CHEM LAB

Exam Tips 2.ppt

SODIUM FUSION(LASSAIGNES) TEST

THE ORGANIC COMPOUND TO BE TESTED IS FUSED WITH METALLIC SODIUM.IN THIS WAY SODIUM CYANIDE,SODIUM SULPHIDE AND/OR SODIUM HALIDES IS FORMED WHICH CAN BE READILY IDENTIFIED.

TEST FOR NITROGEN

THE CYANIDE FORMED CAN BE DETECTED BY PRUSSIAN BLUE TEST.

STEP 1: FESO4 + 6NACN=Na4[Fe(CN)6]+Na2SO4

STEP 2: 3Na4[Fe(CN)6] + 2Fe2(SO4)3=Fe4[Fe(CN)6]3(PRUSSIAN BLUE)+6Na2SO4

TEST FOR SULPHUR

THIS IS TESTED AS SULPHIDE TEST 1: THE COMPOUND IS TREATED WITH DIL. ACETIC ACID AND

THEN WITH LEAD ACETATE.A BLACK PRECEPATE OF LEAD ACETATE INDICATES THE

PRESENCE OF SULPHUR

TEST 2:THE COMPOPUND IS TREATED WITH DIL.SOLN. OF

Na2[Fe(CN)5NO] A PURPLE COLOURED COMP. OF Na4[Fe(CN)5NOS] IS FORMED INDICATING THE PRESENCE OF SULPHUR.

TEST FOR HALOGENS

THE FUSION SOLN IS ACIDIFIED WITH DIL.HNO3 AND THEN EXCESS OF AgNO3 IS ADDED.

COLOUR SOLUBILITY IN Aq. Ammonia

HALOGEN

WHITE COMPLETELY SOLUBLE

Cl

PALE YELLOW

PARTIAL SOL.

Br

YELLOW IN SOLUBLE. I

_OH (ALCOHOLIC)

TEST 1::SODIUM TEST 2ROH+2Na=2RONa+H2(GAS) TEST 2:: ACETYL CHLORIDE TEST

acetyl chloride reacts vigorously with primary and secondary alcohols with evolution of HCl.

HCl +NH4OH =NH4Cl(WHITE FUMES)+ H2O

PHENOL

GIVES VIOLET COLOUR WITH FeCl3 SOLN.

FeCl3+6C6H5OH= [Fe(OC6H5)6]-3+3HCl

CARBONYL TEST

FOR ALDEHYDES AND KETONES.

2,4-DINITROPHENYL HYDRAZINE-TEST

-> FORMATION OF CRYSTALLINE PRECIPITATE WITH THE REAGENT INDICATES THE PRESENCE OF ALDEHYDES AND KETONES.

SPECIFIC FOR ALDEHYDES

SCHIFF’S TEST

->APPEARANCE OF PINK RED OR MAGENTA COLOR WITH REAGENT.

TOLLEN’S TEST ->SILVER MIRROR WITH REAGENT(Ag+).

FEHLING’S TEST ->RED PRECIPITATE OF Cu2O WITH ALDEHYDE GROUP.

CARBOXYLIC GROUP

LITMUS TEST (BLUE TO RED). SODIUM BICARBONATE

TEST(NaHCO3).CO2 MOVES OUT FROM NaHCO3.

ESTER TEST: REACTS WITH ALCOHOL TO GIVE SWEET SMELLING COMPOUND(ESTER).

ALIPHATIC AMINO GROUP

WITH HNO2 PRIMARY GROUP GIVES ALCOHOL

WITH HNO2 SEC GIVES NITROSOAMINES YELLOW OILY LIQUID(R2N-NO).

WITH HNO2 TERTIARY GROUP GIVES TRIALKYLAMMONIUM NITRITE (R3 N+ HONO-)

AROMATIC AMINES

WITH HNO2 PRIMARY GIVES BENZENE DIAZONIUM CHLORIDES(PhN2+ Cl-).

SECONDARY GROUP GIVES N-ALKYL-N-PHENYL NITROSOAMINE.

TERTIARY GROUP GIVES P-NITROSOANILINE.

SPECIFIC FOR PRIMARY AMINE(ALI+ARO) UNPLEASANT ODOUR OF ISOCYNIDE(RNC) WITH CHLOROFORM+KOH.

NITRO GROUP

THE PRESENCE OF NITRO GROUP CAN BE DETYECTED BY REDUCING THE COMPOUND WITH Sn/HCl AND THEN CONDUCTING CARBYL AMINE TEST.