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Important Questions for Class 12 Chemistry Chapter 11 Alcohols, Phenols and Ethers Class 12 Important Questions

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Important Questions for Class 12 Chemistry Chapter 11 Alcohols, Phenols and Ethers Class 12 Important Questions

Alcohols, Phenols and Ethers Class 12 Important Questions Very Short Answer Type

Question 1.
Give the IUPAC name of the following compound : (Delhi 2009)
Important Questions for Class 12 Chemistry Chapter 11 Alcohols, Phenols and Ethers Class 12 Important Questions 1
Answer:
Important Questions for Class 12 Chemistry Chapter 11 Alcohols, Phenols and Ethers Class 12 Important Questions 2
IUPAC name : 2-Bromo-3-methyl-but-2-ene-1-ol

Question 2.
Give the IUPAC name of the following (All India 2009)
Important Questions for Class 12 Chemistry Chapter 11 Alcohols, Phenols and Ethers Class 12 Important Questions 3
Answer:
Important Questions for Class 12 Chemistry Chapter 11 Alcohols, Phenols and Ethers Class 12 Important Questions 4

Question 3.
Write the structure of the molecule of a compound whose IUPAC name is 1-phenylpropan-2-ol. (All India 2010)
Answer:
1-phenylpropan-2-ol
Important Questions for Class 12 Chemistry Chapter 11 Alcohols, Phenols and Ethers Class 12 Important Questions 5

Question 4.
How would you convert ethanol to ethene? (All India 2011)
Answer:
Important Questions for Class 12 Chemistry Chapter 11 Alcohols, Phenols and Ethers Class 12 Important Questions 6

Question 5.
Draw the structure of 2, 6-Dimethylphenol. (All India 2011)
Answer:
Important Questions for Class 12 Chemistry Chapter 11 Alcohols, Phenols and Ethers Class 12 Important Questions 7

Question 6.
Draw the structural formula of 2-methylpropan- 2-ol molecule. (Delhi 2012)
Answer:
Important Questions for Class 12 Chemistry Chapter 11 Alcohols, Phenols and Ethers Class 12 Important Questions 8

Question 7.
Draw the structure of hex-l-en-3-ol compound. (Delhi 2012)
Answer:
CH2 = CH – CH(OH) – CH2 – CH2 – CH3

Question 8.
Ortho nitrophenol has lower boiling point than p-nitrophenol. Why ? (Comptt. Delhi 2012)
Answer:
Ortho-nitrophenol has lower boiling point due to formation of intramolecular H-bonding whereas p-nitrophenol forms intermoleeular H-bonding.

Question 9.
Ortho-nitrophenol is more acidic than ortho-methoxyphenol. Why? (Comptt. Delhi 2012)
Answer:
NO2 group is an electron withdrawing group while methoxy group is electron donating in nature. The release of H+ is easier from O-nitrophenol while it is difficult from O-methoxyphenol.

Question 10.
The C-O bond is much shorter in phenol than in ethanol. Give reason. (Comptt. Delhi 2012)
Answer:
Carbon of C-O bond of phenol is Sp2 hybridised, so it acquires a partial double bond character but in ethanol it is Sp3 hybridised and a single bond. Double bond is shorter than a single bond.

Question 11.
Write the IUPAC name of the following : (Comptt. All India 2012)
Important Questions for Class 12 Chemistry Chapter 11 Alcohols, Phenols and Ethers Class 12 Important Questions 9
Answer:
IUPAC name : 2-Bromo-3-methyl but-2-en-l-ol.

Question 12.
Of the two hydroxy organic compounds ROH and R’OH, the first one is basic and other is acidic in behaviour. How is R different from R’? (Comptt. Delhi 2013)
Answer:
When R = alkyl, ROH behaves as a bronsted base and when R’ = aryl, R’OH behaves as a bronsted acid.

Question 13.
Give a chemical test to distinguish between 2-Pentanol and 3-Pentanol. (Comptt. Delhi 2013)
Answer:
2-pentanol gives Iodoform test with yellow ppt. of Iodoform while 3-pentanol does not give this test.

Question 14.
Write the chemical reaction to explain Kolbe’s reaction. (Comptt. Delhi 2013)
Answer:
Kolbe’s reaction : Phenol reacts with CO2 in presence of sodium hydroxide (NaOH) at 4 – 7 Atm and 390 – 410 K giving salicylic acid
Important Questions for Class 12 Chemistry Chapter 11 Alcohols, Phenols and Ethers Class 12 Important Questions 30

Question 15.
How would you obtain ethane-1, 2-diol from ethanol? (Comptt. All India 2013)
Answer:
Important Questions for Class 12 Chemistry Chapter 11 Alcohols, Phenols and Ethers Class 12 Important Questions 10

Question 16.
How would you obtain acetophenone from phenol? (Comptt. All India 2013)
Answer:
Important Questions for Class 12 Chemistry Chapter 11 Alcohols, Phenols and Ethers Class 12 Important Questions 11

Question 17.
Write IUPAC name of the following : (Comptt. All India 2013)
Important Questions for Class 12 Chemistry Chapter 11 Alcohols, Phenols and Ethers Class 12 Important Questions 12
Answer:
IUPAC name : 2~Bromo-3-methylbut -2-ene-l-ol

Question 18.
How would you obtain phenol from benzene? (Comptt. All India 2013)
Answer:
Important Questions for Class 12 Chemistry Chapter 11 Alcohols, Phenols and Ethers Class 12 Important Questions 13

Question 19.
Write IUPAC name of the following (Comptt. All India 2013)
Important Questions for Class 12 Chemistry Chapter 11 Alcohols, Phenols and Ethers Class 12 Important Questions 14
Answer:
IUPAC name : 2-Methoxy-5-methyl phenol

Question 20.
Which of the following isomers is more volatile : o-nitrophenol or p-nitrophenol? (Delhi 2014)
Answer:
o-nitrophenol is more volatile than p-nitrophenol due to intramolecular hydrogen bonding.

