollen's & Fehling test's too.

8. Carboxylic acids :

(a) Brisk effervescence with aq. NaHCO₃ solution.

(b) HCOOH alone gives silver mirror test with Tollen's reagent.

(c) Blue litmus →  red

(d) give fruity smell of reaction with alcohols.

9. Phenols :

(a) Violet colouration with neural FeCl₃

(b) Liebermann test

(c) White ppt. with Br₂ water

(d) Brisk effervescence with aq. NaHCO₃ is observed in case of Nitrophenols.

10. Primary amines :

(a) Carbylamine reaction →  Isonitriles have very distinctive foul odours.

(b) Hoffmann mustard oil reaction →  Oily liquid with mustard like smell.

11. Aromatic 1º amine →  diazo test

12. Amide boil with NaOH →  NH₃

13. Nitrobenzene →  Mullikqn Baker test: Treat it with ZnNH₄Cl then boil with Tollen's reagent →  Silver mirror will appear

14. Proteins :

(a) Biuret test : Also used for urea →  Alkaline solution of protein treated with a drop of aq CuSO₄ when bluish violet colour is obtained.

(b) Ninhydrin test: Protein treated with a pyridine solution of ninhydrin give colour ranging from deep blue to violet pink.

DIFFERENTATION TEST

D1. 1º, 2º & 3º alcohols :

(a) Luca's test : Lucas reagent is conc. HCl ZnCl₂

(b) Victor Meyer's test (RBC test)

(i) 1º Alcohol →  Blood red colour

(ii) 2º Alcohol →  Blue

(iii) 3º Alcohol →  Colourless

D2. 1º, 2º & 3º amines :

(a) Hinsberg's reagent:

(i) 1º Amine yield a clear solution from which upon acidification an insoluble material separated.

(ii) 2º Amine yield an insoluble compound which is unaffected by acid.

(iii) 3º Amine yield insoluble compound.

(b) Reaction with HNO₂.

SOME IMPORTANT PRACTICAL QUESTIONS:

1. Natural rubber is a polymer of

(1) Chloroprene (2) Isoprene (3) 1,3-Butadiene (4) None

2. Hydroylsis of sucrose is called

(1) saponification (2) Inversion (3) Esterification (2) Hydration

3. In vulcanization of rubber

(1) Sulphur reacts to form a new compound

(2) Sulphur cross-links are introduced

(3) Sulphur forms a very thin protective layer over rubber.

(4) All statements are correct.

4. Which of the following belong to the class of natural polymers ?

(1) Proteins (2) Cellulose (3) Rubber (4) All of the above

5. The reaction of glucose and red P HI is called

(1) Sandmeyer's reaction (2) Reformatsky reaction

(3) Gattermann's reaction (4) Reduction

6. The reagent used in Ruff degradation is :

(1) Baeyer's reagent (2) Tollen's reagent

(3) Fenton's reagent (4) Benedict's reagent

7. Number of possible isomers of glucose is:

(1) 10 (2) 14 (3) 16 (4) 20

8. Glucose reacts with acetic anhydride to form

(1) Monoacetate (2) Tetra acetate

(3) Penta acetate (4) Hexa acetate

9. Glucose or aldohexose contains

(1) One CHO group

(2) Five OH groups

(3) One primary alcoholic group and four secondary alcoholic groups

(4) All are correct

10. When glucose is heated with nitric acid, the product is

(1) Gluconic acid (2) Glucaric acid

(3) Glycolic acid (4) Oxalic acid

11. Cane sugar is made of

(1) 5 membered glucose ring and 5 membered fructose ring

(2) 6 membered glucose ring and 6 membered fructose ring

(3) 6 membered glucose ring and 5 membered fructose ring

(4) 6 membered galactose ring and 6 membered fructose ring

(A) ELEMENTAL ANALYSIS

Lassaigne Method (Detection of Elements)

Element Sodium Extract (S.E.) Confirmed Test Reactions

S.E. FeSO₄,  NaOH, FeSO₄  2NaOH Fe(OH)₂  Na₂SO₄

Nitrogen Na C N NaCN(S.E.) boil and cool, Fe(OH)₂  6NaOH Na₄[Fe(CN)₆] 2NaOH

FeCl₃  conc. HCl Na₄[Fe(CN)₆] FeCl₃ Fe₄[Fe(CN)₆ ]₃  3NaCl

Blue or green colour Prussian blue

(i) S.E. sodium nitro

prusside (A) (i) Na₂S Na₂[Fe(CN)₅NO] Na₄[Fe(CN)₅NOS]

A deep violet colour (A) deep violet

Sulphur 2Na S Na₂S(S.E.) (ii) S.E. CH₃COOH (ii) Na₂S (CH₃COO)₂Pb PbS ¯ 2CH₃COONa

(CH₃COO)₂ Pb black ppt.

A black ppt.

S.E. HNO₃  AgNO₃

(i) White ppt. soluble

in aq. NH₃ confirms Cl NaX AgNO₃ AgX ¯

(ii) Yellow ppt. ppt.

Halogen Na Cl NaCl(S.E.) partially soluble in

aq. NH₃ confirm Br

(iii) Yellow ppt. AgCl 2NH₃(aq)[Ag(NH₃)₂]Cl

in soluble in aq. NH₃ white ppt. soluble

confirms I

As in test for nitrogen;

instead of green or blue