The presence of unsaturation in an organic compound can be detected by
Baeyer’s reagent
Detecting Unsaturation in Organic Compounds
Organic compounds can contain different types of bonds between carbon atoms. When a compound contains only single bonds between carbon atoms, it is called saturated. If a compound contains double or triple bonds, it is considered unsaturated. Detecting the presence of unsaturation is a common task in organic chemistry, and specific chemical tests are used for this purpose.
Understanding Chemical Tests for Unsaturation
Several chemical reagents are used in organic chemistry to identify specific functional groups. The question asks about detecting unsaturation in an organic compound. Let's look at the given options:
| Reagent | Primary Use | Indicates |
|---|---|---|
| Schiff’s reagent | Aldehydes | Presence of aldehyde group (usually a pink or magenta color) |
| Tollens reagents | Aldehydes (and some α-hydroxy ketones) | Presence of aldehyde group (forms a silver mirror) |
| Fehling’s solution | Aldehydes (and some α-hydroxy ketones) | Presence of aldehyde group (forms a red precipitate of &(\text{Cu}_2\text{O})\)) |
| Baeyer’s reagent | Alkenes and Alkynes (unsaturation) | Presence of double or triple bonds (color change from purple to colorless or brown precipitate) |
Baeyer’s Reagent for Detecting Unsaturation
Based on the uses listed above, Baeyer’s reagent is the specific chemical test used to detect unsaturation, which means the presence of carbon-carbon double (\(\text{C}=\text{C}\)) or triple (\(\text{C}\equiv\text{C}\)) bonds in an organic compound. Baeyer's reagent is an alkaline solution of cold, dilute potassium permanganate (\(\text{KMnO}_4\)).
When an alkene or alkyne is treated with Baeyer's reagent, the permanganate ion (\(\text{MnO}_4^-\)) oxidizes the double or triple bond. The purple permanganate ion (\(\text{MnO}_4^-\)) is reduced to manganese dioxide (\(\text{MnO}_2\)), which is a brown precipitate, or in some cases, to the colorless manganate ion (\(\text{MnO}_2^-\) oxidation state +4 vs +6 vs +7). This reaction causes the characteristic purple color of the permanganate solution to disappear, and a brown precipitate may form. This color change and/or precipitate formation indicates the presence of unsaturation in the organic compound.
In contrast, saturated hydrocarbons (alkanes) do not react with Baeyer's reagent under these mild conditions, and the purple color persists. Aldehydes and ketones also do not give a positive Baeyer's test under these specific conditions for detecting carbon-carbon unsaturation.
Therefore, among the given options, Baeyer’s reagent is the correct choice for detecting unsaturation in an organic compound.
Important Questions from Organic Transformations and Reagents
Which of the following boron compounds is used as a reducing agent in organic synthesis?
In elimination reaction of sec-Butyl trimethylammonium hydroxide, major product formed would be ________.
Find out the suitable products in the following Grignard reaction:
What will be the product in the following reaction ?
What is the major product in the following reaction?
