Alcohols Phenols And Ethers(11th And 12th > Chemistry ) Questions and answers for exam Preparation

11th And 12th > Chemistry

ALCOHOLS PHENOLS AND ETHERS MCQs

Total Questions : 30 | Page 1 of 3 pages

Question 1.

The reaction of with HBr gives

Discuss Question

Answer: Option B. ->

:
B

Reaction proceeds by benzyl carbocation formation which is stabilized due to resonance

Question 2.

At low temperature phenol reacts with $B r_{2} i n C S_{2}$ to form

m-bromophenol
o-and p-bromophenol
p-bromophenol
2, 4, 6-tribromophenol

Discuss Question

Answer: Option B. -> o-and p-bromophenol
:
B

In presence of non-polar solvent $(C S_{2})$ the ionization of phenol is suppressed. The ring is slightly activated and hence mono substitution occurs with p-bromophenol as the major product.

On the other hand with water phenol forms 2, 4, 6-tribromo phenol. $(C S_{2})$

In aqueous solution phenol ionizes to give phenoxide ion. Due to the presence of negative charge of

oxygen the benzene ring is highly activated and hence trisubstituted product is obtained.

Question 3.

The best reagent to convert pent-3-en-2-ol into pent-3-en-2-one is

Acidic permanganate
Acidic dichromate
Chromic anhydride in glacial acetic acid
Pyridinium chloro-chromate

Discuss Question

Answer: Option C. -> Chromic anhydride in glacial acetic acid
:
C
Strong oxidising agents like acidified

K M n O_{4}

K_{2} C r_{2} O_{7}

oxidised alcohols to carboxylic acids. For oxidation of primary alcohols to ketones, Pyridinium chloro-chromate(PCC) is used and for oxidation of secondary alcohols to ketones, Chromic anhydride in glacial acetic acid is used.

Question 4.

Which of the following will maximum $p K_{a}$ value?

Phenol
o-cresol
ethanol
o-nitrophenol

Discuss Question

Answer: Option C. -> ethanol
:
C

Order of $A c i d i t y - o - n i t r o p h e n o l > p h e n o l > o - c r e s o l > e t h a n o l .$ $o - n i t r o p h e n o l$ is more acidic than phenol due to electron withdrawing nature of nitro group. o-crseol is less acidic than alcohol due to electron-releasing nature of methyl group. Phenoxide ion is resonance stabilized but ethoxide ion is not. Thus, phenol is more acidic than alcohol. Greater the $p K_{a}$ value, less is the acidity.

Question 5.

The compound which is not isomeric with diethyl ether is:-

n-propylmethyl ether
Butan-1-ol
2-methylpropan-2-ol
Butanone

Discuss Question

Answer: Option D. -> Butanone
:
D
Diethyl ether is

C_{4} H_{10} O

. n-propylmethylether, butan-1-ol

&

2-methyl~propan-2-ol is

C_{4} H_{10} O

. Butanone is

C_{4} H_{8} O .

Question 6.

Chlorination of toluene in the presence of light and heat followed by treatment with aqueous NaOH gives:-

o-cresol
p-cresol
2, 4-dihydroxy toluene
Benzyl alcohol

Discuss Question

Answer: Option D. -> Benzyl alcohol
:
D

Question 7.

Ortho-nitrophenol is steam volatile whereas para-nitrophenol is not. This is due to
$1.$ Intramolecular hydrogen bonding present in ortho-nitrophenol
$2.$ Intermolecular hydrogen bonding present in para-nitrophenol
$3.$ Intramolecular hydrogen bonding present in para-nitrophenol
$4.$ Inter-molecular hydrogen bonding present in ortho-nitrophenol.

$1 & 3$
$1, 3 & 4$
$1 & 2$
$2 o n l y$

Discuss Question

Answer: Option C. ->

1 & 2

:
C

Para-nitro phenol has higher boiling point than ortho-nitrophenol due to intermolecular hydrogen bonding present in para-nitrophenol, which requires more energy to break these bonds during boiling. In o-nitrophenol, intramolecular hydrogen bonding is present to greater extent. Thus, o-nitrophenol is steam volatile due to low boiling point.

Question 8.

Propan-1-ol can be prepared from propene by alcohol

$H_{2} O / H_{2} S O_{4}$
$H g (O A c)_{2} / H_{2} O$ followed by $N a B H_{4}$
$B_{2} H_{6}$ followed by $H_{2} O_{2}$
$C H_{3} C O_{2} H / H_{2} S O_{4}$

Discuss Question

Answer: Option C. ->

B_{2} H_{6}

followed by

H_{2} O_{2}

:
C

When propene reacts with mercuric acetate followed by $N a B H_{4}$ , it gives secondary or tertiary alcohols, in accordance with Markownikoff’s rule. But, with diborane followed by $H_{2} O_{2},$ it gives primary alcohols which is in accordance with Anti-Markownikoff’s rule. $6 C H_{3} - C H = C H_{2} + B_{2} H_{6} H_{2} O_{2} - -- \to C H_{3} - C H_{2} - C H_{2} O H$

Question 9.

Major product in Friedel-Craft's acylation of anisole is:-

Chlorobenzene
4-Chloro-1-methoxy benzene
4-Methoxy-acetophenone
3-Methoxy-acetophenone.

Discuss Question

Answer: Option C. -> 4-Methoxy-acetophenone
:
C
Friedel-Craft's acylation of anisole with acetyl chloride in presence of anhydrous

A l C l_{3}

gives 4-methoxy acetophenone(para) as a major product. Methoxy group in anisole is activating and ortho-para directing with major product being para isomer.

Question 10.

Which of the following will not react with $N a O H ?$