EXPERIMENT 8B Qualitative Analysis
Pa Part E: Tests fo for Al Alcohols and and Phen Pheno ols
Methodology: Test for alcohols Reaction with Sodium Metal 5mL test tube: ! ! 20 drops of n-butyl alcohol/ sec-butyl alcohol/ tert-butyl ! Tiny piece of sodium metal
Lucas Test 5mL test tube: ! 20 drops of Lucas ! reagent 10 drops of n-butyl ! alcohol/ sec-butyl alcohol/ tert-butyl alcohol ! Shake test tube vigorously & stopper
Test for Alcohols Reactions with Potassium Dichromate 5mL test tube ! 20 drops of n-butyl alcohol/ sec-butyl/ tert-butyl ! 2M H2SO4 classifies ! !
5 drops 3% potassium dichromate solution
Experimental Results
Theoretical Results
Discussion Test for Alcohols Reaction with Sodium Metal Rate of the reaction depends on the alcohol’s structure: differentiates primary, secondary, and tertiary alcohols Sodium metal reacts with the hydroxyl group (proton donor) to release hydrogen gas & form the salt of alcohol (alkoxide ion). Acidity: Primary alcohols > secondary alcohols > tertiary alcohols Steric effects ! ! Primary alcohols: not sterically hindered, easily solvated and stabilized by the solvent. ! Tertiary alcohols: sterically hindered, less easily solvated.
Test for Alcohols Alcoho ls Lucas Test Lucas reagent: HCl and ZnCl2 dissolved in water Certain alcohols react with ZnCl2 in acidic aqueous solution to form alkyl halides Substitution reaction: OH is replaced with Cl Involves carbocation intermediate ! Only secondary and tertiary alcohols react to form alkyl halide ! Tertiary alcohols react readily (stable) ! Secondary alcohols react slowly ! Primary alcohols react negligibly slowly or do not react at all.
Test for Alcohol Alcohols s Reaction with potassium dichromate Alcohols can be oxidized oxidized using potassium dichromate Hydrogen atoms are removed ! OH group Carbon attached to the OH group ! Carbon attached to the OH group must at least have 1 hydrogen Primary alcohols- oxidized into an aldehyde ! ! Secondary alcohols- oxidized into a ketone ! Tertiary alcohols are not oxidized Green: oxidation has occurred (Cr+3 ion).
Methodology: Test for Phenol Ferric Chloride Test 5-mL test tube: ! ! 20 drops of 95% ethanol + 2 drops of liquid phenol/ "naphthol/ catechol/ resorcinol + 5 drops of 3% Ferric Chloride (FeCl3) solution Mixed !
Bromine Water Test 5-mL test tube: ! ! 20 drops of 95% ethanol + 5 drops of phenol/ "-naphthol/ catechol/ resorcinol + Bromine water (dropwise while shaking until persistence of bromine color)
Test for Phenol Millon’s Test 5mL test tube ! 5 drops Millon’s reagent + 5 drops phenol/ "-naphthol/ catechol/ ! resorcinol Shake test tube ! ! Heat in water bath (2 minutes)
Results Ferric Chloride Test Sample
Bromine Water Test Visible
Results Phenol Catechol Resorcinol
-naphthol
!
Sample
Visible
Results Dark brown Dark blue Upper Layer: Olive green Bottom Layer: Dark green Upper Layer: Dark purple Bottom Layer: Light purple
Phenol Catechol
Resorcinol
-naphthol
!
Copper Brown
Upper Layer: Olive green Bottom Layer: Dark green
Clear
Millon’s Test Sample
Visible
Results Phenol Catechol
Amethyst Brown
Resorcinol Pink
-naphthol
!
