Carboxylic Acids Test

Result

Carboxylic Acids Test - 8

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Weekly Quiz Competition

Question 1
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Consider the following reaction,

Q.

The appropriatensequence of reagent that can best bring about the above conversion is

A
(i) CH₃ MgBr (1.0 equiv.) (ii) Conc. H₂ SO₄ / Heat

B
(i) CH₃ Li(1.0 equiv.)(ii)Conc. H₂ SO₄ /Heat

C
(i) C₂ H₅ OH (2.0 equiv.); H⁺ (ii) CH₃ MgBr (iii) Conc. H₂ SO₄ /Heat

D
(i) HOCH₂ CH₂ OH; H⁺ (ii) CH₃ MgBr (iii) Conc. H₂ SO₄ /Heat (iv) H₃ O⁺ /H₂ O

Solution
Question 2
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What is the major product in the following reaction?

A

B

C

D

Solution

Acetal is form ed by cyclisation
Question 3
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Which of the following has greater enol content than keto counter part?

A
C₆ H₅ —CH₂ CHO

B

C

D

Solution

It is 1, 3-dik eto compound, forms stable enol.
Question 4
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Arrange the following in the increasing order of acidic strength

I. H₂ CO
II. CH₃ CHO
III. C₆ H₅ CH₂ CHO

A
I < II < III < IV

B
IV < III < II < I

C
III < IV < II < I

D
III < IV < I < II

Solution

IV is most acidic as its conjugate base is resonance stabilised by two carbonyl groups, followed by III whose conjugate base is resonance stabilised by a carbonyl group and phenyi ring.
Question 5
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One or More than One Options Correct Type

Direction : This section contains 5 multiple choice questions. Each question has four choices (a), (b), (c) and (d), out of which ONE or MORE THAN ONE are correct.

Q.

Which of the following has (have) more than one enol tautomers?

A

B

C
CH₃ CH₂ CHO

D
Option B,C are Correct

Solution
Question 6
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Which can be deduced correctly regarding keto-enol tautomerism in general?

A
Increasing temperature increases the enol content at equilibrium

B
Mono-enols are usually more stable than dienols

C
Enols of ketones are generally more stable than enols of aliphatic aldehydes

D
All are correct

Solution

Increasing temperature increases equilibrium content of less stable enol tautomers.
Enolisation decreases stability, hence introducing two or more enol groups are further more difficult.
Enols of ketones are more substituted at double bond, hence more stable.
Both acid and base catalyses keto-enol tautomerism.
Question 7
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The correct statement(s) regarding hydrates of aldehyde and ketone is/are

A
Usually hydrates have lower thermodynamic stability than anhydrous form

B
Hydrate content of acetone is greater in water than in hexane

C
CH₃ CHO when treated with H₂O¹⁸ in acidic medium, gets converted into CH₃CHO¹⁸

D
All are correct

Solution

Hydrates of aldehydes and ketones are less stable than anhydrous form (gem diols are unstable).
Hydrates form H-bonds with water, hence hydrate content is more in water than in hexane.
This exchange occur via hydrate.
Question 8
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For which of the following equilibrium, K_c is greater than 1?

A

B

C

D
Option A,B are Correct

Solution

Five and six-membered cyclic hemiacetals are more stable than its hydroxy aldehydes/ketones, predominate at equilibrium. Cyclic acetals are highly stable, predominate at equilibrium.
Question 9
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Consider the reaction below,

The correct statement(s) regarding the above process is/are

A
Equilibrium favours product

B
Pair of enantiomers of acetals are formed

C
Pair of diastereomers of acetals are formed

D
Option A,C are Correct

Solution

Product is an acetal, more stable than hemiacetal reactant. Acetal is formed via carbocation, both diastereomers are formed.
Question 10
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Comprehension Type

Direction : This section contains a paragraph, describing theory, experiments, data, etc. Three questions related to the paragraph have been given. Each question has only one correct answer among the four given options (a), (b), (c) and (d).

Passage

In general, ketones are less reactive than aldehydes in nucleophilic addition reaction, for both steric and electronic reasons.
Hence, if a keto-aldehyde is treated with nucleophilic reagent, reaction occur first at aldehyde group.

Q.

The major final product in the following reaction is

A

B

C

D
Mixture of (b) and (c)

Solution

The more reactive aldehyde functional group is reduced in preference to ketone group.
Question 11
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In general, ketones are less reactive than aldehydes in nucleophilic addition reaction, for both steric and electronic reasons.
Hence, if a keto-aldehyde is treated with nucleophilic reagent, reaction occur first at aldehyde group.

Q.

How the following transformation can be best brought about?

A
{(CH₃ )₂ CHO}₃ AI;H₃ O⁺

B
then NaBH₄ followed by H₃O⁺

C
H₂ /Ni; high p and T

D
N₂ H₄ /NaOH/Heat

Solution

Aldehyde being more reactive, protected first by acetal formation followed by reduction of ketone group.
Question 12
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In general, ketones are less reactive than aldehydes in nucleophilic addition reaction, for both steric and electronic reasons.
Hence, if a keto-aldehyde is treated with nucleophilic reagent, reaction occur first at aldehyde group.

Consider the following reaction,

Q.

Major product is

A

B

C

D

Solution
Question 13
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One Integer Value Correct Type

Direction : This section contains 4 questions. When worked out will result in an integer from 0 to 9 (both inclusive).

Q.

How many different enols exist for 4-methyl-3- hexanone ?

A
6

B
4

C
3

D
1

Solution
Question 14
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If all the mono and dienols are considered, how many enols are possible for 2,4-pentanedione?

A
1

B
8

C
4

D
2

Solution
Question 15
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If butanone is treated with D₂ O¹⁸ /DCI, isotopic exchange occur. What maximum gain in molecular mass is possible in the present case?

A
8

B
5

C
7

D
9

Solution

Gain of 7 units in molar mass is observed, five units due to 'D 'and tw o units due to `O¹⁸ '.
Question 16
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When acetaldehyde is treated with catalytic amount of H₂ SO₄ , a stable association product X is formed. How many lone pair of electrons are present in XI

A
1

B
2

C
3

D
6

Solution