Unknown Analysis TESTS

I.

Solubility Test 5 drops of solvent in test tube 1- 2 drops/pinch drops/pinch test compound Shake and check solubility 

UNKNOWN ANALYSIS TIPS/STEPS:

 

1. 2.

water

3.

Soluble: Ether Soluble: S1 Insoluble: S2

Insoluble: 5% NaOH Soluble: 5% NaHCO3 Soluble: A1

4.

Insoluble: 5% HCl Soluble: B

Insoluble: A2

5. 6.

Insoluble

w/ N or S: M

w/o N or S: conc. H2SO4

Soluble: N

Do Solubility Test Do the tests found under the assigned solubility class/es. Once identified, do general tests for those found in other solubility classes. (See note) Check presence of carboxylic acid, alcohol or phenol, carboxylic acid derivative, amide, amines, hydrocarbons, etc. (usually first row of each table is the general test) If negative result, proceed with the general tests for other tables. If it gives positive result, proceed with rows below to get the specific functional group attached.

NOTE: Compound assigned may belong to different solubility classes. This is due to the presence of different functional groups in the compound given. Sometimes, other functional groups may be present even if a negative result is obtained while checking the solubility class. Doing two tests for confirmation purposes would do no harm :P

Insoluble: I II.

S1 

Few H bonds (most on one side) Less than 5C



Many H bonds (OH 1:1 with H)



III.

CARBS

S2

Molisch

Reagent sample + 2 drops rgt: α-naphthol + 10 drops conc. H2SO4

5 drops

Benedict's

1mL rgt: CuSO4, Sodium Citrate, NaHCO3. Heat in boiling water abth.

5 drops

brick red ppt, Cu2O

Bial's

Sample + 10 drops rgt: orcinol, H2SO4 + Heat over Bunsen until soln boils.

5 drops

blue green solution

Sample+ rgt: resorcinol, H2SO4. Heat in water bath. 1mL rgt: Cu(OAc) 2 in acetic acid. Heat in water bath.

5 drops 5 drops with (+) result in Benedict’s

Seliwanoff's Barfoed's

Test

(+) Result red violet/purple ring at interphase

bright red solution within 20-30secs

(-)Result

yellow to brown solution

Implication aldopentose, aldohexose

Probable Cp free or combined forms

free carbs, mono and di (exc. sucrose)

free vs combined C

pentose

pentose vs hexose

ketohexose

ketohexose vs aldohexose mono vs di reducing sugars

Osazone formation Hydrolysis of Polysaccharides

Sample + 10 drops C6H5NHNH2 + 1 drops conc HCl. Heat in boiling water bath. Record odor. Cool in ice bath.

5 drops

same osazone

HCl, Δ (see bottom) 

polysaccharide

Benedict's

CuSO4, Sodium Citrate, NaHCO3

brick red ppt, Cu2O

Iodoform

I2 in KI

yellow solution

HYDROLYSIS: micro test tube: 10drops 10% sucrose soln +10drops distilled water.

+boiling stone, +2drops conc HCl. Boil over flame for 3mins.

Cool and neutralize with 10% NaOH. Stir at each base addition.

IV.

Perform at 1-min intervals 3x until same color.

hydrolyzed polysaccharide blue violet complex

hydrolyzed polysaccharide

polysaccharide vs disaccharide hydrolyzed vs unhydrolyzed polysaccharide hydrolyzed vs unhydrolyzed polysaccharide

Cool and neutralize with 10% NaOH. Stir after each addition of base.

mortar: Grind 0.5g starch w/ ditilled water.

Filter paste and wash w/ min. distilled water.

Immediately, spotplate: drop of heated starch soln + drop of I2 in KI. Record color.

Rest of filtrate, +5drops conc HCl. Heat water bath at 80 ⁰C

spot plate: drop of filtrate + drop of I 2 in KI. Record color.

A1 - Strong acids

CARBOXYLIC ACIDS Solubility Formation of esters Solubility Solubility

epimers

Reagent 1 drop 5% or 0.5M NaHCO3 Sample + 5 or 10 drops alcohol + (if A1: 1 drop conc H2SO4.) Litmus: 2 drops 2% NaOH + sample + 2-3 drops 0.1M FeCl3 3 drops water + sample + (Heat until solid dissolves Cool.) Litmus: 0.3M NH4OH. Boil excess ammonia. + 1 drop 0.1M FeCl3

Test Pinch or drop 2 drops dropwise

Positive Result bubbles/effervescence, soluble plastic balloon scent tomato red solution, Fe(OH)2

Implication Carboxylic Acid Carboxylic Acid Aliphatic carboxylic acid

Pinch or drop

flesh colored ppt, Fe(Ar-COO-)

Aromatic carboxylic Acid

V.

