Chem 31.1 Unknown Analysis Cheat Sheet

Chem 31.1 Unknown Analysis Cheat Sheet Test

Reagents

Positive Result

Postive for?

Short Procedure

2,4-DNPH

2,4 – DNPH

Yellow/ yellow-orange precipitate

All carbonyl compounds

Tollen’s

Silver mirror

Aldehydes

Brick red precipitate

Aliphatic Aldehydes

Schiff’s

Ammoniacal [Ag(NH3)2]NO3 CuSO4 ,atrate & NaHCO3 Leucofuchsin

Violet solution

Aldehydes

Iodoform

I2 in KI, NaOH

Light yellow precipitate

2 – alkanols Methyl Ketones

20 drops. If no result yet, heat for 5 mins 5 drops then observe 5 drops then put to hot water bath 5 drops then observe after 3-4 minutes 5 drops 10% NaOH warm to 60 degrees, add I2 in K until brown, Add NaOH to make it colorless and then cool after 2 min. to observe result

Test

Reagents

Positive Result

Positive for?

Short Procedure

Lucas

ZnCl2 in HCl

Formation of layers (may be cloudy)

Water Soluble Alcohol

KMnO4

KMnO4

Decolorization of KMnO4 and/or formation of brown precipitate

FeCl3

FeCl3

Colourful solution

Br2 in H2O

Br2 in H2O

White precipitate

All oxidizable groups (primary and secondary alcohols, phenols, aldehydes and alkenes) Phenol and substituted phenols Phenols

2 mL reagent then observe time required to form layer One drop then shake. Wait for decolorization

Test

Reagents

Positive Result

Positive for?

Short Procedure

Osazone

Phenylhydrazine, conc. HCl

Yellow/yellow-orange precipitate

Monosaccharide and reducing disaccharide

Molisch

Alpha naphthol & H2SO4

Red/violet ring at interface

General carbohydrate

Bial’s

Orcinol, HCl & FeCl3

Aldoses

Selliwanof’s Test

Resorcinol and H2SO4

Blue green (pentose) yellow to brown (hexose) Bright red in 20-30 seconds

15 drops DNPH, 3 drops conc. HCl, heat for 20 mins, cool afterwards if no crystals formed 4 drops reagent then mix. Tilt tst tube then add 15 drops H2SO4 1 mL reagent then heat for 30-45 min

Benedict’s

Brick red precipitate

Reducing sugars

Barfoed’s Test

Na-atrate, NaHCO3 CuSO4 Cu acetate

Brick red precipitate

monosaccharide

Starch

I2 in KI

Blue complex

starch

Benedict’s

Aldehydes and Ketones

Alcohols and Phenols

Rainier Mendoza 2013 – 38229

Ketoses

One drop reagent Add drop by drop while shaking

15 drops reagent then heat for 15 mins. 1 mL reagent then heat for 15 mins. 1 mL reagent then heat for 10 mins. Add I2 in starch solution

Chem 31.1 Unknown Analysis Cheat Sheet Carbohydrates

Test Hinsberg’s

Reagent Benzenesulfonyl Chloride and x’s NaOH HCl

Positive Result Primary – soluble in NaOH, pt in HCl Secondary – insoluble in NaOH and HCl Tertiary – soluble in NaOH and in

Positive for? Amines

Short Procedur 5 drops benzenesulfonyl, observe, add 4 mL dropwise NaOH. Shake after each addition. Cool and decant any residu Test solubility of residue in water and HCl

Amines Aliphatic and Aromatic Compounds

Solubility Class Determination

Test

Reagents

Positive Result

Positive for?

Short Procedure

Flame Test

O2 and Heat

Alkane, alkene and aromatic compounds

Friedel Crafts Alkylation

Tert-butyl chloride and FeCl3

Blue flame (alkane) Yellow flame (alkene) Sooty and Yellow (aromatic) Yellow/orange crystals

5 drops sample in an evap dish then ignite. Observe color of flame 2 drops tert-butyl chloride. Put FeCl3 crystal near mouth of test tube, make sure it doesn’t drop then tilt and wet crystal. Note color change.

Rainier Mendoza 2013 – 38229

Aromatic Compounds