Question 21.
Name the alcohol that is used to make the following ester : (Comptt All India 2014)
Important Questions for Class 12 Chemistry Chapter 11 Alcohols, Phenols and Ethers Class 12 Important Questions 15
Answer:
Alcohol used : Propan-2-ol

Question 22.
Write the IUPAC name of the given compound (Delhi 2015)
Important Questions for Class 12 Chemistry Chapter 11 Alcohols, Phenols and Ethers Class 12 Important Questions 16
Answer:
2, 5-dinitrophenol.

Question 23.
Write the IUPAC name of given compound: (All India 2015)
Important Questions for Class 12 Chemistry Chapter 11 Alcohols, Phenols and Ethers Class 12 Important Questions 17
Answer:
IUPAC name : 1-Ethoxy-2-methylpropane

Question 24.
Write the IUPAC name of the given compound: (All India 2016)
Important Questions for Class 12 Chemistry Chapter 11 Alcohols, Phenols and Ethers Class 12 Important Questions 18
Answer:
2-Phenylethanol

Question 25.
Write equation of the nitration of anisole. (Comptt. Delhi 2016)
Answer:
Important Questions for Class 12 Chemistry Chapter 11 Alcohols, Phenols and Ethers Class 12 Important Questions 19

Question 26.
Out of CH3OH and
Important Questions for Class 12 Chemistry Chapter 11 Alcohols, Phenols and Ethers Class 12 Important Questions 20, which one is more acidic? (Comptt. All India 2016)
Answer:
Important Questions for Class 12 Chemistry Chapter 11 Alcohols, Phenols and Ethers Class 12 Important Questions 21 is more acidic, as Phenoxide formed is more stabilized by Resonance.

Question 27.
Write the IUPAC name of the following compound: (All India 2017)
Important Questions for Class 12 Chemistry Chapter 11 Alcohols, Phenols and Ethers Class 12 Important Questions 22
Answer:
2-Bromo-3-methylbut-2-enol-1 -ol

Question 28.
Write the IUPAC name of the following compound: (All India 2017)
Important Questions for Class 12 Chemistry Chapter 11 Alcohols, Phenols and Ethers Class 12 Important Questions 23
Answer:
3-phenylprop-2-en-1-ol

Question 29.
Write IUPAC name of the following compound : (Comptt. Delhi 2017)
Important Questions for Class 12 Chemistry Chapter 11 Alcohols, Phenols and Ethers Class 12 Important Questions 24
Answer:
2, 3-Dinitro phenol.

Question 30.
What happens when phenol is oxidized by Na2Cr2O7/H2SO4?
Answer:
Phenol forms benzoquinone on oxidation with Na2Cr2O7 / H2SO4,
Important Questions for Class 12 Chemistry Chapter 11 Alcohols, Phenols and Ethers Class 12 Important Questions 25

Question 31.
What happens when phenol is heated with zinc dust? (Comptt. All India 2017)
Answer:
Benzene is formed when phenol is heated with zinc dust.
Important Questions for Class 12 Chemistry Chapter 11 Alcohols, Phenols and Ethers Class 12 Important Questions 26

Question 32.
What happens when phenol is treated with bromine water? (Comptt. All India 2017)
Answer:
2, 4, 6-tribromophenol is formed when phenol is treated with bromine water.
Important Questions for Class 12 Chemistry Chapter 11 Alcohols, Phenols and Ethers Class 12 Important Questions 27

Question 33.
Give simple chemical tests to distinguish between the following pairs of compounds: Benzoic acid and Phenol (All India 2017)
Answer:
Ferric chloride test. Add neutral FeCl3 in both the solutions, phenol reacts with neutral FeCl3 to form an iron-phenol complex giving violet colour but benzoic acid does not.

