Question

A test that can be used to distinguish \(1^{\circ}, 2^{\circ}\) and \(3^{\circ}\) alcohols is (a) Victor Meyer's test (b) Liebermann's test (c) Hinsberg's test (d) Lassaigne's test

Short answer

a) Victor Meyer's test b) Liebermann's test c) Hinsberg's test d) Lassaigne's test e) Lucas test Answer: e) Lucas test

Step-by-step solution

Victor Meyer's test

Victor Meyer's test is a test for determining the molecular weight of volatile substances, especially for distinguishing between pairs of isomeric compounds. It is not specific for distinguishing between 1°, 2°, and 3° alcohols.

Liebermann's test

Liebermann's test is used for detecting the presence of phenols and amines in a sample. This test is also not useful for distinguishing between primary, secondary, and tertiary alcohols.

Hinsberg's test

Hinsberg's test is a test for distinguishing between primary, secondary, and tertiary amines in a sample. While the purpose of this test aligns with the exercise goal, it unfortunately does not work for alcohols.

Lassaigne's test

Lassaigne's test is a test used to detect the presence of halogens, nitrogen, and sulfur in organic compounds. Its function is not focused on distinguishing between primary, secondary, and tertiary alcohols. Given that none of the listed tests are specifically meant for distinguishing between 1°, 2°, and 3° alcohols, it seems there may be an error in the original question. A better-suited test for distinguishing between primary, secondary, and tertiary alcohols is the Lucas test. The Lucas test uses Lucas reagent (ZnCl2 and concentrated HCl) to distinguish between 1°, 2°, 3° alcohols based on the speed of reaction.

Key concepts

Victor Meyer's Test

The Victor Meyer's test is typically used in organic chemistry to determine the molecular weight and structure of compounds by measuring the volume of gas displaced upon the evaporation of a liquid sample. To perform this test, a known volume of an organic compound is vaporized in a special apparatus and the displaced gas is collected. The test identifies isomeric differences but is not suitable for classifying alcohols by order of their degree (primary, secondary, or tertiary).
The importance of this test lies in its ability to distinguish isomeric structures, which can have vastly different properties despite having the same molecular formula. For example, it can differentiate between isomers like n-butanol and isobutanol based on their vapor densities.

Liebermann's Test

Liebermann's test is a chemical reaction that is used to detect the presence of phenols or aromatic amines. When a substance containing these groups reacts with potassium nitrite and concentrated sulfuric acid, it forms colored complexes. The characteristic color change signifies the presence of the functional groups.
This test is not applicable for distinguishing between different types of alcohols as it is specific to compounds with pronounced aromatic structures. It is useful for identifying compounds like phenol, which will produce a deep green or blue color that eventually turns red upon the addition of an alkali.

Hinsberg's Test

Hinsberg's test is a qualitative analysis method for distinguishing primary, secondary, and tertiary amines by their reactivity with Hinsberg reagent (benzenesulfonyl chloride). The test is based on the solubility differences of the resultant compounds in an alkaline medium.
While this test is excellent for classifying amines, it does not extend to alcohols, as their chemical behavior in this setting does not yield a clear differentiation. Therefore, it isn't the correct choice for distinguishing 1°, 2°, and 3° alcohols, which the original exercise inquired about.

Lassaigne's Test

The Lassaigne's test is used to detect elements such as nitrogen, sulfur, halogens, and phosphorus in organic compounds. To carry out the test, the organic compound is fused with sodium metal, which converts these elements into soluble sodium salts. The resulting mixture can be tested chemically for the presence of these specific elements through various color changes or precipitates.
While informative for elemental analysis, Lassaigne's test doesn't provide information on the degree of alcohols. It serves a different purpose in the field of qualitative organic analysis and is primarily used when other more delicate analytical techniques are not available.

Lucas Test

The Lucas test enables chemists to differentiate between primary (1°), secondary (2°), and tertiary (3°) alcohols using the Lucas reagent, a mixture of zinc chloride and concentrated hydrochloric acid. The reaction occurs at room temperature with varying reaction times for different types of alcohols.
Tertiary alcohols react quickly, forming a cloudy solution almost immediately due to the formation of insoluble alkyl chlorides. Secondary alcohols take a moderate amount of time to react and become cloudy, while primary alcohols either do not react at room temperature or the reaction is very slow, often needing heating. The Lucas test is an excellent example of an exercise improvement suggestion for distinguishing different types of alcohols, which was the intent of the original textbook question.