Aldehyde and Ketone MCQ Questions & Answers in Organic Chemistry | Chemistry
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61.
A mixture of benzaldehyde and formaldehyde on heating with aqueous \[NaOH\] solution gives
A
benzyl alcohol and sodium formate
B
sodium benzoate and methyl alcohol
C
sodium benzoate and sodium formate
D
benzyl alcohol and methyl alcohol
Answer :
benzyl alcohol and sodium formate
TIPS/Formulae :
Both compounds do not contain \[\alpha \text{-}\] hydrogen hence
undergo Crossed Cannizzaro reaction.
Initially \[\text{O}{{\text{H}}^{-}}\] attacks at the carbonyl carbon of \[HCHO\] than that of \[PhCHO\] because carbonyl carbon of \[HCHO\] is
(i) more electrophilic
(ii) less sterically hindered to give hydroxyalkoxide which acts as hydride donor in next step to give sodium formate.
\[{{C}_{6}}{{H}_{5}}CHO+HCHO\xrightarrow[{}]{NaOH}\,HCOONa+{{C}_{6}}{{H}_{5}}C{{H}_{2}}OH\]
62.
\[C{H_3} - C \equiv CH\xrightarrow[{1\% \,HgS{O_4}}]{{40\% \,{H_2}S{O_4}}}A\] \[\xrightarrow{\text{Isomerisation}}C{{H}_{3}}\underset{\begin{smallmatrix}
\parallel \\
O
\end{smallmatrix}}{\mathop{-C-}}\,C{{H}_{3}}\]
Structure of $$'A'$$ and type of isomerism in the above reaction are respectively
A
prop-1-en-2-ol, metamerism
B
prop-1-en-1-ol, tautomerism
C
prop-2-en-2-ol, geometrical isomerism
D
prop-1-en-2-ol, tautomerism
Answer :
prop-1-en-2-ol, tautomerism
63.
Ketones \[(R\overset{\begin{smallmatrix}
O \\
\parallel
\end{smallmatrix}}{\mathop{-C-}}\,R')\] can be obtained in one step by ( where $$R$$ and $$R'$$ are alkyl groups )
A
hydrolysis of esters
B
oxidation of primary alcohols
C
oxidation of secondary alcohols
D
reaction of alkyl halides with alcohols
Answer :
oxidation of secondary alcohols
No explanation is given for this question. Let's discuss the answer together.
64.
Study the given reaction and identify the process which is carried out.
A
It is used for purification of aldehydes and ketones.
B
It is used to distinguish aldehydes from ketones.
C
It is used to prepare cyclic aldehydes and ketones.
D
It is used to study polar nature of aldehydes and ketones.
Answer :
It is used for purification of aldehydes and ketones.
Aldehydes and ketones form insoluble crystalline compounds with $$NaHS{O_3}$$ which can be filtered. These on distillation with saturated solution of $$N{a_2}C{O_3}$$ again give the aldehydes and ketones.
65.
In the following sequence of reaction, the final product $$(Z)$$ is \[CH\equiv CH\xrightarrow[{{H}_{2}}S{{O}_{4}}]{H{{g}^{2+}}}X\xrightarrow[{{H}_{2}}O]{C{{H}_{3}}MgX}\] \[Y\xrightarrow{\left[ O \right]}Z\]
A
ethanal
B
propan-2-ol
C
propanone
D
propan-1-ol
Answer :
propanone
66.
Which one of the following on treatment with $$50\% $$ aqueous sodium hydroxide yields the corresponding alcohol and acid?
A
B
C
D
Answer :
Aldehydes which do not have any $$\alpha $$ - hydrogen atom when heated with a concentrated solution of $$NaOH$$ undergo a simultaneous oxidation and reduction (disproportionation) forming a salt of carboxylic acid and alcohol. This reaction is called Cannizaro reaction.
$$2{C_6}{H_5}CHO + NaOH \to $$ $$\mathop {{C_6}{H_5}C{H_2}OH}\limits_{{\text{Benzyl alcohol}}} + \mathop {{C_6}{H_5}CO\mathop O\limits^ - N\mathop a\limits^ + }\limits_{{\text{Sodium benzoate}}} $$
67.
An organic compound of molecular formula $${C_3}{H_6}O$$ did not give a silver mirror with Tollens' reagent but give an oxime with hydroxylamine. It may be
A
$$C{H_2} = CH - C{H_2} - OH$$
B
$$C{H_3}COC{H_3}$$
C
$$C{H_3}C{H_2}CHO$$
D
$$C{H_2} = CH - OC{H_3}$$
Answer :
$$C{H_3}COC{H_3}$$
No explanation is given for this question. Let's discuss the answer together.
68.
Which of the following reaction can produce \[R-CO-Ar?\]
$$ArCOR$$ can be prepared by the combination of $$ArH + RCOCl$$ and not by $$ArCOCl + RMgX$$ because here the $$ArCOR$$ formed will further react with $$RMgX$$ to form \[{{3}^{\circ }}\] alcohol, \[ArC\left( OH \right){{R}_{2}}\] as the final products.
69.
Alkene $$\left( X \right)\left( {{C_5}{H_{10}}} \right)$$ on ozonolysis gives a mixture of two compounds $$(Y)$$ and $$(Z).$$ Compound $$(Y)$$ gives positive Fehling's test and iodoform test. Compound $$(Z)$$ does not give Fehling's test but give iodoform test. Compounds $$(X), (Y)$$ and $$(Z)$$ are
A
(a)
B
(b)
C
(c)
D
(d)
Answer :
(b)
\[\underset{\left( X \right)}{\mathop{C{{H}_{3}}-CH}}\,\underset{\begin{smallmatrix}
| \\
\,\,\,C{{H}_{3}}
\end{smallmatrix}}{\mathop{=C-}}\,C{{H}_{3}}\xrightarrow[\left( \text{ii} \right)\frac{Zn}{{{H}_{2}}O}]{\left( \text{i} \right){{O}_{3}}}\] \[\underset{\begin{smallmatrix}
\text{Positive Fehling }\!\!'\!\!\text{ s} \\
\text{and iodoform test}
\\
\left( Y \right)
\end{smallmatrix}}{\mathop{C{{H}_{3}}CHO}}\,+\underset{\begin{smallmatrix}
\text{Positive Iodoform test} \\
\left( Z \right)
\end{smallmatrix}}{\mathop{C{{H}_{3}}\overset{\begin{smallmatrix}
O \\
\parallel
\end{smallmatrix}}{\mathop{-C-}}\,C{{H}_{3}}}}\,\]
70.
Which of the following IUPAC names is not correctly matched?