Alcohols, Phenols and Ethers Class 12 Important Questions Short Answer Type -I [SA – I]

Question 34.
Complete the following reaction equations : (Delhi 2009)
Important Questions for Class 12 Chemistry Chapter 11 Alcohols, Phenols and Ethers Class 12 Important Questions 28
Answer:
Important Questions for Class 12 Chemistry Chapter 11 Alcohols, Phenols and Ethers Class 12 Important Questions 29

Question 35.
Illustrate the following reactions giving a chemical equation for each :
(i) Kolbe’s reaction
(ii) Williamsons synthesis of an ether (Delhi 2010)
Answer:
(i) Kolbe’s reaction : Phenol reacts with CO2 in presence of sodium hydroxide (NaOH) at 4 – 7 Atm and 390 – 410 K giving salicylic acid
Important Questions for Class 12 Chemistry Chapter 11 Alcohols, Phenols and Ethers Class 12 Important Questions 30
(ii) Williamsons synthesis of an ether : The reaction involves the nucleophilic substitution of the halide ion from the alkyl halide by the alkoxide ion by SN2 mechanism.
Example :
Important Questions for Class 12 Chemistry Chapter 11 Alcohols, Phenols and Ethers Class 12 Important Questions 31

Question 36.
Explain the following reactions with an example for each :
(i) Reimer-Tiemann reaction
(ii) Friedel-Crafts reaction. (Delhi 2010)
Answer:
(i) Reimer-Tiemann reaction : Treatment of phenol with CHCl3 in presence of aqueous NaOH at 340K followed by hydrolysis gives salicylaldehyde.
Important Questions for Class 12 Chemistry Chapter 11 Alcohols, Phenols and Ethers Class 12 Important Questions 32
(ii) Friedel-Crafts reaction : This reaction is used for introducing an alkyl or an acyl group into an aromatic compound in presence of Lewis acid catalyst (AlCl3)
Example:
Important Questions for Class 12 Chemistry Chapter 11 Alcohols, Phenols and Ethers Class 12 Important Questions 33

Question 37.
How are the following conversions carried out?
(i) Propene to propan-2-ol
(ii) Ethylmagnesium chloride to propan-1-ol. (Delhi 2010
Answer:
(i) Propene to propan-2-ol
Important Questions for Class 12 Chemistry Chapter 11 Alcohols, Phenols and Ethers Class 12 Important Questions 34
(ii) Ethylmagnesium chloride to propan-1-ol
Important Questions for Class 12 Chemistry Chapter 11 Alcohols, Phenols and Ethers Class 12 Important Questions 35

Question 38.
How are the following conversions carried out?
(i) Benzyl chloride to benzyl alcohol,
(ii) Methyl magnesium bromide to 2-methylpropan-2-ol. (All India 2010)
Answer:
(i) Benzyl chloride to benzyl alcohol
Important Questions for Class 12 Chemistry Chapter 11 Alcohols, Phenols and Ethers Class 12 Important Questions 36

Question 39.
Explain the following giving one example for each :
(i) Reimer-Tiemann reaction.
(ii) Friedel-Craft’s acetylation of anisole. (Delhi 2011)
Answer:
(i) Reimer-Tiemann reaction : Treatment of phenol with CHCl3 in presence of aqueous NaOH at 340K followed by hydrolysis gives salicylaldehyde.
Important Questions for Class 12 Chemistry Chapter 11 Alcohols, Phenols and Ethers Class 12 Important Questions 32
(ii) Friedel-Craft’s acetylation of anisole :
Important Questions for Class 12 Chemistry Chapter 11 Alcohols, Phenols and Ethers Class 12 Important Questions 37

Question 40.
How would you obtain
(i) Picric acid (2, 4, 6-trinitrophenol) from phenol,
(ii) 2-Methylpropene from 2-methylpropanol? (Delhi 2011)
Answer:
(i) Picric acid from phenol :
Important Questions for Class 12 Chemistry Chapter 11 Alcohols, Phenols and Ethers Class 12 Important Questions 38

Question 41.
Explain the mechanism of acid catalysed hydration of an alkene to form corresponding alcohol. (All India 2012)
Answer:
Acid catalysed hydration : Alkenes react with water in the presence of acid as catalyst to form alcohols
Important Questions for Class 12 Chemistry Chapter 11 Alcohols, Phenols and Ethers Class 12 Important Questions 39
Mechanism : It involves three steps :
(i) Protonation of alkene to form carbocation by electrophilic attack of H3O+
Important Questions for Class 12 Chemistry Chapter 11 Alcohols, Phenols and Ethers Class 12 Important Questions 40

Question 42.
Explain the following behaviours :
(i) Alcohols are more soluble in water than the hydrocarbons of comparable molecular masses.
(ii) Ortho-nitrophenol is more acidic than ortho-methoxyphenol. (All India 2012)
Answer:
(i) Alcohols can form H-bonds with water and break the H-bonds already existing between water molecules. So they are soluble in water.
Important Questions for Class 12 Chemistry Chapter 11 Alcohols, Phenols and Ethers Class 12 Important Questions 41
On the other hand, hydrocarbons cannot form H-bonds with water and hence are insoluble in water.

(ii) Due to strong – R and -1 effect of the – NO2 group, electron density in the – OH bond decreases and hence the loss of a proton becomes easier. Moreover O-nitrophenoxide ion is stabilized by resonance, 1 thereby making O-nitrophenol a stronger acid.
In O-methoxyphenol, due to + R effect of the – OCH3 group the electron density in the O – H bond increases thereby making the loss of proton difficult. Furthermore, the Q-methoxyphenoxide ion left after the loss of a proton is destabilized by resonance because the two negative charges repel each other. So O-methoxyphenol is a weaker acid.

