Alcohols, Phenols And Ethers MCQ Quiz in मल्याळम - Objective Question with Answer for Alcohols, Phenols And Ethers - സൗജന്യ PDF ഡൗൺലോഡ് ചെയ്യുക

Concept:

The acidity of compounds:

• The acidity of compounds is determined by their ability to donate hydrogen ions in solution.
• The greater the ease of donation or liberation of the hydrogen ions, the stronger is the acid.
• The acidic proton of the compound is generally attached to an electronegative atom
•  The strength of the acidity is greatly influenced by the substituents or groups attached to the ring and their position.

Factors influencing the acid strength-

• The stability of the conjugate base-
  • if the negative charge is resonance stabilized in the conjugate base, then the compound is more acidic compared to the compound whose conjugate base has the charge localized.
• Electronegative substituents or groups like F, Cl, Br, I increase the acidity via inductive electron withdrawal (-I).
  • The closer the substituent is to the carboxyl group, the greater is its effect.
  • The more the number of substituents, the stronger is the acid.
• Electron donating groups such as - OR, -Me, -Et, NH2 or –NR, OH, etc. decrease the acidity via the +R and +I effect.
• Electron withdrawing groups such as NO2,-CF3, -COOH, -CN increases the acidity via the –R effect.
• The order of strength of -R Effect is: -NO₂>-CN>-SO₂>-CHO>-CO>COOCOR>-COOR>-COOH>-CONH₂>-COO^-
• The order of strength of +R Effect is: O->-NH₂>-OR>-NHCOR>-OCOR>-F>-Cl>-Br>-I
• Hydrogen attached to sp2 Carbon is more acidic than hydrogen attached to sp3 carbon.
  • The acidity order is sp> sp2>sp3.

​Explanation:

• Phenol is acidic in nature because it liberates the acidic proton easily and the conjugate base is also resonance stabilized.

and :

• When the Chloride group is introduced at the para position, it Has a -I effect towards the ring. Also, the +R effects operate at the ortho and para positions.
• We know that -I of Cl is dominating and hence it helps in increasing the overall acidity of phenol.
• But, the -R effect of the nitro group dominates the -I of chlorine making nitro phenols more acidic than chlorophenols.

Comparison between

 and 

• In the case of ortho nitrophenol, the negative charge is delocalized by -R of the nitro group.

• But -R does not operate in the case of meta nitrophenol and thus it is less acidic than ortho nitrophenol.

Comparison between

 and :

• There exists an intramolecular H bonding in ortho nitrophenol which makes the release of proton much more difficult.

Hence the most acidic compound is .

Explanation-

⇒ Lucas test is used to differentiate and categorize primary, secondary and tertiary alcohols using a solution of anhydrous zinc chloride in concentrated hydrochloric acid.

⇒ This solution is commonly referred to as the Lucas reagent.

Primary, Secondary, and Tertiary Alcohols are classified based on their reactivity with the Lucas reagent.

⇒ The reaction that occurs in the Lucas test can be seen as a nucleophilic substitution reaction.

⇒ In this reaction, the Chloride in the zinc-chloride bond is replaced with a hydroxyl group originating from the given alcohol.

Butan-2-ol reacts with Lucas reagent and milkiness appears within 5 min. but 2-methyl propane-2-ol reacts with the same to give milkiness immediately.

Explanation:

⇒ On refluxing alkaline solution of phenol with CHCI₃ at 330 K, and on subsequent acidification, o-hydroxy benzaldehyde (salicylaldehyde) is obtained.

⇒  It is called the Reimer-Tiemann reaction, o-isomer predominates but is separated from p-isomer by steam distillation.

If the "o-position" is already occupied, the aldehyde group goes to the "p-position"

Explanation:

The strength of acidity of an acid can be explained in terms of its ease with which it can release its proton and it is directly proportional to the no of ''-I '' groups attached to it.

• When a chlorine atom, which is an electron-withdrawing group is present in the chain attached to a carboxyl group, It exerts -I effect and withdraws electrons from the carbon of the carboxyl group as well as from the oxygen of the O-H bond.
• This decreases electron density at the oxygen atom of the O-H bond.
• Consequently, the O-H bond gets weakened and the release of H+ ion is favoured.
• Moreover, the negative charge present on the carboxylate ion gets dispersed and its stability is increased.
• Thus, the acid strength of the acid increases.
• So now the H+ atom can easily come out and the stability of the carboxylate ion has also increased.
• Hence both the conditions make chloroacetic acid more acidic than acetic acid. 
• Inductive effect is responsible for the acidity of chloroacetic acid. 

