Download App

Alcohols, Phenols and Ethers — Chemistry STD 12 Science — Question

Gujarat BoardEnglish MediumSTD 12 ScienceChemistryAlcohols, Phenols and Ethers3 Marks
Question
Why a compound in which hydroxyl group attached to an aromatic ring is more acidic than the one in which hydroxyl group attached to an alkyl group?
✓

Answer

→ The ionization of an alcohol and a phenol takes place as follows:
Image
→ Due to the higher electronegativity of sp2 hybridised carbon of phenol to which -OH is attached, electron density decreases on oxygen. This increases the polarity of O-H bond and results in an increase in ionization of phenols than that of alcohols.
→ Now let us examine the stabilities of alkoxide and phenoxide ions. In alkoxide ion, the negative charge is localised on oxygen while in phenoxide ion, the charge is delocalised.
→ The delocalisation of negative charge (structures I-V) makes phenoxide ion more stable and favours the ionization of phenol.
→ Although there is also charge delocalisation in phenol, its resonance structures have charge separation due to which the phenol molecule is less stable than phenoxide ion.
Image

Need a full question paper?

Generate a complete, print-ready paper with questions like this in minutes — across 16+ boards, with answer keys.

Start Generating Free

Explore more

More "3 Marks Question" from Alcohols, Phenols and Ethers→Alcohols, Phenols and Ethers — all question types→Chemistry STD 12 Science question papers→Gujarat Board STD 12 Science question papers→Gujarat Board question paper generator→

Similar questions

Match the items of Column I and Column II.
 
Column I
 
Column II
(i)
Diamond.
(a)
Short interval of time.
(ii)
Instantaneous rate.
(b)
Ordinarily rate of conversion is imperceptible.
(iii)
Average rate.
(c)
Long duration of time.
→
An organic compound (A) has characteristic odour. On treatment with NaOH, it forms compounds (B) and (C). Compound (B) has molecular formula C7H8O which on oxidation gives back (A). The compound (C) is a sodium salt of an acid. When (C) is treated with soda-lime, it yields an aromatic compound (D). Deduce the structures of (A), (B), (C) and (D). Write the sequence of reactions involved.
→
The following data were obtained during the first order thermal decomposition of SO2Cl2 at a constant volume:
SO2Cl2(g)$\rightarrow$SO2(g) + Cl2(g)
Experiment
Time/s-1
Total pressure/atm
1
2
0
100
0.4
0.7
Calculate the rate constant.
(Given: log4 = 0.6021, log2 = 0.3010)
→
How are the following conversions carried out?
Propanol to propan-2-ol
→
How would you account for the following:
Cr2+ is reducing in nature while with the same d-orbital configuration (d4) Mn3+ is an oxidising agent.
→
Henry’s law constant for CO2 in water is 1.67 x 108 Pa at 298 K. Calculate the quantity of CO2 in 500 mL of soda water when packed under 2.5 atm CO2 pressure at 298 K.
→
Explain the following reaction of $C _2 H _5 OH$ :
(a) Schotten Baumann reaction
(b) Reaction with concen. $HNO _3$
(c) Reaction with excess of $NH _3$
(d) Reduction with Red P and HI
→
A special thermometer (Beckmann thermometer) is used to determine molecular weight by freezing point depression method instead of ordinary thermometer. Why?
→
  1. Explain the following giving suitable examples:
  1. Sandmeyer’s reaction.
  2. Coupling reaction of a diazonium salt.
  1. Explain the observed Kb order:

Et2NH>Et3N>EtNH2 in aqueous solution.

→
Give the products of following carbonyl compounds when oxidised with acidic $KMnO _4$ or acidic $K _2 Cr _2 O _7$.
(i) $CH _3 CHO$
(ii) $CH _3 COCH _3$
Image
→