Question 43.
Explain the mechanism of following reaction: (Delhi 2013)
Important Questions for Class 12 Chemistry Chapter 11 Alcohols, Phenols and Ethers Class 12 Important Questions 42
Answer:
Important Questions for Class 12 Chemistry Chapter 11 Alcohols, Phenols and Ethers Class 12 Important Questions 43

Question 44.
How will you convert:
(i) Propene to propan-2-ol?
(ii) Phenol to 2, 4, 6-trinitrophenol? (Delhi 2013)
Answer:
(i) Propene to propan-2-ol:
Important Questions for Class 12 Chemistry Chapter 11 Alcohols, Phenols and Ethers Class 12 Important Questions 34

(ii) Phenol to 2, 4, 6-trinitrophenol?
Important Questions for Class 12 Chemistry Chapter 11 Alcohols, Phenols and Ethers Class 12 Important Questions 44

Question 45.
How will you convert the following?
(i) Propan-2-ol to propanone
(ii) Phenol to 2, 4, 6-tribromophenol (Delhi 2013)
Answer:
(i) Propan-2-ol to propane
Important Questions for Class 12 Chemistry Chapter 11 Alcohols, Phenols and Ethers Class 12 Important Questions 45
(ii) Phenol to 2, 4, 6-tribromophenol: Phenol reacts with bromine in presence of polar solvent H2O to form 2, 4, 6-tribromophenol (white ppt.)
Important Questions for Class 12 Chemistry Chapter 11 Alcohols, Phenols and Ethers Class 12 Important Questions 46

Question 46.
How will you convert:
(i) Propene to Propane-1-ol?
(ii) Ehtanal to Propan-2-ol (Delhi 2013)
Answer:
(i) Propene to Propane-1-ol
Important Questions for Class 12 Chemistry Chapter 11 Alcohols, Phenols and Ethers Class 12 Important Questions 47

Question 47.
Explain the mechanism of the following reaction: (All India 2013)
Important Questions for Class 12 Chemistry Chapter 11 Alcohols, Phenols and Ethers Class 12 Important Questions 48
Answer:
Important Questions for Class 12 Chemistry Chapter 11 Alcohols, Phenols and Ethers Class 12 Important Questions 49

Question 48.
Write the equations involved in the following reactions:
(i) Reimer-Tiemann reaction
(ii) Williamson’s ether Synthesis (All India 2013)
Answer:
(i) Reimer-Tiemann reaction : Treatment of phenol with CHCl3 in presence of aqueous NaOH at 340K followed by hydrolysis gives salicylaldehyde.
Important Questions for Class 12 Chemistry Chapter 11 Alcohols, Phenols and Ethers Class 12 Important Questions 32
(ii) Williamson’s ether synthesis : The reaction involves the nucleophilic substitution of the halide ion from the alkyl halide by the alkoxide ion by SN2 mechanism.
Example :
Important Questions for Class 12 Chemistry Chapter 11 Alcohols, Phenols and Ethers Class 12 Important Questions 31

Question 49.
Write the equations involved in the following reactions :
(i) Reimer – Tiemann reaction
(ii) Williamson synthesis (All India 2014)
Answer:
(i) Reimer-Tiemann reaction : Treatment of phenol with CHCl3 in presence of aqueous NaOH at 340K followed by hydrolysis gives salicylaldehyde.
Important Questions for Class 12 Chemistry Chapter 11 Alcohols, Phenols and Ethers Class 12 Important Questions 32
(ii) Williamson’s ether synthesis : The reaction involves the nucleophilic substitution of the halide ion from the alkyl halide by the alkoxide ion by SN2 mechanism.
Example :
Important Questions for Class 12 Chemistry Chapter 11 Alcohols, Phenols and Ethers Class 12 Important Questions 31

Question 50.
Write the mechanism of the following reaction : (All India 2014)
Important Questions for Class 12 Chemistry Chapter 11 Alcohols, Phenols and Ethers Class 12 Important Questions 50
Answer:
Important Questions for Class 12 Chemistry Chapter 11 Alcohols, Phenols and Ethers Class 12 Important Questions 75
Important Questions for Class 12 Chemistry Chapter 11 Alcohols, Phenols and Ethers Class 12 Important Questions 76

Question 51.
Write the equations involved in the following reactions:
(i) Williamson ether synthesis
(ii) Kolbe’s reaction (Comptt. Delhi 2014)
Answer:
(i) Williamson ether synthesis : The reaction involves the nucleophilic substitution of the halide ion from the alkyl halide by the alkoxide ion by SN2 mechanism.
Example :
Important Questions for Class 12 Chemistry Chapter 11 Alcohols, Phenols and Ethers Class 12 Important Questions 31

(ii) Kolbe’s reaction : Phenoxide ion generated by treating phenol with sodium hydroxide is more reactive than phenol and undergoes electrophilic substitution with carbon dioxide. Ortho hydroxybenzoic acid is formed as the main reaction product.
Important Questions for Class 12 Chemistry Chapter 11 Alcohols, Phenols and Ethers Class 12 Important Questions 51

Question 52.
How are the following conversions carried out?
(i) Propene to Propan-2-ol
(ii) Ethyl chloride to Ethanal (Comptt. Delhi 2014)
Answer:
(i) Propene to propan-2-ol
Important Questions for Class 12 Chemistry Chapter 11 Alcohols, Phenols and Ethers Class 12 Important Questions 52

