Marie Loriele C. Achas, Marianne Angelica C. Alvarez *, Keithy Angela O. Bangot, Kate P. Bayani Department of Biology, University of Santo Tomas, Manila, Philippines
The experiment dealt with differentiating the various types of oxygen-bearing organic compounds through several tests, namely Dichromate Test, Tollen’s Test, DNPH Test, Iodoform Test, and Lucas Test. It was through the use of different reagents and techniques that the characteristics of each standard compounds were observed and distinguished. After the reactions have been noted, it was compared to the reactions with that of the unknown.
The Analysis of Oxygen-bearing Organic Compounds was used to identify the kind of alcohol, whether primary, secondary, or tertiary, or functional group present in the mixture. This experiment focused on distinguishing the several kinds of functional groups from each other. Standard compounds were used to identify the characteristics of each group present. The following reagents were used as standards:
Primary (1º) alcohol (Figure 1) has a characteristic where a carbon atom with the hydroxyl group has at least two hydrogens and any organic group (represented as R) attached on it. The Carbon atom and R form an alkyl group.
A secondary (2°) alcohol has a characteristic of only one hydrogen attached on a carbon with a hydroxyl group. This carbon is then attached to two alkyl groups.
Tertiary alcohol has a characteristic of no hydrogens attached on a carbon with a hydroxyl group. The carbon is then connected to three alkyl groups.
This functional group has a carbonyl group attached to an alkyl or aromatic group. This can be reduced to primary alcohol. Figure 4
This functional group has a carbonyl group attached on two alkyl or aromatic groups. Figure 5
There were five tests that were used to determine their nature. These were: * Dichromate Test
Dichromate Test or Jones Test is used to test the presence of compounds with reducing property. These are the substances that can be oxidized. This kind of test was used to convert primary alcohols to aldehydes and carboxylic acids, and secondary alcohols to ketones in laboratories. However, it cannot oxidize tertiary alcohols, and that it would yield negative result in the test. Dichromate test uses 10% K2Cr2O7 and 6M H2SO4 reagents to oxidize the substance being treated.
* Tollen’s Test
Tollen’s test or Silver –mirror test is used to detect the presence of aldehydes. It distinguishes an aldehyde from a ketone because the former is readily oxidized than the latter. As the name suggests, the reagent used in this test is the Tollen’s Reagent.
* DNPH Test
DNPH test or 2,4-Dinitrophenylhydrazone test is used to detect the presence of a carbonyl group in a ketone or aldehyde. The resulting color of this test determines the orientation of the carbonyl group, whether it is a ketone or an aldehyde.
* Iodoform Test
This test is used for methyl carbonyl and methyl carbinol groups. This test is where secondary alcohols with adjacent methyl group are oxidized to methyl ketones.
* Lucas Test
This test differentiates primary, secondary and tertiary alcohols based from their reaction with HCl and ZnCl2. This reaction occurs when the alcohols are transformed into alkyl halides. The reagent used for this test is Lucas Reagent.
The experiment aims to:
* Differentiate the various types of oxygen-bearing organic compounds * Device a scheme to distinguish each functional group
* Characterize an unknown sample through parallel chemical tests Results and Discussion
There were five tests that were conducted to discern the reactions of each standard substance. The data that were collected are presented in the table below. Sample| | Dichromate Test|...