A2 - Weak acids Phenolic and alcoholic compounds 

ALCOHOLS, PHENOLS, ETHERS

Reagent

Lucas

2mL Lucas rgt: ZnCl2 in HCl

3-4 drops alcohol

formation of layers

Alcohol

Baeyer's

1 drop KMnO4

5 drops

white ppt

1 or 2 Alcohol

Oxidation of Phenols

1 drop KMnO4

5 drops

Phenol

Reaction (EArS)

Br 2 in H2O while shaking

3 drops

brown ppt white ppt (2,4,6tribromophenol)

Complexation

1 drop FeCl3

3 drops

decolorization

Phenol

VI.

Test Sample/ Compound

Positive Result

Implication

Probable Compound 1, 2, or 3 Alcohol

Phenol

B - Base  

N containing  Ammonia derivatives: R –NH2, RNHR, R-NR2, -N=

AMINES

Reagent

Hinsberg's

2 drops benzenesulfonyl chloride + 1mL 10% NaOH dpwise. If it heats, cool. If not alkaline, + more NaOH.

Solubility Solubility Solubility

5% HCl Water + residue of 2 or 3 amine 5% HCl + residue of 2 or 3 amine

VII.

Negative Result

Test

2 drops

Positive Result

(-)Result

Implication

with visible reaction separation of layers No separation formation of ppt dissolved dissolved

NVR

amine group present 2 or 3 amine 1 amine 1 amine 2 or 3 amine 3 amine

undissolved undissolved

Probable Cpd

1, 2, or 3 amine

2 or 3 amine

M - Miscellaneous Contain N but not basic With S but not acidic  Amides, nitro compounds, 2HN-C=O   

CARBOXYLIC ACIDS & Derivatives Hydrolysis of C. Acid Derivatives VIII.

Reagent Sample + 5 drops 2% NaOH. Heat.

Test Sample/ Compound

Positive Result

Small pinch

ammonium scent after heating

N - Neutral With double bonds (unsaturation) Unsaturated compounds: Alkene or alkynes, compounds with O, ketones, ethers, most carboxylic acid derivatives  

Negative Result

Implication Amides

ACYL COMPOUNDS

Tollens Schiff's Benedict's

Iodoform CARBOXYLIC ACIDS Derivatives Formation of esters

Hydroxamic Acid Hydrolysis of C. Acid Derivatives

IX.

Reagent

Test

Positive Result

5 drops 95% CH 3CH2OH + 1mL 2,4-DNPH

2 drops

5 drops Tollens rgt: Ag(NH3)+ 4 drops Schiff’s rgt: leucofuschin (pink) 5 drops Benedict’s rgt: CuSO4, Sodium Citrate, NaHCO3 5 drops 10% NaOH + sample + I2 in KI dpwise. Add until pale yellow. Warm bath. If colorless, add more I2. Repeat

1 drop 1 drop

yellow ppt/crystals silver mirror (may need heat) purple solution

1 drop

brick red ppt, Cu2O

2 drops

yellow ppt, CHI3

Reagent Sample + 5 or 10 drops alcohol + (if A1: 1 drop conc H2SO4.) Sample + 1 drop ether + 1 drop alcoholic NH 2OH-HCl + 1 drop KOH. Heat to almost boil. Cool Acidify with alc. HCl + 1 drop 0.1M FeCl3 Round bottom 10mL: sample + 5mL 25% NaOH. Reflux. Disappearance of smell. + 6.0M HCl 5 drops water + sample + moisten blue litmus.

Implication

Probable Compounds

aldehydes, ketones aromatic or aliphatic aldehydes aldehydes

carbonyl compounds

aliphatic aldehydes methyl ketones or reduced form of ketone (alcohol) Negative Result

aldehydes vs ketones aliphatic vs aromatic aldehydes

methyl vs aromatic ketones

Test

Positive Result

Implication

2 drops

almond scent

Acyl Halide

1 drop

magenta colored

Esters

2mL 3 drops

Sour smell 2 carboxylic acids produced

Esters Acetic Anhydrides

I - Inert  

Hydrocarbons

With double or triple bonds Saturated & aromatic hydrocarbons, alkanes Reagent

Test Sample/ Compound

1 drop 0.05M Br 2 in light 1 drop 0.05M Br 2 in dark

2 drops 2 drops

Oxidation Combustion

Drops of 0.005m KMnO4 Ignite under hood

2 drops 5 drops on evap dish

 Alkylation

2 drops t-butyl Cl (mix) + anhydrous AlCl3 (while inclined test tube)

1 drop

i

i

Negative Result yellow orange solution

 IMPERIAL, Ria Edeliza S. CHEM 31.1 Organic Chemistry.

Positive Result decolorization: orange solution no decolorization (partial) purple decolorization or (complete) brown ppt blue flame, clear smoke yellow flame, sooty smoke

decolorization

Negative Result

Implication alkane, alkene alkane, alkene

no decolorization

alkene alkane alkene, aromatic

aromatic