Question 53.
Explain the mechanism of dehydration steps of ethanol : (Comptt. Delhi 2015)
Important Questions for Class 12 Chemistry Chapter 11 Alcohols, Phenols and Ethers Class 12 Important Questions 53
Answer:
Important Questions for Class 12 Chemistry Chapter 11 Alcohols, Phenols and Ethers Class 12 Important Questions 54

Question 54.
Write the mechanism of acid dehydration of ethanol to yield ethene. (Comptt. All India 2015)
Answer:
The mechanism of dehydration of ethanol involves the following steps :
Step 1 : Formation of protonated alcohol
Important Questions for Class 12 Chemistry Chapter 11 Alcohols, Phenols and Ethers Class 12 Important Questions 55
Important Questions for Class 12 Chemistry Chapter 11 Alcohols, Phenols and Ethers Class 12 Important Questions 56

Question 55.
Write the mechanism of the following reaction: (Delhi 2016)
Important Questions for Class 12 Chemistry Chapter 11 Alcohols, Phenols and Ethers Class 12 Important Questions 57
Answer:
Mechanism:
Important Questions for Class 12 Chemistry Chapter 11 Alcohols, Phenols and Ethers Class 12 Important Questions 58

Question 56.
(a) Arrange the following compounds in the increasing order of their acid strength: p-cresol, p-nitrophenol, phenol
(b) Write the mechanism (using curved arrow notation) of the following reaction: (All India 2016)
Important Questions for Class 12 Chemistry Chapter 11 Alcohols, Phenols and Ethers Class 12 Important Questions 59
Answer:
(a) Order of acidic strength:
p-cresol < phenol < p-nitrophenol
(b) Mechanism of acid catalysed hydration of alkene:
Step 1: Protonation of alkene to form carbocation by electrophilic attack of H3O+.
Important Questions for Class 12 Chemistry Chapter 11 Alcohols, Phenols and Ethers Class 12 Important Questions 60

Question 57.
Write the structures of the products when Butan-2-ol reacts with the following:
(a) CrO3
(b) SOCl2 (All India 2016)
Answer:
Important Questions for Class 12 Chemistry Chapter 11 Alcohols, Phenols and Ethers Class 12 Important Questions 61

Alcohols, Phenols and Ethers Class 12 Important Questions Short Answer Type -II [SA – II]

Question 58.
Explain the mechanism of the following reactions :
(i) Addition of Grignard’s reagent to the carbonyl group of a compound forming an adduct followed by hydrolysis.
(ii) Acid catalysed dehydration of an alcohol forming an alkene.
(iii) Acid catalysed hydration of an alkene forming an alcohol. (Delhi 2009)
Answer:
(i) Carbonyl group undergoes nucleophillic addition reaction with Grignard reagent to form an adduct which undergoes hydrolysis to give alcohol in the following manner:
Important Questions for Class 12 Chemistry Chapter 11 Alcohols, Phenols and Ethers Class 12 Important Questions 62
(ii) The mechanism of dehydration of ethanol involves the following steps :
Mechanism : It involves the following three steps :
Step 1 : Formation of protonated alcohol
Important Questions for Class 12 Chemistry Chapter 11 Alcohols, Phenols and Ethers Class 12 Important Questions 63

(iii) Acid catalysed hydration : Alkenes react with water in the presence of acid as catalyst to form alcohols. Mechanism : It involves the following three steps :
Step 1 : Protonation of alkene to form carbocation by electrophilic attack of H3O+
Important Questions for Class 12 Chemistry Chapter 11 Alcohols, Phenols and Ethers Class 12 Important Questions 64
Important Questions for Class 12 Chemistry Chapter 11 Alcohols, Phenols and Ethers Class 12 Important Questions 65

Question 59.
Explain the following observations :
(i) The boiling point of ethanol is higher than that of methoxymethane.
(ii) Phenol is more acidic than ethanol.
(iii) o- and p-nitrophenols are more acidic than phenol. (All India 2009)
Answer:
(i) Due to presence of intermolecular H-bonding, associated molecules are formed, hence ethanol has high boiling point while methoxymethane does not have intermolecular H-bonding.
(ii) Phenol on losing H+ ion forms phenoxide ion, and ethanol on losing H+ ion forms ethoxide ion. Phenoxide ion is more stable than ethoxide ion as phenoxide ion exists in resonance structure. Due to this phenol is more acidic than ethanol.
(iii) Both o- and p-nitrophenols contain the NO2 group which is an electron withdrawing group. Due to -R and -I effect of the -NO2 group, electron density in the OH bond of substituted phenol decreases and hence the loss of proton becomes easy and therefore more acidic.

Question 60.
How would you convert the following :
(i) Phenol to benzoquinone
(ii) Propanone to 2-methylpropan-2-ol
(iii) Propene to propan-2-ol (All India 2010)
Answer:
(i) Phenol to benzoquinone
Important Questions for Class 12 Chemistry Chapter 11 Alcohols, Phenols and Ethers Class 12 Important Questions 66

Question 61.
How would you obtain the following ;
(i) Benzoquinone from phenol
(ii) 2-Methylpropan-2-ol from ethylmagnesium chloride
(iii) Propan-2-ol from propene (All India 2010)
Answer:
(i) Benzoquinone from phenol
Important Questions for Class 12 Chemistry Chapter 11 Alcohols, Phenols and Ethers Class 12 Important Questions 67

(ii) Ethylmagnesium chloride to propan-1-ol
Important Questions for Class 12 Chemistry Chapter 11 Alcohols, Phenols and Ethers Class 12 Important Questions 35

(iii) Propene to propan-2-ol
Important Questions for Class 12 Chemistry Chapter 11 Alcohols, Phenols and Ethers Class 12 Important Questions 34

Question 62.
Draw the structure and name the product formed if the following alcohols are oxidized. Assume that an excess of oxidising agent is used.
(i) CH3CH2CH2CH2OH
(ii) 2-butanol
(iii) 2-methyl-l-propanol (Delhi 2012)
Answer:
Important Questions for Class 12 Chemistry Chapter 11 Alcohols, Phenols and Ethers Class 12 Important Questions 68

Question 63.
(a) Illustrate the following name reactions :
(i) Reimer-Tiemann Reaction (ii) Williamson Synthesis.
(b) Give a chemical test to distinguish between 2-propanol and 2-methyl-2-propanol. (Comptt. Delhi 2012)
Answer:
(a)  (i) Reimer-Tiemann reaction : Treatment of phenol with CHCl3 in presence of aqueous NaOH at 340K followed by hydrolysis gives salicylaldehyde.
Important Questions for Class 12 Chemistry Chapter 11 Alcohols, Phenols and Ethers Class 12 Important Questions 32
(ii) Williamson’s ether synthesis : The reaction involves the nucleophilic substitution of the halide ion from the alkyl halide by the alkoxide ion by SN2 mechanism.
Example :
Important Questions for Class 12 Chemistry Chapter 11 Alcohols, Phenols and Ethers Class 12 Important Questions 31

(b) 2-Propanol is a secondary alcohol. When it reacts with I2 in NaOH, it forms a yellow ppt of iodoform but 2-methyl-2 propanol does not respond to this test.

Question 64.
(a) Give a seperate chemical test to distinguish between the following pairs of compounds:
(i) Ethanol and Phenol (ii) 2-Pentanol and 3-Pentanol
(b) Explain Kolbe’s reaction with the help of suitable example. (Comptt. Delhi 2012)
Answer:
(a) (i) Ethanol on reacting with I2 in NaOH gives yellow ppt of iodoform whereas phenol does not respond to this test.
(ii) 2-Pentanol on reacting with I2 in NaOH gives yellow ppt of iodoform whereas 3-pentanol does not respond to this test.

(b) Kolbe’s reaction : Phenol reacts with NaOH to give sodium phenoxide which on reaction with CO2 in acid gives salicylic acid.
Important Questions for Class 12 Chemistry Chapter 11 Alcohols, Phenols and Ethers Class 12 Important Questions 69

Question 65.
(a) How would you obtain the following :
(i) 2-methylpentan-2-ol from 2-methyl-1-pentene
(ii) Acetophenone from phenol
(b) Write IUPAC name of the following : (Comptt. All India 2012)
Important Questions for Class 12 Chemistry Chapter 11 Alcohols, Phenols and Ethers Class 12 Important Questions 70
Answer:
(a) (i) 2-Methylpentan-2-ol from 2-methyl-1-pentene
Important Questions for Class 12 Chemistry Chapter 11 Alcohols, Phenols and Ethers Class 12 Important Questions 71
(b) IUPAC name : 1 -ethoxy-2-nitrocyclohexane.

Question 66.
(a) Give mechanism of preparation of ethoxy ethane from ethanol.
(b) How is toluene obtained from phenol? (Comptt. Delhi 2013)
Answer:
(a) Mechanism of formation of ethoxy ethane
Step 1 : Protonation of ethanol
Important Questions for Class 12 Chemistry Chapter 11 Alcohols, Phenols and Ethers Class 12 Important Questions 72

Question 67.
(a) Give chemical tests to distinguish between the following pairs of compounds :
(i) Pentan-2-ol and Pentan-3-ol (ii) Methanol and Phenol
(b) o-nitro phenol is more acidic than o-methoxy phenol. Explain why. (Comptt. All India 2013)
Answer:
(a) (i) 2-pentanol gives Iodoform test with yellow ppt. of Iodoform while 3-pentanone does not give this test.
(ii) Distinction between Methanol and Phenol :
By FeCl3 test : Phenol gives violet coloured solution with FeCl3 while methanol does not.
Important Questions for Class 12 Chemistry Chapter 11 Alcohols, Phenols and Ethers Class 12 Important Questions 73

(b) O-nitro phenol is more acidic than o-methoxy phenol due to presence of NO2 group which has -I effect. It weakens the O-H bond of phenol by withdrawing their electrons and thus releases H+ ion easily while due to +I, +R effect of OCH3, o-methoxy phenol is less acidic.

Question 68.
(a) Write the mechanism of the following reaction :
Important Questions for Class 12 Chemistry Chapter 11 Alcohols, Phenols and Ethers Class 12 Important Questions 74
(b) Write the equation involved in Reimer-Tiemann reaction. (Delhi 2014)
Answer:
Important Questions for Class 12 Chemistry Chapter 11 Alcohols, Phenols and Ethers Class 12 Important Questions 75
Important Questions for Class 12 Chemistry Chapter 11 Alcohols, Phenols and Ethers Class 12 Important Questions 76
(b) Ortho-nitrophenol has lower boiling point due to formation of intramolecular H-bonding whereas p-nitrophenol forms intermoleeular H-bonding.

Question 69.
Explain the following with an example for each :
(i) Kolbe’s reaction
(ii) Reimer-Tiemann reaction
(iii) Williamson ether synthesis (Comptt. All India 2014)
Answer:
(i) Kolbe’s reaction: Phenoxide ion generated by treating phenol with sodium hydroxide is more reactive than phenol and undergoes electrophilic substitution with carbon dioxide. Ortho hydroxybenzoic acid is formed as the main reaction product.
Important Questions for Class 12 Chemistry Chapter 11 Alcohols, Phenols and Ethers Class 12 Important Questions 51

(ii) Reimer-Tiemann reaction : Treatment of phenol with CHCl3 in presence of aqueous NaOH at 340K followed by hydrolysis gives salicylaldehyde.
Important Questions for Class 12 Chemistry Chapter 11 Alcohols, Phenols and Ethers Class 12 Important Questions 32
(iii) Williamson’s ether synthesis : The reaction involves the nucleophilic substitution of the halide ion from the alkyl halide by the alkoxide ion by SN2 mechanism.
Example :
Important Questions for Class 12 Chemistry Chapter 11 Alcohols, Phenols and Ethers Class 12 Important Questions 31

Question 70.
How are the following conversions carried out?
(i) Propene → 4 Propan-2-ol
(ii) Ethylmagnesium chloride → 4 Propan-l-ol
(iii) Benzyl chloride → Benzyl alcohol (Comptt All India 2014)
Answer:
(i) Propene to propan-2-ol
Important Questions for Class 12 Chemistry Chapter 11 Alcohols, Phenols and Ethers Class 12 Important Questions 77

(ii) Ethylmagnesium chloride to propan-1-ol
Important Questions for Class 12 Chemistry Chapter 11 Alcohols, Phenols and Ethers Class 12 Important Questions 35
(iii) Benzyl chloride → Benzyl alcohol
Important Questions for Class 12 Chemistry Chapter 11 Alcohols, Phenols and Ethers Class 12 Important Questions 103

Question 71.
How do you convert the following :
(i) Phenol to anisole
(ii) Propan-2-ol to 2-methylpropan-2-ol
(iii) Aniline to phenol (Delhi 2015)
Answer:
Important Questions for Class 12 Chemistry Chapter 11 Alcohols, Phenols and Ethers Class 12 Important Questions 78

Question 72.
(a) Write the mechanism of the following reaction :
Important Questions for Class 12 Chemistry Chapter 11 Alcohols, Phenols and Ethers Class 12 Important Questions 79
(b) Write the equation involved in the acetylation of Salicylic acid (Delhi 2015)
Answer:
Important Questions for Class 12 Chemistry Chapter 11 Alcohols, Phenols and Ethers Class 12 Important Questions 80

Question 73.
Give reasons for the following :
(i) Phenol is more acidic than methanol.
(ii) The C—O—H bond angle in alcohols is slightly less than the tetrahedral angle (190°28′).
(iii) (CH3)3C—O—CH3 on reaction with HI gives (CH3)3C—I and CH3—OH as the main products and not (CH3)3C—OH and CH3—I. (All India 2015)
Answer:
(i) Phenol is more acidic than methanol because in phenol, phenoxide ion formed is more stabilized by resonance than phenol. There is no resonance in methanol.
(ii) The C—O—H bond angle in alcohols is slightly less than tetrahedral angle due to repulsion between the lone pairs of electrons of oxygen.
(iii) (CH3)3C+ is 3° carbo-cation which is more stable than \mathrm{CH}_{3}^{+} for SN1 reaction.

Question 74.
How are the following conversions carried out?
(i) Propene to propan-2-ol
(ii) Benzyl chloride to Benzyl alcohol
(iii) Anisole to p-Bromoanisole (Comptt. Delhi 2015)
Answer:
(i) Propene to propan-2-ol
Important Questions for Class 12 Chemistry Chapter 11 Alcohols, Phenols and Ethers Class 12 Important Questions 81

Question 75.
Write the major product in the following equations : (Comptt. All India 2015)
Important Questions for Class 12 Chemistry Chapter 11 Alcohols, Phenols and Ethers Class 12 Important Questions 82
Answer:
Important Questions for Class 12 Chemistry Chapter 11 Alcohols, Phenols and Ethers Class 12 Important Questions 83
Important Questions for Class 12 Chemistry Chapter 11 Alcohols, Phenols and Ethers Class 12 Important Questions 84

Question 76.
Write the main product(s) in each of the following reactions: (Delhi 2016)
Important Questions for Class 12 Chemistry Chapter 11 Alcohols, Phenols and Ethers Class 12 Important Questions 85
Answer:
Important Questions for Class 12 Chemistry Chapter 11 Alcohols, Phenols and Ethers Class 12 Important Questions 86
Important Questions for Class 12 Chemistry Chapter 11 Alcohols, Phenols and Ethers Class 12 Important Questions 87

Question 77.
Write the final product(s) in each of the following reactions: (All India 2016)
Important Questions for Class 12 Chemistry Chapter 11 Alcohols, Phenols and Ethers Class 12 Important Questions 88
Answer:
Important Questions for Class 12 Chemistry Chapter 11 Alcohols, Phenols and Ethers Class 12 Important Questions 89

Question 78.
How are the following conversions carried out?
(i) Propene → Propan-2-ol
(ii) Benzyl chloride → Benzyl alcohol
(iii) Ethyl magnesium chloride → Propan-1-ol (Comptt. Delhi 2016)
Answer:
Important Questions for Class 12 Chemistry Chapter 11 Alcohols, Phenols and Ethers Class 12 Important Questions 90

Question 79.
Explain the following with an example in each :
(i) Kolbe’s reaction
(ii) Reimer-Tiemann reaction
(iii) Williamson ether synthesis (Comptt. All India 2016)
Answer:
(i) Kolbe’s reaction : Phenol reacts with CO2 at 390-400 K under pressure 4-7 giving Selicyle Acid
Important Questions for Class 12 Chemistry Chapter 11 Alcohols, Phenols and Ethers Class 12 Important Questions 91
Important Questions for Class 12 Chemistry Chapter 11 Alcohols, Phenols and Ethers Class 12 Important Questions 92

Question 80.
(a) What happens when CH3—O—CH<sub3 is heated with HI?
(b) Explain mechanism for hydration of acid catalyzed ethene :
CH2 = CH2 + HzO \stackrel{\mathrm{H}^{+}}{\longrightarrow} CH3—CH,—OH (Comptt. Delhi 2017)
Answer:
(a) Methyl Iodide (CH3I) and Methanol (CH3OH) are formed when CH3—O—CH3 is heated with HI.
Important Questions for Class 12 Chemistry Chapter 11 Alcohols, Phenols and Ethers Class 12 Important Questions 93

(b) Acid catalysed hydration : Alkenes react with water in the presence of acid as catalyst to form alcohols.
Mechanism : It involves the following three steps :
Step 1: Protonation of alkene to form carbocation by electrophilic attack of H3O+.
Important Questions for Class 12 Chemistry Chapter 11 Alcohols, Phenols and Ethers Class 12 Important Questions 94

Question 81.
(a) Why phenol is more acidic than ethanol?
(b) Write the mechanism of acid dehydration of ethanol to yield ether:  (Comptt. All India 2017)Important Questions for Class 12 Chemistry Chapter 11 Alcohols, Phenols and Ethers Class 12 Important Questions 104
Answer:
(a) Phenol on losing H+ ion forms phenoxide ion, and ethanol on losing H+ ion forms ethoxide ion. Phenoxide ion is more stable than ethoxide ion as phenoxide ion exists in resonance structure. Due to this phenol is more acidic than ethanol.
Important Questions for Class 12 Chemistry Chapter 11 Alcohols, Phenols and Ethers Class 12 Important Questions 95
Important Questions for Class 12 Chemistry Chapter 11 Alcohols, Phenols and Ethers Class 12 Important Questions 96

Question 82.
(i) Write Reimer-Timann reaction.
(ii) Write the mechanism of acid dehydration of ethanol to yield ethene :  (Comptt. All India 2017)Important Questions for Class 12 Chemistry Chapter 11 Alcohols, Phenols and Ethers Class 12 Important Questions 105
Answer:
(i) Reimer-Timman reaction—
Important Questions for Class 12 Chemistry Chapter 11 Alcohols, Phenols and Ethers Class 12 Important Questions 97

Alcohols, Phenols and Ethers Class 12 Important Questions long Answer Type (LA)

Question 83.
(a) Write the product(s) in the following reactions: (Delhi 2017)
Important Questions for Class 12 Chemistry Chapter 11 Alcohols, Phenols and Ethers Class 12 Important Questions 98
(b) Give simple chemical tests to distinguish between the following pairs of compounds:
(i) Ethanol and Phenol
(ii) Propanol and 2-methylpropan-2-ol
Answer:
Important Questions for Class 12 Chemistry Chapter 11 Alcohols, Phenols and Ethers Class 12 Important Questions 99
Important Questions for Class 12 Chemistry Chapter 11 Alcohols, Phenols and Ethers Class 12 Important Questions 100

Question 84.
Write the formula of reagents used in the following reactions:
(i) Bromination of phenol to 2,4,6-tribromophenol
(ii) Hydroboration of propene and then oxidation to propanol.
(b) Arrange the following compound groups in the increasing order of their property indicated:
(i) p-nitrophenol, ethanol, phenol (acidic character)
(ii) Propanol, Propane, Propanal (boiling point)
(c) Write the mechanism (using curved arrow notation) of the following reaction: (Delhi 2017)
Important Questions for Class 12 Chemistry Chapter 11 Alcohols, Phenols and Ethers Class 12 Important Questions 101
Answer:
Important Questions for Class 12 Chemistry Chapter 11 Alcohols, Phenols and Ethers Class 12 Important Questions 102

Important Questions for Class 12 Chemistry

The post Important Questions for Class 12 Chemistry Chapter 11 Alcohols, Phenols and Ethers Class 12 Important Questions appeared first on Learn CBSE.


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