What will decolorize alkaline kmno4

Ketones aren't that easy to oxidize, and so there is no further action. But see note in red below. If the groups attached either side of the original carbon-carbon double bond were the same, then you would end up with a single ketone. If they were different, then you would end up with a mixture of two. For example:. In this case, you would end up with two identical molecules called propanone. On the other hand, if one of the methyl groups in the original molecule was replaced by an ethyl group, you would get a mixture of two different ketones - propanone and butanone.

What would you get if there was a methyl and an ethyl group on both sides of the original carbon-carbon double bond? Again, you would get a single ketone formed - in this case, butanone. If you aren't sure about this, draw the structures and see. This last section is a gross over-simplification. In practice, ketones are oxidized by potassium manganate VII solution under these conditions. The reaction is untidy and results in breaking carbon-carbon bonds either side of the carbonyl group.

Potassium manganate VII is such a devastating oxidizing agent that it is rarely used in organic chemistry. In this case, the first product molecule has a methyl group and a hydrogen attached to the carbonyl group.

This is a different sort of compound known as an aldehyde. Aldehydes are readily oxidized to give carboxylic acids, containing the -COOH group. The acid structure has been turned around slightly to make it look more like the way we normally draw acids, but the net effect is that an oxygen has been slotted in between the carbon and hydrogen.

The overall effect of the potassium manganate VII on this kind of alkene is therefore:. Obviously, if there was a hydrogen atom attached to both carbons at the ends of the carbon-carbon double bond, you would get two carboxylic acid molecules formed - which might be the same or different, depending on whether the alkyl groups were the same or different. Play around with this until you are happy about it.

Draw a number of alkenes, all of which have a hydrogen attached at both ends of the carbon-carbon double bond. Vary the alkyl groups - sometimes the same on each end of the double bond, sometimes different. But it doesn't! That's because methanoic acid is also easily oxidized by potassium manganate VII solution. In fact, it oxidizes it all the way to carbon dioxide and water.

So the equation in a case like this might be, for example:. The exact nature of the other product in this example, propanone will vary depending on what was attached to the right-hand carbon in the carbon-carbon double bond. If there were two hydrogens at both ends of the double bond in other words, if you had ethene , then all you would get would be carbon dioxide and water. Working back from the results helps you to work out the structure of the alkene. For example, the alkene C 4 H 8 has three structural isomers:.

Work out which of these would give each of the following results if they were treated with hot concentrated potassium manganate VII solution.

Acids are produced when there is a hydrogen atom attached to at least one of the carbons in the carbon-carbon double bond. Previous Years Papers. Important Questions. Supplementary Books. SnapSolve Tutor. Follow us on Youtube. Follow us on Facebook. Download APP. About SnapSolve. Join Now. Question Chemistry Class Which of the following hydrocarbons can decolorize the alkaline potassium permanganate solution?

Total number of optically active compounds obtained when n-pentane is subjected to monochlorination is KEAM Which one of the following conformation of cyclohexane is chiral? AIIMS Chemistry Most Viewed Questions. Identify a molecule which does not exist. Identify the incorrect match.

Which of the following set of molecules will have zero dipole moment? On electrolysis of dil.