Aldehydes, Ketones and Carboxylic Acids

NEET Chemistry · 42 questions · Page 4 of 5 · Click an option or "Show Solution" to reveal answer

Q31

Which of the following represents the correct order of the acidity in the given compounds ?

A FCH 2 COOH > CH 3 COOH > BrCH 2 COOH > ClCH 2 COOH

B BrCH 2 COOH > ClCH 2 COOH > FCH 2 COOH > CH 3 COOH

C FCH 2 COOH > ClCH 2 COOH > BrCH 2 COOH > CH 3 COOH

D CH 3 COOH > BrCH 2 COOH > ClCH 2 COOH > FCH 2 COOH

Correct Answer

Option C

Solution

Acidity decreases as the –I effect of the group decreases, F is the most electronegative atom and hence it has highest –I effect among the halogens.

FCH 2 COOH > ClCH 2 COOH > BrCH 2 COOH > CH 3 COOH

Q32

The product formed in Aldol condensation is

A a beta-hydroxy aldehyde or a beta-hydroxy ketone

B an alpha-hydroxy aldehyde or ketone

C an alpha, beta unsaturated ester

D a beta-hydroxy acid.

Correct Answer

Option A

Solution

The aldehydes or ketones containing $\alpha$ -H atom in presence of dilute alkali undergo self condensation reaction to form $\beta$ -hydroxyaldehyde or $\beta$ -hydroxyketone.

This reaction is known as Aldol condensation.

Q33

Nucleophilic addition reaction will be most favoured in

A CH 3 CHO

C (CH 3 ) 2 C

=

D CH 3 CH 2 CHO

Correct Answer

Option A

Solution

Aldehydes are more reactive than ketones due to +I effect of –CH 3 group.

There are two –CH 3 group in acetone which reduces +ve charge density on carbon atom of carbonyl group.

More hindered carbonyl group too becomes less reactive.

So in the given case CH 3 CHO is the right choice.

Q34

The

-

OH group of an alcohol or the

-

COOH group of a carboxylic acid can be replaced by

-

Cl using

A phosphorus pentachloride

B hypochlorous acid

C chlorine

D hydrochloric acid

Correct Answer

Option A

Solution

ROH + PCl 5 $\to$ RCl + POCl 3 + HCl RCOOH + PCl 5 $\to$ RCOCl + POCl 3 + HCl

Q35

Which one of the following can be oxidised to the corresponding carbonyl compound?

A 2-Hydroxypropane

B ortho-Nitrophenol

C Phenol

D 2-Methyl-2-hydroxypropane

Correct Answer

Option A

Solution

Carbonyl compounds (aldehydes and ketones) are obtained by the oxidation of 1° and 2° alcohols respectively.

Among the given options, only (a) is 2° alcohol hence it can be oxidized to ketone.

Q36

are

A resonating structures

B tautomers

C geometrical isomers

D optical isomers.

Correct Answer

Option A

Solution

They are resonating forms because the position of the atomic nuclei remain the same and only electron redistribution has occurred.

Q37

Which of the following is incorrect?

A FeCl 3 is used in detection of phenol.

B Fehling solution is used in detection of glucose

C Tollen's reagent is used in detection of unsaturation.

D NaHSO 3 is used in detection of carbonyl compound.

Correct Answer

Option C

Solution

Tollen's reagent is used to detect aldehydic group.

Tollen's reagent is an ammonical solution of silver nitrate.

When aldehyde is added to Tollen's reagent, silver oxide is reduced to metallic silver which deposits as mirror.

RCHO + Ag 2 O $\to$ RCOOH + 2Ag

Q38

Which of the following give positive Fehling solution test?

A Sucrose

B Glucose

C Fats

D Protein

Correct Answer

Option B

Solution

Glucose reduces Fehling solution because glucose has free –CHO group which is readily oxidised.

Q39

Benzoic acid may be converted into ethyl benzoate by reaction with :

A ethyl alcohol

B ethyl alcohol and dry HCl

C ethyl chloride

D sodium ethoxide.

Correct Answer

Option B

Solution

Here H 2 O is continuously removed from reaction so that reaction always proceeds to product formation i.e., Ethyl benzonate.

Q40

Given below are two statements : Statement I : Ethyl pent-4-yn-oate on reaction with CH3MgBr gives a 3

^\circ

-alcohol. Statement II : In this reaction one mole of ethyl pent-4-yn-oate utilizes two moles of CH3MgBr. In the light of the above statements, choose the most appropriate answer from the options given below :

A Both Statement I and Statement II are false.

B Statement I is false but Statement II is true.

C Statement I is true but Statement II is false.

D Both Statement I and Statement II are true.

Correct Answer

Option C

Solution

Statement I is true But it consume 3 moles of CH3MgBr. So Statement II is false.

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