Turned to purple
Discussion Test for Phenol
Bromine Water Test Phenol undergoes bromination Positive: Decoloration of bromine, formation of white precipitate Tri brominated product - white precipitation HBr: not observed
Discussion Test for Phenol
Ferric Chloride Test Iron(III) ions form strongly coloured complexes Color of complexes vary from compound to compound Positive: Intense color ranging from purple to reddish brown to
Discussion Test for Phenol
Millon’s Test Millon’s: Mercuric and mercurous ions in nitric and nitrous acids Formation of mercury salts after heating Positive: Pink to red-colored solution, formation of precipitate
Part F: Test for Aldehydes and Ketones
Methodology for 2,4-DNPH test
a. Place 5 drops of 2,4-DNPH solution + 3 drops of formaldehyde in 5mL test tube b. Heat in water bath for 5 minutes c. Repeat procedure using other test samples (acetaldehyde, acetone, and benzaldehyde)
Results *Experimental Sample
Results
Formaldehyde
Orange
Acetaldehyde
Red orange
Acetone
Benzaldehyde
red
Results *Theoretical Sample
Results
Formaldehyde
Acetaldehyde POSITIVE RESULTS Acetone
Benzaldehyde
Discussion - They yield dinitrophenylhydrazones that are insoluble solids - precipitate may be oily first and become crystalline - alcohols may give positive test because of the air oxidation
Methodology for Bisulfite Test
a. Place 20 drops of methylamine and 5 drops of benzenesulfonyl chloride in 5mL test tube b. Mix and cool in an ice bath c. Repeat procedure using the other samples (acetaldehyde, acetone, and benzaldehyde)
Results *Experimental Sample
Results
Formaldehyde
clear with white precipitate
Acetaldehyde
clear
Acetone
Benzaldehyde
Formation of layers
Results *Theoretical Sample
Results
Formaldehyde
With precipitate
Acetaldehyde
With precipitate
Acetone
No precipitate
Benzaldehyde
With precipitate
Discussion -
To differentiate ketones and aldehyde
- Aldehyde has precipitate -
The carbon atom of the carbonyl group acquires a partial positive charge
- Aldehydes is steric and inductive. -
Nucleophilic addition process, the substrate is the ketone or aldehyde, while the nucleophile is the bisulfite ion
Methodology for Schiff’s Test
a. Place 20 drops of Schiff’s reagent + 5 drops of formaldehyde b. Repeat procedure using other test samples (acetaldehyde, acetone, and benzaldehyde)
Results *Experimental Sample
Results
Formaldehyde
magenta
Acetaldehyde
violet
Acetone
Benzaldehyde
Formation of layers; top: pink, bottom: clear
Results *Theoretical Sample
Results
Formaldehyde
Positive test
Acetaldehyde
Positive test
Acetone
Negative test
Benzaldehyde
Positive test
Discussion
Discussion
- Schiff’s test reacts with an aldehyde and not with ketone, since a ketone has a hindered electrophile. The -NHSO2H of the Schiff’s reagent bonds with the electrophilic carbon
Methodology for Tollen’s Test
a. Place 20 drops of the Tollen’s Reagent + 5 drops of formaldehyde b. Heat in water bath c. Repeat using other test samples (acetaldehyde, acetone, and benzaldehyde)
Results *Experimental Sample
Results
Formaldehyde
Positive for silver glass
Acetaldehyde
Positive for silver glass
Acetone
Benzaldehyde
Positive for silver glass
Results *Theoretical Sample
Results
Formaldehyde
Positive for silver glass
Acetaldehyde
Positive for silver glass
Acetone
Positive for silver glass
Benzaldehyde
Positive for silver glass
Discussion -
The silver mirror indicates the presence of aldehydes
-
This test involves redox reaction
-
Positive test: aromatic amine, phenols, "-alkoxy and "dialkylaminoketones, compounds with triple bonds
-
False negative test: water insoluble aldehydes
Methodology for Iodoform Test
a. Place 4 drops of formaldehyde / acetaldehyde / acetone / benzaldehyde in a test tube b. Add 10 drops of water, 5 drops of 6M NaOH solution c. Add 5 drops of water, 5 drops I2/KI solution
Results *Experimental Sample
Results
Formaldehyde
Clear
Acetaldehyde
Yellow Precipitate
Acetone
Benzaldehyde
Clear
Results *Theoretical Sample
Results
Formaldehyde
-
Acetaldehyde
+
Acetone
+
Benzaldehyde
-
Discussion - The yellow precipitate indicates the presence of aldehyde or ketone with this grouping:
http://www.chemguide.co.uk/organicprops/
Methodology for Fehling’s Test
a. Place 20 drops of Fehling’s reagent and 5 drops of formaldehyde / acetaldehyde / acetone / benzaldehyde in a test tube b. Heat in a water bath
Results *Experimental Sample
Results
Formaldehyde
Aquamarine
Acetaldehyde
Green
Acetone
Benzaldehyde
Blue-Green
Results *Theoretical Sample
Results
Formaldehyde
+
Acetaldehyde
+
Acetone
-
Benzaldehyde
+
Discussion - The green suspension and red precipitate indicates a positive test. - Aldehydes: + - Ketones: - (except for alpha-hydroxyketones)
- Complexed copper(II) ions with tartrate ions in a NaOH solution
http://www.chemguide.co.uk/organicprops/
Methodology for Benedict’s Test
a. Place 20 drops of Benedict’s reagent and 5 drops of 1% glucose / 1% maltose / 1% sucrose / 1% boiled starch in a test tube b. Heat in a water bath
Results *Experimental Sample
Results
Glucose
Light Brown with white ppt.
