Aldehyde and Ketone MCQ Questions & Answers in Organic Chemistry | Chemistry
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161.
In the reaction
the structure of the product $$T$$ is :
A
B
C
D
Answer :
162.
Which of the following does not undergo Cannizzaro reaction?
A
Benzaldehyde
B
2-Methylpropanal
C
$$p$$ - Methoxybenzaldehyde
D
2, 2-Dimethylpropanal
Answer :
2-Methylpropanal
Aldehydes containing no $$\alpha {\text{ - }}H$$ atoms on heating with concentrated alkali solution (50%) undergo Cannizzaro's reaction. Thus 2-methylpropanal containing one $$\alpha $$ - hydrogen cannot undergo Cannizzaro reaction.
163.
Which among the following is most reactive to give nucleophilic addition?
A
$$FC{H_2}CHO$$
B
$$ClC{H_2}CHO$$
C
$$BrC{H_2}CHO$$
D
$$IC{H_2}CHO$$
Answer :
$$FC{H_2}CHO$$
$$FC{H_2}CHO$$ is most reactive towards nucleophilic addition since presence of most electronegative $$F$$ withdraws electrons from carbon of carbonyl group making it more polar.
164.
Hydrogenation of benzoyl chloride in the presence of $$Pd$$ on $$BaS{O_4}$$ gives
A
Benzyl alcohol
B
Benzaldehyde
C
Benzoic acid
D
Phenol
Answer :
Benzaldehyde
NOTE : This reaction is known as Rosexamnd's
reaction.
\[{{C}_{6}}{{H}_{5}}COCl+{{H}_{2}}\xrightarrow[Bas{{O}_{4}}]{Pd}{{C}_{6}}{{H}_{5}}CHO+HCl\]
165.
Among the given compounds, the most susceptible to nucleophilic attack at the carbonyl group is
A
$$MeCOCl$$
B
$$MeCHO$$
C
$$MeCOOMe$$
D
$$MeCOOCOMe$$
Answer :
$$MeCOCl$$
More the magnitude of positive charge on the carbonyl carbon, higher will be its reactivity toward nucleophilic attack.
Chlorine being more electron-withdrawing than $$O$$ develops more positive charge on carbonyl carbon. The order of reactivity of the various carboxyl derivatives toward nucleophile is \[\underset{\text{Most reactive}}{\mathop{RCOCl}}\,>RCHO>{{\left( RCO \right)}_{2}}O>\underset{\text{Least reactive}}{\mathop{RCOOR}}\,\]
166.
Which of the following compounds will give a coloured crystalline compound with
A
$$C{H_3}COCl$$
B
$$C{H_3}COO{C_2}{H_5}$$
C
$$C{H_3}COC{H_3}$$
D
$$C{H_3}CON{H_2}$$
Answer :
$$C{H_3}COC{H_3}$$
No explanation is given for this question. Let's discuss the answer together.
167.
Tollen’s reagent and Fehling solutions are used to distinguish between
A
acids and alcohols
B
alkanes and alcohols
C
ketones and aldehydes
D
$$n$$ - alkanes and branched alkanes
Answer :
ketones and aldehydes
All aldehydes and ketones show reaction with Tollen's reagent and Fehling solutions, but ketones do not show this reaction.
Note: Benzaldehyde do not give reaction with Fehling solution.
168.
The condensation product of benzaldehyde and acetone is
A
$${C_6}{H_5}CH = C{\left( {C{H_3}} \right)_2}$$
B
\[{{C}_{6}}{{H}_{5}}C{{H}_{2}}\overset{\begin{smallmatrix}
O \\
\parallel
\end{smallmatrix}}{\mathop{-C-}}\,CH=C{{H}_{2}}\]
C
\[{{C}_{6}}{{H}_{5}}\overset{\begin{smallmatrix}
O \\
\parallel
\end{smallmatrix}}{\mathop{-C-}}\,CH=CH-C{{H}_{3}}\]
D
\[{{C}_{6}}{{H}_{5}}-CH=CH\overset{\begin{smallmatrix}
O \\
\parallel
\end{smallmatrix}}{\mathop{-C-}}\,C{{H}_{3}}\]
Answer :
\[{{C}_{6}}{{H}_{5}}-CH=CH\overset{\begin{smallmatrix}
O \\
\parallel
\end{smallmatrix}}{\mathop{-C-}}\,C{{H}_{3}}\]
169.
Propanone can be prepared from ethyne by
A
passing a mixture of ethyne and steam over a catalyst, magnesium at $${420^ \circ }C$$
B
passing a mixture of ethyne and ethanol over a catalyst zinc chromite
C
boiling ethyne with water and $${H_2}S{O_4}$$
D
treating ethyne with iodine and $$NaOH$$
Answer :
passing a mixture of ethyne and steam over a catalyst, magnesium at $${420^ \circ }C$$