Page 41 - FPGEE Medicinal and Organic Chemistry Q&A Book

Krisman

An aldehyde + Ag(NH ) OH A carboxylate ion + Silver Mirror
3 2
Ammoniacal silver
nitrate solution

A ketone + Ag(NH ) OH No reaction
3 2
Ammoniacal silver
nitrate solution

(Fig: 11.26)

Iodoform Tests:

O
I / NaOH
2 CHI 3
CH 3 C CH 3
Iodoform
Acetone

O I / NaOH
2
CH CH C CH CH No reaction
3 2 2 3
(since no methyl gp)
Diethyl ketone
O I / NaOH
2 CHI
H C CH 3
3
Iodoform
Acetaldehyde
O
I / NaOH
2
CH 3 CH 2 OH H C CH 3 CHI 3

Ethanol Acetaldehyde Iodoform

CH CH CH O I / NaOH
3 3 2
OH CH 3 C CH 3 CHI 3
Iodoform
(Secondary alcohol) Acetone

(Fig: 11.27)

This is because ethanol is subsequently oxidized 482. (b) With an alkaline solution of iodine, ac-
to acetaldehyde and secondary alcohols are oxi- etaldehyde forms yellow precipitates of iodo-
dized to methyl ketones under the condition form whereas formaldehyde does not react.
used for the test. The test is also used to distin-
guish ethanol from methanol since the latter one 483. (d) Fehling's solution is a solution used to
does not give a positive iodoform test. The test distinguish aldehyde from the ketone functional
is also used to distinguish methyl ketone from groups, although ketose monosaccharides (such
other ketones, (fig: 11.27). as fructose) will also test positive, due to con-

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