Maltose
-----
Sucrose
Blue
Boiled Starch
Blue
Results *Theoretical Sample
Results
Glucose
+
Maltose
+
Sucrose
-
Boiled Starch
-
Discussion - The brick-red precipitate indicates a positive test. - Reducing sugars (aldehydes, alpha-hydroxy-ketone): + - Non-reducing sugars: - Complexed copper(II) ions with citrate ions in a Na 2CO3 solution http://www.chemguide.co.uk/organicprops/
Discussion - Reducing Sugars: has a free aldehyde group or free ketone group; galactose, glucose, fructose, maltose, lactose, starch - Non-reducing sugars: sucrose, trehalose
Methodology for Molisch Test
a. Place 20 drops of Molisch reagent and 5 drops of 1% glucose / 1% maltose / 1% sucrose / 1% boiled starch in a test tube b. Incline the test tube and run down through the walls about 2mL of conc. H2SO4
Results *Experimental Sample
Results
Glucose
Violet Ring
Maltose
-----
Sucrose
Violet Ring
Boiled Starch
Violet Ring
Results *Theoretical Sample
Results
Glucose
+
Maltose
+
Sucrose
+
Boiled Starch
+
Discussion - The purple ring indicates a positive test. - +: carbohydrates, glycoproteins, nucleic acids - Alpha-naphthol in ethanol
Part G: Test for Amines
Methodology 1. Hinsberg Test ! ! !
20 drops of 10% NaOH 5 dropys methylamine 5 drops of benzenesulfonyl chloride
Repeat using: ! Dimethylamine ! Trimethylamine ! Aniline N-methylaniline
Cover with cork and shake for about 5 minutes
Add 3 M HCL (if it has precipitates). Observe
Test the solution with litmus. Add 10% NaOH if still not basic. *BASIC
Add water if it has precipitates. Shake and observe
Results Experiment Methylamine
--
--
--
Dimethylamine
BASIC
Has cloudy solid # nothing happened
+
Trimethylamine
BASIC
Clear light brown
-
Anline
BASIC
Reddish brown
-
N-methylaniline
BASIC
Reddish brown# brown
+
Discussion Hinsberg Test - to differentiate primary, secondary, & tertiary amines Benzenesulfonylchloride - reacts w/ amines in basic/alkali Solutions
SALTS
#
NaOH - makes the solution basic Water - to test solubility HCl - to test precipitation reactions, solubility, & precipitation differentiates the amines
#
Discussion 1) Methylamine (PRIMARY)
!+
H2O
!+
HCl # acidification = PRECIPITATION
soluble salts = NO PRECIPITATION
#
2) Dimethylamine (SECONDARY) !+
H2O
insoluble salts = PRECIPITATION
!+
HCl # acidification = NO CHANGE
#
“ Secondary amines undergo reaction with benzenesulfonyl chloride to precipitate the sulfonamide, and acidification does not result in any change” Shriner
3) Trimethylamine (TERTIARY)
!+
H2O # insoluble salts = PRECIPITATION; quaternary ammonium sulfonate salts => sodium sulfonates
!+
HCl # acidification = NO PRECIPITATION; sulfonic acids
4) Aniline (PRIMARY)
!+
H2O
soluble salts = NO PRECIPITATION
!+
HCl # acidification = PRECIPITATION (milky)
#
5) N-methylaniline (SECONDARY)
!+
H2O
insoluble salts = PRECIPITATION
!+
HCl # acidification = NO CHANGE (reddish brown
#
brown)
#
Part H: Test for Carboxylic Acid and its Derivatives
Methodology - Formation of Esters - Reaction of Carboxylic Acid and Alcohol -
In 10 mL test tube: -
Pinch of salicylic acid
-
20 drops of methanol
-
5 drops of conc. H2SO4
-
Mix and shake well
-
Heat in water bath for 5 mins.