So acidic strength will be in the order:

Trichloro acetic acid > Dichloro acetic acid > Monochloro acetic acid > Acetic acid.

Concept:

• LiAlH₄ is used as a reducing agent in organic synthesis, especially for the reduction of esters, carboxylic acids, and amides.
• The solid is dangerously reactive toward water, releasing gaseous hydrogen (H₂).
• LiAlH₄ does not reduce double bond (C = C bond) but it reduces ester into alcohol.
• LiAlH₄ reduces a C-C double bond which is in conjugation i.e. resonance.
• LiAlH₄ reduces double bond in case of only when it is conjugation with phenyl ring but “cinnamic acid” is an exception because it has both carbonyl carbon as well as phenyl ring in its conjugation.

Here, it reduces an ester given above into alcohol.

\({\rm{C}}{{\rm{H}}_3}{\rm{CH}} = {\rm{CH}} - {\rm{C}}{{\rm{O}}_2}{\rm{C}}{{\rm{H}}_3} \xrightarrow[]{\text{LiAlH}_4}{\rm{C}}{{\rm{H}}_3}{\rm{CH}} = {\rm{CHC}}{{\rm{H}}_2}{\rm{OH}}\)

Explanation:

Acetamide, acetonitrile and methyl acetate contains an unsaturated carbon atom which can be easily attacked by a nucleophile such as hydroxide ion.

Also C=O group in which oxygen is electronegative so carbon electron-deficient on which nucleophile can attack.

In diethyl ether, all carbon atoms are saturated.

Hence, it resists attack by hydroxide ion so, the correct answer is Diethyl ether

Concept:

Alcoholic KOH is used to form Alkene from Alkyl Halides whereas aqueous KOH is used to form alcohols from Alkyl Halides. Alcoholic KOH used for dehydrohalogenation.

Benzoic acid (C₆H₅COOH) reacts with PBr₃ which undergoes reduction reaction and so it eliminates H₂O present on the acid. It further reacts with alcoholic KOH to form alkenes with the formation of H₂O and KBr.

Ans. (4)

Sol. 

Concept:

1. Acidity and Resonance Stabilization:
   The acidity of a compound is influenced by the stability of its conjugate base. The more stable the conjugate base, the stronger the acid.
2. Phenol and Acetic Acid:
   - Phenol (C₆H₅OH) dissociates to form the phenoxide ion (C₆H₅O⁻).
   - Acetic acid (CH₃COOH) dissociates to form the acetate ion (CH₃COO⁻).
3. Resonance Structures:
   - Phenoxide ion has resonance structures, but the negative charge is delocalized over the aromatic ring and oxygen, which does not provide as much stabilization. - Acetate ion has equivalent resonance structures where the negative charge is delocalized equally over the two oxygen atoms, providing more effective stabilization.
4. Solubility in Water:
   Solubility affects the extent of dissociation in water, but it is not the primary factor governing the inherent acidity of a compound.

Explanation:

1. Phenoxide ion is better stabilized by resonance than acetate ion:
   This statement is incorrect. Although phenoxide ion is stabilized by resonance, the stabilization is not as effective as in the acetate ion.
2. Acetate ion is better stabilized by resonance than phenoxide ion:
   This statement is correct. The acetate ion's resonance stabilization is more effective due to equivalent resonance structures, making acetic acid a stronger acid than phenol.
3. Phenol is less soluble in water than acetic acid:
   While this might be true, it is not the primary reason phenol is a weaker acid than acetic acid.
4. Both phenoxide ion and acetate ion are stable:
   This statement is true, but it does not address the difference in stabilization that determines the relative acidity of phenol and acetic acid.

Conclusion:

The correct reason why phenol is a weaker acid than acetic acid is Acetate ion is better stabilized by resonance than phenoxide ion.

Concept:

The major product contains the alcohol group and with amine group which are reacted in the presence of ethyl formate C₃H₆O₂ and triethylamine to final product.

The given alcohol group is 4-Amino-2-butanol with molecular formula as, C₄H₁₁NO.

The ethyl formate on reacting with 4-Amino-2-butanol, gains a lone pair of electrons from the amino end. So, by the electron, the 4-Amino-2-butanol becomes extra positively charged and the ethyl amine becomes negatively charged due to the breaking of bond at carbon and oxygen as given in the equation.

Then they both reacted to form a complex compound with 7 carbon in it.

Since the compound contains one positive charge in the amino end and one negative charge in the oxygen end, hence in the presence of triethyl amine the product is formed along with the formation of C₂H₅OH. The final product formed as in the option (b) with molecular formula of C₅H₁₁O₂N i.e.