The best way to distinguish between ethanal and propanal is iodoform test; Ethanal responds to the iodoform test whereas propanal does not respond to the iodoform test.
Ethanal and propanal are simple aldehyde compounds. They differ from each other according to the number of carbon atoms present in their molecules; therefore, they have different chemical and physical properties as well. Ethanal is a colorless liquid with an ethereal odor while propanal is a colorless, flammable liquid having a slightly fruity odor.
CONTENTS
1. Overview and Key Difference
2. What is Ethanal
3. What is Propanal
4. What is Iodoform Test
5. Side by Side Comparison – Ethanal vs Propanal in Tabular Form
6. Summary
What is Ethanal
Ethanal or acetaldehyde is an organic compound having the chemical formula CH3CHO. This compound is composed of a methyl group attached to an aldehyde functional group; thus, we can abbreviate it as MeCHO where Me refers to Methyl. This is an important aldehyde compound that occurs widely in nature, e.g. occurs naturally in coffee, bread, and ripe fruit. However, it is also produced on a large scale for industrial purposes. Another biological route exists for its preparation; this route involves the partial oxidation of ethanol by the liver enzyme alcohol dehydrogenase and this preparation helps the hangover after alcohol consumption.
Figure 01: Structure of Ethanal Molecule
At room temperature and pressure, ethanal occurs as a colorless liquid. Some chemical facts about this substance are as follows:
- Chemical formula is C2H4O
- Molar mass is 44.053 g/mol.
- Appears as a colorless liquid.
- This substance has an ethereal odor.
- The melting point is -123.37 Celsius degrees.
- Boiling point is 20.0 Celsius degrees.
- Miscible with water, ethanol, ether, benzene, toluene, etc.
- The molecule has trigonal planar around the carbonyl carbon atom and tetrahedral geometry around the methyl carbon
There are many different uses of ethanal, including its role as a precursor to acetic acid production, as a starting material in the synthesis of 1-butanol, perfumes, flavorings, aniline dyes, plastics, synthetic rubber, etc.
What is Propanal?
Propanal or propionaldehyde is a simple aldehyde organic compound having the chemical formula CH3CH2CHO. This is the third member of the aldehyde series. We can observe this substance as a colorless, flammable liquid having a slightly fruity odor.
Figure 02: Chemical Structure of Propanal
When considering the production of propanal, we can produce this compound industrially via hydroformylation of ethylene. Annually, this method is used to produce thousands of tons of propanal. Other than that, there are some laboratory methods we can use to make this substance, such as the oxidation of 1-propanol with a mixture of sulfuric acid and potassium dichromate.
There are different uses of propanal including its use as a precursor to trimethylolethane (a triol), synthesis of several common aroma compounds such as helional, reduction of propanal to form propanol and oxidation of propanal gives propionic acid, etc.
What is Iodoform Test
Iodoform test is an important analytical test that is used to identify organic compounds containing carbonyl carbon centers that are attached to a methyl group. In other words, the test identifies –C(=O)-CH3 centers. The chemical reaction used in this test includes iodine, a base and the analyte sample which gives a yellow color precipitate if the unknown compound has the above chemical structure. Moreover, this reaction gives an antiseptic smell. Ethanal molecule contains a carbonyl carbon bonded to a methyl group but there is no such structure in propanal, so we can easily distinguish between ethanal and propanal using this test.
How to Distinguish Between Ethanal and Propanal
Ethanal and propanal are aldehyde organic compounds. The best way to distinguish between ethanal and propanal is by performing the iodoform test. Tethanal responds to the iodoform test whereas propanal does not respond to the iodoform test. Moreover, ethanal has an ethereal odor while propanal has a fruity and pungent odor. Ethanal is made by the oxidation of ethylene by Wacker process while propanal is industrially manufactured via hydroformylation of ethylene.
The below infographic tabulates the important differences between both compounds that are helpful to distinguish between ethanal and propanal.
Summary – Ethanal vs Propanal
Ethanal and propanal are aldehydes having a different number of carbon atoms per molecule. The best way to distinguish between ethanal and propanal is by performing the iodoform test. Tethanal responds to the iodoform test whereas propanal does not respond to the iodoform test.
Reference:
1. Helmenstine, Anne Marie. “Hangover Remedies and Prevention.” ThoughtCo, Aug. 25, 2020, Available here.
Image Courtesy:
1. “Acetaldehyde-2D-flat” By UAwiki – Own work (CC BY-SA 3.0) via Commons Wikimedia
2. “Propionaldehyde flat structure” By Cacycle – Own work (Public Domain) via Commons Wikimedia