Single Correct MCQ Of Aldehydes, Ketones And Carboxylic Acids, Past Year Questions JEE Advance, Class 12, Chemistry


37 Questions MCQ Test Class 12 Chemistry 35 Years JEE Mains &Advance Past yr Paper | Single Correct MCQ Of Aldehydes, Ketones And Carboxylic Acids, Past Year Questions JEE Advance, Class 12, Chemistry


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QUESTION: 1

The reagent with which both acetaldehyde and acetone react easily is

Solution:

Fehling solution, Schiff’s reagent & Tollen’s reagent react only with aldehydes but Grignard reagents react both with aldehydes and ketones.

QUESTION: 2

When acetaldehyde is heated with Fehling’s solution it gives a precipitate of

Solution:

QUESTION: 3

The Cannizzaro reaction is not given by

Solution:

TIPS/Formulae : The compound containing α-H atom does not undergo Cannizzaro's reaction.
Acetaldehyde does not undergo Cannizzaro reaction since it has a-H atoms while formaldehyde, trimethylacetaldehyde and benzaldehyde undergo Cannizzaro reaction since they do not contain α-hydrogen atoms.

QUESTION: 4

The compound that will not give iodoform on treatment with alkali and iodine is :

Solution:

TIPS/Formulae :

Iodoform test is given by compounds having –COCH3 group.
In acetone –COCH3 group is present. Further ethanol and isopropyl alcohol get oxidised to acetaldehyde and acetone respectively (both having –COCH3 group) in presence of I2 and they in turn give the test. Thus only diethyl ketone does not give this test.

QUESTION: 5

Polarisation of electrons in acrolein may be written as

Solution:

NOTE : –CHO produces –R effect i.e. it withdraws electrons from the double bond or from a conjugated system towards itself.

QUESTION: 6

The enolic form of acetone contains

Solution:

No. of σ bonds in enolic form : 3 + 1 + 1 + 1 + 1 + 2 = 9
No. of π bonds in enolic form : 1
No. of lone pairs of electrons in enolic form = 2

QUESTION: 7

m-Chlorobenzaldehyde on reaction with conc. KOH at room temperature gives

Solution:

NOTE : m-Chlobenzaldehyde does not contains α-H atom. It is an example of Cannizzaro reaction

QUESTION: 8

Hydrogenation of benzoyl chloride in the presence of Pd on BaSO4 gives

Solution:

NOTE : This reaction is kn own as Rosen mun d's reaction.

QUESTION: 9

The organic product formed in the reaction

Solution:

TIPS/FORMULAE :

LiAlH4 is a reducing agent, it reduces –COOH group to –CH2OH group.

QUESTION: 10

The reaction products of 

Solution:

QUESTION: 11

In the Cannizzaro reaction given below,

the slowest step is

Solution:

The possible mechanism is



NOTE : The slowest step is the transfer of hydride to the carbonyl group as shown in step (ii).

QUESTION: 12

When propionic acid is treated with aqueous sodium bicarbonate, CO2 is liberated. The ‘C’ of CO2 comes from

Solution:

QUESTION: 13

The enol form of acetone, after treatment with D2O, gives.

Solution:

Remember that α - H's of carbonyl group are easily replaced by D of D2O

QUESTION: 14

Which one of the following will most readily be dehydrated in acidic condition ?

Solution:

Compound (a) undergoes dehydration easily as the product obtained is conjugated and thus more stable.

QUESTION: 15

Benzoyl chloride is prepared from benzoic acid by

Solution:

Benzoyl chloride is prepared from benzoic acid be SOCl2.
|C6H5 COOH + SOCl2 → C6H5COCl + SO2 + HCl

QUESTION: 16

The appropriate reagent for the following transformation is

Solution:

Zn(Hg), HCl cannot be used when acid sensitive group like –OH is present, but NH2NH2, OH can be used.

QUESTION: 17

A mixture of benzaldehyde and formaldehyde on heating with aqueous NaOH solution gives

Solution:

TIPS/Formulae : Both compounds do not contain a-hydrogen hence undergo Crossed Cannizzaro reaction.
Initially OH- attacks at the carbonyl carbon of HCHO than that of PhCHO because carbonyl carbon of HCHO is
(i) more el ectrophilic
(ii) less sterically hindered to give hydroxyalkoxide which acts as hydride donor in next step to give sodium formate.

QUESTION: 18

The product of acid hydrolysis of P and Q can be distinguished by

Solution:

TIPS/Formulae : Ketone (non-reducing) and aldehyde (reducing) can be distinguished by Fehling solution.


QUESTION: 19

Major product is :

Solution:


               

QUESTION: 20

Ethyl ester  The product P will be

Solution:

Recall that, esters react with excess of Grignard reagents to form 3º alcohols having at least two identical alkyl groups corresponding to Grignard reagent.

QUESTION: 21

An enantiomerically pure acid is treated with a racemic mixture of an alcohol having one chiral carbon. The ester formed will be

Solution:

The optically active acid will react with d and l forms of alcohol present in the racemic mixture at different rates to form two diastereomers in unequal amounts leading to optical activity of the product.

QUESTION: 22

The correct order of reactivity of PhMgBr with

Solution:

TIPS/Formulae :
Reaction  of PhMgBr with carbonyl compounds is an example of nucleophilic addition on carbonyl group which increases with the increase in electron-deficiency of carbonyl carbon.

Thus acetaldehyde is most reactive while C6H5COC6H5 least

QUESTION: 23

How will you convert butan-2-one to propanoic acid?

Solution:

QUESTION: 24

The compound (X) is

Solution:

TIPS/Formulae : This reaction is an example of “Perkin reaction”.
The compound X should be (CH3CO)2O.
In this step the carbanion is obtained by removal of an α–H atom from a molecule of an acid anhydride, the anion of the corresponding acid acting as a necessary base.

QUESTION: 25

4-Methylbenzenesulphonic acid reacts with sodium acetate to give

Solution:

This is simply an acid-base reaction.

QUESTION: 26

In the following reaction sequence, the correct structures of E, F and G are

 [* implies 13C labelled carbon)

Solution:


QUESTION: 27

The correct acidity order of the following is    

Solution:

Car boxylic acid is stronger acid th an phenol. The presence of electron withdrawing group (e.g. Cl) increases acidic strength, while presence of electron donating group (e.g. CH3) decreases acidic strength.

QUESTION: 28

In the reaction

the structure of the product T is :

Solution:


QUESTION: 29

The compounds P, Q and S

were separately subjected to nitration using HNO3/H2SO4 mixture. The major product formed in each case respectively, is :

Solution:




(Benzene ring having –O– is activated)

QUESTION: 30

The major product of the following reaction is    

Solution:


QUESTION: 31

The carboxyl functional group (– COOH) is present in

Solution:


QUESTION: 32

The major product H of the given reaction sequence is

Solution:



                     

QUESTION: 33

The compound that undergoes decarboxylation most readily under mild condition is

Solution:

β-Ketoacids undergo decarboxylation easily.

QUESTION: 34

The compound that does NOT liberate CO2, on treatment with aqueous sodium bicarbonate solution, is

Solution:

Carbolic acid (Phenol) is weaker acid than carbonic acid and hence does not liberate CO2 on treatment with aq. NaHCO3 solution.

QUESTION: 35

The major product in the following reaction is

Solution:

QUESTION: 36

The correct order of acidity for the following compounds is

Solution:




∴ acidity order is I > II > III > IV

QUESTION: 37

The major product of the following reaction sequence is

Solution: