Aldehydes Ketones and Carboxylic Acids Test

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Aldehydes Ketones and Carboxylic Acids Test - 75

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Question 1
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Directions For Questions

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The compound (C) is:

A

B

C

D

Solution

$$KMnO_4$$ is a strong oxidising agent which is used to oxidise aldehyde to carboxylic acid. The aldehyde group present in compound (B) gets oxidised to carboxylic group.
Hence correct option is (A).
Question 2
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Aldehyde and ketones do not react with

A
Sodium bisulphide

B
Phenylhydrazine

C
Dihydrogen sodium phosphate

D
Semicarbazide

Solution
Question 3
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Which of the following reagent are not correctly matched with the reaction ?

A
$$ CH_{3}CH = CHCHO \rightarrow CH_{3}CH = CHCOOH :$$ Ammonical $$ AgNO_{3}$$

B
$$ CH_{3}CH = CHCHO \rightarrow CH_{3}CH =CHCH_{2}OH : H_{2}/Pt$$

C
$$ R - COOH \rightarrow R - CH_{2}OH : NaBH_{4}$$

D
$$ CH_{3}CH_{2}COCl \rightarrow CH_{3}CH_{2}CHO : H_{2}CH_{2}CHO : H_{2}, PD /NASO_{4} $$

Solution

The incorrect reaction from the given reactions is reaction"B"

Corrected Reaction: $$\mathrm{CH_{3}CH = CHCHO \overset{H_{2}/{Pt}}{\rightarrow} CH_{3}CH_{2}CH_{2}CH_{2}OH}$$

Hence, Option "B" is the correct answer.
Question 4
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Match column I with column II and mark the appropriate choice.

A
$$ (A) \rightarrow (i) , (B) \rightarrow (ii) , (C) \rightarrow (iii) , (D) \rightarrow (iv)$$

B
$$ (A) \rightarrow (iv) , (B) \rightarrow (iii) , (C) \rightarrow (ii) , (D) \rightarrow (i)$$

C
$$ (A) \rightarrow (ii) , (B) \rightarrow (iv) , (C) \rightarrow (iii) , (D) \rightarrow (i)$$

D
$$ (A) \rightarrow (iii) , (B) \rightarrow (i) , (C) \rightarrow (ii) , (D) \rightarrow (iv)$$

Solution

Hint: Aldehydes and ketones can undergo both oxidation and reduction reduction.
Step 1: Oxidation and reduction reaction of aldehydes and ketones.
Carbonyl compounds are the ones that consist of a carbonyl group ($$-C=O$$) in their structure. Aldehydes and ketones are examples of carbonyl compounds. Carbonyl compounds like aldehydes and ketones can undergo oxidation reactions to form carboxylic acid and sodium salt of carboxylic acid. Also, it can undergo reduction reactions to form alkanes and alcohols.
Step 2: Given oxidation and reduction reactions of aldehydes and ketones.
Aldehyde and ketones undergo reduction reactions in the presence of reducing agent $$LiAlH_4$$ to form alcohols. In this, the carbonyl group $$-C=O$$ gets converted into $$-CH_2OH$$. Aldehyde and ketones can also be reduced to alkanes in the presence of Zn/HCl and conc. HCl. During this reaction, $$-C=O$$ group gets converted into $$-CH_2$$ group.
Oxidation reaction of aldehyde and ketones in the presence of $$Ag_2O/OH^-$$ leads to the formation of carboxylic acid. In this oxidation reaction, $$-C=O$$ group is converted into $$-COOH$$. Similarly, the oxidation of aldehyde and ketones can also occur in the presence of NaOX but the product formed in this reaction is sodium salt of carboxylic acid. The carbonyl group $$-C=O$$ in this reaction is changed into $$-COONa$$.
Final step:
Hence, the option B is correct.
Question 5
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$$ \alpha $$ - Hydroxypropanoic acid can be prepared from ethanal by following the steps given in the sequence .

