How do we know if a compounds undergoes iodoform test or nt?

SOHAN SARANGI, 12 years ago

Grade:12

10 Answers

vamsi aditya

37 Points

12 years ago

the compound must have either a CH3-C=O group or CH3-CH-OH group

bhanuveer danduboyina

95 Points

12 years ago

The iodoform test or iodoform reaction is a qualitative chemical test for the detection of ketones and aldehydes carrying an alpha methyl group. The reagents are iodine and sodium hydroxide.

Only methyl ketones, or alcohols with the feature:

CH3CH(OH)-R
may undergo this reaction.

There are three steps to the iodoform reaction when starting from an alcohol. If the reaction starts from a methyl ketone, the first step is not needed.

Addition of I2(aq) (usually I2 dissolved in KI, shown here reacting with 2-propanol)
2 NaOH + I2 + CH3CH(OH)CH3 → 2 NaI + CH3COCH3 + 2 H2O
oxidizes the hydroxyl group to a ketone,

The ketone formed reacts with the I2(aq) in a substitution reaction to produce a triiodoketone, for example triiodoacetone.
CH3COCH3 + 3I2 → CH3COCI3 + 3HI
(Thus, ketone and aldehyde with structure -COCH3 also show positive results). Ethanal is the only aldehyde to give the iodoform reaction.

Finally, OH- (aqueous) is added, which reacts with, for example, the triiodoacetone.
CH3COCI3 + OH- → CHI3 + CH3COO-

Iodoform, or triiodomethane (I3CH) is a pale yellow substance. It is therefore a solid at room temperature. It is insoluble in water and has an antiseptic smell.

PLEASE APPROVE MY ANSWER!!

Approved

Godfrey Classic Prince

633 Points

12 years ago

Dear SOHAN SARANGI,

The compounds that will undergo Iodoform test will be having a

CH₃CH(OH)- group (or) CH₃C=O group .

All the Very Best & Good Luck !!

Hope this helped you immensely...

Regards,

AskIITians Expert,

Godfrey Classic Prince

IIT-Madras

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Annesha Debroy

14 Points

12 years ago

aldehydes containing hydrogen attached to carbonyl group can easily be hydrated ,hence can easily give tollen's test.just see the mechanism and find the r.d.s and u know wht will effect reactivity!!!!!!!!

if u need further help contact me!!!!

-annesha debroy(iit karagpur)

Disapproved

Debanuj Chatterjee

14 Points

12 years ago

see..iodoform test is given by (normally) compounds with a keto methyl group but, if there is a secondary or primary alcohol with an adjacent methyl group then also it will be oxidised to give keto methyl gr and thus will give iodofrm tst

vibhu

19 Points

8 years ago

The compound must have either ch3-c=of or ch3-ch-oh

nikul lathiya

12 Points

7 years ago

Oh very eas1).any COMPOUND which cobtain CH3 -CO- or. Methyle carbonyl grp will give +ve iodoform test2) also primery and secondary alcohole Which contain CH3 CH(OH)- grp will give +test

Amay chugh

29 Points

7 years ago

This test is generally done to detect the aldehyde and ketone from other carbonyll members idoform test is only positive for aldehyde and ketone having a( CH3-C=O ) |group in their molrcules i.e the methyl keto group acetaldehyde is the only aldehyde which gives iodoform test positive .Alcohols having OH | (CH3-CH-) in their molecule also gives iodoform test as it gets oxidized to methyl keto group

Abhigyan Ghosh

26 Points

6 years ago

Basically any compound with CH3－CO－ group or CH3－CH(OH)－ group will give iodoform test except those which contain a more acidic hydrogen than that of the CH3 group.Eg: CH3－CO－CH2－CO－R doesnot give iodoform test under normal conditions as hydrogen in the active methylene group is more acidic. It however does give iodoform test when excess of reagents is added.

Rishi Sharma

askIITians Faculty 646 Points

3 years ago

Dear Student,
Please find below the solution to your problem.

The iodoform test or iodoform reaction is a qualitative chemical test for the detection of ketones and aldehydes carrying an alpha methyl group. The reagents are iodine and sodium hydroxide.
The compounds that will undergo Iodoform test will be having a
CH3CH(OH)- group (or) CH3C=O group

Thanks and Regards