Results -
Presence of white precipitate -
Salicylic Acid
-
From white mixture
-
Formula of compound responsible for visible results : Phenyl ester
*H2SO4 = acid catalyst
Clear
#
Discussion ESTERIFICATION ! !
Mainly the reaction between alcohols and carboxylic acids to make esters. Also looks briefly at making esters from the reactions between acyl chlorides (acid chlorides) and alcohols, and between acid anhydrides and alcohols.
!
Both reactions are slow and reversible.
!
To have a positive test, the reaction must be subjected to: heat and an acid catalyst to favor the forward reaction.
Discussion "
Positive test
Ester, in big amounts, gives off a fruity smell Formation of an oily layer on top of the water is a positive test
Methodology - Hydrolysis of Acid Derivatives
-
Hydrolysis of Benzamide
-
In 5 mL test tube: -
Pinch of Benzamide
-
20 drops of 10% NaOH
-
Hold pc of red litmus paper over the mouth of the test tube
-
Heat to boiling in water bath
Hydrolysis of Acid Derivatives
- Hydrolysis of an Ester -
In 5 mL test tube: -
20 drops ethyl acetate
-
5 drops 25% NaOH soln
-
Loosely cover with cork
-
Heat in water bath (15 mins) - Add 3M HCl dropwise until neutral to litmus -
** note color change
Hydrolysis of Acid Derivatives
- Hydrolysis of an Anhydride -
-
In 5 mL test tube: -
20 drops of water
-
Pc of red & blue litmus paper
-
20 drops acetic anhydride
Gently shake & feel test tube
Results Acid Derivatives:
Litmus paper
Odor
Hydrolysis of Benzamide
Turned blue
Vinegar smell
Hydrolysis of an Ester
Turned Red
Vinegar smell
Hydrolysis of an Anhydride
Blue turned red Red stayed red
Vinegar smell
Discussion Hydrolysis of Acid Derivatives !
Hydrolysis reactions are said to be acid-catalyzed or basecatalyzed, heat is also used to speed up the reaction.
!
In the overall process of hydrolysis, a bond in an organic molecule is broken and an O-H bond in a water molecule also breaks. Then, from the water molecule, an O-H group adds to one part from the organic molecule, and an H atom to the other.
Discussion Hydrolysis of Benzamide Amide Functional group: Alkyl or aromatic group attached to an amino-carbonyl / nitrogen atom much-less reactive than acid chlorides, acid anhydrides, or esters. Undergo hydrolysis to yield carboxylic acids plus amine on heating in either aqueous acid or aqueous base.
Discussion Hydrolysis of Benzamide Acidic hydrolysis: Nucleophilic addition of water to the protonated amide, followed by the loss of ammonia. Basic hydrolysis: Nucleophilic addition of hydroxide to the amide carbonyl group, followed by the deprotonation of the hydroxide group and elimination of amide ion. When heated with a base, ammonia gas is given off.
Discussion Hydrolysis of Anhydride Functional group: Anhydride Anhydrides hydrolyze to form acid, in the experiment. Hydrolysis of an anhydride produces carboxylic acid and heat. Unpleasant odor will be observed.
Hydroxamic Acid test for Acid Derivatives
-
In 5 mL test tube: -
5 drops ethyl acetate
-
20 drops 7% methanolic hydroxylamine hydrochloride soln
-
10% methanolic KOH (until it turns blue)
-
10 drops more of methanolic KOH
-
Heat to boiling in water bath
-
Cool slightly -
7% methanolic HCl (until litmus turns red)
-
10 drops 3% FeCl3 soln
** Repeated with Benzamide, Acetic Anhydride, Benzoyl choride
Results
Results
Acid Derivatives:
# of drops until litmus turned BLUE
# of drops until litmus turned RED
Ethyl Acetate
7 (white ppt)
26
Benzamide
15 (white ppt)
56
Acetic Anhydride
25 (change in temp)
53
Benzoyl Chloride
28 (Presence of smoke, change in temp)
43
Discussion Hydroxamic acid test for acid derivatives
A class of chemical compounds sharing the same functional group in which an hydroxylamine is inserted into a carboxylic acid. !
Usually conducted to test ester.
Discussion
Hydroxamic acid test for acid derivatives
Discussion
Hydroxamic acid test for acid derivatives
Too much hydrochloric acid prevents the development of colored complexes. The solution must be cooled before adding FeCl3 since an acid will be produced, precipitation is also expected.
"
A distinct burgundy or magenta color of the ferric hydroxamate complex is a positive test.
