Organic Tests

Organic Tests Test 1. Solubility

2. Odour 3. Combustion

4. pH of Solution

5. Bromine Water Measure 1cm3 of unknown into test tube. Add equal amount of Bromine water, stopper the test tube and carefully shake. If organic is gas, bubble through bromine water.

6. Acidified Potassium Manganate

Observation Layers/cloudy

Deduction Insoluble: non-polar e.g. alkanes, alkenes, halogenoalkanes

Miscible/colourless solution forms Characteristic Odour: Vinegar Nail varnish remover Ease of ignition? Burns with sooty/smoky/yellow flame

Soluble: polar/forms H-bonds/low molecular mass e.g. carboxylic acid Ethanoic acid Propanone

Burns with non-luminous/clean/blue flame with no smoke/soot

Could be saturated low molecular mass with possibly oxygen

No residue

Could be saturated low molecular mass with possibly oxygen

Black residue Indicator turns red/orange/yellow

Carbon residue from a unsaturated or high molecular mass compound with possible functional C=C pH < 7 Acidic  carboxylic acid

Indicator turns dark blue/green Liquids do not mix. Two layers are formed. Orange bromine layer turns colourless.

pH > 7 Acidic  group 1 salts of carboxylic acid Immiscible in water. Confirms unknown is unsaturated alkene. (Electrophilic addition takes place)

 Two colourless layers formed, organic layer  orange, aqueous layer  orange to pale yellow Liquids mix to form an even layer. Mixture turns orange to colourless immediately Liquids do not mix together. Two layers form. Potassium manganate turns purple to colourless

Add 2cm3 of unknown with 2cm3 of  sulphuric acid and 1cm3 of PM. Stopper and shake carefully.

7. PCl5 Add half a spatula to dry test tube to 1cm3 of unknown. Test with damp blue litmus paper.

8. Bubble Through Silver Nitrate 9. Acidified Potassium Dichromate Add 1cm3 of unknown organic substance to a test tube followed by 1cm3 of dilute sulphuric acid and 6 drops of PD, warm in water bath.

10.Silver Nitrate 1cm3 of unknown, add 1cm3 of ethanol with 2cm3 of dilute sodium hydroxide. Warm mixture in water bath for 3 minutes. Add 2cm3 of nitric acid, then 6 drops of silver nitrate.

11. Addition of Ammonia

Unsaturated (alkene) or high molecular mass, possible functional group with C=C

Bromine is more soluble in organic solvent than water, but does not react so no alkene is in it.

 Two liquids are miscible, confirms is an unknown unsaturated compound with a C=C present. R = H or alkly group (Electrophilic addition takes place) Immiscible in water. Confirms is a unsaturated compound such as an alkene. C=C is present. Electrophilic addition may take place

Vigourous fizzing. Misty steamy fumes which turn damp litmus paper blue to red.

Gas evolved is acidic – HCl. Unknown compound contains hydroxy group. Alco Alcoho holl can be be ident identif ifie ied d R-CH R-CH22-OH OH R = H or an alkyl group and halogenation of alcohol is occurred.

White precipitate is formed when fumes bubbled through solution

HCl dissolves dissolves in water, alcohol is identified identified from this. Halogenation of alcohol has occured

Orange solution turns green when warming. Odour may be detected

Alcohol has been oxidised. Primary alcohols can be further oxidised from aldehyde to carboxylic acid Secondary alcohols are oxidised to ketones. Two R groups attatched to C-OH

No colour change. Remains orange On addition of silver nitrate Pale Yellow (Iodine) Cream (Bromine) White (Chlorine)

No redox reaction has taken place, tertiary alcohol is present. 3 R groups attached to C-OH Halide ion produced during hydrolysis of halogen atom (alkaline hydrolysis)

Precipitate dissolves in dilute ammonia to leave colourless solution

Chlorine is found

Precipitate dissolves in conc ammonia to leave colourless solution

Bromine is found

12. Brady’s Reagent 13. Fehling/ Benedict

Precipitate doesn’t dissolve in any ammonia Yellow/ orange crystals a re re forme d Turns solution from blue to brown/red

14. Tollen’s Reagent

Creates a silver mirror on the test tube

Iodine is found Eithe r an alde hy hyde or ke to tone pre se se nt nt. Can be distinguished with melting po in int test. Aldehyde present. Ketone the test does not work. (Elimination) Aldehyde present. Careful not to let dry and set alight. Can be explosive.

16. Alkane 17. Addition of Magnsium 18. Addition of Sodium

PROCESS OF ELIMINATION Bubbling/fizzing/metal dissolving S te te ad ad y b ub ub bl bli ng ng /f /f iz izz in in g/ g/ me me ta ta l d is is so so lv lv es es

Carboxylic acid is present, hydrogen gas is given off   H yd yd ro ro ge ge n g as as is is gi gi ve ve n o ff ff . I on on ic ic co co mp mp ou ou nd nd th th at at is is a w hi hi te te so so lili d. d. Pr Pr ob ob ab ab ly ly an an al alc oh oh ol ol (p (p ri ri ma ma ry ry, secondary or tertiary)