Lab Report

Detection and confirmation test for unknown functional group.

Course Title: Chemistry for biologist ICourse code: CHE 108

Prepared by:

Md. Shabab Mehebub

Department of

Genetic engineering and Biotechnology

East West University, Dhaka

Title: Detection and confirmation test for unknown functional group.

Principal: Carbon and hydrogen are invariably present in the organic compounds it is not necessary to test for these elements. In fact, if the test for other elements e,g. nitrogen, sulpher and halogens are negative it is assumed that the compound belongs to this category. Nevertheless the presence of carbon and hydrogen may be ascertained tests described under detection of elements. For detection of oxygen there is no direct test but if the substance is readily soluble in water then the presence of oxygen in the compound is almost certain. The tests for various functional group should be performed in the following order only if the compound responds positively to these tests, then the presence of that group is certain.

Materials: Equipment:

1. Test tube2. Test tube holder 3. Wash bottle4. Dropper5. Spatula

Reagent:

1. Tollene A2. Tollene B3. Fehling solution 14. Fehling solution 25. Sodium bicarbonate6. Litmus paper7. HCl 8. NaNo2

9. Dilute HCl10. Sodium bicarbonate SoLn 11. Ferric chloride SoLn 12. 2, 4-dinitrophenyl hydrazine

Supplied Compound:

1. Sample-5

Procedure:

(A)Test for carboxylic acid group, -COOH: (i) Bicarbonate Test: At first, I had taken saturated solution of bicarbonate in a test tube. Then warmed it and added a pinch of the Sample-5.

Sample 5 + NaHCO3 =

(ii) Litmus paper test: Took a dilute aqueous solution of the Sample-5 organic compound and added litmus paper.

(B) Test for Phenolic group:

Ferric Chloride test: 0.05 gm the Sample-5 compound had been dissolved. Added 5 ml of water. Then 1drop of ferric chloride solution had added. Appearance of blue, green, red or violet coloration will indicate the presence of phenolic group.

Sample 5 + FeCl3 =

(C) Test for Aldehydes:

Fehling’s test: In a test tube, I had mixed 1 ml each of Fehling A and Fehling B solutions when a deep blue color appeared. I added 0.1 gm of Sample-5 substance. Then boiled 5 minutes.

(D) Test for Ketones: At first, I had taken 0.5 gm Sample-5 substance. Added 5 ml dilute HCL acid. Then added 2 ml of solution of 2,4-dinitrophenylhydrazine. Then cooled in a ice pot and allow to stand for 2 minutes. When yellow, orange or red colored crystalline will precipitate indicated the presence of ketonic group.

(E) Test for –NH2 Group : Azo-dye Test: Dissolved 0.5gm of Sample-5 in a test tube. Added a slight excess of dil. HCL then cooled in ice water. Added sodium nitrate drop by drop till there was a slight excess of the nitrate. 1 cc of a strong solution of beta-naphthol in Sodium hydroxide had added.

Observation:

(A)Test for carboxylic acid group, -COOH:

(i) Bicarbonate Test: An effervescence was occurred and indicated the present of a –COOH group.

(ii) Litmus paper test: litmus paper turned red, so the organic compound might be a carboxylic acid.

(B) Test for Phenolic group: No change found.

(C) Test for Aldehydes: No change found.

(D) Test for Ketones: Yellow colored crystalline precipitate had obtained.

(E) Test for –NH2 Group: No change found.

Result: -COOH and –CO group had presented in that compound [Sample-5].

Discussion:

(A)Test for carboxylic acid group, -COOH: The effervescence rate was increased by excess warmed of saturated solution of bicarbonate in a test tube. Normally, properly warmed of saturated solution of bicarbonate in a test tube given good effervescence. Blue litmus paper was turned in Red.

(B) Test for Phenolic group: no change found.

(C) Test for Aldehydes: Mixed of Fehling A and Fehling B solutions gives deep blue color and when Sample-5 added no change obtained and that was not Aldehyde.

(D) Test for Ketones: -CO group had given yellow colored crystalline precipitate.

(E) Test for –NH2 Group: No change obtained when Sample-5 gad been added.

Precaution:

1. I had worn Lab coat.2. Volume had carefully measured. 3. The observation had recorded.4. All apparatus had handled carefully.5. Test tubes were cleaned by water during the experiment time.