Answer
Verified
394.2k+ views
Hint- we must remember that the \[{\text{C}}{{\text{H}}_{\text{3}}}{\text{CHO}}\] known as acetaldehyde and has aldehyde as the functional group. The carbon-oxygen double bond of \[{\text{ - CHO}}\]is polarised due to higher electronegativity of oxygen relative to carbon. Therefore we can understand the carbonyl oxygen is a nucleophilic (Lewis base) centre and the carbonyl carbon is an electrophilic (Lewis acid) and which can undergo nucleophilic addition reactions.
We must understand that the propanal is an aldehyde and propanone is a ketone, so we need to find a test to distinguish between aldehyde and ketone. Therefore we can use Iodoform test to inspect the presence of carbonyl compounds with the structure \[{\text{R - CO - C}}{{\text{H}}_{\text{3}}}\]or alcohols with the structure\[{\text{R - CH}}\left( {{\text{OH}}} \right){\text{ - C}}{{\text{H}}_{\text{3}}}\].
Complete step by step solution:-
(a) (i) when we react aldehydes and ketones with hydrogen cyanide $(HCN)$ which yield cyanohydrins. So in the given question, acetaldehyde (\[{\text{C}}{{\text{H}}_{\text{3}}}{\text{CHO}}\]) reacts with hydrogen cyanide \[{\text{HCN}}\] to give 2-hydroxypropanenitrile as product. We can represent the reactions as
(ii) When we reacts acetaldehyde (\[{\text{C}}{{\text{H}}_{\text{3}}}{\text{CHO}}\]) with hydroxylamine (\[{{\text{H}}_{\text{2}}}{\text{N - OH}}\]) to give acetaldoxime (oxime) as a product.
\[{\text{C}}{{\text{H}}_{\text{3}}}{\text{CHO}}{\text{ + N}}{{\text{H}}_{\text{2}}}{\text{OH}} \to {\text{C}}{{\text{H}}_{\text{3}}}{\text{ - CH = NOH + }}{{\text{H}}_{\text{2}}}{\text{O}}\]
(iii) Also the reaction of acetaldehyde (\[{\text{C}}{{\text{H}}_{\text{3}}}{\text{CHO}}\]) with acetaldehyde (\[{\text{C}}{{\text{H}}_{\text{3}}}{\text{CHO}}\]) in the presence of dilute\[{\text{NaOH}}\], we know this is a type of aldol reaction by which we obtained 3-hydroxybutanal as product. Further, we heat the reaction mixture, we get aldol condensation product (but-2-enal).
(b) We can use the Iodoform test to distinguish propanal and propanone. We must understand that when we treat this compound with iodine in the presence of base like\[{\text{NaOH}}\], we get a pale yellow precipitate of triiodomethane (iodoform) for carbonyl compounds with the structure \[{\text{R - CO - C}}{{\text{H}}_{\text{3}}}\]or we get alcohols with the structure\[{\text{R - CH}}\left( {{\text{OH}}} \right){\text{ - C}}{{\text{H}}_{\text{3}}}\]. Now we can distinguish, propanone has \[{\text{R - CO - C}}{{\text{H}}_{\text{3}}}\]structure gives positive result with iodoform while propanal do not contain any such structure gives negative result.
\[
\begin{array}{*{20}{l}}
{{\text{C}}{{\text{H}}_{\text{3}}}{\text{COC}}{{\text{H}}_{\text{3}}}{\text{ + }}{{\text{I}}_{\text{2}}}{\text{ + NaOH }} \to {\text{CH}}{{\text{I}}_{\text{3}}}{\text{ (iodoform) + C}}{{\text{H}}_{\text{3}}}{\text{COONa + NaOH}}} \\
{\text{Propanone}} \\
{\text{C}}{{\text{H}}_{\text{3}}}{\text{C}}{{\text{H}}_{\text{2}}}{\text{CHO + }}{{\text{I}}_{\text{2}}}{\text{ + NaOH }} \to {\text{No reaction}} \\
{\text{Propanal}} \\
\end{array} \\
\\
\]
Note- (a) we must know that all the reactions of acetaldehyde with corresponding reactants is a result of polarised C-O bonds in the aldehyde.
(b) We must look for carbonyl compounds with the structure \[{\text{R - CO - C}}{{\text{H}}_{\text{3}}}\]or alcohols with the structure \[{\text{R - CH}}\left( {{\text{OH}}} \right){\text{ - C}}{{\text{H}}_{\text{3}}}\]in order to carry out iodoform test.
We must understand that the propanal is an aldehyde and propanone is a ketone, so we need to find a test to distinguish between aldehyde and ketone. Therefore we can use Iodoform test to inspect the presence of carbonyl compounds with the structure \[{\text{R - CO - C}}{{\text{H}}_{\text{3}}}\]or alcohols with the structure\[{\text{R - CH}}\left( {{\text{OH}}} \right){\text{ - C}}{{\text{H}}_{\text{3}}}\].
