MCQ Of Aldehydes, Ketones And Carboxylic Acids, Past Year Questions JEE Mains, Class 12, Chemistry


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


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QUESTION: 1

What is B?

Solution:


QUESTION: 2

On vigorous oxidation by permanganate solution.

(CH3)2C = CH - CH2 - CHO gives

Solution:

Aldehydic group gets oxidised to carboxylic group.
Double bond breaks and carbon gets oxidised to carboxylic group.

QUESTION: 3

Picric acid is:

Solution:

2,4,6-trinitrophenol is also known as picric acid.

QUESTION: 4

When CH2 = CH — COOH is reduced with LiAlH4, the compound obtained will be

Solution:

LiAlH4 can reduce COOH group and not the double bond.

QUESTION: 5

On mixing ethyl acetate with aqueous sodium chloride, the composition of the resultant solution is

Solution:

There is no reaction hence the resultant mixture contains CH3 COOC2H5 + NaCl.

QUESTION: 6

Acetyl bromide reacts with excess of CH3MgI followed by treatment with a saturated solution of NH4Cl gives

Solution:

QUESTION: 7

Which one of the following is reduced with zinc and hydrochloric acid to give the corresponding hydrocarbon?

Solution:

It is Clemmensen’s reduction

QUESTION: 8

Which one of the following undergoes reaction with 50% sodium hyroxide solution to give the corresponding alcohol and acid?

Solution:

This reaction  is known as cannizzaro’s reaction. In this reaction benzaldehyde in presence of  50%. NaOH undergoes disproportionation  reaction and form one mol of Benzyl  alcohol (Red. product) and one mole of sod. benzoate (ox. product)

QUESTION: 9

Among the following acids which has the lowest pKa value?

Solution:

pKa = –log Ka; HCOOH is the strongest acid and hence it has the highest Ka or lowest pKa value.

QUESTION: 10

Reaction of cycloh exan on e with dimethylamine in th e presence of catalytic amount of an acid forms a compound if water during the reaction is continuously removed. The compound formed is generally known as

Solution:

QUESTION: 11

The increasing order of the rate of HCN addition to compound A – D is

(A) HCHO
(B) CH3COCH3
(C) PhCOCH3
(D) PhCOPh

Solution:

NOTE : Addition of HCN to carbonyl compounds is nucleophilic addition reaction. The order of reactivity of carbonyl compounds is Aldehydes (smaller to higher) Ketones (smaller to higher), Then                    

HCHO > CH3COCH3 > Ph.COCH3 > PhCOPh

NOTE : The lower reactivity of Ketones is due to presence of two alkyl group which shows +I effect.
The reactivity of Ketones decreases as the size of alkyl group increases.

QUESTION: 12

Th e correct order of increasing acid stren ght of the compounds

(A) CH3CO2H
(B) MeOCH2CO2H
(C) CF3CO2H

is

Solution:

The correct order of increasing acid strength

CF3 . COOH > MeOCH2COOH > CH3COOH > (Me)2CH.COOH

[NOTE : Electron withdrawing groups increase the acid strength and electron donating groups decrease the acid strength.]

QUESTION: 13

A liquid was mixed with ethanol and a drop of concentrated H2SO4 was added. A compound with a fruity smell was formed. The liquid was :

Solution:

Fruity smell is due to ester formation which is formed between ethanol and acid.

QUESTION: 14

Which of the following on heating with aqueous KOH, produces acetaldehyde?

Solution:

QUESTION: 15

In Cannizzaro reaction given below

the slowest step is :

Solution:


QUESTION: 16

Which of the following reagents may be used to distinguish between phenol and benzoic acid?

Solution:

Phenol gives a violet colour with neutral ferric chloride solution whereas benzoic acid does not give this test.

QUESTION: 17

Trichloroacetaldehyde was subjected to Cannizzar o’s reaction by using NaOH. The mixture of the products contains sodium trichloroacetate and another compound. 

The other compound is :

Solution:

In Cannizzaro’s reaction the compounds which do not contain a-hydrogen atoms undergo oxidation and reduction simultaneously i.e undergo disproportion ation and form one molecule of sodium salt of carboxylic acid as oxidation product and one molecule of alcohol as reduction product.

QUESTION: 18

The strongest acid amongst the following compounds is :

Solution:

The electron withdrawing (–I) group – Cl withdraws electrons from O – H bond and thus helps the cleavage of the O – H bond releasing hydrogen as H+.

QUESTION: 19

Sodium ethoxide has reacted with ethanoyl chloride. The compound that is produced in the above reaction is :

Solution:

*Multiple options can be correct
QUESTION: 20

Silver Mirror test is given by which one of the following compounds?

Solution:

Both for maldeh yde an d a cetaldeh yde give silver mirror with Tollen’s reagent.

QUESTION: 21

Iodoform can be prepared from all except : 

Solution:

Iodoform is given by 
1) methyl ketones R-CO-CH3
2) alcohols of the type R-CH(OH)CH3
where R can be hydrogen also

QUESTION: 22

In the given transformation, which of the following is the most appropriate reagent ?

Solution:

Aldehydes and ketones canbereduced to hydrocarbons by the action (i) of amalgamated zinc and concentrated hydrochloric acid (Clemmensen reduction), or (b) of hydrazine (NH2NH2) and a strong base like NaOH, KOH or potassium tert-butoxide in a high-boiling alcohol like ethylene glycol or triethylene glycol (Wolf-Kishner reduction)

QUESTION: 23

The most suitable reagent for the conversion of R - CH2 - OH → R- CHO is:

Solution:

An excellent reagent for oxidation of 1° alcohols to aldehydes is PCC.

QUESTION: 24

In the reaction,

the product C is:

Solution:

QUESTION: 25

In the following sequence of reactions :

the product C is :

Solution: