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Hint:
Haloform reaction: Compounds having ${ CH }_{ 3 }{ C=O }$ group or ${ CH }_{ 3 }{ OH }$ group react with sodium hypohalite to give haloform. This method is used for the detection of the methyl keto group.
Complete step-by-step answer:
The Iodoform test is given by aldehydes and ketones having alpha-methyl group ${ CH }_{ 3 }{ C=O }$. Even alcohols having alpha-methyl group show iodoform test.
${ CH }_{ 3 }{ COCH }_{ 3 }$: In acetone, ${ CH }_{ 3 }{ C=O }$ The group is present, so it shows the iodoform test.
${ HCHO }$: There is no beta hydrogen in formaldehyde to deprotonate, so they will not deprotonate and hence, do not show iodoform test.
${ CH }_{ 3 }{ CH }_{ 2 }{ Br }$: As there is no ${ CH }_{ 3 }{ C=O }$ or ${ CH }_{ 3 }{ OH }$ in ethyl bromide, so it will not give a haloform reaction.
${ CH }_{ 3 }{ OCH }_{ 3 }$: Methoxy methane does not show iodoform reaction as there is no presence of the ${ C=O }$ group.
The correct option is A.
Additional Information:
In the Iodoform test, carbonyl compound (aldehyde or ketone) or a compound containing ${ CH }_{ 3 }{ C=O }$ group, reacts with ${ I }_{ 2 }$, in presence of ${ NaOH }$, to give ${ CH }_{ 3 }{ I }$ (yellow precipitate).
The iodoform test is a very useful method to identify the presence of these methyl ketones or acetaldehyde in an unknown compound.
The reaction of iodine, a base, and a methyl ketone gives a yellow precipitate along with an “antiseptic” smell.
Note:
The possibility to make a mistake is that you may choose option B. As I discussed above, carbonyl compounds give the iodoform test but only those compounds having an alpha-methyl group and there is no alpha carbon in formaldehyde, so it does not give iodoform test.
Haloform reaction: Compounds having ${ CH }_{ 3 }{ C=O }$ group or ${ CH }_{ 3 }{ OH }$ group react with sodium hypohalite to give haloform. This method is used for the detection of the methyl keto group.
Complete step-by-step answer:
The Iodoform test is given by aldehydes and ketones having alpha-methyl group ${ CH }_{ 3 }{ C=O }$. Even alcohols having alpha-methyl group show iodoform test.
${ CH }_{ 3 }{ COCH }_{ 3 }$: In acetone, ${ CH }_{ 3 }{ C=O }$ The group is present, so it shows the iodoform test.
${ HCHO }$: There is no beta hydrogen in formaldehyde to deprotonate, so they will not deprotonate and hence, do not show iodoform test.
${ CH }_{ 3 }{ CH }_{ 2 }{ Br }$: As there is no ${ CH }_{ 3 }{ C=O }$ or ${ CH }_{ 3 }{ OH }$ in ethyl bromide, so it will not give a haloform reaction.
${ CH }_{ 3 }{ OCH }_{ 3 }$: Methoxy methane does not show iodoform reaction as there is no presence of the ${ C=O }$ group.
The correct option is A.
Additional Information:
In the Iodoform test, carbonyl compound (aldehyde or ketone) or a compound containing ${ CH }_{ 3 }{ C=O }$ group, reacts with ${ I }_{ 2 }$, in presence of ${ NaOH }$, to give ${ CH }_{ 3 }{ I }$ (yellow precipitate).
The iodoform test is a very useful method to identify the presence of these methyl ketones or acetaldehyde in an unknown compound.
The reaction of iodine, a base, and a methyl ketone gives a yellow precipitate along with an “antiseptic” smell.
Note:
The possibility to make a mistake is that you may choose option B. As I discussed above, carbonyl compounds give the iodoform test but only those compounds having an alpha-methyl group and there is no alpha carbon in formaldehyde, so it does not give iodoform test.
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