Complete step by step solution:-
(a) (i) when we react aldehydes and ketones with hydrogen cyanide $(HCN)$ which yield cyanohydrins. So in the given question, acetaldehyde (\[{\text{C}}{{\text{H}}_{\text{3}}}{\text{CHO}}\]) reacts with hydrogen cyanide \[{\text{HCN}}\] to give 2-hydroxypropanenitrile as product. We can represent the reactions as
(ii) When we reacts acetaldehyde (\[{\text{C}}{{\text{H}}_{\text{3}}}{\text{CHO}}\]) with hydroxylamine (\[{{\text{H}}_{\text{2}}}{\text{N - OH}}\]) to give acetaldoxime (oxime) as a product.
\[{\text{C}}{{\text{H}}_{\text{3}}}{\text{CHO}}{\text{ + N}}{{\text{H}}_{\text{2}}}{\text{OH}} \to {\text{C}}{{\text{H}}_{\text{3}}}{\text{ - CH = NOH + }}{{\text{H}}_{\text{2}}}{\text{O}}\]
(iii) Also the reaction of acetaldehyde (\[{\text{C}}{{\text{H}}_{\text{3}}}{\text{CHO}}\]) with acetaldehyde (\[{\text{C}}{{\text{H}}_{\text{3}}}{\text{CHO}}\]) in the presence of dilute\[{\text{NaOH}}\], we know this is a type of aldol reaction by which we obtained 3-hydroxybutanal as product. Further, we heat the reaction mixture, we get aldol condensation product (but-2-enal).
(b) We can use the Iodoform test to distinguish propanal and propanone. We must understand that when we treat this compound with iodine in the presence of base like\[{\text{NaOH}}\], we get a pale yellow precipitate of triiodomethane (iodoform) for carbonyl compounds with the structure \[{\text{R - CO - C}}{{\text{H}}_{\text{3}}}\]or we get alcohols with the structure\[{\text{R - CH}}\left( {{\text{OH}}} \right){\text{ - C}}{{\text{H}}_{\text{3}}}\]. Now we can distinguish, propanone has \[{\text{R - CO - C}}{{\text{H}}_{\text{3}}}\]structure gives positive result with iodoform while propanal do not contain any such structure gives negative result.
\[
\begin{array}{*{20}{l}}
{{\text{C}}{{\text{H}}_{\text{3}}}{\text{COC}}{{\text{H}}_{\text{3}}}{\text{ + }}{{\text{I}}_{\text{2}}}{\text{ + NaOH }} \to {\text{CH}}{{\text{I}}_{\text{3}}}{\text{ (iodoform) + C}}{{\text{H}}_{\text{3}}}{\text{COONa + NaOH}}} \\
{\text{Propanone}} \\
{\text{C}}{{\text{H}}_{\text{3}}}{\text{C}}{{\text{H}}_{\text{2}}}{\text{CHO + }}{{\text{I}}_{\text{2}}}{\text{ + NaOH }} \to {\text{No reaction}} \\
{\text{Propanal}} \\
\end{array} \\
\\
\]
Note- (a) we must know that all the reactions of acetaldehyde with corresponding reactants is a result of polarised C-O bonds in the aldehyde.
(b) We must look for carbonyl compounds with the structure \[{\text{R - CO - C}}{{\text{H}}_{\text{3}}}\]or alcohols with the structure \[{\text{R - CH}}\left( {{\text{OH}}} \right){\text{ - C}}{{\text{H}}_{\text{3}}}\]in order to carry out iodoform test.
Recently Updated Pages
Basicity of sulphurous acid and sulphuric acid are
Three beakers labelled as A B and C each containing 25 mL of water were taken A small amount of NaOH anhydrous CuSO4 and NaCl were added to the beakers A B and C respectively It was observed that there was an increase in the temperature of the solutions contained in beakers A and B whereas in case of beaker C the temperature of the solution falls Which one of the following statements isarecorrect i In beakers A and B exothermic process has occurred ii In beakers A and B endothermic process has occurred iii In beaker C exothermic process has occurred iv In beaker C endothermic process has occurred
What is the stopping potential when the metal with class 12 physics JEE_Main
The momentum of a photon is 2 times 10 16gm cmsec Its class 12 physics JEE_Main
How do you arrange NH4 + BF3 H2O C2H2 in increasing class 11 chemistry CBSE
Is H mCT and q mCT the same thing If so which is more class 11 chemistry CBSE
Trending doubts
Difference Between Plant Cell and Animal Cell
Difference between Prokaryotic cell and Eukaryotic class 11 biology CBSE
How do you solve x2 11x + 28 0 using the quadratic class 10 maths CBSE
Select the correct plural noun from the given singular class 10 english CBSE
What organs are located on the left side of your body class 11 biology CBSE
The sum of three consecutive multiples of 11 is 363 class 7 maths CBSE
What is the z value for a 90 95 and 99 percent confidence class 11 maths CBSE
Fill the blanks with the suitable prepositions 1 The class 9 english CBSE
How many squares are there in a chess board A 1296 class 11 maths CBSE