Given below are two statements:
Statement I: Dimethyl ether is completely soluble in water. However, diethyl ether is soluble in water to a very small extent.
Statement II: Sodium metal can be used to dry diethyl ether and not ethyl alcohol.
In the light of given statements, choose the correct answer from the options given below:
A.textStatement I is false but Statement II is true$\text{Statement I is false but Statement II is true}$
B.textBoth Statement I and Statement II are false$\text{Both Statement I and Statement II are false}$
C.textStatement I is true but Statement II is false$\text{Statement I is true but Statement II is false}$
D.textBoth Statement I and Statement II are true$\text{Both Statement I and Statement II are true}$
Solution & Explanation
### Core Logic
Statement I: Dimethyl ether (CH_3OCH_3$CH_3OCH_3$) is highly soluble in water because its smaller alkyl chain allows substantial hydrogen bonding with water molecules. In contrast, diethyl ether has a larger hydrophobic ethyl group which drastically reduces its water solubility (to about 7.5text g$7.5\text{ g}$ per 100text mL$100\text{ mL}$). Thus, Statement I is true.
Statement II: Sodium metal (Na$Na$) reacts violently with alcohols like ethyl alcohol to release hydrogen gas:
2textC_2textH_5textOH + 2textNa rightarrow 2textC_2textH_5textONa + textH_2uparrow$$2\text{C}_2\text{H}_5\text{OH} + 2\text{Na} \rightarrow 2\text{C}_2\text{H}_5\text{ONa} + \text{H}_2\uparrow$$
Since diethyl ether has no active acidic hydrogen, it does not react with sodium metal. Hence, sodium can dry diethyl ether but cannot be used for ethyl alcohol. Statement II is true.
### Pattern Recognition
Ethers are miscible with water primarily when the non-polar alkyl parts are very small. Active hydrogen presence (-textOH$-\text{OH}$ group in alcohols) prevents the use of alkali metals like sodium for moisture removal.
### Evaluation Rubric / Model Answer
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### Chapter Mix
Class 12 Chemistry: Alcohols, Phenols and Ethers
Keywords:#Solubility of dimethyl ether in water#JEE Main 2025 Morning Q31#Sodium drying agent for ethers#Hydrogen bonding of smaller ethers
More Alcohols, Phenols and Ethers Previous-Year Questions — Page 3
Q66jee_main_2024_30_january_eveningPreparation of Alcohols
Product A and B formed in the following set of reactions are:
The diagram shows a reaction pathway for synthesizing product A and B.
A.textA = mathrmCH_2OH text, B = mathrmCH_2OH$\text{A = } \mathrm{CH_2OH} \text{, B = } \mathrm{CH_2OH}$
B.textA = mathrmCH_3OH text, B = mathrmCH_3OH$\text{A = } \mathrm{CH_3OH} \text{, B = } \mathrm{CH_3OH}$
C.textA = mathrmCH_2OH text, B = mathrmCH_3OH$\text{A = } \mathrm{CH_2OH} \text{, B = } \mathrm{CH_3OH}$
D.textA = mathrmCH_3OH text, B = mathrmCH_3OH$\text{A = } \mathrm{CH_3OH} \text{, B = } \mathrm{CH_3OH}$
Solution
### Core Logic
The given substrate is an alkene attached to a benzene ring (styrene derivative).
Reaction 1: Acid-catalyzed hydration (H^+ / H_2O$H^+ / H_2O$)
This proceeds via Markovnikov's rule. The proton attacks the alkene to form the most stable carbocation (benzyllic and secondary). Water then attacks this carbocation to yield the alcohol at the substituted position (product A: Ph-CH(OH)-CH_3$Ph-CH(OH)-CH_3$).
Reaction 2: Hydroboration-Oxidation (B_2H_6$B_2H_6$, then H_2O_2/NaOH$H_2O_2/NaOH$)
This proceeds via anti-Markovnikov addition of water across the double bond without carbocation rearrangement. The OH$OH$ group adds to the less substituted carbon atom of the alkene (product B: Ph-CH_2-CH_2-OH$Ph-CH_2-CH_2-OH$).
The diagram shows a reaction pathway for synthesizing product A and B.
### Pattern Recognition
H^+/H_2O$H^+/H_2O$ = Markovnikov hydration (carbocation intermediate).
B_2H_6 / H_2O_2, OH^-$B_2H_6 / H_2O_2, OH^-$ = Anti-Markovnikov hydration (concerted, no rearrangement).
### Evaluation Rubric / Model Answer
null
### Chapter Mix
Class 12 Chemistry: Alcohols Phenols and Ethers
Class 11 Chemistry: Hydrocarbons
Q69jee_main_2024_31_jan_morningChemical Reactions of Alcohols
Given below are two statements: One is labelled as Assertion A and the other is labelled as Reason R:
Assertion A: Alcohols react both as nucleophiles and electrophiles.
Reason R: Alcohols react with active metals such as sodium, potassium and aluminum to yield corresponding alkoxides and liberate hydrogen.
In the light of the above statements, choose the correct answer from the options given below:
A.textA is false but R is true.$\text{A is false but R is true.}$
B.textA is true but R is false.$\text{A is true but R is false.}$
C.textBoth A and R are true and R is the correct explanation of A.$\text{Both A and R are true and R is the correct explanation of A.}$
D.textBoth A and R are true but R is NOT the correct explanation of A.$\text{Both A and R are true but R is NOT the correct explanation of A.}$
Solution
### Core Logic
Assertion (A) is correct. Alcohols can act as nucleophiles (in reactions involving O-H bond cleavage) and as electrophiles (in reactions involving C-O bond cleavage after protonation).
Reason (R) is correct. Alcohols react with active metals to form alkoxides and H_2$H_2$ gas.
However, Reason (R) only explains the acidic nature of the O-H bond (which relates to nucleophilic behavior when broken) but does not explain the electrophilic behavior (C-O cleavage). Thus, (R) is not the correct explanation for (A).
### Evaluation Rubric / Model Answer
null
### Chapter Mix
Class 12 Chemistry: Alcohols, Phenols and Ethers
Q74jee_main_2024_31_jan_morningAcidity of Phenols
Given below are two statements: One is labelled as Assertion A and the other is labelled as Reason R:
Assertion A: pK_a$pK_a$ value of phenol is 10.0 while that of ethanol is 15.9.
Reason R: Ethanol is stronger acid than phenol.
In the light of the above statements, choose the correct answer from the options given below:
A.textA is true but R is false.$\text{A is true but R is false.}$
B.textA is false but R is true.$\text{A is false but R is true.}$
C.textBoth A and R are true and R is the correct explanation of A.$\text{Both A and R are true and R is the correct explanation of A.}$
D.textBoth A and R are true but R is NOT the correct explanation of A.$\text{Both A and R are true but R is NOT the correct explanation of A.}$
Solution
### Core Logic
Assertion A is true: Phenol has a pK_a$pK_a$ of around 10.0, and ethanol has a pK_a$pK_a$ of around 15.9.
Reason R is false: A lower pK_a$pK_a$ value implies higher acidity. Therefore, phenol is a stronger acid than ethanol. This is because the conjugate base of phenol (phenoxide ion) is resonance-stabilized, whereas the ethoxide ion is destabilized by the +I effect of the ethyl group.
### Evaluation Rubric / Model Answer
null
### Chapter Mix
Class 12 Chemistry: Alcohols, Phenols and Ethers
More Alcohols, Phenols and Ethers Questions — jee_main_2025_07_april_morning
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