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Analysis of Oxygen-Bearing Organic Compounds

Autor:   •  November 7, 2018  •  4,042 Words (17 Pages)  •  5 Views

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Five classification tests were used in the course of experiment. Thus, five reference standard organic compounds were used: three alcohols, aldehyde, and a ketone. The first chemical test was Dichromate Test. Dichromate Test, also known as Jones Oxidation Test, is mainly used to distinguish between primary, secondary, and a tertiary alcohol based on their oxidation reactions. It is a functional-class test for alcohols and aldehydes. Positive visible result is the presence of intense blue-green solution (Pavia, Lampman, Kriz, & Engel, A microscale approach to organic laboratory techniques, 2013).

The second test is Tollen’s Test. It is also called “Silver-Mirror Test.” It is used to distinguish between an aldehyde and a ketone, a functional class test for aldehydes based on their oxidation reactions. Positive visible result is the formation of silver-mirror coating in the test tube (Pavia, Lampman, Kriz, & Engel, A microscale approach to organic laboratory techniques, 2013).

Thirdly, the Lucas Test is used to classify alcohols in accordance with their reactivity. It is both a functional-class test and chemical test that provides structural information of alcohols. Positive Visible result yields a turbid solution (Pavia, Lampman, Kriz, & Engel, A microscale approach to organic laboratory techniques, 2013).

The fourth test is DNPH Test. This test is further called 2,4-dinitrophenylhydrazine test. This chemical test is used to detect the carbonyl group functionality in aldehydes and ketones basing from condensation reaction; therefore, it is a functional-class test for aldehydes and ketones. Positive visible result yields to formation of red-orange precipitate (Pavia, Lampman, Kriz, & Engel, A microscale approach to organic laboratory techniques, 2013).

Lastly, the Iodoform Test is mainly used to identify methyl ketones. This test provides structural information not only for ketones, but also for alcohols basing from the oxidation reactions. Positive visible result yields a yellow precipitate (Pavia, Lampman, Kriz, & Engel, A microscale approach to organic laboratory techniques, 2013).

In this experiment, the different structural features of oxygen-bearing compounds were identified. Qualitative chemical analyses characterized the identity of each oxygen-bearing organic compounds based from their chemical reactions. Also, the structural feature and identity of an unknown compound was deduced. Lastly, chemical equations involved in each test were derived.

II. Methodology

The materials needed were prepared first. Twenty-six small-sized (13x100 mm) test tubes were first prepared. The following reagents were procured from the laboratory technician: 10% potassium dichromate (10% K2Cr2O7), 6M sulfuric acid (6M H2SO4), Tollen’s Reagent, concentrated hydrochloric acid (HCl), anhydrous zinc chloride (ZnCl2), DNPH Reagent, 10% potassium iodide (10% KI), and 5% aqueous sodium hypochlorite (5% NaClO). Alongside with the reagents were the reference standards—formaldehyde, acetone, n-Propanol, 2-Propanol, t-butanol—and the two unknown sample compounds, A and B. Parallel chemical testing was followed all throughout the whole experiment. Five chemical tests were conducted:

Dichromate Test

The reference standards and samples used were n-propanol, 2-propanol, t-butanol, formaldehyde, acetone, and the two unknown samples. Eight drops of the standards and the samples were placed and mixed with two drops of 10% K2Cr2O7 and five drops 6M H2SO4 in separate test tubes assigned for each substance. The results were observed and recorded.

Tollen’s Test

The reference standards and samples used were formaldehyde, acetone, and the two unknown samples. Ten drops of the standards and the samples were placed and mixed with 40 drops (2 mL) of Tollen’s Reagent. The chemical reactions were timed five minutes. The results were observed and recorded.

Lucas Test

The reference standards and samples used were n-propanol, 2-propanol, t-butanol, and the two unknown samples. Ten drops of the standards and the samples were placed and mixed with 20 drops of concentrated HCl in separate test tubes assigned for each substance. The test tubes were shaken well and turbidity was observed. If no turbid solution was observed, anhydrous ZnCl2 was added. The results were observed and recorded.

DNPH Test

The reference standards and samples used were t-butanol, formaldehyde, acetone, and the two unknown samples. Ten drops of the standards and the samples were placed and mixed with 20 drops of DNPH Reagent in separate test tubes assigned for each substance. The results were observed and recorded.

Iodoform Test

The reference standards and samples used were 2-propanol, t-butanol, , acetone, and the two unknown samples. Ten drops of the standards and the samples were placed and mixed with 20 drops of 10% KI and 20 drops 5% NaClO(aq) in separate test tubes assigned for each substance. The results were observed and recorded.

III. Results and Discussion

Table 1. Data of Results of the Chemical Tests for the Reference Standards. The gray cells indicate that standards were not subjected to a particular test.

Standards

Chemical Tests

Dichromate Test

Tollen’s Test

Lucas Test

DNPH Test

Iodoform Test

Before adding ZnCl2

After adding ZnCl2

n-propanol

Blue-green solution

(+)

Clear solution

Clear solution

(-)

2-propanol

Blue-green solution

(+)

Clear solution

Slightly turbid

(+)

Yellowish white precipitate turned to yellow

(+)

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