FAQ's On iodoform test

1)WHAT IS IODOFORM TEST?

When aldehyde and Ketone having methyl keto group (CH3-CO-) is warmed with alkaline iodine solution, iodoform is formed.

The reaction in detail:

When alcohol which has CH3-CH-OH group that is oxidizable to methyl keto group (CH3-CO-) is warmed with alkaline iodine solution, iodoform is formed.

The reaction in detail:

2)WHAT IS REAGENT OF IODOFORM TEST?

Alkaline Iodine solution is the reagent for the iodoform test.

3)WHAT ARE THE CHARACTERISTIC FEATURES OF PRODUCT OF IODOFORM TEST?

Iodoform is the product formed during iodoform test and its characteristic features are is pale yellow color and has hospital smell.

4)WHAT ARE THE STRUCTURAL REQUIREMENT FOR IODOFORM TEST?

Aldehyde and ketone should have the following structural requirement for the iodoform test.

Alcohol should have the following structural requirement for the iodoform test.

5)HOW IS IODOFORM TEST CARRIED OUT?

It is carried out in the following steps:

• 1 ml of iodine solution is taken in a clean and dry test tube.
• Then, NaOH solution is added till red color of the iodine solution disappears.
• To this, a small amount of organic sample is added.
• Then it is warmed at 60-70C.
• Hospital smell confirms the test is positive. 

6`) DOES ALL PRIMARY ALCOHOL GIVE IODOFORM TEST?

Primary alcohol upon analysis, it can be concluded only Primary alcohol that gives iodoform test is ethanol because all other primary alcohol lacks CH₃-CH-OH group.

 

7`) DOES ALL SECONDARY ALCOHOL GIVE IODOFORM TEST?

Only Secondary alcohol having –OH group at 2^nd Carbon gives the iodoform test. For example: 2-propanol, 2-butanol,etc.

8`) DOES TERTIARY ALCOHOL GIVE IODOFORM TEST?

None of the tertiary alcohol gives the iodoform test.

9) DOES ALL ALDEHYDE GIVE IODOFORM TEST?

Aldehyde upon analysis, it can be concluded only Aldehyde that gives iodoform test is ethanal as other aldehyde lacks CH₃-CO- group.

10) DOES ALL KETONE GIVE IODOFORM TEST?

No, only some ketone gives the iodoform test. Ketone having CO group at second position gives the iodoform test. For example:

11)  NAME TWO EXAMPLES OF SECONDARY ALCOHOL THAT GIVES IODOFORM TEST.

2-propanol and 2-butanol are examples of two secondary alcohol that gives the iodoform test.

13)CAN IODOFORM TEST BE USED  AS A TEST OF ETHANOL?

Yes, iodoform test can be used as a test of ethanol. Esterification reaction and KMnO₄ test can also be used as its alternative.

 

14) CAN IODOFORM TEST BE USED TO DISTINGUISH TWO ALDEHYDE?

Yes, Iodoform test be used to distinguish two aldehydes however, one aldehyde must be ethanal (acetaldehyde).

 

15) CAN IODOFORM TEST BE USED TO DISTINGUISH TWO KETONE?

Yes, Iodoform test be used to distinguish two ketones, however, only one ketone must have CH3CO group.

 16) CAN IODOFORM TEST BE USED TO DISTINGUISH Propanal & Propanone?

Yes, Iodoform test be used to distinguish Propanal and Propanone. Instead of this test, Tollen’s test or Fehling test can also be used.

17)2-propanol GIVES IODOFORM TEST BUT 1-propanol DOESNT GIVE THIS TEST, WHY?

2-propanol gives iodoform test but 1-propanol doesn’t give this test. This is because 2-propanol has CH3CHOH group which oxidizes to CH3CO group. Whereas, 1-propanol lacks such a group.

 

18)NAME THE ISOMER OF C₃H₆O THAT GIVES IODOFORM TEST.

Propanone is the desired isomer of C₃H₆O that gives the iodoform test.

 

19)NAME THE ISOMER OF C₄H₈O THAT GIVES IODOFORM TEST.

Butanone is the desired isomer of C₄H₈O that gives the iodoform test.

20)NAME THE ISOMER OF C₅H₁₀O THAT GIVES IODOFORM TEST.

2-pentanone and 3-methylbutanone are the desired isomer of C₅H₁₀O that gives the iodoform test.

 

21)NAME THE ISOMER OF C₃H₈O THAT GIVES IODOFORM TEST.

2-propanol is the desired isomer of C₃H₈O that gives the iodoform test.

22) CAN SODIUM CARBONATE BE USED INSTEAD OF SODIUM HYDROXIDE?

Yes, it can be used and overall reaction in case of ethanol becomes: 

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About MY CHEMISTRY TUTORIAL

This site provides notes on different chapters of Chemistry of Grade XI and XII (NEB Board). Also, it posts number of blogs on Collection of past questions and solution. Conversion chart, rules, Chemical test are some additional features.

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