A
Treat with HCN followed by acidic hydrolysis

B
Treat with $$ NaHSO_{3} $$ followed by reaction with $$ Na_{2}CO_{3}$$

C
Treat with $$ H_{2}SO{4}$$ followed by hydrolysis

D
Treat with $$ K_{2}Cr_{2}O_{7} $$ in presence of sulphurilic acid .

Solution

Reaction for obtaining $$\mathrm{\alpha}$$-Hydroxypropanoic acid from ethanal is:
$$\mathrm{\underset{Ethanal}{H_3C-CHO} + HCN \xrightarrow{\ \ \ \ } H_3C-C(OH)-CN \xrightarrow{H_3O^+} \underset{\alpha- Hydroxy \ Propnoic \ Acid}{H_3C-CH(OH)-COOH}}$$

Hence, Option "A" is the correct answer.
Question 6
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Identity reactant (X) in the given reaction sequence .
$$ \mathrm{CH_{3}COCH_{3} + X \rightarrow (CH_{3}) _3C - (OMgCl) \overset{H_{2}O}{\rightarrow} (CH_3)_3C-OH}$$

A
$$ CH_{3}Mg Cl $$

B
$$ CH_{3}COCl + Mg $$

C
$$ Mg Cl_{2}$$

D
$$ CH_{3} CH_{2} MGCl $$

Solution

Complete Reaction:

$$\mathrm{ CH_{3}COCH_{3} + CH_3MgCl \rightarrow (CH_{3}) _3C - (OMgCl) \overset{H_{2}O}{\rightarrow} (CH_3)_3C-OH}$$

So, X is $$\mathrm{CH_3MgX}$$
Hence, Option "A" is the correct answer.
Question 7
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Which of the following compounds is most reactive towards nucleophilic addition reactions?

A

B

C

D

Solution

Aldehydes are generally more reactive than ketones in the nucleophilic reaction due to steric and electronic reasons. Benzaldehyde is less reactive than ethanal as the polarity of the carbonyl group is reduced in benzaldehyde due to resonance.
So, Benzaldehyde is most reactive towards nucleophilic addition reactions.
Hence, Option "B" is the correct answer.
Question 8
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A compound (X) having molecular formula $$ C_{4}H_{8}O_{2}$$ is hydrolysed by water in presence of an acid to give a carboxylic acid (Y) and an alcohol (Z) . (Z) on oxidation with chrome acid gives (Y), (X), (Y) and (Z) are

A
X $$ CH_{3}COOCH_{3}$$
Y $$ CH_{3}COOH$$
Z $$CH_{3}OH $$

B
X $$ CH_{3}COOC_{2}H_{5}$$
Y $$ CH_{3}COOH $$
Z $$C_{2}H_{5}OH$$

C
X $$ C_{2}C_{5}COOCH_{3}$$
Y $$ C_{2}C_{5}COOH $$
Z $$C_{2}H_{5}OH $$

D
X $$ CH_{3}COOC_{2}H_{5}$$
Y $$ C_{2}H_{5}COOH$$
Z $$CH_{3}OH $$

Solution

As the compound on hydrolysis gives carboxylic acid, so, the given compound X is a ketone.
Ketones possible with molecular mass $$\mathrm{(C_4H_8O_2)}$$ are $$\mathrm{CH_3-COO-C_2H_5}$$ and $$\mathrm{C_2H_5-COO-CH_3}$$

X is $$\mathrm{CH_3-COO_C_2H_5 \ or \ C_2H_5-COO-CH_3 }$$
Y is $$\mathrm{CH_3COOH \ or \ C_2H_5COOH}$$
Z is $$\mathrm{CH_3-CH_2OH \ or \ C_2H_5-CH_2OH}$$

Hence, Option "B" is the correct answer.
Question 9
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Which functional group does $$CH_{3}COCH_{3}$$ contains ?

A
$$-CHO$$

B
$$-\overset {\overset {\displaystyle {\text O}}{||}} C-$$

C
$$-COOH$$

D
$$-OH$$

Solution

The functional group present in the given compound is ketone.
Optioon B is correct.
Question 10
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Product $$A$$ and $$B$$ for the following reactions are as follows:

A

B

C

D
None of the above

Solution

Hence, option (C) is the correct answer.