Org Chem Unknown Analysis Guide

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Classification for Functional Groups

Alcohols

Lucas test
(Differentiates primary, secondary, and tertiary alcohols)
Reagent: ZnCl2 in conc. HCl
Observation: Rate of reaction (tertiary alcohol> secondary alcohol> primary alcohol) Procedure: 2mL Lucas Reagent in test tube+ 3-4 drops of alcohol, stopper, shake vigorously, NOTE time required (less than 10m mins only) to form an emulsion or separate layers.

Oxidation
(Confirms if alcohol is oxidizable: presence of H in C-OH bond) Reagent: Neutral KMnO4
Observation: purple color ( brown ppt
Procedure: 5 drops test sample in test tube+ 1 drop dilute neutral KMnO4, if NO DECOLORIZATION warm mixture.

Primary Alcohol( carboxylic acid
Secondary Alcohol( ketones
Tertiary( none

Phenols

Reaction with bromine/water
(Confirms if phenol compound)
Reagent: bromine in H2O
Observation: Disappearance of orange-brown bromine color, then formation of white precipitate Procedure: 3 drops phenol soln on test tube+ Br in H2O drop by drop while shaking, observe formation of ppt

Oxidation by KMnO4
(Confirms if phenol compound)
Reagent: aqueous neutral KMnO4
Observation: purple color( brown color (formation of quinone) Procedure: 3 drops phenol soln on test tube+ 1 drop aqueous neutral KMnO4, observe decolorizaton

Reaction with Ferric Chloride
(Confirms if phenol compound)
Reagent: FeCL3 solution
Observation: Complex formation (deep colored compounds)
Procedure: 3 drops of phenol soln in test tube + 1 drop FeCl3 soln

Aliphatic and Aromatic Hydrocarbons/ Alkenes

Bromination in Light (Free Radical Bromination)
(Reacts with alkanes)
Reagent: Br2 in H2O
Observation: decolorization, brown ( colorless
Procedure: 2 drops of test compound in test tube+ 1 drop 0.05 M Br2 in H2O, shake well, record observations

Bromination in Dark (Electrophilic Addition Halogenation)
(Reacts with alkenes)
Reagent: Br2 in H2O
Observation: decolorization, brown ( colorless
Procedure: 2 drops of test compound in test tube+ 1 drop 0.05 M Br2 in H2O, shake well, record observations

Oxidation with potassium permanganate
(Reacts with alkenes)
Reagent: KMnO4 soln
Observation: formation of brown ppt
Procedure: 2 drops of test compound in test tube+ 2 drops 0.005 KMnO4 soln shake well, record results

Combustion
(Identifies alkanes, alkenes, and aromatic compounds)
Observation: alkane- not sooty, yellow flame, alkene- a little sooty, yellow flame, extensive sootiness Procedure: 5 drops of test compound in evaporating dish, observe character of flame

T-butyl chloride and AlCl3
(Reacts with aromatic compounds)
Reagent: tert-butyl chloride, small crystal anhydrous AlCl3
Observation: white crystal( orange/red crystal
Procedure: 1 drop test compound in test tube + 2 drops tert-butyl chloride, mix, incline test tuce then place small anhydrous AlCl3 crystal near mouth, allow soln to wet crystal, observe CRYSTAL’S CHANGE OF COLOR

Aldehydes and ketones

Reaction with 2,4-dinitrophenylhydrazine
(Confirms aldehydes and ketones, carbonyl compounds)
Reagent: 95% CH3CH2OH, acetone, benzaldehyde, 2,4-DNPH in HCl solution Observation: formation of yellow ppt/ orange ppt
Negative result: yellow solution
Procedure: 5 drops 95% CH3CH2OH + 2 drops test compound + 1 mL 2,4-DNPH in HCl solution, record color of ppt formed, if no ppt forms immediately, let stand for a few minutes.

Tollen’s Test
(Confirms presence of ALDEHYDES ONLY)
Reagent: ammoniacal AgNO3 or [Ag(NH3)2] NO3
Observation: Silver mirror (Ag)
Negative result: turbid solution, colorless soln
Procedure: 5 drops Tollen’s reagent in test tube + 1 drop test compound, observe formation of silver mirror, if no reaction take place, warm in hot H2O bath. (Aromatic aldehydes may require heating)

Schiff’s Test
(Confirms presence of ALDEHYDES ONLY)
Reagent: Schiff’s Reagent
Observation: purple solution
Negative result: pink solution
Procedure: 4 drops Schiff’s reagent in test tube + 1 drop test compound,...
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